ML20057A815

Summary of 930715 Meeting W/Numarc & PWR Owners Groups in Rockville,Md Re Primary Water Stress Corrosion Cracking (PWSCC) of Control Rod Drive (CRD) Penetration at Reactor Vessel Head.List of Meeting Attendees & Handouts Encl

ML20057A815
Person / Time
Issue date:	09/08/1993
From:	Strosnider J Office of Nuclear Reactor Regulation
To:	Wiggins J Office of Nuclear Reactor Regulation
References
NUDOCS 9309150362
Download: ML20057A815 (39)

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{{#Wiki_filter: ( .f*g i j '[ UNITED STATES (. NUCLEAR REGULATORY COMMISSION WASHINGTON. D C Pouwnct L SEP 0 81993 MEMORANDUM FOR: Jones T. Wiggins, Acting Director Division of Engineering FROM: Jack R. