-m. .NOTICE -THE ATTACHED FILES ARE OFFICIAL RECORDS OF THE DIVISION OF DOCUMENT CONTROL. THEY HAVE BEEN CHARGED TO YOU FOR A LIMITED TIME PERIOD AND MUST BE RETURNED TO THE RECORDS FACILITY BRANCH 016. PLEASE DO NOT SEND DOCUMENTS CHARGED OUT THROUGH THE MAIL. REMOVAL OF ANY PAGE(S) FROM DOCUMENT FOR REPRODUCTION MUST BE REFERRED TO FILE PERSONNEL.

DEADLINE RETURN DATE

RECORDS FACILITY BRANCH

1.0 PURPOSE:

FEEDWATER HAMMER INVESTIGATION APRIL 6, 1984 OCCURRENCE SALEM GENERATING STATION

UNIT NO. 2

The purpose of this engineering evaluation is to evaluate the cause, effect and safety implications of the water hammer that occurred on Unit No. 2 on April 6, 1984, as a result of the 23BF22 stop check valve failing to close completely, allowing water to flow in the reverse direction.

2.0 SCOPE:

This engineering evaluation specifically addresses the incident of April 6, 1984, at 1633 hours.

3.0 REFERENCES:

3.1 Appendix A - Pr~liminaFY Occurrence Report.·from Station to Engineering.

3.2 Appendix R - Final Report - Analysis of Feedwater System Transient Occurrence of April 6, 1984, Salem Generating Station - Unit No. 2 (including Supporting Analysis of Stoner Consulting Engineers, Inc.)

4.0 DISCUSSION:

4.1 DESCRIPTION OF OCCURRENCE

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On April 6, 1984, in-service testing of Mode Dependent Valves on Unit No. 2, in accordance with Surveillance Procedure SP(0)4.0.5-V-MD, was in progress. The valves that were being tested were the Feedwater Regulating Valves (21-24 BF19s) and the Feedwater Regulating Bypass Valves (21-24 BF40s). The test procedure requires each valve to be opened and then timed closed. Testing had just been satisfactorily completed on 21BF19, 21BF40, 22BF19 and 22BF40.

At 1633 hours, 23BF19 was opened, at which time, a loud "rumbling noise" was heard. 23BF19 was closed, the setpoints on all MSlOs were decreased and 21-24 BF13s, 2BF65 and 2BF66 were closed. The transient lasted for approximately 20-30 seconds •

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Primary plant parameters were observed to be steady and stable and no change was observed in RP-4 status nor in T-ave. Other observations are as follows:

1. Normal pressure on all steam generators,

2. No. 23S/G level indicated swell and then decrease.

3. A drop of appro~imately 15% level on No. 23 S/G Narrow Range Level Indication and approximately 3% on the Wide Range Indication (from start to finish of the transient) ,

4. "Rumbling" noise appeared to stop prior to closing of the 23BF19. This was confirmed by the Salem Generating Station Operations Department Departmen£ personnel. This noise lasted approximately 20 to 30 seconds. No bangs or other shocks were heard

.at the time. The rumbling noise stopped at about the instance the control room operator activated closure of the 23BF19 valve. Shortly thereafter, a plant I & C supervisor arrived at the 23BF19 valve and found it still closing.

5. No indication of high steam flow. Observed 23 S/G level "Program Deviation Setpoint to Actual", "Feedwater Greater than Steamflow" and "No. 23 S/G Hi-Hi Level" alarms.

6. Auxiliary feed flow to all steam generators remained steady throughout the transient,

7. All console push-button bacKlights (which were lighted) were varying in intensity, and all meter indications were fluctating (only observed by the board operator).

4.2 CONDITIONS PRIOR TO OCCURRENCE:

Mode 3 - Reactor Power 000% - Unit Load 000 MWe

Primary Plant Parameters:

RCS Temperature - 547°F

RCS Pressure - 2240 psig

Przr. Level - Approx. 26%

S/G Level - 30% to 40% (all)

S/G Pressure - 1000 psig

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All Reactor Coolant Pumps were in service, with normal charging and letdown. All steam generators were being supplied with Auxiliary Feedwater. The MSlO valves were steaming.

Secondary Plant Lineup:

1. 21 Condensate Pump in-service for secondary cleanup through the condensate polisher.

2. All feedwater heater strings in-service

3. 21CN48 and 22CN48 (S/G Feed Pump Bypass Valves) - OPEN

4. 21-24 BF19s (S/G Feedwater Reg. Valves) - CLOSED

5. 21-24 BF40s (S/G Feedwater Reg. Valve Bypass Valves) -CLOSED

6. 21-24 BF13s (S/G Feedwater Reg. Valve Isolation Valves) - OPEN

7. 21-24 BF22s (S/G Feedwate( Stop Ch~ck V~lves) - Motor Operator Controls in OPEN position (this does not.mean that the valve~ are open: it means the valves are not held shut, and sho~ld act as. check valves)

8. 2BF65 (Feed Full-Flow Recirc. Stop Valve) - OPEN

9. 2BF66 (Feed Full-Flow Recirc. Reg. Valve) - OPEN

See Appendix A for a detailed description of the event.

4.3 DAMAGE ASSESSMENT

Immediately after the occurrence, an organization was mobilized to evaluate the damage to the feedwater lines.

An engineering team was immediately put in place to evaluate the damage. Four separate groups of Engineering and Design personnel were dispatched to evaluate the damage on the feedwater headers to each steam generator as well as the bypass line to the Condenser and the Auxiliary Feedwater lines to the Auxiliary Feedwater pumps. The information obtained from this walkdown was evaluated to determine the cause and effect of the feedwater hammer and to implement a program to evaluate the condition of the equipment and piping in each of the feedwater headers. The information obtained from the walkdown confirmed that damage was limited to the No. 23 feedwater header to the steam generator: this was to be expected since the incident occurred during the actuation of the 23BF19 valve .

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To facilitate an orderly review of the damage, the feedwater line to the No. 23 steam generator was divided into three separate zones •.•••• Zone 1 was from the steam generators to the 23BF19 and 23BF40. valves; this zone was later subdivided for purpose of analysis into. Zone lA from the steam generator to the BF22 valves and Zone lB from the BF22 valves to the BF19/BF40 valves. Zone 2 was from the 23BF19 and 23BF40 upstream through the common header to the condensate recirculation strainer line and all remaining feedlines up to their respected BF19 and BF40 valves. Zone 3 included the balance of plant condensate and feedwater up to the BF9 stop check valves.

The damage found was:

1. Damage to piping supports and snubbers on the highest elevation of the piping run on the Condenser side of the BF22 valve between the BF22 valve and the RF19 valve.

2. Damage to trunnions supporting the jet impingement elements on the lowest elevation on the riser to the No. 23 steam generate~ ..

3. Pressure gauges found overranged. The gauges were calibrated. No damage was found to the bourdon tubes •

4. Valve 23BF40s positioner was damaged. was recalibrated.

The positioner

5. 23BF19 was found to have the positioner cam detent sheared off. This was determined not to be as a result of the incident.

6. Displacement of No. 23 flow metering nozzle toward the 2~BF13 valve this was found during attempts to restart the Unit.

These zones were chosen as a result of conclusions reached from visual inspections of the damage to instrumentation located in the feedwater header from the steam generators back to the condensate system. That is to say, Zone 1 was chosen since a damaged 2,000 psi pressure gauge indicated that the pressure spike experienced by this zone differed from Zone 2 (where a 600 psi gauge was damaged whereas a 1500 psi gauge experienced no damage) and from Zone 3 where no damage was experienced by any pressure gauges •

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Since damage was limited to the No. 23 steam generator feedwater header, efforts were concentrated but not limited to this header with the understanding that, if significant damage to piping or· equipment was found, the scope of the evaluation would be expanded to the other feedwater headers.

The following actions were immediately implemented upon the identification of the damage to the No. 23 feedwater header:

1. An identification of all welds at fittings such as elbows, tees, bends, etc. was initiated. This was initiated so that the welds at the most stressed components in the piping system would be evaluated for damage (Appendix C).

2. Visually inspect the 23BF22, 23BF19, 23BF40 and 23AF22 valves for damage. These valves were all within the boundary valves of the incident. The 21., 2 2, 2 3BF9 valves were al so to be tested to determine their checking capability.

3. Evaluate the damage to the instrumentation and Control's equipment in the No. 23 steam generato·r feedwater header. This consisted of a review of the as found condition and the as calibrated condition.

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4.3.l

Evaluate the damage to the internals of the steam generator, specifically, the feedwater nozzle, the feedring, the primary and secondary moisture separators, the J-nozzles, and the plugs at the bottom of the feedrings.

Piping System Evaluation

To evaluate the damage to the piping system, "high stress" welds throughout the system had non-destructive examination performed on them; "High Stress" welds were defined for the purpose of this evaluation as those welds in the piping system where the direction of the flow changes, such as at elbows.

From the 23BF22 valve to the steam generator, the welds identified in the ISI Program were evaluated. This decision was made due to the availability of baseline data for the purpose of comparison. Also, all of the lugs attached to the pipe wall were magnetic particle inspected.

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4.3.3

From the BF22 to the BF19s, a random sampling of welds consisting of approximately 50% of the "high stress" welds were evaluated and again, all the lugs were magnetic particle· examined.

Another sample of approximately 50% of the total "high stress" welds from the Auxiliary Feedwater Valve 23AF23 to the Auxiliary Feedwater Valve 23AF920 were evaluated.

All of the damage found was limited to supports, snubbers, and the feed flow nozzle on the steam generator feedwater piping in the non-nuclear portion of the system between the 23BF22 valve and the 23BF19 valve. Damage was also found on the trunnions supporting the pipe whip restraints on the vertical riser to the No. 23 Steam Generator. It is~anticipated that these trunnions were damaged as a result of vibration experienced on the header during the incident. No piping weld damage was found.

Valve Evaluation

Valves 23BF22, 23BF19, 23BF40 and 23AF23 were dismantled and evaluated for potential damage. No damage was found to the internals of these valves • Valve 24BF22 which is of the same design as the 23BF22 valve was also dismantled to determine whether a reason could be found for the stem piston arrangement being in an open position on the 23BF22. Furthermore, although the similar valves in Unit #1 (11, 12, 13, and 14BF22) were radiographed to determine the actual position of the piston plug arrangement, no conc.lusion could be reached on the position of the pistons due to lack of clarity of the radiographs. However, since the similar Unit 1 valves 11, 12, 13, and 14 BF22 are being modified to install motor operators on them during the current on Unit 1 outage, they will be visually inspected to attempt to determine the cause for the failure of the 23BF22 valve sticking in an open position.

Steam Generator Evaluation

The No. 23 steam generator secondary manway was opened for inspection of the internals for damage as a result of this feedwater hammer. Westinghouse and the In-Service Inspection Group performed the investigation and no damage was found.

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4.3.4 Balance of Plant and Auxiliary Feed Evaluation

The balance of plant evaluation consisted of:

1. Verification of Stop/Check valve 21, 22, 23BF9 integrity

2. Feedwater Heater Leakage Testing 3. Main Condenser Shell Inspection 4. Startup Strainer inspection 5. Condensate Pump Performance Evaluation

The results of this evaluation is found in Appendix F. Specifically, no damage was found in the balance of plant area except for damage to the main steam dump condensate spray header. This damage, however, was determined not to be as a result of this feedwater hammer transient.

The Auxiliary Feedwater Pump and Condensate pump were performance tested and found to be acceptable with no problems noted. A partial Hydrotest was also performed using a condensate pump.

4.3.5 Instrumentation and Cont~ols Evaluation

The I&C portion of this evaluation consisted of physically inspecting gauges and control equipment for damage. Several gauges were found overranged and the positions on valves 23BF40 and 23RF19 were found to have various degrees of damage.

4.4 SYSTEMS ANALYSIS

Appendix ·I details the results of the analysis performed to evaluate the water hammer event. Based on the facts that were obtained from the observed event and detailed in Appendix A several conclusions can be reached:

1. The blowdown from the steam generator continued for 20-30 seconds and approximately 300 cubic feet of liquid evacuated the steam generator. Therefore, the critical flow rate achieved was not greater than 15 cubic feet per second. This implies that the 23BF22 Stop Check Valve was only marginally opened during the entire event. It is believed that debris had collected in either the valve mechanism or under the seat which did not prevent the valve from closing but did prevent proper contact of the seat and thus prevented boundary isolation. Since the check valve manufacturer's field

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representative inspected the valve and reported that no unusual conditions existed that would have prevented the closure of the check valve, it is reasonable to assume that the continuous high velocity of reverse flow through the valve and the pressure applied to the closure mechanism as a result of this flow rate, dislodged debris allowing the valve to close leaving no evidence behind. Also, before the operator initiated the closure of the 23BF19 valve, the rumbling noise had stopped which implies that the 23BF22 did, in fact, isolate the event.

The damage incurred as a result of the water hammer had to be evaluated in two separate sections. Zone 1 is limited to the piping between the steam generator and the BF22 valve. Results of the computer simulation of a full open check valve slam for various cases with water temperatures ranging from 60°F to 550°F; show that surge pressures within the range of 1400 psig to 2400 psig are possible. These pressures translate in to maximum axial piping forces ranging from 40 to 150 kips.

However, it is· believed that the v·altie of lSOO·psig.is the most real i"st ic and results in a peak axial force on the order of 80 kips. It should be noted that the values obtained are conserva~ive since they assume a check valve slam from full open and further conversatism exists in the assumptions and calculations. Forces of this magnitude would occur on the horizontal piping directly downstream of the check valve. It is less likely that these pressure surges would be generated in the vertical riser since- the pressure would decay rapidly being suppressed by the reservoir effects of the steam generator. This was demonstrated by the computer simulation, and indicated that no greater than 10 psig was developed across the feedring header. This correlates with the damage reports that stated that movement was detected at the lower elevations of the piping such as the damage trunnions and no movement was noted at the higher elevations.

Zone lA, is the piping section between the BF22 a.nd BF19 valve. The check valve closure subjected the fluid to vaporization due to flashing and/or vapor column separation under the principles of water hammer. These effects would be most prevalent in the region directly upstream of the check valve. The vapor would rise through the pipe to highest elevation (El 13R ft) in the zone upstream of BF22 where a large vapor cavity would collect. When the pressure wave

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from the recovery of the condensate pump flow is established, the portion of the vapor below the recovery pressure would collapse. The computer simulation estimates that axial· forces in the range of 60 kps to 140 kips would be generated. It is believed that these forces would be sufficient to cause the damage evidenced on the piping downstream of the check valve.

Although the event involves multi-phase flows, stratified cold water and indeterminable thermal boundary conditions, which can only be approximated and never simulated, we are confident that the event which occurred on April 6, 1984, is represented fairly well by this computer analysis.

Based on the known facts surrounding the feedwater hammer event, the evaluation performed provides a reasonable understanding of this scenario and its effects on the system are well established. we further realize that minimal damage was impaired by the system and that operating practices have been revised to circurnven~ future reoccurrence of ·this type of event and we conclude that the plant ~an continue to operate in a safe manner. ·

5.0 ACTIONS TAKEN TO PREVENT FURTHER FEEDWATER HAMMERS:

The following actions were taken to prevent a similiar occurrence:

1) Procedures have been modified to require that prior to stroking the BF19 valves, that the BF22 valves be locked in a closed position by using the motor operators on the valves.

2) A review of the existing piping systems supports on the feed piping will be performed to determine whether any modifications will be required to prevent similar damage due to water hammer.

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APPENDIX A

PRELIMINARY OCCURRENCE REPORT From Station to Engineering

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Occurrence Date:

Occurrence Time:

Report Date:

FEEDVATCR WATER ffjMMER PRELIMINARY REPORT UNIT 2 .

April 6, 1984

1633

April 7, 1984

CONDITIONS PRIOR TO OCCURRENCE!

Mode 3 - Reactor Po'.1e~· OOOS - Unit I.cad 000 MWe

Plant Parameters:

RCS Tempera~ure .·547°F

· RCS Pressure

Przr. I.evel

S/G Level

S/G Pressure

224rJ psi g

lf.pprox. 26S

-·30s to'40S (all)·

- 100CJ psig_

All Reactor Coolant Pumps were in service, with normal charging and letdown; feeding all Steam GenErators with Auxiliary Feed; and, steaming with MS10's.

Secondary Plant I.ine11p:

1. 21 CondenS1te Pu~p in-~ervice for secondary cleanup through the conden::5ate P'·.o.isher.

2. All Feedwater He ter SLrings in-service

3. 21CN48 and 22CN4l (S/G Feed Pump Bypass Valves) - OPEN

4. 21-24 BF19's (S/:; Feedwater Reg. Valves) - CLOSED

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s. ~1-24 Bf40's (S/~ Feedwater Reg. Valve Bypass Valves) - CLOSED

6. 21-24 BFi!•s CS/~ Feedwater Reg. Valve Isolation Valves) - OPEN

7. 21-'4 BF22's CS/~ Feedwater Stop Check Valves) - Motor Operator Controls in OFEN position (this does not mean that.the valves are open; it means the valves are not held shut, and should act as check vai··es)

8. 2BF65 (Feed Full-Flow Reci re. Stop Valve) - OPEN . .

9. 2BF66 ( Fef J Full-~low Recirc • Reg. Valve) - OPEN

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J»:SCRIPTIOI OE OCCURRENCE;

Shift Personnel on Duty:

1. Senior Shift Supervisor

2. Unit 2 Shift Supervisor

3 • Unit 1 Shift Supervisor

4. Unit 2 Board Operator

5 • Unit 2 Desk Operator

On April 6, 1984, in-service testing of Mo~e Depend~nt Valves in accordance.with. Surveillance Proced~re SP(0)4.0.S-V-MC was in progress. The valves tha·t were beir~g tested. were t!1e Feed1i1ater Reg. Valves (21-24 BF19's). and the Feedwater Reg. Valve ~,ypass Valves (21-24 BF40's). The test procedure ~requires each valve to be opened, and then timed closed. Testing had just been sati~factorily completed on 21BF19, 21BF40, 22BF19 and 22BF40~

. At 1 6 3 3 hours , 2 3 BF 1 9 was o pen e d ; at which time, a la'. · d " rum bl i n g nois~ wa~ he~rd. 23BF19 was closed, the setpoints ~" ~ll MS10's we~~·. decr•.ased, and 21-24 BF13's, 2BF65 c:nd 2BF66 were .:lu~ed. The _. tran~ient lasted for approximately 20-30 seconds.

Prim1ry pl ant parameters were obser1. ed to be steady a~ :1 stable, no change was observed in RP-4 status, and no change in 1-ave. Other observations are as follows:

1 . No rm al pressure on all .s teat.' e;en era tors,

2. No. 23 S/G indicated swell, then decreas.: (s_t1 ip charts),

3. A drop of approximately ioi level on No. '3 JIG Nz,.row Range Level Indication, and approximately 3~ on the ~ide Range Indication (start to finish of transient}

4. "Rumbling" noise appeared to stop either j 1st prior to, o .. · ju.st after closing 23BF19,

S. No indi-i:ation of high steam flow,

6. Observed 23 S/G level "Program Deviation ~:etpoint to Actual", "Fcedwater Greater than Steamflow" and "~~. 23 S/G Hi-Hi · Level" alarms,

7. Auxiliary· feed flow to all steam generat~rs remained steady throughout the transient,

8. All console push-button backl~.ghts (which were ligbted).. ... were varying in intensity, and all meter indications were fluctuating (Only obseryed by the Board Operator),

• pESCBIPTIOM OF 0CCUIREMCE; (cont'd)

9. No. 21 Auxiliary Feed Pump discharge pressure gauge was very erratic, and

10. The Auxiliary Typewriter indicated that the fre-operational Strainer High.Pressure alarm was received at 1633 hours.

APPABEJIT CAUSE OF OCCUIBEHCE: . .

23BF22 (Ni. 23 S/G Feedwater Stop Check Valve) apparently failed to "check~ closed against steam ienerator pressure. When 23BF19 was opened, the feed line and auxlliary feed ltne experienced a severe pressul e transient with resultant water nammer.

IIITI~L IISPECTIOI RESULTS:

The e1ti1e feed line (from No. 23 S/Gr through the recirc llne to the conde11sHl was visually-. in.spected. ·The feed li.ne.insi.de of . •

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contai nmE it SOOWS no ev.idence Of damage, al though there cip!•ears to_~b~ .. a gap in :he insulation where the llne erters the S/G. In ;ide of th~· turbin b1Jilding and the South Penetration, the feed line insulation:·· is missit.l or damaged in various places. The feed line contains two (2) broken hangers, one (1) bent hanger ind one (1) snubber which appear~ to be "locked-up".. There i.·re th.·ee ( 3) Type PSA-3 and two ( 2) Type PSA· 1 snubbers that were poss: bly d.1maged during the transient. 23BF22 apoears to be leaking. The Ai.:Iil:.ary Typew1 iter jammed just afte: th~ "Pre-operational Strainer High Pressure" alarm was received at .1f33 h~urs; therefore, th~ exac~ leng·;h of th~ transient is not docur .. eJ ~..:.

The ;·,1.:.o·~ing is a status of affec·;'!d I&'; equipment:

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2~BF40 Position Transmitte~ - Int~rnal parts loose and damaged

23BF19 Positioner - Sustai~~d internal damage - ..

23 S/G ~dwater Pr:essure ~luge (Pl.-66.5) - .Overranged

Pre-operational Pressure C~uge CPL-10167), before strainer -Over ranged

?1BF19 Flexible Tubing (air supply to valve diaphrag~) -Broken

23 Auxiliary Feed Flow Tr~nsmitter CFA-1095) - Possibla·damage

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ANTICIPATED CORRECIIYE ACTIONS:

Iu addition to repair of the damages already noted, the following actions are anticipated:

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A detailed inspection of the entire feed l.ine, including all welds, elbows, bends, fittings and valvoes.

A stress analysis of this piping, inclu~ing dead-weight and thermal analysis.

Inspection of No. 23 SIG, including thf :eed nozzle, the feed ring and the J-Tubes.

A visual inspection of the condenser iP~e~nals.

Tests and inspections of the Feedwater·~•aters and Valves.

A detailed inspection of the Auxiliary J'eedwater line.

An inspection of all hangers and snubbqr~ 3ssociated with the feedline.

:nvestig3te potential problem with flic~erihg ·d6n~ole l.g~ts~. and met~r fluctuations.

Resolve problem with Auxili~ry Typewriter.

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APPENDIX B

FINAL REPORT - ANALYSIS OF FEEDWATER SYSTEM TRANSIENT OCCURRENCE OF APRIL 6, 1984,

SALEM GENERATING STATION UNIT NO. 2

(INCLUDING: Supporting Analysis of Stoner Consµlting Engineers, Inc.)

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OPS~G P-ublic Servic:;e .Electric and Gas Company P.O. Box 236 Hancocks Bridge. New Jersey 08038

Nuclear Department

TO: H. G. Berrick ~rincipal Engineer - Nuclear Systems E~gineering ·

M. o. Bandeira Principal Engineer - Nuclear Systems Engineering

FROM: c. M. Williamson Lead Engineer - Nuclear ~ysterns Engineering

_SUBJECT: FINAL REPORT

DATE:

ANALYSTS OF .. FEEDWATER SYSTEM TRANSIENT OCCURRENCE OF APRIL-6, 1984

.SALEM G2NERATING STA'IlON, UNIT.NO. 2

Mayl 7 .. ; 1984

.~ .

As you are aware. we have been i~VE:·stigating the.conditions surrounding the ,:eedwater system tr ::i.nsient of April 6, 1984, Urtit No. 2. The emph"'1sis has been direc.;ted.toward the identification of waterhammer effects if any, the behavior of the componenb· during the _senario, and the restilt~ng forcing functions that were responsible for the inccurred damage.

In order' to expedite the analysis, we solicited 'the as:JistanC"e of Stoner Consultarits Inc., Carlial~, ;A. Their assistanc~ in conjunction with our own engineerin~ efforts allowed us to evaluate many potential senari:.~ '..n. a. timely manner. An evaluation produce by the Ston::r or~ani.zation is at tac: .ed. fo -yo~r referral. ·

Based on our evaluation of the ~lets surrounding this occurr1~ce, we believe that a thorough unde: 3tanding of the senario and : :s effects on the system can be es .>tblished. We further realiz :_ that minimal damage was incurn:~ by the system components, t·v\t oper~ting practices have beeri LJvised to circumvent future .. reoccurence, and therefore the.plant can continue to operatec:n a safe manner.

The following condition were eva:;J~tJd by our personnel to 1-~ the pertinent facts and were either confirmed by independent investigatio~ or agreed upon by scientific princtple •

The Energy People·

35-2 I 68 ,dQMI '' ·32

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The unit was operating in Mode III with Steam Generator temperature at 547°F. Therefore saturated stea~ piessure was approximately 1000 psig.

2. Auxiliary feedwater was feeding the 23 s.G. at 30 gpm and a temperature of 60°F •

. 3. The Sed6ndary plant was operating in the Condenstate Polisher Recirculation mode which means:

Feedpump System was out of service and bypassed No. 21 Condensate Pump was operating at 7500 gpm The feedwater header presure upstream of the control valve (BF19) was approximately 475 psig C~ndensate Water Temperature was approximately 70°F Flow was exiting the system thru the Condensate Polisher Recirculation Valve (BF.66), which was-heavily throttled to break down 490 psia of system pres~ure.

4. Nos. 21, 22 and 24 BF19 and 40 valves were all isolated and are considered physical boundary conditions. Therefore the hydraulic perturba~ions did not affect their representative Stearn Generator feedwater lines.

s . Station Operators were performing feedwater control valve strok~ tests, which normally does not affect the independent oper~ting conditions upstream and downstream of the BF22 stop check valve. Therefore, the 238~22 stop check valve was riot iso·la ted.

6. All witnesses to the event indicated th~t they obvserved a loud rumbling sound eminating from the Yard and Turbine Buildin~ 'for a period of 20 to 30 seconds. Some people felt that !~:he sound became louder as the event continued.

7. Two (2) witnesses (A control room operator and I&C Supe ·visor;. both independently rep'orted that the rumbling stopped before the 23BF19 valve had been isolated. Befbre the Operat0~.initiated the closure of the 23BF19 valve, the rumbling h~d stopped, which implies that 23BF22 did isolate the event. - The full ~-·troke closure time of the Coopes Vulcan BF19 . Valves i'; 25 .o seconds.

8. The No. ~3·~tearn Generator Level Recorder (attached) indicated • 15% d~op in level which relates to a maximum loss in in,entroy of 300 cubic feet of liquid. The actual volume wa~ less if we took credit for internal baffles and void ratio.

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The 23BF19 valve positioner was damaged. The shear pin was dislocated indicating a rapid change in load to positioner and inability to report the true. position to the control room operator. ·The operator reported that the valve position indicator hesitated in response and then indicated a 40% open position, at which time the rumbling sound began.

Th~ final analysis as we have evaluated it as follows. Based on information provided by other sources in this invest.igation and

. re·sults of fluid flow compLtt3r simulations, the following senario is postulated. A schematic sketch of the system is attached and should be referred to for clarification.

For the purposes of clarity,. we define the pl~e subjected to the transient in terms of·zone~. Originally w& considered the section of No. 23 feedline-from the 23BF19 valve to S/G 23 as Zone 1. Later we subdivided ths pipe into two sections, limiting Zone 1 to 23BF22 stop chec~ valve thru the steam generator inclusive and zone lA as 23BF19 valve thr\ to the 23BF22 valve.

Initially the Main Feedwater System was o~er~ting with one condensate pump recirculating flow thru the BF66 valve back to condenser. All BF19 and 40 valves were isolated. No. 23BF22 stop check valve [assumed closed] was not isolated. The Auxiliary Feedwater System was injecting 30 g~m into the No. 23 Steam Generator· (·S/G 23). The partia.lly oper,~d 23BF22 check valve permitted the 1000 p~ .. ig S/G pressure to displace thru the system to the downstream sr:;ction of the 23BF19&40 flow control valves. The temperature of the water throughout the pipel1ne was approximately 60°F to 70°F.

The operator initiated a valve stroke test of the 23BF19 control valve which was subjected t·.o a negative diff?:·ential pressure in excess of 500 psig. During normal operation this valve is subjected to only ~ slight positive differ~ntial pressure because the 23RF40 valve is operating as a pressure balancing bypass valve. We therefore postulate that the va.l ve remained closed until actuator pressure was saturated to overcome the forces and. the valve then popped off the seat to some position in excess of 40% possibly 100%, therefore damaging the positioner. In the computer simulation we characterized this valve profil~ as an instantaneous full open and a normal strc~e closure to 40%. The removal of this boundary condition initiatas the transient event.

