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Report on Visit to Japan

Japan Atomic Energy Research Institute

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Science and Technoloay Agency

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Clifford Anderson-

Generic Issues Branch

Division of Safety Technology

Office of Nuclear Reactor Regulation

Nuclear P.egulatory Comission

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October 13 - 17, 1980

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PDR FOIAMORROW 85-782 PDR

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Abstract.

During the week of October 12, 1980, Professor Robert Scanlon of PrincetonUniversity (NRC Consultant) and I visited the Japan Atomic Energy ResearchInstitute (JAERI) near Mito, Japan and the Science and Technology Agency(STA) in Tokyo, Japan. The purpose of this trip was to discuss theresults of recent Mark II tests and analysis at JAERI and future Mark IIrelated work at JAERI. We also discussed Mark II licensing efforts inJapan with personnel from the nuclear regulatory body in Japan, (STA),and members of the Japanese Mark II owners. It was also our purpose toencourage information exchance related to Mark II containment designverification.

Some progress was made relative to resolution of the instrumentationquestions raised by the USNRC and the US Mark II owners during a previoustrip in June 1980. However, questions still remain in this area. Heencouraged the JAERI people to resolve these questions prior to conductingadditional tests.

Mr. Shiba of JAERI indicated that significant progress has been madetowards resolving certain liark II containment pool swell related licensingissues in Japan. However, it was not apparent that much progress hadbeen made towards development of Japanese licensing positions related to

. steam loads (i.e., condensation oscillations, chugging and lateralloads). In these areas, it appears that the US is still taking the<

lead in developing load specifications.

Dr. Nozawa, head of the Division of Reactor Safety at JAERI statedthat recent progress has been made related to improve US access to MarkII test results for the tests conducted at JAERI.

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Contents .

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1. Chronoloaical Summary2. Persons Contacted3. Pool Swell4. Steam Loads5. Witness of Test 31046. Instrumentation7. Shaker / Hammer Tests8. Mark II Containment Licensing in Japan9. JAERI/USNRC Relations10. List of Documents Received

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1. Chronological Summary,

Monday (10/13/80) we arrived at JAERI. We were introduced to thestaff working on Mark II programs and toured the Mark II Containmenttest facility. We briefly discussed each of the week's discussiontopics including JAERI instrumentation problems, future tests, poolswell loads, steam loads, structural modifications of the testfacility, Fluid Structure Interactions (FSI), and future shakertests. Comprehensive discussions were conducted relative to poolswell observations in the JAERI facility.

Tuesday we continued discussions related to JAERI pool swellobservations and discussed air mass analysis for the JAERI tests.Dr. Kukida presented observations related to condensation oscillations

(CO) and Ch' gging Loads observed in the JAERI Mark II test facilityu

(CRT). On Tuesday night we witnessed test #3104 in the CRT.

Wednesday we discussed our concerns related to CRT instrumentationwith Mr. Namatame. Mr. Takashita discussed the upcoming shakertests of the JAERI test facility and their proposed structuralmodification of CRT to address FSI questions. We presented thesteam loads under consideration in the US and the role of the JAERItests in confirming these loads.

p' Thursday we traveled to the STA offices in Tokyo. I presented theUSNRC position on steam (C0 and Chugging) loads and load combinations.L

We also discussed the results of preliminary evaluation studies of USand Japanese Mark II Containments to pool dynamic loads. Thesediscussions were conducted between personnel representin'g theUSNRC, JAERI, STA and the Japanese Mark II owners and vendors

Friday we discussed the status of Japan's Mark II licensing activities.* and summarized the week's activities.

| 2. Persons Contacted .

Dr. M. Nozawa, Head, Reactor Safety Research, JAERIMr. M. Shiba, Chief, Engineering Safety Lab I, JAERIMr. K. Namatame, CRT Program Manager, JAERIDr. Y. Kukita, CRT Research Leader, JAERIMr. S. Takashita, CRT Research Engineer, JAERIDr. Ushio, Science and Technology Agency (STA), Nuclear Safety

Bureau, Atomic Energy BureauDr. Ebine, Ministry of International Trade and Industry, (MITI)Mr. T. Enomoto, Asst. Mar., Nuclear Power Construction Dept.,

Tokyo, Electric Power Co.Mr. T. Horiuchi, Mgr., Nuclear Power Plant Engineering Dept.,

Hitachi Ltd.Mr. H. Aoki, Safety Engineer, Nuclear Engr. Dept., Toshiba Corp.

