a review of in-service surveillance methods …

A REVIEW OF IN-SERVICE

SURVEILLANCE METHODS APPLICABLE

TO LIQUID SODIUM PIPING

T E C H N I C A L REPORT 243

PREPARED FOR

US ATOMIC ENERGY COMMISSION

CONTRACT NO AT(04-3)-781

BRAUN PROJECT 4122-W

UNITED NUCLEAR PROJECT 2351

C F B R A U N & CO

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

C F B R A U N & C O Engineers

A L H A M B R A C A L I F O R N I A 9 1 8 0 2

January 7, 19 70

H B Fry, Contracting Officer Contract AT(04-3)-781 AEC San Francisco 2111 Bancroft Way Berkeley, California 94704 BAL-96

Dear Mr Fry IN-SERVICE SURVEILLANCE TECHNICAL REPORT 243 LMFBR PIPING DESIGN GUIDE PROJECT 4122-W

Transmitted herewith are two copies of the final report covering a review of In-Service Surveillance Methods applicable to Liquid Sodium Piping.

The purpose of the review was to compile information on various types of surveillance methods in the areas of sodium leak detection, pipe movement, alignment and vibration, material inspection, strain measurement, crack detection, and logging of records. The results of the review will be utilized in preparing recommendations to be presented in the piping design guide.

Comments on the report from reviewers will be welcome but further revision is not contemplated.

Sincerely yours

/ur^f /Qj^Cu, 'Ut^StsK.

RFD IV R0ger Detman Project Manager

C F B R A U N & C 0

Project 4122-W AEC Contract AT(04-3)-781

H B Fry, Contracting Officer Page 2 January 7, 1970

CC H B Fry, Contracting Officer -original and one Director, RDT, HQ Asst Director, Project Management, RDT, HQ Asst Director, Plant Engineering, RDT, HQ Asst Director, Engineering Standards, RDT, HQ Asst Director, Reactor Engineering, RDT, HQ Asst Director, Reactor Technology, RDT, HQ Chief, Liquid Metal Projects Br., RDT, HQ Project Manager, LMEC, RDT, HQ -2 Program Manager, LMFBR, RDT, HQ Chief, Facilities Br., RDT, HQ Chief, Components Br., RDT, HQ Chief, Instrumentation & Control Br., RDT, HQ Chief, Liquid Metal Systems Br., RDT, HQ Project Manager, FFTF, RDT, HQ Manager, SAN-AEC Director, LMFBR Program Office (ANL) RDT Senior Site Representative (AI) -2 Director, LMEC -3 Contract Representative, CP-AEC RDT Senior Site Representative (PNL) Project Administrator, FFTF Project Office (RL) Manager, FFTF Division (BNW) Manager, FFTF Fluid Systems (BNW) Manager, FFTF Engineering (BNW) Manager RL-AEC

CFB-4122-243

A REVIEW OF IN-SERVICE SURVEILLANCE METHODS

APPLICABLE TO LIQUID SODIUM PIPING

TECHNICAL REPORT

243

L E G A L N O T I C E This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.

P r e p a r e d for US Atomic Energy Commission

Contract No AT (04-3) -781

Braun Project 4122-W

United Nuclear Project 2351

C F B R A U N & C O

Alhambra California

January 7, 1970

DISTRIBU JTION OF THIS DOCUMENT IS UMLIMTTEDO J j

PREFACE

This Technical Report i s one of a se r i es designed to present the findings of s tudies made by the authors in the development and ve r i f i ca t ion of a Piping Design Guide for LMFBR sodium piping systems. I t c r i t i c a l l y reviews methods of in-serv ice survei l lance of a LMFBR piping system with an aim toward se lec t ing those methods most su i tab le to t h e i r design.

The following studies have so far been ident i f ied

TECHNICAL REPORT NO

100

110

210

214

217

220

223

228

231

234

237

240

243

TITLE

The Development and V e r i f i c a t i o n of a Des ign Guide f o r LMFBR Sodium P i p i n g

LMFBR System R e q u i r e m e n t s

A Study of F a i l u r e T h e o r i e s a s R e l a t e d To LMFBR P i p i n g Sys tems

A Review of P i p i n g F a i l u r e E x p e r i e n c e

A Review of P i p i n g and P r e s s u r e V e s s e l Code Des ign C r i t e r i a

A Review of F a b r i c a t i o n and I n s t a l l a t i o n R e q u i r e m e n t s f o r LMFBR P i p i n g

A Study of H e a t i n g and I n s u l a t i o n Methods f o r LMFBR Sodium P i p i n g

A Review of LMFBR P i p i n g M a t e r i a l s

A Study of LMFBR System I n t e r f a c e s

A Study of S c a l e Model T e s t i n g Methods A p p l i c a b l e t o LMFBR P i p i n g D e s i g n

A Study of Dynamic A n a l y s i s Methods a s R e l a t e d t o LMFBR P i p i n g Sys tems

A S tudy of I n s t a b i l i t y A n a l y s i s Methods a s R e l a t e d t o LMFBR P i p i n g Sys tems

A Review of I n - S e r v i c e S u r v e i l l a n c e Methods A p p l i c a b l e t o L i q u i d Sodium P i p i n g

u n d e r t h i s t a s k .

*ISSUE DATE

7-23-69 (F)

1 0 - 2 5 - 6 8

1-31-69

3 - 2 8 - 6 9 ( F )

4 - 1 8 - 6 9 ( F )

6 -6 -69 (F)

2 - 2 8 - 6 9

Feb 70 (F)

3 -28 -69

5 -6 -69

5 - 1 4 - 6 9 ( F )

2 - 1 3 - 6 9

1-7-70 (F)

* ( F ) D a t e of f i n a l i s s u e . A l l o t h e r d a t e s a r e f o r p r e l i m i n a r y i s s u e .

C F Braun & Co United Nuclear Corporation Alhambra, California Elmsford, New York

C F B R A U N & CO

1

1

2

3

IN A REVIEW OF

-SERVICE SURVEILLANCE METHODS APPLICABLE TO LIQUID SODIUM PIPING

TECHNICAL REPORT 243

CONTENTS

INTRODUCTION

SODIUM LEAK DETECTION 2.1 2.2

2.3

2.4 2.5

PIPE 3.1 3.2

3.3 3.4

3.5 3.6

GENERAL DISCUSSION INSTRUMENTATION 2.2.1 ELECTRICAL RESISTANCE TYPE

DETECTORS 2.2.2 THERMAL TYPE DETECTORS 2.2.3 OPTICAL TYPE DETECTORS 2.2.4 RADIATION TYPE DETECTORS 2.2.5 LEVEL TYPE DETECTORS 2.2.6 SODIUM CHEMISTRY DETECTORS OPERATING CRITERIA 2.3.1 ELECTRICAL RESISTANCE TYPE

DETECTORS 2.3.2 THERMAL TYPE DETECTORS 2.3.3 OPTICAL TYPE DETECTORS 2.3.4 RADIATION TYPE DETECTORS 2.3.5 LEVEL TYPE DETECTORS 2.3.6 SODIUM CHEMISTRY DETECTORS APPLICATION FUTURE REQUIREMENTS

MOVEMENT, ALIGNMENT AND VIBRATION GENERAL DISCUSSION VISUAL INSPECTION 3.2.1 LIMITATIONS CLOSED CIRCUIT TELEVISION TELESCOPES, PERISCOPES, BORESCOPES, AND MIRRORS FIBER OPTICS PIPE DISPLACEMENT INSTRUMENTATION

PAGE

1-1

2-1 2-1 2-2

2-2 2-2 2-5 2-5 2-5 2-5 2-5

2-5 2-11 2-11 2-11 2-11 2-12 2-12 2-14

3-1 3-1 3-1 3-1 3-2

3-4 3-4 3-7

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5

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7

CONTENTS

MATERIALS INSPECTION 4.1 4.2

4.3 4.4

4.5

GENERAL DISCUSSION INSPECTION METHODS 4.2.1 BY-PASS SYSTEM 4.2.2 DIRECT INSERTION INTO MAIN TEST SCOPE TEST SPECIMENS 4.4.1 MATERIAL 4.4.2 SPECIMEN DESIGNS 4.4.3 NUMBER OF SPECIMENS 4.4.4 SPECIMEN EVALUATION SODIUM PURITY

STRAIN MEASUREMENT AND CRACK DETECTION 5.1

5.2

5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12

GENERAL DISCUSSION 5.1.1 SCOPE 5.1.2 REQUIREMENTS 5.1.3 MATERIAL FLAWS AND DEFECTS STRAIN GAGES 5.2.1 VARIABLE RESISTANCE

PIPING

TRANSDUCERS 5.2.2 VARIABLE CAPACITANCE STRAIN GAGE 5.2.3 VARIABLE INDUCTANCE STRAIN 5.2.4 PIEZORESISTIVE STRAIN GAGE PHOTOELASTIC COATING HOLOGRAPHY X-RAY DIFFRACTION BRITTLE COATING NUCLEAR METHODS CHEMICAL METHODS PIEZOELECTRIC TRANSDUCERS ACOUSTIC EMISSION ULTRASONIC METHODS RADIOGRAPHY

LOGGING OF RECORDS 6.1 6.2

SCOPE NECESSITY

BIBLIOGRAPHY

TABLE

TABLES

I DETECTOR EFFECTIVENESS PIPE FAILURES

GAGE

FOR VARIOUS

PAGE

4-1 4-1 4-2 4-2 4-5 4-5 4-7 4-7 4-7 4-7 4-8 4-8

5-1 5-1 5-1 5-1 5-2 5-2 5-2 5-3 5-3 5-4 5-4 5-4 5-6 5-6 5-7 5-7 5-7 5-9 5-13 5-14

6-1 6-1 6-1

7-1

2-15


3

FIGURES

PAGE

2.1 ELECTRICAL RESISTANCE TYPE DETECOTRS 2-3 2.2 OPTICAL SMOKE DETECTOR 2-6 2.3 LEVEL TYPE DETECTORS 2-7 2.4 SODIUM CHEMISTRY DETECTORS 2-9 2.5 INSTALLATION OF RESISTANCE TYPE DETECTORS 2-13

3.1 HEAVY DUTY TELEVISION CAMERA INSTALLATION 3-2 3.2 ARTICULATABLE FIBERSCOPE FOR INSPECTING

REMOTE AREAS AROUND NUCLEAR REACTORS 3-6

4.1 TAB EXPOSURE FACILITY IN SRE-PEP 4-3 4.2 MATERIALS EVALUATION FACILITY ASSEMBLY,

INTERIOR VIEW OF SPECIMEN HOLDING FIXTURE 4-4

5.1 HOLOGRAPHIC INTERFEROGRAM OF A STRESSED FLOW CONTROL ELBOW FROM THE TRW LUNAR MODULE DECENT ENGINE 5-5

5.2 TRANSDUCERS EPOXY BOUNDED TO THE REACTOR OUTLET DUCT ON THE SM-lA POWER PLANT TO OBTAIN ACOUSTIC EMISSION DATA 5-8

5.3 THE SOURCE AREA OF ACOUSTIC "BURSTS" WAS LOCATED ON THE SM-lA REACTOR VESSEL BY TRIANGULATION OF TRANSDUCER DATA 5-11

5.4 ACOUSTIC EMISSION SYSTEM ON THE PM-2A REACTOR PRESSURE VESSEL UNDERGOING EMBRITTLEMENT STUDIES AT THE NATIONAL REACTOR TESTING STATION 5-12

PV C F BRAUN & CO

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1 INTRODUCTION

C F Braun & Co with United Nuclear Corporation as a principal subcontractor has been awarded a contract'1-) by the US Atomic Energy Commission for the development and verification of a Piping Design Guide for sodium-cooled fast breeder reactor power plants (LMFBR). The work is a Priority 1 Task under the LMFBR Program Plan'2) prepared for the USAEC Division of Reactor Development and Technology (RDT) by the LMFBR Program Office, Argonne National Laboratory. It is identified in the Program Plan as Task 3-8.2, Development of Design Technology for Piping. Technical Report 100, already issued under this contract, gives a detailed description of the work plan for the project.

Technical Report 214, "A Review of Piping Failure Experience," concluded that . . . . "Many of the failures reported in the literature studied might have been avoided - or at least detected before failure ensued - if adequate in-service surveillance methods had been in operation. The consequence of failure in the LMFBR are such that in-service surveillance becomes mandatory." Surveillance methods must therefore be given careful consideration due to its primary place in the safety of LMFBR systems.

The purpose of the study is to describe in-service surveillance requirements and compile information on the various types of surveillance methods. The study addresses itself to five areas of concern - sodium leak detection, pipe movement, alignment and vibration, material inspection, strain measurement and crack detection, and the logging of records.

Advantages and disadvantages of the various surveillance methods are outlined in the study and the applicability of each method is evaluated.

It is anticipated that the criteria developed in this Technical Report will be subject to revision and/or expansion as the work progresses. A review procedure has been established to ensure consistency between interdependent studies currently being performed under this and other task areas of the LMFBR Program Plan.

Under the review procedure, the Liquid Metal Engineering Center, (LMEC), is the corrdinating agency. Technical Reports prepared by Braun under this contract will be distributed by LMEC to appropriate Review Agencies designated by USAEC. Comments from Review Agencies will be evaluated to Braun to determine their validity. Valid comments will then be incorporated into subsequent revisions to the Technical Reports.

(1) AT(04-3)-781, AEC San Francisco Operation Office (SAN (2) Liquid Metal Fast Breeder Reactor Program Plan, LMFBR Program

Office, Argonne National Laboratory - AEC R&D Report, Reactor Technology, WASH-1101, August 1968

PV C F BRAUN & CO

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2 SODIUM LEAK DETECTION

2.1 GENERAL DISCUSSION

A literature search was conducted to determine the state-of-the-art on leak detection devices and methods. This survey was confined to the detection of sodium leaks, not to finding the exact location of a leak.

Although this survey was reasonably extensive, comparatively few published reports were found, thus limiting the information presented in this section. Most of the information was gathered from the references listed in two LMIC computer printouts on (1) leak detection instrumentation and (2) failure, crack propagation, and sodium leak detection. A sodium leak detection state-of-the-art study was conducted concurrently by LMEC and has also been used for reference (13). In some instances, the information has been from experience with liquid metal facilities.

Based on principle of operation, the various types of detectors are as follows.

1) Electrical resistance 2) Thermal 3) Optical 4) Radiation 5) Sodium level 6) Sodium chemistry

In the event of pipe failure, three major classes of leaks as related to size of hole or crack may be defined as follows.

1) Leak through a pin hole - hole is small enough to allow some of the surrounding air or gas to diffuse to the sodium but prevent any significant loss of sodium

2) Leak through a small hole or crack - characterized as an oozing or seeping rate of sodium flow

3) Leak through a large hole - characterized as a rapid or massive rate of sodium flow

A tabulation reflecting the application of the various types of detectors with respect to the type of pipe failure is presented in Table I.

This section has been divided into the following categories. Instrumentation, Design, Application, and Future Requirements. Within each category, attention is placed in the various types of leak detectors suitable for liquid sodium service.

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2.2 INSTRUMENTATION

2.2.1 ELECTRICAL RESISTANCE TYPE DETECTORS There are several detector designs based on changes in electrical resistance of the device, because of the presence of the leaking fluid. The first two designs described below are simple, inexpensive and respond to the presence of liquid sodium. The other designs respond directly to smoke (sodium oxide) and indirectly to smoke (sodium vapor or oxide is dissolved in water to form an electrolytic solution which is monitored for resistance changes).

One design is based on two wire-conductors strung through specially shaped ceramic beads. Refer to Figure 2.1(a), (b), and (c). These beads allow the leaking sodium to penetrate to the wires, thereby causing a short. Another design (manufactured by the Russell Manufacturing Co) is in the form of a tape made up of two wire conductors insulated from each other by a porous, woven, heat-resistant material. A good tape design should allow the leaking sodium to rapidly penetrate to the wires. These detectors are subject to malfunction because of their sensitivity to moisture and accidental short circuiting. They may also fail to function if leaking sodium does not flow directly onto the exposed wires. There are applications for which moisture is not a problem, e.g., in the annulus of double containment piping. The moisture interference problem might be overcome by improvements in detector design for application in which moisture might be encountered.

A detector design not applicable to liquid sodium as the above designs, is one which is classified as a smoke detector -manufactured by Pyrotechnics, a division of Baker Industries, Inc. This device uses the principle wherein air is made conductive by ionization from a minute source of radium. Two ionization chambers are used - one is open and the other is sealed. Products of combustion become ionized when they enter the open chamber but the ions being of larger size reduce current flow. With the outer chamber open to the air and the inner chamber sealed, any reduction of current in the open chamber increases the voltage at the trigger electrode, causing it to actuate the alarm. Refer to Figure 2.1(d).

Another resistance type detector, investigated by United Nuclear Corporation, depends on sodium vapor or smoke changing the electrical conductivity of water. Air or gas samples, drawn from the vicinity of the piping, is stripped of any sodium or sodium oxide by bubbling it through water which increases in conductivity. The conductivity of the water is compared continuously with the conductivity of water in an adjacent beaker through which there is no air or gas flow. Commercially available conductivity bridges can be used.(10)

The spark plug level detector is another resistance type suitable for limited applications when there are low points or wells on jacketed piping where sodium would collect in the event of a leak.

IV C F B R A U N &i CO

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2.2.2 THERMAL TYPE DETECTORS This type of detector is usually a thermocouple or similar temperature sensitive device that is installed in wells or chambers where leaking sodium could collect and be detected as a sudden temperature change. The temperature change is caused by a significant change in the thermal resistance of the thermocouple environment due to the presence of sodium.

10 STRAND NO. 30 GAGE CONSTANTAN CONDUCTORS

(a) Leak Detector Assembly Obtained from Reference 6

S/a n o J / 32 R.

9 / 6 4 -

—1/32 n

* * 1 ,1"

Mi

"*—*1—

;> ©5

t i

3/32" R.-I

7/32

5/64 DIA. HOLES

(b) Ceramic Bead Detail Obtained from Reference 6

' . FIGURE 2.1 ELECTRICAL RESISTANCE TYPE DETECTORS

IV C F BRAUN &. CO

I < •

' .

STRANDED #18

CHROMEL WIRES

FIBREFRAX OR GLASS WEAVE

(c) Leak D e t e c t i n g Tape Obta ined from Refe rence 1

111-,„: u

T 1 a o - p

BASIC CIRCUIT

A Alpha Source

An Anod*

n M l O Gm-r l l j (horq? Tub*

I l o r t . n q S^.|l

K C i fhodf

O Outrr ThnmU.