The Wavespeed calculated for this system is 4,000 ft/sec. The length of pipe for Zones 1 & lA is 162 ft and 268 ft respectively. Therefore the response tl~e 2(L/A) for the system is less than 0.25 seconds.

The rapid opening of the 23BF19 valve initiated a hydraulic depressurization., which travel~d at. the wavespeed thru the

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-.:!-

pipeline, check valve and steam generator nozzle. As each intergral section of static water column depressurizes a negative flow is established and continues to accelerate until the critical equilibrium of the syst~m is established. During the period of· flow reversal, we would have expected that the 2 3 BF2 2 check valve to complete its closure. But the ·system continued to blowdown after the critical velocity w~s achieved. If the blowdown continued for 20.0 sec and 300 cubic feet of liquid evacuated the steam generator Cconservative) than by simple algebra the critical flow rate achieved was not greater than 15.0 cubic feet/sec. This implies that the 23BF22 stop check valve was only marginally open \effective area less than 15%) during this event.

The check valve manuf~c~urer's field representative later in~pected the valve and reported that no unusual conditions existed that would have prevented the closure of the ch~ck \Jalve. The valve parts were in good condition with no abnopnal wear and there was no debris found. The consensus of opinion of our exper·ts and-the-mar..ufactuer is that debris had collected in either the valve mechartism or under the seat, which did not pr~vent the valve from closing, but did prevent proper contact of the seat and boundary isolation. The continuous high velocity of r.everse flow thru the valve and pressure applied to the closure mechanism dislodged the debris allowing the valve to ~lose and lecving no evidentce behind. We were confident that.the c~eck va~ve did isolate the event and found the valve druing inspection Lo be properly seated and in good wo~king order.

Although we felt the valve was ope~ating in a partially open position during the first segment of the event, we a::.sumed for conservative evaluation a full clo~ure check valve, slam in our computer simulation. Wa .know that. at the time of· isolation, that less 300 cubic feet (7S% = 225 cuft) of water left the steam genr~rator. Assuming f--:>r a moment that a thermal interface is

_formed between the 60°F auxiliary feed water and the 547°F steam generator water, this interface translates down the pipeline for a distance of approximately 270 feet. This correlates with the reports that the sound becama louder as time went on. As the quantity of saturated water increased, the quantity of two phase liquid would also increase, ~hich would increase the sound attenuation of the blowdown =~ndition. The final location of the thermal interface at ·the time of check valve closure is estimated to be somewhere in the vicintiy of damaged hangers (Zone lA) at the 138 ft ele~ation. ·

We. analyzed the effective waterhammer in zone 1 as a result of a check valve s::..drn, by compute,,;· simulations with wa_ter tempera tu re f~om 60°F to 550°F, and negative vel~~ity greater than actual because we are assuming a full open check valve. we calculated absolute pressure surges (including 1000 psig system pressure) within th~ range of 1400 to 2400 psig. The resulting maximum axial pipe forces ranged frcm 40 to. 150_ kps. Because the volume

•• -5-

of 547°F water that evacuated the Steam Generator was greater than the volume of pipe in zone 1, we are confident that the high temperature homgene_ous fluid solution is the· most accurate; which limits the surg~ pressure to 1800 psig and the axial force to 80 kps.

It should be noted as emphasized in the Stoner Report~ the assumption for a specific thermal interface, the correlation of multi density fluid, the presence of vapor column separation all limit the accuracy of computer simulation. Therefore· these vaiues should be viewed as qualitati~e rather than quantitative. The condition mentioned earlier wa~ handled from the most conservative evaluation and so the numb~1rs reported ·are tt?.e maximum possible~

The values given above relate to the zone 1 piping from the check valve to the steam generator. It has aiso been determined that surges of this magnitude would have only ·Qccutred in. th.$:! horizontal·piping (98 ft elevation) directly downstream of the check valve. ~s the pressure surge rises th~u the pipa to the S/G feedring (elevatiori 144 ft) the pre~sure decays off repidly, being surpressed by re~ivoir effects of~the steam generator. In all cases we note no greater than a 10 psig surge press11r~ diCferential across the ~e~dring header. ·Thes~ conditioQs· independently cor~elate with damage reports that in ~ffect said the. piping s4pports at lower elevations were subjected tb notion and damaye, and nd movement was detected at the high elevations. :·he damayed consisted of trunions locat~tj ~t the 98' ele~acio~ which failed due to axial load.

The· co~di tions surround.ing the failure Of h·~ngers and supports in the z~ne lA piping (upstream of the BF22 check valve) is somewhat different. Because there is ndt a definitive method of rno1eling the thermal ·interface of the satuarated 547°F and subc..:ooled 60°F ·fluid,. a number of separate postulates t1ad to be s imula_ted to understand the potential effects. Throughout this even:, the No. 21 condensate pump was operational and th_erefore ths lowest pbssLbl~ p~essure of the common header would be 475 psig.

~hen the check valve closed, any portion of the fluid which w~s · within the temperature range of 460°F and 547°F would r..:ive been · ,. subjected to vaporization d~e to flashing, fluids at te~p~ratures less than 460°F would be subject to vapor col_umn separation under the principals of waterharnmer. These eff.ect would have been most prevalent in the region directly upstream of the check ~alve.

The vapor would rize. thru th~ pipe to the highest elev~tion ln this zone (138 ft), where a large vapor cavity would collett. When the pressure wave from the recove~y of the condensate pump flow is established the portion of the vapor below the saturation pressure would collap~e generating an incaculable force. Computer simulation of. various themes were attempted to recreate

..

•

•

these effect, but the accuracy of the results is again qualitative not quantitative. We feel comfortable that axial forces in the range of 60 kps to 140 kps were experienced in the zone lA· pipes at 138 ft elevation.

It should also be considered that the hangers and supports were designed to handle forward flow. The forces generated in the ~eve~se direction during the blowdown may have initially contributed to the damaae of the zone lA supports, and were later compounded by the waterhanuner effects.

In conclusion the analysis we have performed has maintained reasonable correlation to the damage incurred, it has also helped to explain some ~f the_observation that were reported to us by plant personnel. we realize· however that the fluids problem · outlined in this sc~nario, with multiphase flows, stratified cold water, and ir1determinable thermal boundar1 conditions, can only be approximated never simulated.

Rockwell International (check valve· manufacturer), Stoner Consultants Inc. (fluid transient consultants) and our own in-house experts have agreement of the information that has been presented. Although there are no absolutes we are confident that the ·postulate presented fairly represents ~he event of April 6, 1984.

Epilogue:

Up6n completion of our surveillance, investigation, and rep~irs we attempted tc: resta·rt the plant. The re-start attempts were unsuccessfel due primarily to the relocation of the No. 23 feedflow nozzle. The feedflow nozzle was unable to provide a differential pressure signal-which prevented proper level control of No. 23 S/G.

The nbzzle which was assumed to be circumf rentially welded in the pipe, was a-:::te.:<.ily. secured by four (4) sh.aar pi.1s (3/8" dia). When the system was subjected to the rever3e flow condition, the uncontoured construction of the nozzle was subjected to uriusual f9rces which sheared the four (4) pins. The nozzle was then. pushed up the pipe.22.0" where it came to rest due to a rdduction in radial clearance. The nozzle was replaced and the remaining three nozzles were inspected (radiography) to confirm their operability.

The plant w2s then successfully started up (May 5, 1984), and is functioning properly throughout it's enti~d operating range.

CMW: jab Attachments

cQJE<l f'll. uJ-@~ fG. c:--

C Manager - Nuclear Systems Engineering Manager - Nuclear Plant Engineering Technical Manager - Sal~m Operations

PERMlH 1-7

•

NO. 23 STEAM GENERATOR LEVEL RECORDER

APRIL 6, 1984 PM

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..

•

ANALYSIS of

APRIL 6 , .L98 4 TP.ANSIENI' EVEN!' IN FEECWA'.IER SYSI'EM, UNIT 2

SALEM Nt.:CJ:.E.AR GE?JEFATING Sl'ATICN

for

POBLIC SERVICE ELEX:TR.l:: AND C!AS COMPANY HANCCCKS BRIDGE, NEW J!PSEY

By

Dr. J.L. CaV·""~' P.E.

aro

May 14, ·~ c:94

stoner Consul ti;:g : .ngineers , Inc . P.O. Box 629

Carlisle, Pennsy · . .;ania 17013

LO

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Lisr OF FI~'RES

LIST OF TA3I..ES

EXEC!JTIVE Sl.M~

INI'RQCUCTICN

SOJPE AND OSJECTIVES OF SCE WJRK

AVAILABLE DATA

ANALYSIS·APPFOAOi

6.l 6.2 6.3 6.4

6.5

LIQ!' PRX'.EDt.1m: APPLICATIOO OF LIQ!' SALEM UNIT 2 FEECWATER SYSTEM SIML'LATIONS AND RESULTS

6.4.1 6.4.2 6.4.3

. CASE SYSTSA CASE SYST6A CASE SYST9A

DISCUSSION OF .RESt."LTS

OI'HER CDNSIDEBATICNS

7 .1. 7.2

iJISPIK:EMENI' OF FI.CW :1E.TI:RING ~'.:ZIE MJVEMENI' OF ~R i?U.:GS

CCNCLUSIONS

8.1 S.2

FiwPES

EVENI' SCENARIO FOFCES AND P.RESSUF.E.S

TABLES

APPEND I CFS

ii

iv

1

2

. 3

4

6

9

15 17 18

20

22

22 23

24

24 26

27

28

SS

A. Feedwater Waterhamrer Prel.iminar/ Report, Unit 2 B. Subject. Transient Analysis - Occurrence of 4/06/84,

Prel.iminar/ Evaluation

i

UST OF FIQJRES -

FIGURE TITIE PAG::

Unit 2 Feedwater Systen ~el Schematic (Plan) 28

2 Unit 2 Feedwater Syste;n ~el Schelf'! Jt ic (Profile) 29

., Apparent Water level in Stean Genetator ~. 23 ~

(S/G 23) 30

4 Vat:0r '!-'ressure ard Temperature CUrv~s 31

5 Volun~ of ·'ain Feedline Curve 32

CASE SYSTSA

FIGURE TIT!E PAG::

6 23BF 9 T~•1 33

7 23BE :.2 Flo•111 33

8 Canmcn 8e~er Flow 34

9 BF9 Ta:.u 34

10 BF9 Pt .assure (S/G sid~) 35

1 1 Recir.;·1Jlation Line Flow 35

12 23BF22 Flow 36

l3 23BF22 PresslJre (S/G side) 36

14 Vat:0r cavity at 23BF22 (23BF19 side) 37

15 23BF22 Pressure (23BF19 side) 37

16-19 Axial Force Plots 3~ - 39

ii

CASE SYSTEA

FIGUm: TIT!£ PAG:

20 23BF19 Tau· . 40

21 23BF19 Flow 41

22 23BF22 Flow 41

23 BF9 Pressure (S/G side) 42

24 Recirculation Line Flow 42

25 Vat:er Cavity at 23BF22 (S/G side) 43 ..

25 23BF22 Pressure (S/G side) 43

?.7 Vai;;or Cavity at 23Br'22 ( 23BF 19 side) . 44

28 23BF22 -Pressure ( 2::BF19 side) 44

29-32 Axial Force Plots 45 - 46

• CASE SYS19A

FTGJRE TITIE PAG:

:~3 BF9 Pressure (S/G side) 47

34 23BF19 Flow 48

::-.s Recirculation Line Flow 48

36 Vap::>r Cavity at 238F22 (S/G side) 49

37 23BF22 Pressure (S/G side) 49

33-40 Force Plots 50 - 51

41 Vap::>r Cavity at 23822 (23BF19 side) 52

• 42 23BF22 Pressure (23aF19 side) 52

43-45 Axial Force Plots 53 - 54

ili

•

•

•

TABLE

l

2

LIST OF TABU:S .

TITT.....E

LJ(lr Si.nul.ation Sumra.ry

M;tXimJm Pressures and Forces

iv

P.'\GE

55

56

1 • 0 EXJ:D11'IVE SUl91MY

Analyses of the Salen Nuclear Generating Stations Unit 2 .feedwater systen have

been perfccmed to gain a better understan:iing of the fluid transient event that

occurred on April 6, 1984. 'lhe incident took place when a routine timing test

was bei11;1 made of. a main feed line control valve while the unit was in a sate

shutd~1 mode. SUbsequent inspection by Public Service Electric aro Gas (PSE&G l.

perscnr.el revealed minor danage to the systen.

·'lhe transient.r.'f':inditicns involving blC"lridown fran the tb. 23 stean generator,

occurred as-a r·esult of the· 23BF22 stop check valve t:ieing_ ~tµ:k in an open

fOSition.

The initial state of :he systen i~ quite well established. ~wever, data

docunenting tl.e transient flow period is very spa-=:se. Major uncertainties

inclooe the behavior of the 23BF19 valve (the valve being tested), the behavior

of the 23BF22 .~ieck v.tlve, and the thetmal-hydraulic characteristics of the watr:

in the feedwat er pipi.g.

In an attenpt to a:idress the uncertainties, ccmputer simulations were ma:ie

considerirg St:v~ral rarges of i;:ossible conditions. 'lhese results, together with

the avail ab-le dr!ta, indicate that the folla-1ing E't'Obably occurred:

o A stea.'~y, high rl'.!te of blai.down (9,000-11 ,000 gpn) throu;h the 23BF19

valve established 2-3 secords after the: 23BF19 valve opened.

o ~piase flow and vap:>r cavities occurred in p:>rtions of the main feed

line reached by_ 547 F water backflowing fran the stean generator.

•

•

o After 20-30 secords, the bl~O\lln was sto~ by the closure of the 23BF22

check valve.

o 'lbe check valve closure caused vapjr cavity collapse ard high pressures

and forces in the pi r i :q.

o 'lbe 547 F water fian '~P. stean generator {~ich prcgressively·replaf"ec· the

60 F water initiallj' -in the line) never reached the 23BF19 valve.

'!he danage to pipe supp:>rts in the containnent structure ard in the yard area was

most 1 ikely caused by the tnmsient pressures ~ssociated with the check valv~

closure.· Althou;h expl~atic:1 of the check va~Lv'" .t eh.aVior .was beyond ~·~ ~pe of this anal~is, it is clear that this particular· type of event could easily be .

prevented by chan;ing the te· til'l3 procedure.