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3. Pool SwellPool Swell Height

JAERI tests were compared to the USNRC The USMark II owner's pool swell model (PSAM) pool swell criteria.yields conservative resultsfor the pool motion parameters of velocity, acceleration and maximumheight. However, significant froth was observed in the tests.Observations of the froth height varied considering the levelprobes used. Short probes indicated a greater amount of frothactivity than the long probes. The short probes data is in question.JAERI plans to use an increased number of long probes in futuretests. The significant froth activity appears to be due to ventbraces above the suppression pool surface. This bracing configurationis typical of plants in Japan but not in the US. Other reasonscited for the froth include Taylor instability in the JAERI 3Dtests and the non-flat pool shape resulting from the tight ventcluster in the JAERI tests.

Diaphraam Uploads

The JAERI tests exhibited several higher then anticipated diaphragmuploads. The diaphragm separates the drywell and the wetwell

, volumes. One test indicated an upload a little above 2.5 psi.This upload occured during a test when the wetwell/drywell vacuumbreaker failed in the closed position. The USNRC criteria uploadcriteria applied to CRT yields a value of 4.3 psi. Dr. Kukidaquestioned the basis for our criteria. Additional CRT tests may beconducted to investigate the effect of break size, vacuum breakeroperability and pool temperature on diaphragm uploads.

Mass and Energy Release (Liquid Break)*

Pool swell loads for Mark II plants are determined from the PoolSwell Analytical Model (PSAM). They are a function of the inputmass and energy release. Dr. Kukida raised questions regardingtreatment of the subcooled inventory for calculation of recirculationline liquid breaks. His studies have indicated that the Henry -Fauski critical flow model yields good comparison with the Marviken3 data during the first few seconds following a LOCA and that thiscorrelation should be used in pool swell calculations.

The US Mark II owners have stated in the past that the design basisbreak for pool swell analysis is a steam line break. Additionaldiscussions were held regarding mass and energy release for liquidbreaks during for the week of November 2,1980 between Dr. Kukidaand the NRC staff (CSB).

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4. Steam LoadsCondensation Oscillation Loads

Preliminary observations of the condensation oscillation (CO)phenomenon in the JAERI tests indicate that C0 phenomenon do notshow the strong periodicity nor the strong vent to vent coherenceanticipated. The US Mark II owners have conservatively proposed aaeneric C0 load that does not take credit for the potential loadreduction that might result from these observations. The WPPS-2plant in the US (the only US Mark II steel containment vessel) hasindicated that they are considering a plant unique load that willreflect these JAERI observations. This new load is currently underdevetopment by Burns & Roe and will be discussed with the staff inFebruary 1981. There was considerable interest in Japan in therefinement of the US Mark II Long Term C0 load specification sincethe Mark II containment designs in Japan are all steel.

Chugaing Load Specification

Dr. Kukida presented the results of his studies to characterize thechugging pheonmenon in the JAERI tests. This consisted of characterizationof the chugaing oscillations according to magnitude, wave form and

([] interval. The character of chugging was observed to change significantlywith vent mass flux. These observations are consistent with thosemade in other Mark II large scale tests conducted in the US andGermany. The US approach towards development of a chugging load isconservative in that only the worst characteristics of the observedchugging loads are used to construct a chugging load.

Lateral Loads.

j Our discussions indicated that it is difficult to use the available. JAERI data to. confirm the proposed Mark II dynamic lateral load

specification proposed by the US Mark II owners group. The difficultiesarise in several areas; insufficient number of strain aauges wereused, the data sampling rate was too long and the JAERI bracingconfiguration resulted in large induced thermal stresses. Futuretests are directed towards resolution of these problem areas.;

|| S. Witness of Test 3104

Three tests were to be conducted this fall to address instrumentationquestions posed in our June 1980 meeting with JAERI personnel.Prof. Robert Scanlon (NRC consultant from Princeton) and I witnessedthe second of these tests,#3104. This 75mm liquid break test was a

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repeat of a previous test. Significant low frequency shaking ofthe control room was observed. The control room was located about60 feet from the test facility. The events at each of the 7 ventsoccured together at approximately 2 seconds intervals. Smalldifferences (i.e.10-50 milli-seconds) in the time of individualvent chugging during a gross pool chug could not be distinguishedwith the. ear.