T f n - l r n l P n

R Alarm P. Iity

S SloitPr r i f r f m d r

W Innff , h * , , ! , , I|«

X Innnr Cliamljiir

DfTfCTOR HEAD

(d) Smoke D e t e c t o r Obta ined from R e f e r e n c e 2

2-4

FIGURE 2 . 1 ELECTRICAL RESISTANCE TYPE DETECTORS

C F BRAUN & CO

2-5

2.2.3 OPTICAL TYPE DETECTORS This detector is used in situations where sodium vapor escapes into an inert gas atmosphere or the escaping sodium comes in contact with air and reacts to produce smoke. The vapor or smoke fills a chamber passing a light beam from a low pressure sodium lamp. This beam, passing through the vapor or smoke is partially adsorbed or scattered and affects the photocell response. A reference beam path and light source are used as a self-checking system to differentiate between smoke or possible instrument faults when the alarm circuit is activated. Refer to Figure 2.2.

Another type of smoke detector is known as a flame photometer. Salts of sodium are easily ionized in a flame and emit light of specific wavelengths. The intensity of this light can be measured with a photocell behind filters specific for sodium. Refer to Figure 2.2.

2.2.4 RADIATION TYPE DETECTORS In nuclear applications where the sodium becomes radioactive, a leak could be readily detected by monitors responding to radioactivity. The principle of operation for one type of unit, Model 900-56 manufactured by the Victoreen Instrument Co, is based on the adsorption of particles of radioactive matter, such as sodium oxides, on a roll of filter paper. A fan forces the gas through this filter which in turn is continuously advanced and monitored for radioactivity levels. An alarm is activated when the preset level is exceeded. The example given has a probe for alphas and betas as well as for gammas, and has the additional advantage of collecting particulate matter. This is a standard procedure for detecting radioactive particles in gas streams.

2.2.5 LEVEL TYPE DETECTORS These detectors would be used to monitor physical changes in a system such as liquid level. The usual liquid level detectors are contact (spark plug) probes, thermocouples, inductance probes, or resistance probes. Refer to Figure 2.3.

2.2.6 SODIUM CHEMISTRY DETECTORS If a leak develops in a sodium loop which is exposed to air or moisture, the oxygen impurity level increases. The higher oxygen content can be detected in principle with detectors which measure oxygen, directly or indirectly, in sodium. Direct measurements are obtained with the Liquid Metal Oxygen Meter, indirect measurements are obtained with Rhometers and plugging meters. Refer to Figure 2.4. The usefulness of these instruments depends on the size of leak to be detected, the sodium inventory in the system, etc.

IV C F BRAUN & CO

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' . 2.3 OPERATING CRITERIA

2.3.1 ELECTRICAL RESISTANCE TYPE DETECTORS The two-wire ceramic-bead detectors can have response times as low as a few seconds. This type of detector is one of the best developed to date. It can be placed against a pipe or over electrical heaters because of insensitivity to high temperatures. There are several factors that limit the success of this detector - poor wetting of conductors (temperatures above 300 C usually cause no delay in wetting) - false alarm from accidental shifting of conductors - wide spacing reduces this possibility but if too wide, the response time and sensitivity are adversely affected.

- MANUAL -CHECK

UNIT

ALARM

I

1

ALARM UNIT

D E T E C T O R UNIT

S E L F CHECK SIGNAL

A _ R E F CHECK BEAM PATH

Na L A M P

D E T E C T O R BEAM

-. L O O P A T M O S P H E R E r CdS D E T E C T O R

ROTARY SOLENOID

WHITE LIGHT CHECKING L A M P

I FIGURE 2 . 2 OPTICAL SMOKE DETECTOR

Obtained from Reference 5

IV C F BRAUN & CO

2-7

(a) Liquid Level Detectors Obtained from Reference 2

TO RECEIVER

4 INSULATED, GASTIGHT TERMINALS

-LIQUID METAL

(b) Resistance Type Liquid Level Probe Obtained from Reference 2

FIGURE 2.3 LEVEL TYPE DETECTORS

C F B R A U N &. CO

2-8

1600 CPS POWER SUPPLY

DEMODULATOR

HAND PROBE

DC VOLTMETER

I i I i t i

RELAY

t i t i i i

CHOPPER

SERVO AMPLIFIER

SERVO MOTOR

HI-LO ALARM

CONTINUOUS PROBE

(c) MSAR Induction Probe Obtained from Reference 4

FIGURE 2.3 LEVEL TYPE DETECTORS

' .

C F BRAUN & CO

2-9

(a) Liquid Metal Oxygen Meter Electrode

FIGURE 2.4 SODIUM CHEMISTRY DETECTORS

C F B R A U N & CO

2-10

SODIUM "INLET

THERMOCOUPLE WELL

(b) HNPF PLUGGING METER (Hoschouer, W M, et, al, Design and Thermal Analysis of Sodium Specialties Components for HNPF, NAA-SR-5445, February 1961)

FIGURE 2.4 SODIUM CHEMISTRY DETECTORS

C F B R A U N & CO

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2.3.1 ELECTRICAL RESISTANCE TYPE DETECTORS Continued

Detoured leak - leak may never follow the path to the detector since pipe orientation, shape, and lagging may cause a detour around the detector.(3)

Detectors in the form of woven tapes, carrying two wires have been used with limited success. They have been made to respond fairly well when high voltages are applied between the conductors. The major problem hindering good operation stems from lack of penetration of sodium through the tape insulation. This is especially evident at lower sodium temperatures (<450 C). Use of a more open weave for the insulation and high voltages have improved the efficiency of this type of detector.(1)(3)

The smoke and vapor detector based on the conductivity bridge can be operated remotely and continuously. At a gas flow rate of 1.0 cfh and a sodium concentration of 2 micrograms/liter of gas, a signal would result after 5 minutes of gas sampling.

2.3.2 THERMAL TYPE DETECTORS These detectors are usually thermocouples. No mention of operating criteria was available from the literature. Maximum operating temperatures would correspond to that allowable for the specific thermocouple design.

2.3.3 OPTICAL TYPE DETECTORS The limiting bulk sensitivity is 75 x 10~6 g/irr for smoke and 1.5 x 10 - 3 g/m for sodium vapor. Reference 5. Functions reliably and well with good response time and sensitivity in immediate vicinity of detecting beam. The flame photometer type detector has a limit of 10 x 10"^ g/m3 for sodium vapor or smoke.(5) It is insensitive to smoke and vapors arising from contamination of outside of newly heated sodium installations.

2.3.4 RADIATION TYPE DETECTORS Detects alpha, beta, and gamma radiation. Sensitivity - minimum detectible concentration of 7 x 10~12 curie/m3 (air flow - 10'3/min. and l"/hour filter tape speed). Filter tape 3 inches wide by 300 feet long.

2.3.5 LEVEL TYPE DETECTORS Resistance type probe is difficult to balance and requires wetting of probe. Maximum operating temperature of probe is 1600 F. Induction probe can be made with a * 1/8 inch sensitivity.

Maximum operating temperature of probe is 1200 F. Primary difficulty with the operation of resistance and contact probes is the tendency of sodium to adhere to the probe when the level changes.(4)(5)


2-12

2.3.6 SODIUM CHEMISTRY TYPE DETECTORS There have been numerous instances, not well reported in the literature, of small leaks in alkali metal systems in which the fact that there was a leak and its location was only established after insulation was removed from a component or piping. In many of these instances, a leak was suspected by abnormal system behavior which could be related to increased oxygen levels. An example is to be found in NASA-AEC Liquid Metal Corrosion Meeting, Vol. I, NASA SP-41, 1963, Page 214, Item 17. In this instance a potassium leak was detected by weight measurements of corrosion tabs (a higher weight loss due to oxygen in the potassium). The fact that there was a potassium leak was confirmed by the presence of potassium in a localized area on the external surface of the pipe after removal of insulation. The leak to the outside environment was self-sealing. (The leakage path was never identified.) Oxygen diffused through the leakage path to the potassium inside the loop via an activity gradient (partial pressure of oxygen) even though the total pressure differential would have favored flow in the opposite direction. An example of a leak being detected by a Liquid Metal Oxygen Meter has been reported by R. B. Hand, Nuclear Systems Programs Missile and Space Division, General Electric Company, Cincinnati, Ohio.

In situations where oxygen can leak into sodium, there are several types of detectors available. These detectors (namely, plugging indicators, rhometers, and liquid metal oxygen meters) respond to changes in sodium oxygen level.

The response times in systems containing relatively small quantities of sodium is good, whereas for systems containing large sodium quantities the response time would be poor. It is beyond the scope of this section to cover the operating characteristics of these instruments in detail. (3)(4)

2.4 APPLICATION

Some typical installation of the two-wire resistance type of detectors using ceramic beads are shown on Figure 2.5. The piping itself is not affected by the detector installation. The two-wire tape detectors probably could be installed similarly to the ceramic bead type.

The thermal or thermocouple type of detectors usually are installed in some sort of well, used for collecting leaking sodium, or in a penetration through the loop, surge or expansion tank section.

The optical or smoke detectors (refer to Figure 2.2) could be installed adjacent to the piping or at the outlet of a ventilation duct. A typical length between light source and detector is about 20 inches. With a large complex loop, ventilation air or gas could be blown over the pipe and into a remote cubicle thus monitoring a large area.

IV C F BRAUN & CO

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OF PIPE

3/8" THERMOFLEX RF-1400

CALROD AND SHIELD

U-61

-CERAMIC BEADS

LK-81 PLUG \

SUMP DETAIL ^ COVERING

(a) Installation of Two Wire Ceramic Bead Insulated Detector in Collection Cavity

Obtained from Reference 8

SODIUM AT 350 F, 50 psig

COVERING:

STAINLESS STEEL FOIL (0.005") THERMOFLEX RF-1400 (3 LAYERS METAL SHEATH (0.012")

3 ' -0" APPROX

3 /8" THICK

(b) I n s t a l l a t i o n of Two Wire Ceramic Bead I n s u l a t e d R e s i s t a n c e Type D e t e c t o r - Ob ta ined from R e f e r e n c e 8

FIGURE 2 . 5 INSTALLATION OF RESISTANCE TYPE DETECTORS

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2.4 APPLICATION Continued

In the case of a flame photometer, sampling from several points is allowed for a single installation.

An ideal location for radiation type detectors is the outlet duct for ventilation systems which are generally used for primary system pipe galleries or cubicles. The suction for the radiation detector can be taken from several ducts, if desired. For double containment pipe systems, the suction is taken from the space between pipes, and some make up gas must be provided. The liquid metal oxygen meter, plugging indicator, and rhometer (refer to Figure 2.4) may be installed in a branch line.

2.5 FUTURE REQUIREMENTS

Published literature on detectors and the methods of detecting leaks is presently limited, as revealed during this survey. If new, better performing devices are developed, some emphasis should be given to publishing this information in sufficient detail. More performance and design information is desirable on present-day detectors.

The complex devices have possibilities of improvement and reduction of manufacturing costs. Simple devices like single or double wire resistance detectors and level detectors can not be reduced in cost very much but optimum design specification and standards of construction would be valuable. These simple detectors should be optimized with regard to sensitivity, response time, and reliability. Correlation with more data is required before this can be accomplished.

Based on this survey, efforts toward the following are considered useful for the advancement of sodium leak detection.

1) Development of simple, inexpensive detectors which would be more effective on vertical piping. Detection of leaks on vertical piping is a unique problem because the leaking sodium drains away from the leakage site. The simple resistance type detectors would function at the bottom of the vertical run of pipe, but would not indicate the leak location.

2) Improve the response time and reliability of present detectors.

3) Define and publish design standards after various designs are optimized.

C F BRAUN & CO

r DETECTOR

Type of Detector

Electric Resistance

a) 2 Wires b) Smoke Detector

Thermal

Optical

a) Vapor Detector b) Smoke Detector

Radiation

Sodium Level

Sodium Chemistry

a) Rhometer b) Plugging Meter c) Oxygen Meter

LEGEND Type of Leaks

Effectiveness

Doubl<

TABLE

EFFECTIVENESS

2 Containment Inert Gas in

PH

P NA

P

P NA

P

P

NA NA NA

- PH -

SC -

LH -

G -

P -

NA -

SC

G NA

P

G NA

G

P

NA NA NA

Annulus

LH

G NA

G

G NA

G

G

NA NA NA

FOR

Pin Hole _ Essent.

Small

Large

Good

Poor

Crack -

Hole -

response

to no re

Sod.

I

VARIOUS

Single Inert

PH

P NA

P

P NA

P

P

NA NA NA

Lally no

Lum can

PIPE FAILURES

Containment Gas Ambient

SC

G NA

P

G NA

G

P

NA NA NA

LH

G NA

G

G NA

G

G

NA NA NA

sodium escape seep

Rapid or massive

to

spon

Not applicable

=e to sodium

out

Single Containment Air Ambient

PH

P P

P

P P

P

P

(

( (

leak can occur

leakage

SC

P G

P

NA P G

G

P

See text

LH

G G

G

NA G

G

G

)

)

)

3-1

3 PIPE MOVEMENT, ALIGNMENT AND VIBRATION


In-service inspection of pipe movement, alignment and vibration includes all methods of measurement that can be used advantageously to inspect the operating behavior of an LMFBR piping system. In-service inspection will be required to monitor the following criteria.

1) Verification of pipe movement predicted by flexibility analysis.

2) Assurance that there is no interference between piping components and structures.

3) Assurance that pipe supports function properly over all system loading conditions.

4) Assurance that sliding supports function properly.

5) Assurance that there is no excessive vibration.

3.2 VISUAL INSPECTION

Visual inspection is undoubtedly the oldest method of in-service inspection and can be considered an indispensable tool. To aid the naked eye, borescopes, periscopes, telescopes, binoculars, and mirrors are all commonly used. Television and photography can be used remotely. Fiber optics can be used to enhance the viewing ability of both the television camera and the human eye. Where it is possible, visual methods will be used to detect and locate any cracks, etcetera, that may cause leaks or system failure.

3.2.1 LIMITATIONS There are two severe handicaps to all visual inspection methods in an operating LMFBR system. The use of insulation, annular heating systems, or double containment will prevent examination of the pipe surface. Secondly, the presence of high temperature and radiation levels, in the primary piping system, will limit or exclude human access and will severely limit the inspection techniques used.

Even when these techniques are used under favorable conditions, they are only good enough to detect relatively large defects. For these reasons visual methods will probably only be used to supplement other more reliable methods.

*S7T C F BRAUN & CO

1 3-2

« . 3.3 CLOSED CIRCUIT TELEVISION

Closed circuit television cameras have been successfully used in the past for visual monitoring purposes. See Figure 3.1 below. This method is especially valuable within confined areas of the piping system, where accessibility is limited. Closed circuit television cameras when used in conjunction with telescopes, periscopes, borescopes, and fiber optics becomes even more versatile and offers the engineer a means for the continuous monitoring of a LMFBR system.

,; .M-ii

FIGURE 3.1

Heavy duty television camera installation


3-3

3.3 CLOSED CIRCUIT TELEVISION Continued

Television has the following advantages.

1) The quality of the image is not affected by the distance between the component to be viewed and the viewer.

2) Television cameras can be manufactured as small as 3 inches in diameter, overall.

3) Several people can view the subjects simultaneously.

4) Viewers can be removed from the reactor and out of radioactive areas.

5) Radiation-tolerant cameras are currently available which are rated to a cumulative dosage of 10^ R and 10^-2/cm2 neutrons. (14)

6) Television cameras can be located to observe individual components such as a mixing tee, or to observe the overall condition of the piping and other components by scanning a large area.

Television has the following disadvantages.

1) The components in the camera generally limit the operating temperature to less than 150 F. However, it is possible to provide local cooling systems for the cameras in order to maintain acceptable temperatures.

2) Television camera tubes are degraded with exposure to radiation and require periodic replacement.

3) Television only applies in transparent media.

The technique of applying closed circuit television to monitor operation of remote equipment is very well developed. Television offers the engineer a practical method of periodic or continuous inspection of areas or individual components. Areas of limited accessibility can also be inspected readily with the use of television, This type of inspection can be utilized to detect major and many types of minor damage.

IV C F BRAUN & CO

I 3-4

3.4 TELESCOPES, PERISCOPES, BORESCOPES, AND MIRRORS

Optical telescopes, periscopes, and borescopes have been commonly used for visual monitoring in the past. These methods are especially valuable within confined areas of the piping system, where accessibility is limited.

Telescopes, periscopes, borescopes, and mirrors have the following advantages.

1) They provide a method of observation for such things as pipe support settings, pipe displacement, etcetera.

2) Still cameras can be used in conjunction with closed circuit television for obtaining permanent records.

3) Remote maintenance of monitoring equipment may be accomplished by overhead cranes with manipulation devices capable of such operations as repairing electrical connections or removing faulty equipment. A three-dimensional periscopic viewing system could permit the crane operator to observe his work at close range.

Telescopes, periscopes, borescopes, and mirrors have the following disadvantages.

1) Radiation exposure over a period of time darkens the lenses and impairs viewing capacity.

2) These methods are limited to operation in a transparent medium and therefore are not usable in a complete sodium environment as would be found in the pool-type reactor concept.

3) The lenses must be periodically cleaned before use.

The use of telescopes, periscopes, borescopes, and mirrors appear to be good aids to visual in-service monitoring of LMFBR piping systems.

3.5 FIBER OPTICS

This method of visual inspection works on the principle that light can be conducted by multiple internal reflections within a fiber of glass or other transparent medium. By assembling a bundle of transparent fibers in a systematic array, with the identical fiber arrangement at both ends of the bundle, an image can be transported from one end face to the other.

-fcScr C F B R A U N & CO

3-5

3.5 FIBER OPTICS Continued

The transport of images by flexible fiber bundles permits visual inspection of enclosed areas. See Figure 3.2.

Fiber optics has the following advantages.

1) It can be installed beneath insulation and heating systems.

2) It can be used with television cameras or motion picture cameras.

3) It can be designed to view large or small areas.

4) It can be designed to accommodate the LMFBR temperatures.

Fiber optics has the following disadvantages.

1) The size of the fiber limits the size of the smallest image which can be resolved. (27)

2) The maximum length of a fiber bundle is approximately 25 to 30 feet.

3) Long bundles create many fabrication problems.

4) In a high radiation environment, radiation browning occurs, making it necessary to replace the bundle.

The technique of fiber optics for LMFBR system monitoring is believed to be sufficiently well developed for application. When combined with closed circuit television cameras, it presents a valuable tool for viewing components within confined areas. Further investigation and documentation will be required to establish the life expectancy of such a system when exposed to LMFBR environmental conditions.

iSa-C F BRAIN & CO

I 3 - 6

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i.rirfe*- * !•

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FIGURE 3.2

Articulatable fiberscope for inspecting remote areas around nuclear reactors. The fiber bundle is 12 1/2 feet long and has an 8 x 10 format. This device features a replaceable fiber bundle when the original becomes too absorbing due to radiation browning. (Obtained from Reference 27)

C F B R A U N & CO

V 3-7

3.6 PIPE DISPLACEMENT INSTRUMENTATION

Due to the wide temperature range and high temperatures at which LMFBR systems operate, the piping is subject to considerable amounts of thermal expansion. Measurements of piping displacement are required at selected points to monitor stresses due to differential expansion, and to check for interference between piping and other structures.

These measurements can be made by commercially available displacement transmitters mounted on a stationary base. Applicable instrumentation could include dial indicators, electric contacts (microswitches), displacement transducers using induction coils, resistance sliding-wire strain gages, and mechanical linkages. The displacement signals can be indicated on a control console and combined with an alarm system.

-LSa-C F BRA IN & CO

4-1

4 MATERIALS INSPECTION


This section presents a summary of the methods, systems, and test specimen designs and evaluation procedures which may be used to monitor the effects of LMFBR environments on pipe materials.

The generally accepted approach to the in-service surveillance of the effects of nuclear reactor environments on materials of construction involves the periodic evaluation of specimens placed into such systems at representative locations. The data obtained during these periodic inspections and tests are used to monitor changes in mechanical properties and ascertain the incidence of corrosion attacks on specimens. Evaluation of such results is used to review the validity of design parameters and possible consequences affecting the integrity and life of the reactor system.

The incorporation of in-service test specimens to permit periodic inspection and evaluation of the effects of reactor environment on material properties has proved to be the primary technique for monitoring such developments. The limitations for access to nuclear reactor systems following the start of operation has been apparent since their inception even for water systems. Additional requirements for sodium systems, such as all welded connections, double containment etc, provide further limitations to access for inspection.

The candidate materials for the LMFBR piping which have been selected under Task 100, Technical Report 110, are Type 304 and Type 316 stainless steels, and 2 1/4 percent chromium, 1 percent molybdenum, (2 1/4 Cr 1 Mo) steel.

The anticipated environmental effects on these steels, particularly those of sodium and its contaminants, have been described in Technical Report 228 and have been quantitatively defined under Task 316. Allowable strength properties are being established in Task 315. One important aspect of the materials inspection program is to assure that strength properties are not degraded below the established design limits due to exposure to the coolant system environment. While this section deals mainly with pipe material specimens, a brief discussion on sodium purity monitors has been included at the end of this section. Changes in sodium purity can have a significant effect on corrosion and strength properties.

PV C F BRAUN & CO

4-2

4.2 INSPECTION METHODS

The basic function of the pipe material inspection program is the insertion of a series of specimens into the primary and secondary sodium system piping to allow the monitoring of the effect of reactor coolant environment on the materials. Specimens representing various material compositions and heats used in construction of the installation are mounted for immersion into the coolant flow. At predetermined intervals some specimens are removed for testing and evaluation. If the examination is nondestructive, specimens may be returned for further exposure. New replacement samples may be inserted to replace those taken out for testing. It is essential to provide a sufficient number of specimens to assure comprehensive data, and in particular, for long term exposure in view of the life cycle projected for LMFBR (30 years). It is of equal or perhaps greater importance to include spare specimens for examination following plant excursions, incidents, and abnormalities in operation.

Precautions which are essential to prevent contamination of sodium and specimens require the use of sophisticated techniques for the insertion and removal of material test specimens. Two'basic systems for material inspection may be employed in the various experimental and reactor installation, that is, the bypass loop and direct insertion.

4.2.1 BYPASS SYSTEM The bypass system, as implied by its designation, utilizes an auxiliary loop to the primary or secondary system pipe. The location of such loops coincides with the test sites chosen to represent various environmental conditions.

A schematic diagram of one such bypass system, example, the Tab Exposure Facility (TEF) for SRE-PEP (45) is shown in Figure 4.1. A detailed view of a specimen holding fixture from the SRE, which also includes a sodium sample cup, is shown in Figure 4.2 (46).

The TEF was connected to the hot trap system to permit exposure of various alloy tab specimens at 1200 F in primary sodium. It consists of a tee section in a bypass loop to the hot trap inlet piping. A pipe extension to the tee section leads upward through the vault shielc blocks to facilitate direct access to the loop with protection against incident radiation. The specimens (tabs) are placed in a basket attached to the end of a hanger rod which extends down the pipe into the tee and the sodium flow. The tabs are dimpled in such a fashion that sodium flowing through the basket reaches all tab surfaces. Valves and freeze sections are located at the inlet and outlet of the loop. A gas cooled freeze seal and kerosene coolout coils are positioned around the pipe extension to provide a frozen sodium seal. A shielded gas lock assembly, including a purge vent line and a gate valve, are located outside the vault shield blocks.

IV C F BRAUN & CO

•dh

J<-

WILSON SEAL

PURGE-VENT LINE

SHIELDING

VACUUM TYPE GATE VALVE • 3 in.

FLANGE ADAPTER

PIPE EXTENSION

SSV BLOCKS

SAMPLE HANGER ROD • SECTIONED 6 PLACES

KEROSENE COOLING COILS

FREEZE SEAL, GAS COOLED

SAMPLE HOLDER DISCONNECT

SAMPLE TABS

EXPOSUhE TEE

Figure 4.1 Tab Exposure Facility in SRE-PEP Obtained from Reference (45)

4 - 4

LINER •

HIGH DENSITY CONCRETE

'\

•77.

RING

•SHIELD PLUG

WIRE SCREEN-

SAMPLE HOLDER

METAL SAMPLE-

SPINOLE ASSEMBLY

WIRE BASKET-

HEUUM LINE

FREEZE PLUG ASSEMBLY

— TETRALIN COOLANT LINE

PLUG HOUSING

CORROSION RESISTENT STEEL WOOL

HOUSING

SAMPLER ASSEMBLY (CLOSED)

SODIUM SAMPLE

Figure 4.2 Materials Evaluation Facility Assembly, Interior View of Specimen Holding Fixture

Obtained from Reference (46)

C F B R A U N & CO

4-5

4.2.1 BY-PASS SYSTEM Continued

To remove specimens following exposure, the inlet and outlet valves are closed to exclude sodium flow from the loop. Sodium in the TEF loop is cooled and frozen. The frozen sodium seal around the hanger rod and specimens is then melted to allow their retraction into the gas lock assembly and subsequent removal from the system. Generally, this loop design was found to operate successfully. However, some difficulty with proper sealing causing carry-over of radioactive sodium was encounted and modifications in the design were recommended.

One of the advantages of by-pass systems is the ability to isolate the test loop while continuing operation of the primary or secondary system. Sodium velocity and temperature through the test loop can be controlled to be the same as that of the main coolant flow. However, auxiliary heating along the auxiliary loop may be required to maintain constant temperature if the loop has long piping runs. Since practical considerations limit the diameter of auxiliary loop piping, the Reynolds number at the specimen chamber will not be the same as in the main coolant pipe'. In addition the length and configuration of such loops preclude evaluation of downstream effects.

4.2.2 DIRECT INSERTION INTO MAIN PIPING In order to be representative of Reynolds number and downstream effects, materials specimens should be placed directly into the main coolant pipe. A specimen insertion and removal chamber should be welded to the main piping at the desired test location. Appropriate valves and vacuum and gas connections must be provided to allow isolation of the system following retraction of the test specimens and permit their removal. The insertion mechanism, specimen racks and specimen hold down clamps must be designed to withstand coolant flow induced stresses at operating temperature for the indicated time period. The specimens should not impede the flow to such an extent as to cause an excessive pressure drop.

Our literature search, which was aided by LMIC, has not uncovered any instances where this approach was actually used in power plant size systems.

4.3 TEST SCOPE

The basic premise of surveillance programs is to provide a means for direct comparison of LMFBR environmental effects on materials of construction. To assure the validity of test data obtained during such programs it is important that all the essential elements of the test be representative of actual conditions. Exposure time, ambient temperature and coolant chemistry to which the specimens are subject must be representative of the condition within the main piping loops.

W C F BRA UN & CO

4-6

4.3 TEST SCOPE Continued

It is only under such conditions that the resulting data can be employed to extrapolate the validation of design parameters and operating life of the systems.

In order to minimize interference with the operating efficiency of the power plant, specimen removal may be scheduled to coincide with reactor shut-downs or refueling periods at intervals of 20,000 hours or longer. It is desirable however, to obtain initial data at more frequent intervals, especially during and after system start-up to establish trends. Examinations of primary system specimens prior to nuclear operations would be particularly advisable to evaluate the effects of the initial charge of sodium on the loop before the specified operating purity level is established. The longer intervals during normal operation are justified on the basis that the expected environmental effects will exhibit relatively slow rates. If, however, the initial trends show unexpectedly high rates, or if sodium purity monitors show a purity excursion beyond preset limits, an earlier examination may be indicated. In this respect, bypass systems provide an advantage, in that they can be readily isolated for specimen removal while continuing reactor operation.

Potential material problems, for which inspection programs provide essential data, center about surface attack on piping materials, modification of base metal composition by the reactor environment, metallurgical aging effects which effect the mechanical properties of the materials and surface deposits.

1) Surface Attack - surface removal data as related to the adequacy of the corrosion allowance which is used in design to determine piping wall thickness.

2) Altered Composition - formation of hard or soft layers caused by either addition or depletion of carbon, or nitrogen, or the leaching of chromium nickel, or other alloying elements from the pipewall surfaces. Such layers can produce changes in fatigue and impact strength. Overall changes in composition could cause significant changes in mechanical strength.

3) Surface Deposits - deposition of radioactive isotopes on piping walls.

IV C F BRAl'N & CO

4-7

4.4 TEST SPECIMENS

4.4.1 MATERIAL Test specimens should be fabricated from material including at least one heat of alloy used in construction of the particular system. Preferably all heats of material used in the installation should be represented. A specimen of welds from each type of filler metal composition and welding process employed plus samples matching the maximum and minimum weld thickness should be prepared. For each weld sample sufficient material should be included to incorporate the heat-affected zones and the start of unaffected base metal. Welds corresponding to dissimilar metal joints should be included in the program for insertion into the applicable piping run.

Material used for specimens shall have been subjected to the same, or at least representative fabrication history. Fabrication procedures such as forming operations, heat-treatments, cold work, pre-and post-weld heat treatments performed on specimens shall be the same or sufficiently similar to produce representative properties and micro-structures. Fabrication history, alloy chemistry, base mechanical properties and micro-structure for all material should be documented in detail.

4.4.2 SPECIMEN DESIGNS In general, specimen configuration following ASTM, RDT, and other applicable standards should be used.

1) Specimens for corrosion evaluation and micro-structure analysis could be coupons of suitable dimensions.

2) Material in raw form should be provided to permit machining of tensile, impact, creep and creep-rupture specimens following removal from the test environment.

3) Machined tensile and creep test specimens should be provided to permit direct testing following removal from the piping system.

4.4.3 NUMBER OF SPECIMENS A sufficient number of test specimens should be provided to give assurance of data validity and full characterization of results. ASTM Specification E 185 recommends at least 8 impact specimens and 2 tensile specimens in order to characterize base properties. The following are the minimum number of specimens recommended for test evaluation following each exposure for each variable.

1) Three (3) tensile test samples 2) Eight (8) impact test samples 3) Two (2) coupons for corrosion and metallographic

evaluation

IV C F BRAUN & CO

4-8

4.4.4 SPECIMEN EVALUATION The limited number of specimens which can be accommodated in any installation require full utilization of available material to maximize resultant data.

Coupons for evaluation of corrosion should be visually examined for surface attack or deposition of films or coatings. All samples should be weighed to ascertain gain or loss. Accepted cleaning procedures, preferably ASTM and RDT standards should be followed. ASTM Committee G-l, Sub VIII, Group B is working on recommended practices for preparing, cleaning, and evaluating corrosion test specimens.

Test coupons should be examined for changes in micro-structures in both the longitudinal and transverse direction.

Tensile and impact specimens should be machined from material provided for testing. All mechanical property tests should be conducted in a standard manner.

Chemical analysis can be used to establish changes in composition of surface layers and base material. More sophisticated test analysis can be employed to identify unusual deposits. Electron beam micro-probe analysis and X-ray diffraction are used to identify impurities and micro-structural constituents. Gamma spectroscopy and radiochemical separation are utilized to check for and identify radioactive isotopes. Low level impurities can be ascertained by emission spectroscopy.

4.5 SODIUM PURITY

The requirement of sodium purity monitoring is not unique to pipe systems. Impurities in sodium can have large effects on corrosion and mass transfer and must, therefore, be monitored continuously to assure satisfactory performance of all components in a sodium coolant system. Purity indicators are generally located in small diameter branch lines. Commonly used instruments are plugging meters, rhometers, oxygen meters, and hydrogen meters. Other instruments such as carbon meters are under development. In addition to metering devices, sodium samples should be removed periodically for analysis. It is considered beyond the scope of this report to cover sodium purity indicators in detail.

PV C F BRAIN & CO

5-1

5 STRAIN MEASUREMENT AND CRACK DETECTION INSTRUMENTATION


5.1.1 SCOPE This section covers those surveillance methods that may be used to monitor a piping system or component for incipent crack detection and microstrain measurement during plant operation. However, the strain and crack detection equipment discussed in this section will require further research and development if they are to withstand the most severe environmental conditions of primary and secondary LMFBR systems.

5.1.2 REQUIREMENTS The primary requirement for an LMFBR in-service surveillance system is the ability to operate for extended periods of time under the required environmental conditions. It would be highly desirable to have a surveillance system that would have the same life expectancy as that of the plant (30 years). Such a requirement is at present unattainable because equipment having the necessary reliability under LMFBR service conditions has not yet been developed. Therefore, a surveillance system will be considered satisfactory if it will perform for approximately one year without the need for repair or replacement. If it is determined that one year is too short a time span between planned shutdowns, the life expectancy requirement must be re-evaluated.

The maximum operating temperature for which an LMFBR surveillance system may be designed to operate is 1200 F. However, for some systems the design temperature may be much lower.

The monitoring system for primary coolant piping must be capable of withstanding LMFBR radiation levels. Additionally, for insulated piping it must be able to function beneath the insulation. It must be unaffected by the preheating system where one is employed. Satisfactory bonding techniques must be used that do not cause unacceptable reinforcement or gross discontinuities. And the system should not add restraint to the piping system.

Other requirements are as follows.

1) Must be unaffected by vibration

2) Must be unaffected by changing temperatures

3) Must not be affected by the background noise of the reactor operations or process fluid flows

PV C F B R A U N &: CO

5-2

5.1.3 MATERIAL FLAWS AND DEFECTS It is very important that all material, manufacturing, and installation defects be detected and corrected as early as possible, preferably prior to plant operation. It is considerably easier, less time consuming, and cheaper to detect defects at the factory or jobsite prior to plant operation than to rely upon inspection methods that suffer the handicap of operating under LMFBR environmental conditions. Every effort must therefore be expended to ensure that all materials, components and assemblies are virtually flawless and meet all quality control requirements. However, even the highest quality control will not eliminate the need for in-service inspection of the LMFBR piping system, since defects and flaws small enough to be initially acceptable or undetectable may later propagate under LMFBR operating stresses.

5.2 STRAIN GAGES

A common method for measuring or detecting strain is the use of electrical strain transducers. A strain transducer is an instrument that will translate a small change in dimension into an equivalent change in electrical characteristic. The major types of electrical strain transducers are variable resistance, variable capacitance, variable inductance, and piezoresistive.

5.2.1 VARIABLE RESISTANCE TRANSDUCERS . There are three variable resistance strain transducers in common use.

1) RESISTANCE STRAIN GAGE This gage is the most widely used strain measurement device in industry today. It has been utilized to measure displacement, pressure, friction, torque, and acceleration in a variety of situations.

2) POTENTIOMETER STRAIN GAGE This type of gage uses potentiometers for the mechanical to electrical conversion. It is useful for measuring expansion, contraction, tilt, and vibration. A potentiometer strain gage due to its physical construction has inherently low frequency response.

3) FATIGUE GAGE This gage can be used to predict the fatigue life of the component that the gage is attached to. A comprehensive calibration program is required for application to the particular stress field encountered to assure an acceptable reliability. These gages can detect crack initiation, if the crack is large enough to cause the gage to open, or cause the gage to undergo a marked change in gage resistance.

For further information on gage description, bonding techniques and advantages, disadvantages, and applicability as related to an LMFBR piping system, refer to Technical Report 234, "A Study of Model Test Methods as Related to LMFBR Piping Systems."

IV C F BRAUN &. CO

5-3

5.2.1 VARIABLE RESISTANCE TRANSDUCERS Continued

The overall applicability of variable resistance transducers for use as in-service detection devices in an LMFBR piping system appears to be poor, unless units can be successfully developed to withstand the high temperatures and radiation levels associated with LMFBR primary and secondary piping systems.

Several interested organizations, including most of the major strain gage manufacturers, and the Liquid Metal Engineering Center, (LMEC) are now working toward the development of a gage that will be operable for extended periods of time at temperatures up to 1200 F. Hopefully, this program will result in a strain gage that can be utilized for LMFBR in-service surveillance. At the present time, however, variable resistance transducers are not applicable for LMFBR use at temperatures above about 600 F.

5.2.2 VARIABLE CAPACITANCE STRAIN GAGE The variable capacitor strain gage is used basically as a displacement sensitive device. The electrical output of this type of strain gage varies in proportion to the change in the gage's capacitance. At present, capacitance strain gages have been designed to withstand temperatures up to 1500 F. (19) However, these gages cannot withstand this temperature for extended periods of time. The manufacturers are also not claiming these gages to be radiation resistant. For further information, refer to References 15, 19, and 21.

The applicability of capacitance strain gages to measure displacement and vibration in the primary and secondary coolant piping is considered potentially to be good. Solutions to the life expectancy and radiation problems, however, must be found.

5.2.3 VARIABLE INDUCTANCE STRAIN GAGE The variable inductance type of strain gage measures shock and vibration. This gage is an electromechanical device in which the magnetic characteristics of its circuitry changes proportionally to the motion of the object to which the gage is mounted. The variable inductance gages are extremely stable and can be used where precise measurements are required.

Different types of inductive gages and their various applications appear in THE SHOCK AND VIBRATION HANDBOOK. (41)

At present, variable inductance strain gages have little or no applicability for in-service surveillance of LMFBR primary loop piping. This limitation of their applicability is due mainly to their inability to withstand long term exposure at LMFBR environmental conditions.

PV C F BRAUN & CO

5-4

5.2.4 PIEZORESISTIVE STRAIN GAGE This type of strain gage is composed of a semi-conductor crystal material. As the gage is subjected to compressive or tension forces, the crystal undergoes changes in its electrical resistance. The crystal resistance can vary either positively or negatively, depending on whether the crystal is under a compressive or tensile force. The primary advantage of piezoresistive strain gages is their very high sensitivity to small displacement changes in the material being measured.

For further information on piezoresistive strain gages and their advantages and disadvantages in respect to LMFBR applications, refer to References 14, 16, and 21.

The inability of piezoresistive strain gages to withstand the environmental conditions of the LMFBR for extended periods of time severely limits their applicability at present.