2. 0 INI'OCOCJCTICN

At about 4:30 p.m., April 6, 1984 a fluid tra ;i.ent event occurred in the rinit 2

feedwater systan resul tin; in minor danage to ,,everal ·pressure ga..:~~s, a valve

pjsitioner, flow metering nozzle, pit:e supp:::irt: and sane pipe insulation. It ,.

was initiated by the opening of the 23BF19. CCl"'.t:.Jl valve durin; a routine valve

timin; test being perfotmed fran the control roan. 'lbe rea~rm this routine test

resulted in the fluid transient event was beca:.se the 23BF22 s~of) cneck valve was ~

stu:k open. 'Ibis allowed backflow fran stean ')enerator {S/G) No. 23 to the

condenser when the 23BF19 'valve was opened. At ':he time of occurrence, lhit 2 ..

was operating in li'bde 4, a safe shutdown cordition. PpperxHces A and B gi .·e more

detailed descriptions of the operating conditions and systen danage.

2

•••

3. 0 ~E ~ caJECTIVES OF SCE ~:RK

Stoner Consultin; Engineers, Inc. (SCE) was contacted on April 7 concerning

perfocning of analyses of the event. Mr. Steve Eonema arrived on site on APril 8

to initiate SCE work ·m Dr. Joel Caves· arrived April 10. The objective of the

SCE work was to aid ?.-.blic Service Electric and Gas canpany (PSE&G) personnel il'.I

developirq a transieri':: flow canputet: mcdel and perfocning simulation~ to gain a.

better understaroing ~f the t·ransient conditions that produced the danage.

E'rcm early PSE&G assessnents, it was evident that the eve-.-nt could have been

pr.evented by mcdifying plant. procedJres to incllde motor operated closure of the

BF22 stop check valves before testi~ the opera-..ion of the BF19, and canpanion

BF40, valves. Because a sil.-ilar oc::urrence could be easi:i.y avoided in the

future, and because the apparenc d~nage could be quickly repaired, there was

considerable urgency in per!:tming :he PSE&G/SCE work as exp:!ditiously as

p:>ssible.

OCE engineers participated LT. site meetings with Westinghouse personnel on April

10 and wLth NRC re~esentat:ns on April 13. Initial canputer simulations wiere

perfotmed on April 11-13 •

3

•

•

4. 0 AVAILABLE DATA

Just before opening the 23BF19 valve, the feedwater system was in a stea:iy~state

flow condition with one condensate punp ard t""° ~ ...... il iary feedwater ?-Jnps

runni~. 'lbe stean generator feed punps \.ere not operating. As detecmined by

systen "hydro" tests perfotmed on April L t:o replicate the initial condition,

the condensate punp was forcing 7300 gpn nf approx irnately 60 F water throu;h the

fee:lwater heater circuits (the heaters we:e not heati~ the wat~r), the 8F9 check

valves, the feedwater hea:ier, strainer arq. RF66 throttl i~ v.1lv1.: to the

cOndenser. 'Ihe pressures in this part of the system ~re:

E.le:ation Pressure·

Location :··!et· ·-

Coroenser Et:>t Well ·03. 5 _, .' 6

-:Ondensate Pump Discharge 86.0 195

BF9 Valve Inlets !2~.o 450

Hec3ler 121. 5 43G

BF19 Valve Inlets 121. 5 4.JO

Conder1ser Inlet 12L 5- 0

·PSE&G estimates that auxiliary feedwater punp N::>. 21 was f•!E:liN; a~oximately 3C,

gpn of 60 F water into S/G 23 via its connection to the ma10 fee:l line at the S/G

side of stop check valve 23BF22, and 100 gpn into S/G 24. Other ... han S/G '?4

having a m11101 auxiliary feed punp with S/G 23, the other stean generators were

isolated fran this event by having their BF19 and BF40 valveo; closed. 'lbe S/G 23

was producing stean at a saturated state of about 547 F and 1000 psig. 'Ihe stean

was bei~ vented.

4

•

•

Figures 1 and 2 sl'x>w a plan of the canbined. main ard a~ il iary feedwater systan

model, and a profile of the main feedwater systan. Cetails of the feedwater

heater circuits were anitted as described later. _N:>dal p:>ints used in the mcdel

are identified for later reference.

_Based on PSE'.&G interviews with plant :.ersonnel, the event was accanpi3nied -by a

lou::t runb~ ing noise at an unknown loc .. t:Lon. 'Ihe noise lasted 20-30 seeords. N:>

ban;s or <.Jther sl'x>dc sounds were hear:J at any time. 'Ihe -runbling noise sto~

at about the instant the control roan operator acti,·ated closure of th~ 23BF-19

va:I.ve. Very sl'x>rtly thereafter, a pl =:..nt I°&C ":echnidan arrived at the 23BF19

valve ar..1 fo ... nd it still closing. Other tha:t this 1nf01:mation and the da:age.

rep:>t'ted ir. P.'f'perdix ~(page A-3), the only additional data avaHable on the

event itself 3re the following:

0 Strip Olart sl'x>wing apparent wate,_- level in S/G 23 (Figure 3).

o Dam13e to pip! supp:irts or. the ver'"ical r.in near the condenser side of

check valve 23BF22.

o Jamage to trunnions supp:irtirq tht 1ertlcal pip! run lea:iing up to S/G

23~

o Displacanent of the line No. 23 f:low meteri:'J3 nozzle toward the 23BF13

valve resulting fran shearing of' r!strainil'l1 pins.

It sl'x>uld be noted that the internal danage to the 236!:'19 valve tx=>Sitioner

(mentioned in Apperd ix A) may have r•?sul ted in snal l errors in stbsequent

p:>sition signals. Otherwi.;e, though, the p:>sitioner appeared fully functional.

5

•

•

•••

5.0 JINALYSIS APPRJACH

With 23BF22 check valve open, the pressure on the S/G r.ide of valve 23BF19 would

have been about 1000 psig. Because of the very high ~essure diffeC'ence acnss

the valve, PSE&G has concluded fran the BF19 design th· t. when the operator

activated the valve to open 40" percent it probably st.:ay.':O closed l.%ltil an . .

iJnusually high d iaphrc311 pc-essure developed.. i'llen pist0n m01Jement broke tLa seal,

the high diaphrc311. pc-essure may have caused the valve to junp fully open,

thereafter·ventinc;, excess air pressure until the 40 pt:?rcent p:>sition war,

attained •

i,a,en 23t..F19 opened, the l~r pressure ....ould have pror-igated toward the S;~

causing the 60 F water initially bet\oieen 23BF19 and S/G 23 ·to start accel ... rating

toward the condenser. i,a,en the negative wave reached .. he S/G, 547 F water ....ould

have entered the feed line aro started a blowdown flow moving toward th•·

condenser. 'lhus, the reverse flow to the condenser would have involvee 6 J F

water fallowed by the water ·fran the 5/G.

sane of the prpperties of 60 F (•cold") and 547 F (•mt") water ·are:

6

•• T Density Vap:Jr Pressure Ez1thalPJ'

~L sLS£ psi a Btu/lb

60 0.999 0.26 58

547 0.739 1015 546

Becaui: of the large differences in these propert:' :s, it is quite likely that

mixj,'1.1 of the hot am '.'Old water occurred in a moring transit.ion :zone bet~en the

colci water initially r'.ischarged and the hot water that fr 1llowed later. In

adrlition to the cold wate: initially in the pipe, the au:.iliary feedwater SY?tem· . .

~u·d .have continued to iiject 60 F water durirg much of the tr.msi~nt period,

al:) causirg mixing. Wit 1 such mixing, the "lapor·pressl.l"Ce in t'1e tenperature

tr .. ::ition zone ~uld hc:N, been significantly- lower than the n-;or pressure of

th~ urmixed hot water (Figure 4). From this assessnent. it is :"lident that,

durirg the developnent of <:he flow fran th.e S/G, tre density' ar.:l vapor pres:~ure

of the water "do.nst:eann (for this blcr..dOW'n O:Jotition) fran th: S/G varied in

both space an:l time.

It is also expected t"~dt t\IO-P,ase flow occurred in muc 1 .Jf the pipirx; reached by

the 547 F water. Wl t : its exposure to the lower sys ten t cessures, fl ashirx; of

the hot water an:l siJ1•ltaneous VafOr-liquid flow ....ould o.c;;e occurred. 'Ihus, its

1015 psia VaECr pressure ~uld t>ecane an im"EDrtant mini~.ll\m pressure in the high

pipirg reached by tht:t unnixed hot water. Turbulent· ·""°··t:nase flow is highly

canplex and cannot be mcdeled rigorously ( 6). a:iwever, empirically based

· t"W:>-phase mcdels and h:mogeneous flow mc-Oels have succe ;sfully simulated

transient t'«r~ase cord it ions ( 2, 4) •

7

..

•

•

Since the 23BF19 valve was still closin; .after the runbling noise had ·sto~,

the final phase of.the event must have been initiated by closure of the 23BF22

dieck valve. 'Ihe distance traveled by the oot water when the flO'# f ir!ally

sto~ is not l<nown with certainty. 'n1e only related data availab:.e is the

change in apparent water level in the S/G (Figure 3) • Discounting ·..he initial

wate~ level rise as a S\lllelling effect due to high vai;:orizat ion wher. the negative

~ve reached the S/G, PSE&G has conclu:1ed that the apparent level c~o';:ped fran 41

percent to 26 percent of the 12-foot water level range (i.e., 21.6 ·ir.ches) during

the event:.

N .. :qlecti:i; ·vai;:or bubbles and ir.i:ernal equ{pnen~ in the S/G "p:x>l", ~nis drop

rept"esel'.ltS a dra'..dowr. voll.JTle cf 300 cl.bic feet of water. C.Onsiderii~ ¢e voll.JTle

1.... f the c )i"lnect ing feed line ( Hgure S) , th is w::iuld indicate that i'f a sharp

cold/oot water inter:.ace ex isled, the hot water w::iuld have traveler:" about 350

'~et to 2 i;:oint about 80 feet wpstrean (toward the S/G) of the 23Bf ·9 valve.

kcoJJ"lt i l3 for vai;:or and equipnent in the S/G pool \oiOuld reduce the hot water

pnetrat ion. PSE&G has requested an accurate voll.ltle vs. water lev al curve for

·be S/G :ran West ingoouse. In the meantime, PSE&G est im,ates that the actual

· ~lllTle of water drawn fran the S/G was 70 percent x 300 = 210 ct.Die feet. 'Ihis

• .. c·"1l.d place a sharp interface about 100 feet toward the condenser fran 23BF22 or

'-~ut at the site of the broken pip! han;er ( FWH-22-l 2). If the the:cmal

i.r,::erface was qradual, rather than sharp, the warm mixed wat.er would have

trilYeled beyond this ?Jint, and the oot \.rtlnixed water would not have extended as

t.ar.

8

• ·,

•

6 • 0 1'CtlE1'..I~

The UQI' c .. IQuid ,!ransient) analysis procedure ( 3) develoFed by Stoner

Associates, I~c., and Ors. V. L. Streeter aro E. B~ Wylie of 'Ihe lhiversity

of Michigan . ..,as used by SCE in simuladons of the event. This analysis

procedure, ?o..: liquid pipirq syst'.1Tls of arbitrary configu: -:ltion, simulates

waterhanmet· conditions resulti:13 fran a wide variety of t:r:·ssible forcin;

functions~ · "bdes aro node-cc..:inect irq elements are used to describe the·

P,ysical f~.a'.:.1.'"':.as of a systar.. ~es are pJints in the system ! c -; • , p1 £=ie ..

junctions) h'd node-connect ii g el'!nents re.present syst.en canponer.ts s.u:n as

pip:s, p1.JT1p;,, valves, strain~rs, ·::tc. Different vap::>r pressures for the-

1 iquid can 'e specified with r. Ql' in different parts of tfl.e system~

ho~ver, it does have several limitations that are iinpJrtant rel-3tive t' the

present worlc.

<:rie limitadon is that it cc'.1s-h:~r:; only a sin;le density value tor all

liqu~d in the system. Webb ril j Caves (7) have srown that this~ i.-nitati·m

can be relaxed scme'#hat by !" ••. kln; adjustments to certain model cata. With

this techniqua, a sirqle dens :y canputer progran can be used to accurately

med el systems where the den:;; t·{ variations e.dst in space only . ~ .g .• , a

typical feedwater ~ystem ana1: 'Sis where the water is one density .Jpstrean of

the heaters ard a different mown density downstrean). In the Af•i:il 6

event, however, the density 'in ~he feedwater piping connected b.< the S/G

changed with both time ard distance.

9

•

•

Other· 1 imitations in1olv·~ the techniques it uses for t\oiO-ti"lase

( vap:Jr-liguid) conditions. LIQI' calculates the tirn~varying sizes of vat:er

cavities that exist when liquid pressures drops to the vapor pressure. It

also detei:mines the pressure transients when vapor cavities collapse.

!i:Jwever, UQI' does not account for simultaneous flow of vapor arrl 1 iquid nor

the asscciated effects of such t\oiO-?lase flow (e.g., changes in density,

friction factor, wave speed, and inanen tun) • Being a rano;eneous flow

proet .. :dure, effective friction factors arrl wave speeds must be specified a

pried.

Other than the p:>rtion of the main feed ~- ine. affected by the 'oot water fran

S/G 23, LIQI' can b~ used to accurately mn:lel the main ard a1JXiliary

feedwater systans. D..lring this event, tho1.J3h, most results of interest are

in the port .on of the sys tan bet:\lfeen the S/G and the 23BF19 valve that can

be only approxirnat(d due to the canplexity of the corditions arrl the r...:;:.::-Jr

1 im1tat ions Becalse this is also wtiere most of the transients origniated,

the results rriust b~ interpret-ated as a qualitative picture of sys tan

conCiitions ··ather than as·a·qua~t~tative prediction of all pressures,

forces, etc, that took place.