6. Instrumentation

Questions regarding the JAERI instrumentation were raised at theJune meeting between JAERI personnel, USNRC consultants, the USMark JI owners and t5 e Japanese Mark II owners. The questionsi

dealt with the type of pressure transducers used and the type ofaccelerometer cables used inside the test facility. Three additionaltests were to be conducted this fall to address these questions.

Early tests at JAERI utilized cavity type transducers instead ofthe preferred flush mounted transducers.

The reason for this is: 1) the difficulty in getting flush nountedtransducers produced by US manufacturers in Japan, and 2) temperature

{ sensitivity problems associated with flush mounted transducers.The use of cavity type transducers resulted in several problems.Trapped air in the diaphrahm and oscillations associated with thewater filled column make these cavity type transducers subject tospurious readings. Several modifications were made in the JAERIinstrumentation in an attempt to address the instrumentation questions.This included: the placement of a few flush mounted transducers onthe test floor, a change in the orientation of the floor cavitytransducers from horizontal to vertical and a change in the orientation*

of the vent exit cavity transducers from horizontal to about a 45*| angle. In addition, the type of floor accelerometer cables was' changed to eliminate the cable noise problems. A quick look at

the preliminary results of test #3103 conducted in September 1980indicated partial success in solving the instrumentation problem.

- However, it appears that additional improvements should be made inthis area. In addition to the JAERI full scale tests, a separatetest system was used to investigate the effect of transducerorientation and trapped air on the cavity type transducer response. -The results of these tests conducted since June 1980 were discussedwith us. These tests shed some light on the orientation and airtrapping questions, however, questions still exist regarding the,

| use of the cavity type transducers.

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; 7. Shaker / Hammer Tests

JAERI personnel plan to conduct shaker tests followed by structuralchanges in the test facility to better understand the influence of,

fluid structure interactions (FSI) on pressure histories recordedin the facility. Mr. Takashita discussed the shaker tests scheduledfor January 1981. Prof. Scanlan was not optimistic that the shakertests would provide significant information about the natural modesof the facility. He suggested that thought be given to hammertests, random vibration tests and tests using small explosivecalibrated sources at the vent exits. He recommended that thesetests be considered in addition to the planned shaker tests. Theconcern is that the mass of the shaker must be large to have anaffect on the large test vessel. A mass this large would probablychange the natural modes of the facility.

Future modifications in the facility were discussed to harden thefacility to study the influence of boundary stiffness on observedpressure readings.

Several modifications are under consideration including the placement'

of concrete into the vessel to thicken the flexible end walls andi

the placement of steel beams on the wetwell floor to stiffen the'

(. floor. These modifications are scheduled for the period April -;

| June 1981. Professor Scanlan suggested that the proposed shaker /hammer tests be conducted both before and after the structural'

modifications to assess the impact of these changes on the facilitiesnatural modes.

8. Mark II Containment Licensing in Japan* Japan has 7 plants that utilize the Mark II Containment design. At

least one plant, Tokai-2, is currently in operation. The Japanesegovernment is allowing their plants to operate for a limited timeperiod during which time the issue of pool dynamics is studied.They appear to have made significant progress towards the developmentof licensing positions related to the pool swell loads which wouldoccur in the first few seconds following a loss of coolant accident. 1

They questioned us in depth about the basis for the USNRC loadcriteria for pool swell loads provided in our report NUREG-0487 ofOctober 1978. They are working on a similar report that is now about75 percent complete. It does not appear that they have made muchprogress toward the development of licensing positions-for steamrelated pool dynamic loads (i.e., condensation oscillations, chuggingand vent lateral loads). Thus, they are following US load development I

and licensing efforts in this area with considerable interest. Incontrast to the US Mark II plants, the Japanese plants have notevaluated their plants with respect to dynamic steam loads. Theyuse static loads. In addition they do not combine loss of coolantaccident (LOCA) loads with seismic loads.