5.3 PHOTOELASTIC COATING

This method of strain measurement involves the coating of the actual component under investigation with a photoelastic material which, under load, displays a characteristic fringe pattern when viewed in polarized light. Primarily a design tool, photoelastic coatings have been used during actual operating conditions to study stress distributions in complex structures. For further information, refer to Technical Report 234, "A Study of Model Test Methods as Related to LMFBR Piping Systems."

Photoelastic coating methods are of little or no use for LMFBR monitoring. They are limited to a maximum temperature of approximately 250 F.

5.4 HOLOGRAPHY

The holographic technique, employing a coherent monochromatic light source in association with appropriate optics, records phases and amplitudes of light reflected from an object to a photographic film. By a reconstruction process, it is possible to reproduce a total three dimensional image of the object being studied. Refer to Figure 5.1. With the advent of lasers as a source of monochromatic coherent light, holography has become of practical interest for determining strains and the location of crack-like flaws both internal and external on objects under examination. For further information, refer to Technical Report 234, "A Study of Model Test Methods as Related to LMFBR Piping Systems."

VD C F BRAUN & CO

I 5-5

' .

(a) Ordinary Photograph (b) Holographic Interferogram

FIGURE 5.1

Holographic Interferogram of a stressed flow control elbow from the TRW Lunar module descent engine

C F B R A U N & CO

5-6

5.4 HOLOGRAPHY Continued

Holographic methods, at their present state of development, have no applicable use in an LMFBR system. Currently, all holography must be performed in the laboratory on a test model or segmented parts of the actual system.

Holographic methods, however, appear to be an applicable tool for component design purposes. It is felt that holography can be used for determining (1) strain concentration points in complicated structures such as mixing tees, (2) transient phenomena, and (3) flaw detection.

It is recommended that improvements in holographic techniques be studied for possible future applications on LMFBR piping systems, as the state-of-the-art in holography progresses.

5.5 X-RAY DIFFRACTION

The use of X-ray diffraction techniques for strain measurement has increased in recent years mainly because it can analyze residual surface strains without damaging the object under examination. This technique is a great improvement over the destructive-testing methods used for measuring residual strain. Currently, portable X-ray diffraction equipment for field use is available.

The major drawback to using X-ray diffraction equipment is its inability to withstand elevated temperatures. Therefore, due to the formidible design problems that would be encountered in developing a satisfactory X-ray diffraction system, the applicability of this method for use in an LMFBR during actual plant operation is considered to be poor. However, prior to operation or during plant shutdown, X-ray diffraction techniques appear to have excellent applicability.

5.6 BRITTLE COATING

Brittle coatings are applied directly to the member and then allowed to dry. These coatings work on the principle that, as the object is stressed, strain cracks will appear normal to the direction of maximum primary stress. For further information on brittle coating methods, refer to References 16 and 21.

The major problem encountered with using the brittle coating method for strain measurement is that the piping and other reactor components will be covered by an insulating and heating system which would make it virtually impossible to monitor the brittle coating during actual reactor operation. The temperature range of the coating material is another restriction for LMFBR application.

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5.6 BRITTLE COATING Continued

Therefore, the applicability of the brittle coating method for use in an LMFBR inspection system is considered to be poor. However, the utilization of brittle coating methods during component and system design stages appears to be good.

5.7 NUCLEAR METHODS

While it is theoretically possible to measure displacement and low frequency vibrations utilizing nuclear counting techniques, the usefulness of such methods in a LMFBR piping system has not been established. The main advantage of nuclear methods appears to be the absence of high temperature effects on the radiation rate or on the absorption in the medium between the source and the detector. It appears that alpha, beta, gamma, neutron or X-ray could be used depending on the characteristics desired.

The major disadvantages to using this method of measuring strain are the lack of resolution to small displacement, its limited use to high frequency response due to the statistical nature of the detector output, and the subsequent electrical integration, the expense and intricacy of the required equipment, the inherent danger of the radiation source, and the possible interference from other sources of radiation in the area. (14)

Therefore, more research and development is required before the definite applicability of nuclear methods for in-service surveillance in a LMFBR piping system during operation can be established.

5.8 CHEMICAL METHODS

Several chemical transducers are available for detecting or measuring mechanical displacement such as the solution, porous disc, and mercury electrolyte types. (15) Chemical methods appear to have no advantage over the more common electrical types for use in a LMFBR surveillance system. Additionally, these devices are limited to temperatures below approximately 150 F. Therefore, this method is of little or no use in LMFBR piping systems.

5.9 PIEZOELECTRIC TRANSDUCERS

Piezoelectric crystals can be used to convert mechanical force or motion directly into an electrical signal, Refer to Figure 5.2. This signal results from a self-generated voltage which appears across this type of material when it is mechanically stressed. A large portion of all of the audio frequency vibration transducers and practically all of the ultrasonic transducers now in use are of the piezoelectric type. (14)

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FIGURE 5.2

Transducers epoxy bonded to the reactor outlet duct on the SM-lA power plant to obtain acoustic emission data. (Obtained from Reference 26)

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5.9 PIEZOELECTRIC TRANSDUCERS Continued

Commercial gages are currently limited to temperatures of approximately 650 F and are not able to withstand long term use as required for LMFBR monitoring systems. There is, however, evidence that the effects of high temperature and high nuclear radiation levels may tend to cancel each other out. This should facilitate the development of a high temperature, radiation resistant transducer that could be used for LMFBR inspection. (42)

The applicability of piezoelectric transducers for the verification of LMFBR piping is considered to be good, if gages can be developed to withstand LMFBR environmental conditions for the desired lifetime. At the present, further research and development is required in order to make their use applicable.

5.10 ACOUSTIC EMISSION

Acoustic emission, by definition, is "a phenomenon arising from the release of energy as a solid material undergoes plastic deformation and fracture. Part of this energy is converted to elastic waves which propagate through the material and can be detected at the material surface using high sensitivity sensors." (34)

Acoustic emission is normally utilized as a crack detection method. It has been found that metals under stress generate acoustic signals or stress waves. The initiation or growth of material flaws causes a sudden transient increase in this acoustic activity. These sudden increases are commonly called "bursts."

Acoustic emission can provide accurate measurement of stress-corrosion cracking and is a powerful tool for monitoring structural integrity. This crack detection method also can be used for the study of material failure mechanisms.

The equipment required for sensing acoustic emissions is similar to that of ultrasonic testing as both methods use the same type of transducers. A distinct advantage of this method is that the transducers do not have to be moved or "scanned" over the material surface. They are stationary and can be placed beneath the insulation and heating system. Refer to Figure 5.2. When the acoustic signals travel through the metal, transducers attached to the component pick up these signals for recording.

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5.10 ACOUSTIC EMISSION Continued

Acoustic emission has the following advantages.

1) Sensors have been located as far as 300 feet from the acoustic emission equipment and acoustical signals were still detected rather easily. (35)

2) The position of flaws or cracks can be located, using remote sensors, by determining the difference in signal arrival time at three or more sensors and using this information to triangulate the location. Refer to Figures 5.3 and 5.4. With additional development, acoustic emission methods will be capable of indicating the length of a flaw that is propagating and locate its position within 2 or 3 inches. (26)

3) Tests have demonstrated that acoustic emission is produced by stress-corrosion cracking and this micro-cracking is detectable well before the formation of a visible crack. (25)

4) Acoustic emission activity rises quite abruptly about three or four seconds before a flaw proceeds to failure, or before the material starts gross yielding. (25)

Acoustic emission has the following disadvantages.

1) Difficulty is created by the background noise of the reactor operations and process fluid flows. Operational noises can be filtered out, however, without destroying the acoustic emission signals.

2) A method of recording data from examinations is required for comparison purposes. (Aerojet General Corporation (25)). They have a system which can accept as many as 32 sensor inputs. The system converts the digital values which can then be used to generate a graphic display of the source of the emissions, or to generate a punched paper tape or typewritten output record.

3) Actual experience with acoustic emission has been limited to 700 F. (35)

4) The method is not applicable to detection of static flaws or discontinuities. There must be plastic deformation or flaw growth occurring to generate elastic waves. (35)

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(a) The time expansion of an acoustic "burst" signal shown occurring at six separate transducer locations. (Obtained from Reference 26)

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FIGURE 5 .3

The source area of acoustic "bursts" was located on the SM-lA reactor vessel by triangulation of transducer data.

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FIGURE 5.4

Acoustic emission system on the PM-2A reactor pressure vessel undergoing embrittlement studies at the National Reactor Testing Station.

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5.10 ACOUSTIC EMISSION Continued

Provided that the major design problems connected with acoustic emission can be overcome, this method represents one of the most promising techniques applicable to in-service monitoring.

If these design problems cannot be resolved during the later developmental stages, the acoustic emission method will be of value only during the initial pressure testing of the piping system.

Although acoustic emission technology is currently in the developmental stage, this method could be utilized to monitor portions of the piping system and/or localized areas of known potential flaw growth. (35)

5.11 ULTRASONIC METHODS

An ultrasonic crack detection system operates much like an acoustic radar set. A pulse of ultrasonic acoustic energy is generated in the material to be tested and sensitive receivers listen for the returning echos from internal defects and cracks. Of all transducers that have been used to generate and detect ultrasonic sound, piezoelectric transducers presently are the most promising type for high temperature applications.

Ultrasonic methods have the following advantages.

1) This method has been used in past reactor applications.

2) Ultrasonic methods can detect small cracks which could increase in size under operating stresses.

3) Testing equipment can be remotely located from the component being tested.

Ultrasonic methods have the following disadvantages.

1) Experienced and well qualified personnel are required to operate the equipment and evaluate examination results.

2) Access to the pipewall will be necessary.