After devel· ~.ment of the systan m::del, described in the following

SIJbsection, !he anal~rsis proce:!ure essentially consisted of simulating cases

with diffei::·:~nt predefined water tenperature profiles exterrling fran the S/G

toward the ~3BF19 valve. canparative simulations with ard witrout the mo::lel

adj•:stmenu described 'oy webb w Caves sro'#ed that the de~ity difference

beo.:een the 60 F and 547 F water had much less effect than vap:>r pressure

10

•

•

•

effects. 'Iherefore, the final silnul~tions used the 60 F density thro1.J3l"out

the sys ten m:del aro vap:Jr pressures were specified that correSp'.:>nded \1i th

the ass1.1rted tenperature ptof 11~~.

6. 3 SALEM UNIT 2 FEED~·.l'ER SYSTEM

The steady-state and tr m;ient caitputer mc:delc of the Salem Unit 2 ferow.:te.r

systan were based on ir.t.:mnat ion drawn fra, s1 te bluepc-ints, PSE&.G tec:inical

rt1:emos, and hardl:ooks ( 1. q). Pdd it ional sy~·.ten in format ion was obtainLd fran

previous uo;sa ( LIQuid ,_.,.~teady §.tate) and l'.J:Ql' s imul at ions perfooned by

Olarles Willianson of :J51':&G. l)Je to the O:.inav::lilability of specific

manufacturer's l iteratuz. ·?, generic valve lo~~·s. coefficients ard

openin;/closin; stroke f:':'ofiles fran hardl:ook~ ard PSE&G pers::mnel ~r.e

used.. Al tho1.J3h the put''' head-discharge dat ~ . ~re manufacturer suwl ied,

they may not truly repr·: sent actual punp ~rfoonance.

y;

'Ihe transient models re.:lect the urgent r e€d t.v l?SE&G for simulation -.:esults

durin; the week of April 8 aro therefore r!o not er11.."0'llpass the entire

hi~fraul ic circuitry of the main ard aux L iary feedwater systens. 'Ihe mcdels

cont a in the canp::inents of the sys tens wh fr h could have been ~ .. !l uent ial to

the transient eYent on the afternoon of Af-:.: U 6, 1984.

Figure 1 is a general schenatic of the portions of the main feedwater

systen, auxiliary feedwater systen, and recircuiation line mcdeled in the

canputer simulations.

In the auxiliary feed system, pl.ltlps No. 21 and 22 were ope rat in; at ~he

time of the incident, pr011idin; flow via the auxiliary feed lines to the

11

•

j

.. four stean generators. Since the 218~19, 22BF19, and 24BF19 valves ~re

closed, the ?-O. 21, 22, and 24 auxiliary lines ~re mCdeled as lines

teminating at constant pressure. ( 1COO psig) t::oundaries 'Nhich represent the

respective stean generators. (See ncdes 21F, 22F, and 24F on Figure 1.)

In the main feedwat1r system, only condensate punp ~. 21 was in service at

the time of the inc "d·int. Condensate punps ~. · 22 and 23 were off~line and

isolated fran syste't flow by the closed, CN14 discharge check valves;

consequently, the!X t'f!O p..1t1ps and their respective len;ths of pipe to the

discharge valves we-e not !ncdeled. To address the imnediate need of

transient simulations of t:ie situ.at ion during the week c-f April 8, as well . .

as the econanics of the cauputer simulation, an equiva1 ent pii;:e was used to

represent the main f.eedwa~er systan between tiie conden.;ate punp discharge

check valves arrl the BF9 check v.:lves just dO'mstrean f")f the ~. 26 heaters.

'Ihe equivalent pii;:e reprer.~nt irq this i;:ortion of the me:;. in feedwater sys ten

is denoted by pii;:e CPD-BF9S c'.1 Fi 3ures 1 and '-·

'J'.he ?iys ical characterist, c.s of tie equivalent pii;:e were selected to

approximate the ac·· ual he.O::loss, mcmentLITI, and t~ansient respJnse of that

t;:ortion ot the feedwater oi".-'Stan. 'Ihe length of the typical flaw path

bet....een the cordensate punp check valves ard the BF9 check valves was used

for the equivalent pii;:e to keep the wave travel time the sane. 'Ihe canbined

area of three parallel 18-inch pii;:es (that represent muc~ of the pipirq) ..as

used to. size the dianet.!r of the equivalent pii;:e in order to approximate the

flow manentun. 'Ihe dianet:~r ard length of the equivalent pipe ....ere then

used with the known, initi.al steady-state head drop bet....een the condensate

?JDP check valves ?.nd the BM check valves to calculate the friction factor

for the equivalent pipe.

12

•

The stec3tl generator feed punps were bein; bypassed at th~ time of the ev-:nt

and, therefore, did not have to be considered in the equivalencin;

calculations. Since the three parallel 8F9 valves are ident·ical, they were

mcdeled .as one check valve havin; an equivalent area.

Piping and valving between BF9 and 5/G 23 were mcdeled in detail _based on

available infomation. 5/G 23, becau~'.~ of its voli.me, was r .. cdeled as a

large tank with a constant pressure of. 1000 psig. Lines No. 21, NJ. 22, and

It>. 24 which feed 5/G 21, S/G 22 and ~/G 24 were teminat':Xl at dead ends

(21C, 22C, and 24C on Figure 1) in the 1:i-::del due to the closed 8F40 and BF19

valves on the respective lines. ·''

.'.t the time of·· the incident, fl<=M in t;·e main feedwater sy.sti:!ll ws ·being

recirculated into the cordenser hJtwel. (CCN of Figure 1} v~ 1 the condenser

recirculation line (represented by RC .~rN). 'ltle strainer ir. this 1 ine <Nas

mcdeled as a minor loss element denot. j by pipe R:STI-RCS'ro on Figures 1 ard

2. Losses throu;h the BF66 throttl in; valves ard the gpai::ge- were mcdeled

as an equivalent valve of fixed p:isit ~on (see RC'IVI~Ct- on F'gure 1).

6. 4 SIMJLATICNS AND RESULTS

After several trial simulations were mcde, three cases •···re selected for

simulating the S/G" 23 blO';idown and sli:Jseq\Jent closing c.: the 23BF22 and

238F19 valves. 'lhe ?Jrp:>se of three simulations as o~sed to one was to

take into consideration the uncertainty over the openin:J and ·closing of the

23BF19 at the time of the incident and water tanperatur:es in the feed line

connected to S/G 23 •

13

•

•

A timestep of 0.005 secol"ds was used in the simulations with wave speeds

betlEen 3560 and 4440 fps. '!he ccrre~nding wave travel time bet~en the

238~19 valve al'll the S/G was a.bout O. 11 seccl"ds. nie effects of using a

slower ef feet ive wave speed in the tw:rphase flow reg ion are described in

Section 6. 5.

For ead: case, a stecdy-state s:.1ution procedure, U~(5), was used to­

obta~_n balanced initial conditions thr0ugh:>ut the mcdeled alllCiliary arrl mai'n

feed systens. These initial conditions were based on knOloill'l h~raulic

inf:>cnation obtained fran PSF.&G perSDnr,t"-\ ard the April 12 "hydr_o" tests. -

'Ihf:' t'al \need net'ioOrk secved as input fc:- each of- the -three UQl' simulations •

In e ::ti ~f the transient simulations, the 2381:'19 valve opened at simulation

time t = 0. 02 secon:ls al"d by t = 2-3 SP.cords ' steaJy blao.doW'!"I flow rate to

the conienser had established. D.lring the ac--:ual blC'AdO"wt' periOd, the 547 :'

wa :er ~--an the S/G was_ prcgres~ively replacin.1 the 60 F water initially in

th<! "'· in .:eedl ine.

i\< .-:o•.JTI ing that the rep:Jrted runbl ing nc. ise was .:.sSDciated •-1i th flashing and

vatT-: bubb~e collapse within the 'oot \_rater flowing in the line, the duration

of :iie blcrwdown a~rently was -20-30 st! ;X1l"ds. nie evidence a~so indicates

that it was tetminated by closure of +..!'.':-.! check valve. Since the time period

between the openin;J of '.BBF19 and the closure of 23BF22 is not kn°""1

exact!y, it will be referred to as t • - ~

14

•

It is rot known what caused the check valve to finally close (one £=CSSt)l~

factor· is deseribed in Section 7.2). Therefore, in the simulations the time

at which it started closing was manual:ly specified. Father than using

oonputer time to simulate the entire 20-30 secord blor.o.da.....n pericd, .ho~ver,

a srortened bla..down period was simulated by starting the chec:K valve

closure at t = 4.0 seconds. 'l'hus, in the outpUt plot::; (Figures 6-45), 4.0

sea>nds represents t = t cv in the real system and sub .equen t t irnes must be

interpreted accordingly. Table 2 surm1arizes specific·ttions for the cases

simulated.

6.4.1 OSE S'fSTSA

This case mcrlelee t~e blo.oidown of0

S/G 23 and the slb~.pent closures of the

23BF19 and the i3BF22 valves. Water at 60 F was loca· ad throu:;~ut .the

auxiliary· and main feedwater systems.

The bl~own scenario began by instantaneously openir ; the 23BF19 valve dt t

= 0.02 secorrls to a fully opened i;osition~ A plot of valve opening verS.:s

time is seen in Figure 6_. Since the 238F22 valve was stock open, an

interface of 1000 psi fluid and 500 psi fluid existed at 238F19. 'l'hi~

interface created a negative wave which propagated back to S/G 23 ca~- .. ng ,

backflow into the feed line fran the stean generator. Backflow throu::;I"

238F22 and 23BF19 valves increased quite rapidly and a(:pt"oached a

steajy.:.state rate of 10,100 gpn within 2 secords of the openin; of the Bl:'19.

A_ plot of flow through \:he 23BF22 valve is seen in Figure 7. Backflow

toward the cordenser (Figure 8) caused the 8F9 valve to close, resultir"~ in

a mild transient at t ~ 1.0.secords at the face of the check valve. Plots

of valve operation vers'tts time ard pressure on the S/G side of the valve are

seen in Figures 9 and 10. c:pon closure of the 8F9 valve, the bacl<flow was

routm throu;h the recirculation line (Figure 11 J.

15

••••• •

•

At t = ~, 23BF19 began a linear 25 secon:J closure fran the fully open

p:>sition as depicted in Figure 6 •. niis normal closure sp:!ed was based on

i:'lformat ion pr011ided by the va1·1e manufacturer an:J actual tests on the

va1ve. At this sane instant, tiie 23BF22 began a 0. 26 second closure (Figure

12). ·This closure profile was provided by PSE&G i;>ersonnel. At tcv + 0.26

seconds, the 23BF22 valve was canpletely closed resul t"in; in an abrupt

~;topage of bleloidO'#Tl flow. Qi the S/G side of t,e 23BF22 the sto~age of

Cow caused a pressur~ surge which peake9 at '.bout 2400 psi at tcv + o. 265

se•;oros: A plot cf .pressure on the S/G side :=or the 23BF22 valve is seen in

Figure 13.

' Closure O·f ~he 2 ·:ai:-2.2· created a ~all va;or cavity Oll the. condenser sid-e of . .

the valve (Figure 14). With the.main feed pressure ata~:»cimately 500

psig and vai;:or prr:: .;siT.-e existin; at ncde 23E :corrlenser side of 23BF22l a

steep hjtiraul ic grade line was established towards the the ::heck valve. 'Ihe

return flow fran the nain feed system closed the va~or cavity at

aRJroxirnately tc.., + 0 .45 seconds. A resulti'"'g i;:eak pressur~ of 1350 psi is

sh::lwn on Figure i 5.

Bet-..een the 23BF·i9 and 23BF22 valves, the maxi111un a:, ial pii;:e force was 140

kips, \olhich occunoo on the pii;:e element 2302-2303 '". tcv + O. 6 seconds.

Figures 16, 17 arrl 18 sh::lw plots of axial. pii;:e forCE- .versus time in the

general location c,f the danaged han;ers ( bet'lolleen ncx.:·es 2302-2'.JDS) • Between

23BF22 and S/G 23, the 1t1~imun pip:! ~"."tree was -150 k;:;JS, whiC::h occurred on

the pipe 23G-23H (Fi 3tZ9 19) •.

16

•

••

6.4.2 ~ SYST6A_

The second simulation (SYST6A) mcdeled a blorw.down event with two water

temperature reg ions. '!he first reg ion contained 547 F water ( va?=·C' pressure

= 1000 psig) and was located bet'#een ncrles 2304 and S/G 23. 'lhe -;econd

region, '#hich inchJ:led the aux il iacy feed system and remainder of .t'.1e main

feed system, contained 60 F water.

13low:1011wt1 conditions were established by the instantaneous oi;:enin; :Jf the

~JBF19 'Jalve t~ a 40 percent open t:esition at t = 0 .02 seconds 1 Fi-g:.1r~ 20") ...

~e pressure: reduction caused by the openin; of the· 23BF19 valve r:-.~sul ted in_

a -vap:it cavity focmin; near -icrle 23D4, the. assuned limit of the 5~7 F water. . .

BecauS(! of the high vap:ir pr~ssure and pii;:e elevation at ncrle 230-·, this

cavity never closed durin:; the simulation. '!he cavity essentiall · isolated

the flc.'WS throcqh tie 23BF19 ard tl",e 23BF22 valves (Figures 21 an:\ 22).

As in Case SYS'I'5A, the blo..dC'WT1 flew closed the BF9 valve. ConSt:. 1uently, a

;tec:dy blo..down flo-~ of approximately 9350 gpn was routed through the

cecirculation line. Plots of pressure versus time on the ste~ generator

~ide of the BF9 valve ard flew into the recirculation line versus time are

(iei::iicted in Figures 23 ard 24.

'.~losure of the 23BF22 valve, which is identical to that in case SYSTSA,

began at t ,.. tcv seconds. At the sane time, the 23BF19 valve began a 2

sea::>rd cfosure (Figure 20). 'lhis closure rate was based on the maximun

possible closure rate for this valve. ~n closure of the 23BF22 valve, a

~essure peak of 1370 psi occurred on the S/G side of the valve. A

pressure/flew oscillation then existed between the valve ard 5/G 23 causin:;

17

cavity fotmatio."l ard collapse at the·face of the valve (Figure 25).

Jlcccmpanyirg the cavity collapse ...iere snal l surges at the valve (Figure 26 l.

Qi the other sice of the 23BF22 valve (ncde 23E) a va;or cavity formed as

the flow was nbruptly stopped. The grOolth and collapse of this cavity is

srown on Figu-:e 27. Figure 28 fs a pressure history at 23E and illustrates

the pressure 1~rges that occurred up:>n cavity collapse.