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9. JAERI/USNRC Relations

Mr. Shiba and his staff have continued to cooperate closely withthe USNRC and with the US Mark.II owners to resolve issues relatedto Mark II containment pool dynamic loads. Dr. Nozawa stated thatas a result of his discussions with STA during our visit, informationflow related to the JAERI Mark II tests would be improved. Herequested that the NRC send a letter to JAERI formally requestingdocuments related to the JAERI Mark II containment test program.

10. List of Documents Received

A number of handouts related to the JAERI Mark II tests were givento us during this trip to Japan. A list of these handouts isattached. They are available through C. Anderson at X29424.

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JAERI Trip Handouts

JAERI nemo 9068, Test 3201-

JAERI memo 8987, Tests 0002-3102, blowdown analysis-

JAERI Annual Report-

Report on fluclear Safety Administration in Japan, August 1979-

Preliminary Characterization of Chugging in JAERI CRT, Part 1:-

Categorization of ChuggingPreliminary Characterization of C0 in JAERI CRT, Part 1 and Part 2-

Present status of JAERI Full-Scale Mark II CRT-

JAERI Outline of Pool Swell Discussion Topics-

Water level probe slides-

JAERI evaluation of air mass history-

Pool Swell Slides-

- Preliminary results of test 3103Dynamic Response test of Pressure Transducers-

Phase 1, 2, & 3 instrumentation modifications-

Proposed structural modification for the CRT facility-

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Report on Trip to JAERI.

October 10-19, 1980 -

R.H. Scanlan (with C. Anderson of NRC)

OUTLINE

Friday, October 10, 1980. PanAm Flight 801, JFK-Tokyo Narita.

Saturday, October 11, 1980. Tokyo Shimbashi-Dai-Ichi Hotel.

Sunday, October 12, 1980. Tokyo-Mito (JNR train).Nato-Sannomaru Hotel (October 12, 13, 14, 15, 1980)

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Monday, Oetober 13, 1980. Visit at JAERI sith Drs. Shiba, Takeshita,Kukita, Namatame, Nozawa.

Tuesday, October 14, 1980. Discussions at JAERI. Witnessing of BlowdownTest #3104 at JAERI test facility.

Wednesday, October 15, 1980. Continued discussions at JAERI.

Thursday, Octuber 16, 1980. Tokyo Shimbashi-Dai-Ichi Hotel (October 16, 17, 18,1980). Discussions at Science and Technology Authority, Tokyo, withC JAERI and Japan Utilities personnel, Dr. M. Shiba presiding. Presen-tation and discussion by C. Anderson on HK II CO and chugging accep-tance criteria.

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Friday, October 17, 1980. Discussions in Tokyo on CO, chug, criticismsof JAERI tests.

Saturday, October 18, 1980. Free day, Tokyo.e.

Sunday, October 19, 1980. PanAm Flight 800'to JFK. .

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ACTIVITIES REPORT

The following vill briefly review the principal activities of technicalnature during the October 10-19, 1980 trip. ,

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Monday, October 13, 1980. Introduction to JAERI staff Tokai ResearchEstablishment. Discussions with Kukita, Namatame, Takeshita on1) pressure transducer characteristics, JAERI CRT facility; 2) pro-posed further test program and measurement modifications; 3) inter-pretation of CO data to date by Kukita; 4) pool swell; 5) impli-cations of possible containment reinforcement in Japanese plants as *

a result of CO and chugging loads.

Tuesday, October 14, 1980. Continued discussions on several of the abovetopics, plus: 1) pool swell; 2) air mass inventory analysis;3) FSI. Evening: Witnessing of JAERI test #3104 (prepurged blow-down) in CRT facility (during side' effects of typhoon).

Wednesday, October 15, 1980 Continued discussions on the above topics,plus presentation (mainly by C. Anderson) of status of USNRC chugging,CO, and lateral load specifications. Review of USNRC viewpoint onJAERI blowdown facility test results to date. Discussion of implica-tions for Japanese plants.

Thursday, October 16, 1980 Return to Tokyo, accompanied by JAERI per-({} sonnel. Presentation (by C. Anderson) at Science and Technology -

Authority (Japan) of USNRC position on definition of CO and chuggingloads. Commentary by Scanlan. Present: Representatives of JapaneseMK II owners' group -- Tetsuo Horiuchi (Hitachi, Ltd.),, ToshiakiEnomoto (Tokyo Electric Power Co.) and H. Aoki (Toshiba Corp.).Representative of STA (MITI): T. Ebine. Representatives of JAERI(K. Namatame, Y. Kukita, and M. Shiba (presiding)).

e.Friday, October 17, 1980 Summarizing meeting. Response to questions.