3) A method for establishing bench marks is necessary to orientate and reproduce scans at successive inspections. (33)

4) A method of producing continuous inspection records that can be maintained and compared with previous inspections must be developed. (33)

5) Transducers must be moved or "Scanned" over the material surface.

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5.11 ULTRASONIC METHODS Continued

The applicability of ultrasonic scanning systems is poor. While this method has been used in past reactor applications, it has many inherent design and developmental problems that must be overcome. Acoustic emission, having fewer major design problems to overcome, will probably be considered prior to the ultrasonic method.

Ultrasonic methods, like radiography, however, will be used extensively during the construction and installation of LMFBR piping systems. Ultrasonic methods are excellent for detecting internal defects and checking wall thickness of piping.

5.12 RADIOGRAPHY The design and developmental problems associated with adapting a radiography system to monitor an LMFBR piping system during actual plant operation appears to prohibit this method from further consideration. Therefore, it is considered that radiography is not applicable to a LMFBR in-service inspection system.

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6 LOGGING OF RECORDS

6.1 SCOPE

This section is intended only as a brief discussion on the necessity for maintaining accurate records that relate to the various in-service surveillance methods that have been presented previously. Tasks to be performed later in the development of the LMFBR Design Guide will establish a procedure for accumulating and maintaining appropriate records. These later tasks will define the various records that must be kept, the sources of information to be recorded, recording schedules, responsibility, record retention period, and etc.

6.2 NECESSITY

The main purpose of logging records that reflect the continuous operating experience of the LMFBR system, is to assure that operating conditions do not exceed those for which the plant was designed.

These records will also provide a means for establishing a high degree of confidence in the procedures used in the Design Guide.

Additionally, many methods depend to a great extent upon comparing past records against current information before any conclusion pertaining to present operating conditions can be reached. The acoustic emission method for example, relys upon past operating records to aid in identifying the existence of abnormal conditions.

Components in the LMFBR piping system will be subjected to a variety of stress cycles during their lifetime. Most of these stress cycles will have amplitudes below the endurance limit of the component material. Some cycles may have amplitude, in varying amounts, above the endurance limit of the material. The additive effects of these various cycles, referred to as the cumulative usage factor, determines the life expectancy of the components. This cumulative usage factor is not to exceed unity.

Therefore, records must be maintained in order to determine what portion of the cumulative usage factor or actual plant life is being consumed during day to day operations. Thus by maintaining accurate records, a method of comparing actual plant life against theoretical design plant life will be established.

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7 BIBLIOGRAPHY

1 Nuclear Process Instrumentation and Controls Conference, May, 1958, ORNL 2695 (issued April, 1960), Pages 93 - 97.

2 Yevick, J G Editor, Fast Reactor Technology, Plant Design, The MIT Press, 1966, Pages 646 - 647, and 650 - 651.

3 Jackson, C B Editor, Liquid Metals Handbook, Sodium-NaK Supplement, TID-5277, July 1955, Pages 103-104, 121-125.

4 Proceedings of the Symposium on Liquid Metal Instrumentation and Control, March 1967, ANL-7380, Pages 70-74, 104-108.

5 Symposium on Alkali Metal Coolants, SM 85/16, November, December 1966, Pages 13-14.

6 Liquid Metal Handbook and Sodium-NaK Supplement, Chapter 16, Pages 16.71-16.73.

7 Smith, A W, and Drummond, J L An Examination of Some Methods for Detecting Liquid Metal Leaks in D F R Secondary Heat Exchangers, TRG Memorandum 4089, August 1967. (Report marked "Not for Fabrication" - material not used in this survey. Used as source of information only.)

8 Milich, W, and King, E C Sodium Leak Detection on Vertical Piping, MSA Technical Report 34, November 1954.

9 Martin, A B, and Inman, G M Sodium Graphite Reactor Quarterly Progress Report, NAA-SR-1292, October, December 1954, Pages 113-114.

10 Bolta, C, et. al., Design Development Tests of Some Components for the 10 MWe SDR, NDA 84-21, May 1959, Pages 12-15.

11 Quarterly Technical Progress Report on AEC-Sponsored Activities, APDA-195, June-September 1966.

12 Bischel, N A Status of Liquid Metal Heated Steam Generator Technology, BAW 1105, UC-81, September 1958.

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13 Davis, K A Sodium Leak Detection State-of-the-Art Study, LMEC-TRD-69-5, April 1969

14 Brown, Jr, R L Methods of Measuring Mechanical Displacement and Vibration with Emphasis on FFTF Primary Piping and Vessel, Battelle Memorial Institute Pacific Northwest Laboratory, Richmond, Washington, August 1968

15 Duckwald, C S and Angell, B S Special-Purpose and Miscellaneous Shock and Vibration Transducers, Shock and Vibration Handbook, Volume I, Page 14-1, McGraw Hill, Inc, New York, 1961

16 Dally, J W, and Riley W F Experimental Stress Analysis, McGraw-Hill, Inc, New York, 1965

17 Hetenyi, M Handbook of Experimental Stress Analysis, John Wiley & Sons, Inc, London, 1950

18 Holister, G S Experimental Stress Analysis, University Printing House, Cambridge, Great Britain, 1967

19 Gillette, O L and Vaughn, L E Research and Development of a High Temperature Capacitance Strain Gage, Air Force Flight Dynamics Laboratory, AFFDL-TR-68-27, April 1968

20 Wuerker, R F, and Heflinger, L 0, and Ziui, S M Holographic Interfermetry and Pulsed Lazer Holography, Presented at Holography Seminar Society of Photo-Optical Instrumentation Engineers, San Francisco, California, May 24, 1968

21 A Study of Model Test Methods as related to LMFBR Piping Systems, Technical Report 234, U S Atomic Energy Commission, Contract No AT(04-3)-781, 1969

22 Draft USA Standard Code for In-service Inspection of Nuclear Reactor Coolant Systems, ASME, New York, New York, 1968

23 Incipient Failure Diagnosis for Assuring Safety and Availability of Nuclear Power Plants, CONF-671011, United States Atomic Energy Commission, 1968

24 Pedersen, H N, and Spanner, J C Detection, Location, and Characterization of Flaw Growth in Metals Using Acoustic Emission Methods, Battelle-Northwest, CONF-671011, 1968

25 Green, A T, and Hartbower, C E Stress-Wave Analysis Technique for Detection of Incipient Failure, CONF-671011, 1968

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26 Parry, D L Nondestructive Flaw Detection in Nuclear Power Installations, Phillips Petroleum Co, CONF-671011, 1968

27 Siegmund, W P, The Use of Fiber Optics in Optical Inspection and Monitoring, American Optical Company, CONF-671011, 1968

28 McGonnagle, W J Nondestructive Measurement of Surface Residual Stress, Associated Midwest Universities, CONF-671011 1968

29 Hunter, D 0 An Ultrasonic Method for Nondestructively Detecting Radiation-Induced Embrittlement in Pressure-Vessel Steels, Battelle-Northwest, CONF-671011, 1968

30 Nims, J B Malfunction Detection Systems for Liquid-Metal Fast Breeder Reactors, Atomic Power Development Associates, Inc, CONF-671011, 1968

31 Balderston, H L Incipient Failure Detection: A System Concept, The Boeing Company, CONF-671011, 1968

32 McClung, R W State of the Art of Nondestructive Testing for Service and Postoperation Examination of Reactor Pressure Vessels, Oak Ridge National Laboratory, CONF-671011, 1968

33 Whitman, G D Technology of Steel Pressure Vessels for Water-Cooled Nuclear Reactors, ORNL-SCIC-21 A Review of Current Practice in Design, Analysis, Materials, Fabrication, Inspection, and Test, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1967

34 Hunter, P H, and Spanner, J C Detection of Metal Overstress by Acoustic Emission, Batelle Memorial Institute, BNWL-SA-438, Richland, Washington, January 19, 1966

35 Hutton, P H Use of Acoustic Emission to Study Failure Mechanisms in Metal, ASME Publication 69-MET-8, 1969

36 Wylie, R D Designing for In-service Inspection, Southwest Research Institute, CONF-671011, 1968

37 Optimization Study B-6, Materials Surveillance Station, C F Braun & Co, November 17, 1967

38 Bertodo, R Resistance Strain Gauges for the Measurement of Steady Strains .at High Temperatures, Institute of Mechanical Engineer Proceedings, Volume 178 Pages 907-921, 1963-1964

39 Harting, D R The S/N Fatigue Life Gage, Experimental Mechanics, Page 19A, February 1966

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o o 40 Mullineaux, J L A 1500 F (816 C) Capacitance Strain Gage

Developed, Research and Technology Briefs, AFSCRP 80-1, No 8, Page 12, August 1968

41 Bouche, R R Inductive-type Pickups, Shock and Vibration Handbook, Volume I, Page 15-1, McGraw Hill, Inc, New York, New York, 1961

42 Chapin, W E, and Drennan, J E The Effects of Nuclear Radiation on Transducers, REIC-43, Radiation Effects Information Center, Battelle Memorial Institute, Columbus, Ohio, October 31, 1966

43 Lemcoe, M M Characteristics of Two Commercial High Temperature Ele<-̂ ric Repi stance Strain Gages, NAA-SR-12118, undated.

44 Lemcoe, M M Errors in High Temperature Strain Measurements, Experimental Mechanics, 8, 2, 19N-26N (1968).

45 Gunby, A L Non-nuclear Performance of SRE-PEP Systems, NAA-SR-12408, June 30, 1967

46 Johnson, H E Corrosion and Activity Transfer in the SRE Primary Sodium System, NAA-SR-5363, October 30, 1961

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