MaximlJl1 axial· forces following t'.1e dosur12 of 23BF22 are lit.ted with their.

respective .ti,ne.s of occurrance in Table 1. ·Figures 29, 30, 31, .and 32 sh::w

plots of ax ic-.1. ?i fe force versu'i time at the danaged han;er locat ic.r.s ard

betw:!en '1ode~ 23G and 23H.

6. 4. 3 CASE SY' .r9A

The third sirr- ilation (SYST9A) m::xJeled a blOwr.dawn with three tenp:t ~ture

reg ions. The first reg ion was locar :>d bet"llEen ncdes 2304 ard S/G 23 i:.1nd

contained 54"'." F water (va;or p~e!';s1n:~ = 1000 i;isig). The s...cord re:ion,

located bet'#een nooes 230 arrl 3-~, o:mtained 445 F water ( va;or pr ~ssure

385 psig). The renairrler of t 11'2 moo~·l constitut.ed the thirJ tan~:ature

region ard contained 60 F water.

'nle 23BF19 and 23BF22 valve opec<ations ...iere identical to that in t l•.: SYSTSA

simulation. Within a 1/2 secord: of the openin; of 23BF19, the bac:~flow frcr1

the steam generator forced the dF9 valve closed, resultin; in a pr·::ssure

p:ak of 1110 psi at the face of the valve (see Figure 33). By t = 3

seeords, a stea:ly bla.rloWl'l flow of ai;:p:oximately 10,500 ~ had es.:ablished

throu;h the 23BE'19 valve a.rd recirculation line as presentE"l in Figures 34

and 35.

18

•

'n'le down surge fran the openio; of the 23BF 19 valve caused cavities to open

at 2304, 23F, and 23N. Because of the high vap:Jr pressure ard elevation at

ncdes 230'' and 23N, the cavities at these locations did not close dur iN3 the

simulation. The cavity at ncde 23F coliapsed violently at tcv + 2.9 se<:orx:ls

(Figure 3€.) resultin; in a pressure peak of 2400 psi in -the low pipiN3

betweer. the check valve ard the S/G. '!his pressure spike (Figure 37) was

accanpa11ied by an aJ1.ial force of -150 kips on the pipin; between 23BF22 and·

S/G 23 {Figures 38, 3~ and 40) •.

As in SYST6A, closure of ~h~ 23BF22 valve C"esui. ted in. the form~t ion of _.a

cavity at ncde 23E wh ... ch cloSed with a pref sure t:eak of 950 psi. at ~

approxin.ately tcv + 1.8 secon:Js. Figures 41 and 42 show plots of cavity

· volLJne ard pressure a: ncde 23E versus t ilne.

The pt'""ssures between the check valve ard the coooenser oscillated 9JIT1ewhat

followiN3 the .:neck valve closure. In general, thou;h, the magnitl..des of

· ~he press~es ~re le1M'er after the check valve closed than before because

the check val~~ closure iSJlated the 547 F water (with its 1000 psig vai::or

pressure) frat. ":his part of the systen.

Force versus t ~;.e plots for the danaged han;er locations are srown in Figure

43,- 44 and 45. Peak pr~ssures ard forces are surmarized in Table 1 •

19.

6.5 DISOJSSirn OF RESULTS

The simulations srow that the April 6 event probably consisted of three

distinct periods: An ini t ial-crans"ient period, a quasi-steady blo...down

period, and a final-transient period. 1he initial-transient period began_

with the openin; of the 23sr:-19 valve and lasted 2-3 secon:Js, by which time a

relatively stea:iy blooown i:.a:e had established. The final-transient peri:d

was initiated by the 23BF2'.'.:.cb~k valve closure. CUril'l3 the interveni1'l3

period, the blooown was raLne: steady as the bot water fran the S/G

--------progressed further alorg the feed line~

Of ~he three simulation 9an!.s, the S"ISTSA re!:.il.ts. srould provide th~ best

r'epresentat ion of the init ir:!-transient pericd. '.n the 2-3 second duration

of this period, the _water f·, an the S/G would !"l("t nave penetrated very far

into the pi pin;. 'Iherefore. the S"ISTSA assl.lTlpt io11 that all pi pi1'l3 contained

60 F water si"culd be -a gocd appC'OxiJ:nat ion for thi~ period. Conversely,, case

SYSI'SA is probably not a go.:d representation of t' ~ final-transient pe::~::d.

The assuned water tanperature profiles ( impl eJ by the vap:>r pressure

~cifications) in Cases S"IST6A and SYST9A a.-~ :Hf;:'erent approximations f..ir

the final-transient period. canparin; the m~iroll1l pressures an:J forces for

these two cases (Table 1), it is evident that .he movanent o;: unmixed rot

water ( 1000 psig vap:>r pressure) be~nd the 2Ji.3F22 check valve i,,ould not

have had major effects on the peak presslire~ '\nd forces in the pipirq

bet'#een the 23BF19 and 23BF22 valves. Betwean the 23BF22 check valve and

the S/G, thou;h, the peak pressures and forces appear to be significantly

affected by the el<tent of the unmixed hot water. With the 1000_ LJSig vap::t'

pressure exte~in; to the high pipirg in the yard in Case SYST6A, the

velocity of flow fran the S/G 'litias lo'#er whet} the check valve cl1Jsed.

20

Consequently, the peak pre:>sures aro f(1rces were less in SYSI'6A than in

S\IST9A.

In the 5YST6A and 5YST9A simulations described above, no adjustments were

m~e for the effects of t....c-?iase flow on viscous l~sses or wave sp2ed.

canpared to sirqle phase (liquid) flow, tw:>-piase flow has h_igher friction

an:3 lower wave speErls

'Ib investigate row 3ensitive the results 1;iiere to these factors, tw:>

additional simulations i.oiere made with the .sane tenpe rat ure ( vap:)r pressure)

profiles as Case 5"iST9A. u1e of the runs was m~e with the wave sp2ed in

the rot wter reach ·(5/G t·.: the ijaF22 check. valve) of approximately 1000·

fps, rather than the 4000 fps pre•·iously used. 'Ihe wa\'e speeds in the rest

of the systen i.oiere not chan;ed. this mcdification reduced the peak

pressures between the 5/G ~nd the check valve fran abo~~ 2400 psig to about

1400 psig. 'nle peak force wa1 r~luced fran ct.~ut 150 kips to about 40 kips.

Beyond the coroens··r side of the .:heck valve, the mcdification had no

.:ffect.

'nle other .:~was mc3le with a quadrupled friction factor value in the reach

between the 5/G and the ct~e~k valve. 'nlis reduced the rate of flow fran the

5/G into the feed line am rielayed the closure of the vai;:cr cavity in the

final-transient period. In addition, it reduced the peak pressures between

the S/C c;ana the check val v~ fran about 2400 ps ig to about 1800 ps ig. 'nle

peak force in this reach w::is reduced fran about 150 kips to about 80 kips.

'niis mo:!ification also had no effect b~nd the check valve.

Because the void fraction of the tw:>-£=hase flow is not known, the wave speed

am friction factor adjustments. in t"1e sensitivity runs i.oiere arbitrary.

21

'lbese. investigatL:>ns srow, hO'#ever, that the existence of t...o-P,ase flow

'li.ould have r~duced the peak pressure~ ard forces. 'lberefore, the z6ne a

values presented in Table 1 for Cases SYST6A and SYST9A are felt to be

C'Onservat ively high.

7.0 omER a:NSIDE:RATIOOS

7. 1 . DISPLACE?:£m' OF FLOW 1'£'TERING OOZZLE

Subsequent t~ the systen in5pect ions _rei;orted in ApperxHx A, the flow

met et~ ng no•-.zle located in line It>. 23 between the 23BF13 and the 23BF <9

valvl:s·was ~ound displaced about t».o feet toward the 23BF13 valve. . .

pins that nnmal ly held it· in i;os ~ t ion· were sheared off, ap~rently __ :as ..

resw.t of t'1e high rate.of bla...dO'w'l'l. I

'!be dYSten .rcdel inclu:led a minor loss element for this nozzle but no

attenpt was ma:le to simulate the effects associated with the failure ·or. ti"1e

rest ·aining pins. OJrin; the quasi-stea:ly blor..dO'w'l'l period, the flowrat.es

det(·nnined ')y the simulation were approximately 10,000 gpn in this part of

the .systen, •.dth a corresp:mding· pii;::e velocity of about 26 fps. rbwever,

the il ;,,st likely time of failure was in the initial-transient period when

blCW#--fo•...,, rates of 12,000-13,000 gpn (Figure 7) i;:robably occurred. '!be

noz:zl ! throat area is 36 percent of the pipe area.

'lbe nigh forcn caused by the high backflow velocity and the reduced flow

are~i could. have accelerated the nozzle very rapidly once the pins sheared.

LikF.;wise, the faovement of the nozzle could have decelerated very rapidly

~ hittirg an obstruction or othetwise becaning b:>und. A rapid

deceleration (in less than O. 2 se~nds, the round trip wave travel time)

22

•

·would ·have caused an abrupt reduction in flow velocity and generated a

pt"essure surge which ~uld have propagated toward the S/G. 'l1iis may have

contributed to sane ct the danage but the available information did not

petmit a full evaluation.

7.2 ~1'£m' OF V.\POR PU:GS

~P,ase flow can hare several different. forms (e.g.~ bubbly, s•xatif1ed,

annular, sl\Jg and i?lu:J flow) deperdi~ on a nunber of factors~ <'law in

downcaner pipes, s~-:il as in the vert ~cal run near the S/G, is nqt corduc_ive

to vapjr format ia .. r·.because of the increasing pressure. aJri20ntal runs ··rd

riser pipes are, 1 ~:m:;h, beca~se tht: · l iq.Jid pressure decreases in the . . . . . . .

. direction of flaw. '!his is especially e· ·ident in simulation Case SYST9A

where 547 F water ras considered to e" is.· bet;.,ieen S/G and the 23BF22 check

valve - this sroW!: t a sizable vaEXJr cav il:y forming near the S/G side of the

check valve during the blc::wJown period.

In vertical risen., smal 1 va~r bubl,l·..?~ ci::--rl to coalesce creat i1~ large.

bubbles. If a bubble is large enou:.•r, it can cause a significant tram i:nt

variation in manentun forces as the ·1atxir cavity passes around d berd c.r

othetwise changes direction. '!his ai:::-iect was investigated assuning thrt a

pl u; of v ap::ir (occupying the ful 1 piµ.; area) , prece..ded am fallowed b:

water, passes around a 14" diameter 1 ~O degree elbow. 'lhe calculatiom"

sl'xlwed that if the flow velocity rea.:hes 30 f;s durin:; the bl~, tr.e

max imun transient change in force <..anponents wi 11 be 1. 5 kips. '!his i.· very

small canpared to changes due to pressure waves, and therefore is not

considered imp:>rtant •

23

Flow of a large vap:ir cavity th·::ou;h the 23BF22 checl< valve may, however,

have had s::::me bearin; on its closure. · It is not known '-lkly this valve was

initially·stuck open or '-lk!y it closed. fbwever, if a large blbble develo~

as the flow approached the valve, its passage thro1.13h the valve could have

charged the ma1ent\Jl1 force on the valve. In addition, the pressure

reduction in tt.e converging throat of the valve ....ould be different with

vap:>r flow. Cne or both of these effects may have freed the valve plu;,

allowing it ~o close.

8.0 CCNCWSICNS

8. 1 EVEN!' SCENARIO

Fran the ava-ilable evidenc:e ard other data ard with the aid of the LIQ!'

simulations, the fnllowin<: scenario for the event is probable •.

t(secs)

<O .0

Occurrence

The mair: Eeedwa' er sys ten was operating with cne condensate p.inp

recircul~tin; flow to th~ <Y:rdenser. All BF19 and BF40 valves

\olere clof-ed, but the 23BF22 stop check valve was stuck open. The

auxiliart feedwater system was injectin; 30 gpn throu;h the main

feed 1 fr'! to S/G 23.

a.a The 23Bk: 19 valve t,ein; stroked in the timing test jlltlped open due

+:o the bigh pressi..""Ce difference in connecting pipes. This

initiat~.d bacl<flow of 60 F water moving toward the condenser.

24

•

•

•

o., The negative wave fran the valve opening reached the S/G starti:-ig

outflow of 547 F water fr.:m the S/G.

0.4-0.~ The BF9 check valves temp:rarily closed. The highest blO'#doWTI

flow throu;h the flow metering nozzle occurred causing .the

restraining pins to she~r ard the nozzle to mOl/e towards the

header.

2-3 Steady blowdown flew th~~h 23BF19 was eHablished. !:bt water

fran the S/G continued, to replace 60 F water in the line. A

moving temperature transition zone probal" ly existed between. the

20-30

30-40

60 F and 547 F water. , Hashing and vap::>·: bu ·ble collapse in the o ' • o ' • • • • • I

547 F water flow product.<l a runbling noi'".ie •

'nle 23BF22 check valve .:osed and about the ~.:Ille time the op:rator

started closing 23BF19. The flow stoppage at the check Valve

caused high pressures tetween the valve ard t:·.e S/G, ard prob;::_::;ly

caused a tenp::>rary di;·· upt ion in the int~cw fran the auxiliary

fee:lwater system. Closure of the 23BF2 · ·aiv~! also caused a vap:ir

cavity to fom at its cordenser side. J,.,e le\t: pressure wave or

slbsequent collapse of the cavity caused :iigh transient forces on

the pipirg between the 23BF22 and 23BF1~ ·alves, especia1 ly on the

high pipi!'11 in the yard area where the s:F:rpest berds exist. The

flow st~e also halted the r1.JT1bl ing l"IOise •.

The 23BF19 valve reached fully closed p:isition •

25

.:.::·

•

8 • 2 F'ORCES N-ID PRESSURES

'!he canputer simulations sh:Jw that the generated maximun pc-essures arrl

forces would have deperded greatly on the tenp!rature profile of the water

in the majn feed line at the time the check valve closed. nie three cases

that were exanined are fel.t: to span the 1 i.kely rarge of temp!rature

conditions .an:!, hence, the rarge of results directly attribut.3b1e to the

23BF19 and 23BF22 valve ~C'Vements.