General interchange. Problem review. *.

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Some comments on the above are:in order:-

1. General position' and attitude of Japanese. They are not monolithicin their approach to the JAERI blowdown tests, interpretationof them, and the ultimate use of the results. JAERI personnelare not licensing people and tend to take a more " scientific"

view of the tests, leaning more toward " understanding thephenomena" than answering immediate practical questions fornuclear plant design. Japan licensing 'eople have largely usedpstatic loads in designing existing plants (except for earthquakeconcerns). Thus they are slightly at a loss as to what to do,immediately, with dynamic pressures obtained as JAERI test data.

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Finally, Japan Mark II owners would, broadly speaking, like tosee the whole issue of CO and chugging loads fade away. Allagree, however, that they have not received open-armed coopera- '

tion from G.E., in spite of'the quite open Japanese response.

Cliff Anderson encouraged JAERI personnel to try to direct.(and redirect) the JAERI blowdown tests to more exactly meet theneeds of HK II plant evaluation.

Overall, there was the most cordial and open exchange possiblebetween all Japanese met and the visitors Anderson and Scanlan.

2. JAERI test #3104 and transducer calibration. It certainlypays off on general perceptions and " feel" to witness a blowdowntest. Anderson and Scanlan were the first foreigners to witness

,such a test at JAERI according to our hosts' accounts. We stayedinside the instrumentation shack due to the high typhoon windsand rain outside. Hence we missed the possible view of tankshaking that we might have had during test #3104 Nonetheless,even forewarned, we were rather impressed by 1) the generalsynchrony of all chugs (7 downcomers) "together" into one big" whomp" about every two seconds or so during the chuggingphase. (maybe 50 chugs) of the blowdown; and 2) the way thebuilding shook from each chug. It was not an earthquake, butthe floor got a solid jolt each time -- mostly vertical, to

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Thinking back over the impressive s.ights and sounds of the chuggingthat night, the undersigned got to thinking about $he effectivenessof the pressure transducers during such dynamic events, where FSImay even involve rocking of the whole facility, etc. As a result,a list of comments was drawn up and passed on very informallyto Namatame. In thinking back now, these reflections really con-

* stitute quite a serious indictment of the credibility of JAERIpressure readings to date. For not only are the previouslycriticized floor pressure tranducers vulnerable to accusation;Cliff and I now believe that any one of the large-pot, siliconeoil-filled transducers is likely to be vulnerable to spurious-

readings induced by dynamic shock, which activates the transducerdiaphragm against the oil-filled tube. The details of this trans-

! ducer are discussed in a draft report *by JAERI personnel that| accompanies this.nemo. As an example, transducers on flexible! side walls and downcomers are highly susceptible to shock-

induced responses caused by transducer acceleration, not justlocal fluid pressure..

The implications of this may well be far-reachings as regards theinterpretations made in various places to date both of timing(phasing of chugs) and magnitude of pressure traces. The best

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that can be said at the moment is that it is to be hoped thatthe JAERI tests will be halted until improvements in facility '

(stiffening walls and bottom), in instrumentation (betterpressure transducers), and in test design (more Mark II represen-tative and repeatable tests) may be effected.-

3. Japanese attitude toward U.S. know-how. This is still respectful,but is beginning to shade, with the realization, for example,that the JAERI blowdown facility is really potentially superiorto things like G.E.'s 4T, stateside. (They are already accus-tomed to the situation in automobiles!). They are also rapidlycoming off the attitude that G.E. (o'r NRC) knows best in alldepartments. I shared with them my feeling that, based oneventual good JAERI data, they could come up with their own

.C0 and chugging load definitions that could be more rationallybased than the piecemeal job done by G.E. to date on the sameitems. We also explained that the role of NRC is not automa-tically to develop and endorse "best in the world" methods,but instead to 0.K. an acceptable method put forward by Mark IIowners, no matter what superior one might theoretically be avail-able. The feeling does linger, nevertheless,that JapaneseHK II owners would still be happy to "get the word", from anyU.S. source, on how to get CO and chugging out of their hair.

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