Bet.,.,ieen the 23BF22 chec:~ valve and the S/G, the peak pressure rarged Eran .

ai:>out 1300 to 2400 psig, and the maxim·m axial pipe force rarged fran 40 to

150 .kips. '!he highest values in this t.>art of the system occurred in Case

SYST9A where the urmixed 547 F water was assl.llled not to exterd beyo~ the

check valve~

Between the cl'lE!c.k valve and 23BF19, tre i;:ea.k pressure ran;ed fran about 1200

to 1380 psig, and the pea.k ax icl force: was about 4~-60 'kips. case SYSTSA,

the case where 60 F wat~r was assuned to exist throu:;rout the systen, gave a

•. ~;her axial force ( 150 .kips) 11 this ?art of the line. H:::>wever, it

occurred in the final-transien· period, which is represented better by the

other cases.

At the timt. of this stu:ly, a s~tac;s analysis of the danaged pip:! hargers had

oot been canpleted, so the act 'C'.l forces that caused the danage are not

known. If they are later detem,ined, it would be overly optimistic to

'!l'!p!ct that there will be clo&"' agreenen: with the forces presented herein.

Because of the canplex'ity of t . .o-i;:hase flow in the pipirg connected to the

S/G, and the m~el irg 1 imi tat bns, the results described should be

considered qualitative ~ather than quantitative representation of ~he

conditions that occurred.

26

• REFEFENCT.S

• ' L __

1. Fla.1 of Fluids Through Valves, Fittings, and Pipe, ':':?.C!".nical Paper No. 410, Crane Co., 1972.

2. Martin, C .S., Padmanabhan, M., "Pressure P...ilse Prcpagation in '!\.Ja­Carp:>nent Slug Flow," Journal of Fluids Engine_ ring_, AS-1E, Vol. 101, p. 44-Si, March, 1979.

3. Reference Manual for Liar® Version 4.0, Stcner_.Z.:ssociates, fac., Carlisle, PA, January 1982. >·

4 . Rothe, P .H . , Evans , D. H. , "Bla,.,icicwn with ChecL Valve Slam, " Fluid Transients Structural Interactions and Piping ~~~· (Rothe, P.ii.; Wiggert, D .C. , Eds.) , Fluids Engineering Conference, Boulder, Col··-,rado, June 1981, ASME, p. 31-38, 1981. -

5. User's Guide for LIQ~ Version 1. 0, Stoner Assc:ciates, Inc. , Carl.isl!=, ?A, May, 1983. -

6. Wallis, C:.B., "RE:VIEW - Tr...eoretical r-t:dels bf .:...~-Liouid Flews,·· Journal cf Fluids Engineering, ASME, Vol. 104, p. 279-283, SeptC::i.Tb=;·~, 1982. .

7. Webb, s.w., caves, J.L., "Fluid Transient Anal:sis in Pipelines With Nonunifotm Liquid Density," Journal of FJ . .:.ds Engineering, ASL--1E .. Vol. 105, p. 423-428.

8. West..a'w'ay, C.R., I..ocmis, A.W., C3Ireron Hydrauli: C3.ta, 15th Edition, Ingersoll-?.and, IM:x:rlcliff Lake, ~. 1977 .

27

No.21 CONDENSER llO?Wf.l.L

No. 21 iWXJT. JAR Y

I F:ED l'UHI'

No. 21 COHIJENSER

NOZZLE 2181 I J

~ NOZ7.l.E . JBF'_!.l_ 2J~Fl9

NOZZLE 22BrJJ

~ SALEM NUC~EAR GEN~RATJNG ·STATION

UoHT 2 F"EEOWATER SYSTEM HODEL SCHEHA1JC (PLAN)

AUXILIARY ANO MJ\IN F"EEDWATER

"Fog . ... •

• PIPF:

c11r.rK VAi.Vi:

CON'I Reif. VJ\l.VF.

HI NOR LOSS El.C.'tf:Nl

•

2A

I·

"

i.J ,, "'

llUW

14'1-

110-

11'•-

hJO-

<JO-

RO-

I I

f' Ir JN~ ·_:~~Hl~t '~'

0-0 l'Jl'r.

0\0 CllrCK VAi.VF.

()KO CONTRnl. VIII.VI:

00 MINflfl lllS!=' f.l.f.Mf:NT

IMlllC:l\TF.~ Tlll\T tMlflF: 2

IS l\T .Sl\Mr: r.r.t:V''t.TICIN '11· NOOE I

NOTE: ~u11lli11ry Feedwater System Not Shown. S~,. F'iqure 1.

Fig. 2

.!, ~

I :c J: .. .. " "' c

" :c

• .., ~

I

:::: .., N

,!, I

rl ~ I '" :c J: ...

SALEH NUCLEAR GENERATING STATION UN 1.T 2 FEEDWATER SYSTEM HODEL SCHEMATIC PROFILE

HAIN FEEDWATER

29

5/G 2J

~

w 0

70

60

50

40

30

20·

10 I

• SALl;M NUCLEAH GENL:l{l~'l'ING S'l'A'l'ION

UN l'I' ~ FECDWA'l'EH SYS'l'f.M APPAHEN'l' WA'l'ER LEVEL IN S/G 23

DURING.APRIL 6, 1984 ~VENT

~ 'l'ransient

P.edrawn fran PSE&G 01art

*Total ~qe = 144"

Fig. 3

o l~~~~--:4-:~~~5~~~---::4-:~~~o~~~--:4-:L~~5~~~--=s~:~~=o~~~__,,5~:~~~5~~~-,.-5-=~~o-r-~~~-s-:4~5~~~~-6~:t~10~~~~~

I

' .. .1. ...........

• 900

.800

700

600

-~ (/l :l..

' CJ 1-1 ::l sou (j] (j]

::J 1-1

=... 1-1

~ .::r ;....

400

300

200

100

•

\ \

SALEM NUCLEAR GENERATING STATION UNIT 2 FEEDWATER SYSTE.M

VAPOR PRESSURE AND TE~~ERATURE FCR MIXTURES OF 547°~ AND 60°F WATER

Fig. 4

Vap:ir Pressure of Mixture

P.ER:Ell! (By Volume) of 60 "F Water in ~ih"ture

00

00

r. 0

c. (

500

) : I

00

300

200

100

31

• 350

300

.. ~ 250

w I J

200

150

100

50

SALl::M NUCLEAR GENERA'!' ING S'l'ATION UN l 'l' ~ FEEDWA'l'I::H S YS'l'~M VOLUME Of' MAIN FEEDLINE

Fig. 5

14" Schedule 120 Pipe

I ""2._ 23BF22

/ ~;{_~ ·- ... - I

.• /

L 14" Schedule 80 Pipe

, ..

•

I

I I

I

23BF1 1

•

•

I

I I

I I

I I

I SALEM_UNIT 2 N

I in -I :::l . ...

CI: 1--

LL.I ~ :>SI .....J

~. ,. : 2l"!'l!I ~· ~

SI

~ • '

6

SYSTSA 23C 230 TAU

Fig. 6

\ ~ 1£1··1•1 Urosuwr

I

I ·I

~ I'

I

I .1 ·1

~~i~l~l~.~.~1~1~1~1~1-~l~ll""'P'j~I ~I ~1_,.1...,.1....,1~1~1~.l~l~l'""'"'j~I ~i~l_,.j~l..-~1~1~1~~1 ~I •1•,•1----11 ' il i . l .2 ··3 '4 5 S l · 9 . 9 L~

TIME CSEC) i l

I

•

-s: 0...

~~ =­c ...J u..

.... ,

-· SAL~M UNIT 2 SYSTSA 6 23E· 23F 0

Fig. 7 .

--- 2JBn2 Closes

1..:.. ... ~ c· ..

\ 'lQoldcl.m Flew Thrcu:!ll 2JBF22

.

• I

I

Ll I I I I I :~1 I I I I I I Ii I I I! I I I I I I' I I ' j I I I ' I I I I ! I I I I I I' . 1! " i 2 J .. s s 1 e s t~

__ TIME CSECJ 33- !

•

~ -~s A....:....::::L=-==E~M _...:U=...;....N~I_;._T---::2=----=-s y s T 5 A

I --s::: ~· ~1

=-0 -~-·

LL.

- I!Ut.i.&.L S~tAUI f'l,g,,

........... t .. )

;·

I

6. TOPH:F~DH OD Fig .. 8

! ·-· - BF') Reopl!ns

~ _._ __ _..,..._~_.,...-;:..,..,-I-, -1 1- 1 -1 1-1 -· 1-· ... , _, .-: _, 1-· ~, 1- 1 .... I ... , 1-· .... 1

I N

~ -·1

:::,) . a: -I-

LJ.J ~ > si _J

~. S·

I in

ID I

I -I "

2 3. . q 5 S .?···B 9

. TI ~··E CSECl

SALEM UN~ r 2 SYST5A

2 3

6. 8F~S BF90 TAU

-

5 . s 7

TIME CSEC)

~· 9 : I~.

B 9

~-4

I . \

i I

I N -

UJ . a:: ~~ en UJ a::

I c.. , I i r"• I

I i

· / · BM ClosH

:/

--· Initial 9tmdy-State Pl't!9f. ore: at SF9 v.i.lw

6. BF9D·P

Fig .. 10

I ._..,. ...... ,......,....."""'"'"~..,..,...,..,..,..,...,...~. ~.,~1-1~1~.1~.-1~11~1-.-1~1~,~11~.-,-1.-_1 I ' . ~ 2 ' . . 3. " 5 s 7 . 8· 3" . . . • L

C ______ T_I_ME_._ts_E._cl _____ _

SALEM UN IT 2· SYST5A_ ~1 ~ 6. F\JOH·RC OU 1

P-dtf l"CW "nlroJgh the

J . ~ : .s:iJ:Ql.Laua'l !.J.ne , ..... ~~~ . .

-- · !niti&l S~Statll Flair . : . : ,,~; : . . . . l . . • ... • • • • • • . : • 't.iit2~ '¢1;.,;;,; . . . . I

.Initial Flew Al!slarllll

. . i.D . . . ............. . . . . . . . . . . . . . . . . . . . . . ......... .

TIME· CSECl 35

1 ~_.=....;S A~L=-=E=---M--=--U N __ I ___ T--=--2 ----"'S---Y--=-S""""'--T .=_;,5 A__;,_, _ __,

23E 23F TAU . . .

. . . . . . . . . . . . . . . . . . . . ..

Fig~ 12

~ I

a: -1-- -- 23!1F22 ·c1os.i. q

UJ ~ >s _J c:

I > ·····:········. ,, ;·· ········· ~--- -----·~ SI

•• Ln .. I I

I ·-' "

. I '. I I I I I I : I I ' I I I I I . I I I I I ' I I I I . "' ' I I I I I I I I I I ("TT'· I l

l 2 . 3 . q 5. s . 7 8 ") . l

TIME CSEC)

SALEM UNIT 2 3YST5A I i '' ...... '' .....

I ~

2Jllf'22 cl~ 6. 23F p

I I .... . . ' . ......... . ...... '' '. ...

Fig. 13 -C!J ...... I c.n u:i

.. ' .. ' ' ' . . I . ' • • •' •: • '••••••I•

a.. ..... __,

UJ -a:: ~ . . . . . . . . . . ' .. . . . ' '''

~ -Cf.) Cl) -UJ ! . . . ' . . . . .... 0::: CL.

I ~' . . . ' : 2,W."9 ~

::r-

I I - j " 2 3 ~ 5 s 7 B 9

TIME CSE CJ

•

SAl_EM UN IT 2 SYSTSR

•

·t Fig. 14 ~ ······················· ·········· ................. .

• :=l

!8 i . UJ : S:: N ' :,:,

I tS . :~

I,_ I:~-· .. -·

1--4

: :· : c: '-J

. .

.................... . .

_....._. __ M"T,""" ......, ....... ,..... ....... ~ ....... .........,_ .... ,., 1.j 11.1I11III11' ·'t

LLJ • CZ::: ~ ~ ... CJ) CJ) • UJ ! a:: CL

I

3 . q. 5 8 7 B . 9 ~

TIHE CSECJ

~ 23[ p . . . .

Fig. 15

. . . . . . ~ . . . . . . . . . . . .

--vapor c .. <Y CDllapees . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . ..... · .. . . . . .

2 3 4 5 s 7 B 9

TIME CSECJ

1 ..

•

•

SALEM UNIT 2 SYSTSA ~ 2302 2303 F

Fig .. 16 ·

ID SI . . I ; I I I I I I I I I . I I I I I I I I I I I I I I I I I I I I I I I I I I I I I .I I I p..,-· I I I I . I I '1 "'." iJ · l 2 3 q S B 7 B 9 . l

2 . ~ I l r I r .:J I • ...I ,_,

TIME CSECl

SALEM·U~IT 2 SYST5~~~-·-

~ 2303: 2?:J4 F

Fig.: 17

It • ~~~....,._;.___:... _ _..;_,.... '-: ·­'I •. .£,,

. . . . . . . . . . . . ;. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . .

.__~~~--~~--3 ____ ;_IM_E __

5

C_S_E_C_; ___

7~--a~~9~

•

l~-S~A~L~E~M-~U_N~I_T~2-----=S~Y~S~T.5~A~~

~I Cf.J

di .... lJJ '-l a: • 0 lJ...

_J I

.................................. ' ... . .

........

. .

6. 2304 2305 F . . . . . . . . . . . . . . . . . . . . . ..

Fig.: 18

a: I ... ~ ·: ·.······ .. ....... "';"'

>< a: I

~

I . . . . , . I ·. I

1 . _.: : . · . · . I .. 11 ~"1!!'11' . ., I I I I I I I I I I I I TT"F-j I I I I I I I I I I I I_ I. I .j 1. I·' I I I I I I I I !]· : I '7' i l 2 · ~ . ·l 5 S 7 . B . 9 ~ . l

. . .

. . . . ·;·IME CSEC) · .

SALEM UN IT 2 SYSTS~A _ 6. 2::;G 23H F

Fig~ i 9

. . . ................ ~ . . . . . . .

................... . . . .

TIME CSEC.l 39

Of>

CJ3SJ '3~Il lf!l 6- . 8 L S S b £ .. ~ 1 e ~x ... , ,. ... , , I 1. I. ·I I , 1 .- . , , I 1 , , , , ., , , , , ' , , I , 1 , ·\ . · . 1 ·, , , , 1 , -· l!=t.llll~

i : I

' !·>i'--------------.

OG ·61.::f

iltJl OEC'. JEc V

~0151r u0..i.. /\0

• -., -i

I

11111 ( ,, ~

'SI

a < ~'.".

:0 r

'.;SI < ~

,.,., cs

...of - :D

I c:::

-I N

l:s

~

s A L E M u N I T -=-2----'s=-v--=I S:........;_1-=..6_;,,__rl. _ __,

!:::. 23C 230 0

I Fig. 21

-s:: a.. !D

C!I """"' =- SI 0 i _J lJ')

L.!..

I - ~

'

5l @'a;I

~ -' ~ . L

~;·11ljlll.ji I I I j I I I I I I I I ' i .• 2 J' q 5 !:) ' 7 8 ~ .~:

SALE: I UN IT ~ SYST6A "----------=-------<

~ · 23E 23F 0

Fig. 22

--· 2 '-ll'~2 C.IO!<cs

I· .................................... . -'

1.......,..,.....~......., .......... ........., ............ ~..,...,....~~ ........ ~~ I I I L~ ' I 2 3 5 s 7 8 9

! I

! 41 I TIME CSECl

-~ ....... en I Q_ N ...... -

BF90 P ..

Fig.: 23

........ ·... . . . . . . . ...

. en Clgya

./-~- -----~Br.I AeqJcns I I

I ----------.11ai .

i .-

Q ~~ ................... l""!",mi--. j 11 I ! I I I . , 1 r 1 t • , 1 1 : 1 1 :1 1 1 : 1 1 I 1 1 1 1 1 . . . 1 ·~i . " l . 3 q. s. s 7 . 8 9 ~ l ~

TIME CSEC)

I S A L E :j__u-=--=-N =--..;I T~2=---=S::;._..;_Y-=-S T--=, 6::.....:....A.:.....__..____j U"l -

6. F\JOH RC OU

I Fig. 24

-

. I

. . . . . . . . . . . . . . . . . . . . . . . . .

- ... .. ..... .... . . . .

I I

I ~ ........ ~~.·-11~1~1-1~1~1~1~1-1-11~1-1~1~11~1-1-1~1~11-,-1-1-11-1-1-1-{~11~1-1~1-ii-...... ii

2 3 4 s s 7 8 9 l, .

. TIME CSECJ 42

I

•• ,_. •

t­u.

UJ

SALEM UNIT 2 SYSTGA.REV

C"'9 . . . ...... .

6 23F CAV

Fig .. 25

s: N ····· ...

:::::> -J 0 >· ~ ~-..... > a: u I

j. ·~~~~ ................. ~~..,.........,.~ ....... ~.-. I

....... en . c.. I ..._. N

UJ a:: ffi I en lJJ 0::: . c..

'1 e . · 9 ·2 7 . 3 .· q

TIME CSEC).

SALEM UNIT. 2 SYST6R 23~.P

Fig. 26

./ 2JBF22 Closes / · /cavity col. p..c.s ·

··~ . ' . I

I I _ _...,......~ ...................... ~ ........... ~...,..,..-...~ ....... ,......~-.u

I 2 3 q 5 B 7 9 · 9 • • '1 TI ME CSE Cl 43 i

-=- ........-=...S..;.......;....A L=....::.c:::...:.......:.M_U=--N...;.....=.I ____ T _____ 2=----S '{ S T 6 A . R E V ,...,

• I­LL..

UJ s= N- ..

·~ ~

......J 0 > >-1- -·

. ·~

> a: u

~ ·~

6 23E CAV .

Fig~ 27 :

-I .. .

- ~·I I I I I I I I I I I I I I I I '·I I , ., '

LJ.J a::

f CJ:

~i Cfl UJ 0::: 0..

E t· 2 J q 5

"TIME CSEC)

S A L E M U N I T ~ '.,____S=--Y----=S"'-'"T--=6..:.....:..A _---i

23E P . . Fig. 28

m_,.,.~~~~""l""!""..,.. __ ~.,~.•.~.!~j-.~li~l~l__,.·•1~1--.•,~lj~i•i~l.~j~·.-.1: ~ s s 1 e 9 t~·

44 I " 2 J

TIME [SECJ '--~~~~~~~~~~~~~~~~~~----__J

•

1 __ ~SA~L~E~M~U~N~I~T_2=-~S~Y~ST~B~A~ ~~ ----J

UJ u

2302:2303 F . Fig.: 29 :

a::: • ~~-------------------· ~~ 0 I..!..

cf I ....... 9;'.'

>< a: ;! ISi ID ISi ~ .. ISi . I : I

. '. (l l . 2

I

1-

1 :

''I. 111 I' I I I f--:n-,1 7 8 • 9 - -~ 3 s

TIME CSEC) 1 ..____ __________________ - J

l.JJ u c:: • 0 . u..

~I ...... 7 >< a: I

N I

SAL EM UN I T 2 s. Y S T 6 A

........

Fig~ 30

. . . . . . . . . . ........

I I

' I 1~~ ........... ~....., .............. ~~...-................... ""'"'-__. ~ " 2 3 4 s s 7 8 9 l~

I TIME CSE Cl I

45

•

•

I -~

I - N tr.J

51 "-""' ii ....

s· ;~ L EM UN I T 2 S Y S T 6 R.

6. 2304 2305 F ...

Fig. 31

L~J (::J L~ m ]~~~~~~~~~~~~~~~~L_~~~__j~~~ C) L •. ~· ~ ·~ -x' ~1

I ~ I ~ ~ 1. I I I ' ·' I I I ~-I I I I I I I ! I I I I I I I I I I J. j I ' I I I I I I I I I I I I '· I I I! · ~ l · · ,' 3 ~ · 5 S 1 B 3 · l ~

I...- ~~~~~~~~~~~~~ TIME CSEC) I

I- SALEM UNIT 2 SYST6A ~-

I - N tr.J

6. 23G 23H F . . . . . . . . . . ....

Fig~ 32

::I I ....., IQ

. . . . . . . . .

lJJ

~ · 1 " . t" I" ,- · 1 • I~ WO. • •

lJ..

2E I """"'° ";"' ' )C

cc I ~

I

m

. . . . . . . . . . . . . . .... .......

. . . . . . . . . . . . . . . . . . . . . . . . . . .

I 11111 11111 11111 11111 11111 1111 .. 1111. 11111 11111 11.111 1 c:'1 l 2 J 4 S S 7 8 9 L

TirlE CSECl 46

•

•

L&.J a:

I C\J

::> I (.f.j CQ CJ)

i lJ.J ! a: . IQ..

l ~ I I

. Iii

6. BF90 P

Fig. 33

~-.

I I I I I I I I. I·' I I .I i I I I I ·I I I ,. I I I I ,.. I I ·' I , ·, 2 J 4 . 5· S 7 B 9 - L

TIME CSEC)

47

•

I ·SALEM UN IT 2 3YST8R

23C 230 0

I Fig .. 34

-s: CL, SI

C.!) "-'

2; I .\ Cavi tv ..iit 2lE ::ouarees _J 1.1.'

u. --2JBF22 ClClllCs

I I . I -I

·1 -. .

. I I I I i I I I I I I I ,,.,.Tl I I I I I I I I I I I I I I I I I I I I I I I I 1-· 1 I .,., I I i · L 2 J q s s 1 e e L~

. T ·.·ME CSEC) _j'

---------------'---~-----,,,,,...-- ...,--=--....,........,.---=-=---=----=~=-==-=--:=---- ------.,

~ S~~LEM UN IT 2 SYST9R -~

-s: CL. C.!)

- I ~. F\JC-H RC OU

I

/ St.-fy 13Lo.daoln Flaw

. ..:·-1 Fig; 3f

"

"-' I . . . . . . . . . . . . . . . . . . . . > c· ...J LL

• ••••••••:•••••oo•:•·••••••:••••••• •• • •••••••••••••. ••••••·:·••••···:•••• •••:••••

. . .

. . . . . . . . ' . . . . . . . . . . . . . . . .

. . . I . . . ~-~~:.,........,:......, ... · ............. ~,.,..,...,,~ ...... ~~~ ....... ""'"""'

TIME CSECl 48

SRLEM_l~JN~I_T-=-2~S~,1~ ... S~1~9~A~~~

1 L 23F CRV

/ .... -- 2JBP'22 Closes ·Fig. 36

'/ ...

I I I I I

' '

' i '. '

I

- . i i

I I I I I 2

~ I . I I I . I

3 5 8 7 8. 9 l~

TI ME CSEC)

U N I T-=-2----=S=---Y.-=-S--"-T .=....;..9 A_;.·_ -------l

. . .............

ID . . Si ........ · ........ , ........ , ............... ,, :zo : : :

. . . . . .

. .

23F P . Fig .. 3 7

1----"ressure 9Jrql! D.Je ::o cav l r:y col l.a~ •

• .:1 I I I I I I I I I I I I I I :I I I I I :I I I I I ' I I I I I I I I I I I I I I I I I I I ·, I I I I I Pl l 2 3 4 s. s 1 a e t

TIME CSECl .

•

•

51

~ SI SI M

·1 ~

- N ~

di L1J u c:: Cl

0 Lr..

~I ....... '7' >< cc I

. SR LEM UN IT 2

-~ .lll9 to ca-. 1t',' Col 141- ~t HF

S'l"'STSA

6. 23F 23'G F

Fig~ 3·8

·I· c: i1

...... _ ...... ~ ......... : I I I I I·, I I I I I i~~-1 I I I I I I I I I., I _I I I l1 I I I I 2 3 q 5 s 7 8 9 l

TIME cs~r)

I SALEM JN~I_T~2=--~SY~S~T~9~A--~

I 11:1

- C'\J ~

di L1J u

23G 23H F Fig~ 39

c::: Cl..,._--------~----~ ·O l.J... .

~I ....... 7 >< a: I

N I

I I

. . ...........

. '

Fl:lrC::IR ci. t:c c:avi ~ · · °'U41<·e .!'!:" 2JP

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

L 2 3 4 s 8

TIME CSECl

~ 7 8 9 l

I I

- N .~

di UJ u

SALEM 'UN I T 2 SYS T 9 R ~ 23H 23N F

Fig. ·40

a:-~--------------~ 0 LL.

~I ~ ";" )IC

.a: I ·~

Fcrc:e ClJ9 to -Cav1ty·<:oU . .JC)se at 23F

I ! I

I I· I

1 ........................... .....,. ... · I I I I I l I I I I I ! I I .j.1 '·' I I I I I i I I I I I :I 1.1 I.: ,1 ·· " w .· l . 2 . 3 . . • s 8 1 8 g .- 'i

TIME CSECJ · 1

51

Ii i M

I - C\I Cf.J

di w c...:i a:: -0 l.J...

~·1 ...... ";" )<"

a:' I 15)

. S" 11

I M

I ISi

~ - N U:J

di lJJ c...:i c::: -0 lJ..

~I ..... 7 >< cc I

I

'· I I

6. 2302 2303 Fi

Fig .. 43

' -·-r I i. I I I I I I I I_ I , ,..,..,. I ! I . I . I j.i I I I .1 I I I I .I I . I I I I I .,..,.., 2 3 ~ - s . s 7 - ' 8 . 9· l

TIME CSECJ

SAL~M UNIT 2 SYST9A

2 J" 4 s s

TIME CSECJ

2303 2304 F Fig. 44

.. t I I I I 7 8 9

i I I I I -I I

AXIAL FORCE CLBS> -JiJIHllW -2Mel!ll -1_.,. I

N

'"Tl cc • .,. 01

Ul

l>

f . .) (..) CJ -C

l'0 (.....)

CJ Ul

Tl

-< (J) --1 lD :TI

, I

'rnBLE 1

SALEl1 NUCLEAR GENERA.TDK; STATION UNIT 2 FEED'lATER SYSI'EM

MAXIM.JM PFESSURES AND FO:A:ES

'IAX.

ZONEl u:x:.ATicif P:RE·:;srJRE

CASE Jf:;~~ --SY ST SA

A 23E J..:.4~ •

23D2 ~303

B 23G 23J2.

23G 23H

SYST6A

·A 23E i: 76.

2304 23DS

B 23G 1 i 2.

23G 23H

SYSI'9A

A 2303. 1209.

23D4 2305

B 23G. 2408.

23F 23G

17.one A is line #23 between 23BF19 ani 23BF22

2.o1'1e B is line #23 between 23BF22 and S/G 23 "

~fer to Figures l and 2

3r-orce = F = F 2 - F 1 where Fl_.() PIP!!

MAX3 TIME OF4

FORCE MAX. PRESSURE (kips) (sec.)

··cv + 0.64

140.

tcv + 0.265

-150

+ 2.0 CV

115.

t: CV

+ 0.2 7

-~o.

• TL

60.

t CV

+ 2.9

-150

TIME OF MAX. FORCE

(sec.}

t + 0 CV

6

. t + 0.25. CV .

..

-t

CV + 2.0

t CV

t + ~ .8 CV

t + 2.9 ~v

4Approximate ti.ma (tcv is time between the opening of the 23BF19 valve and s

oi: 23BF22 check valve closure)

55

--------------------~--------------,----------------------------

CASE

SYsr5A

SYST6A

SYST9A

'!'ABLE 2

SALEM NLCLEAR r.F:NPRA'PTl'r, srATIOO UNI'I' 2 FEEDWA'IER SYSTEM LI(!l' SIMUU\'l'IOO SUM-11\1~.Y

VAPOR PRESSURES ('I'I::MPERATURES)

LJJCA'l'ICNS

Entire System

Node 2304 to S/G

~ig_JF)

-14 .4 (60)

1000. (547)

Remainder of systan -14.4 (60)

23BF22 to S/G

23 BF 19 to 23BF22

Rarairrler of system

1000 (547)

385 (445)

-14.4 (60)

t(sec)

0

0.02

4.0

0

0.02

4.0

0

0.02

4.0

VALVE OPERNl'IONS _

2)13Fl9 2313F22

Closed Wide q:..ien Instantly Opened Wide

Began 25. s·ec. linear. ~losure

Closed

Instantly (\Jened 40%

Began 2 sec. linear closure'

Closed

Instantly Open~ Wide

Began 25 sec. linear closun~

Began 0.26 sec. closure

Wide Open

Began 0.26 sec. closure

Wide Open

Began 0.26 sec. closure

NOI'E: t = 4 .0 seconds in the simulatons represents tcv (the tine between opening of 23BF19 valve arrl start of 23BF22 check valve closure in real systen) .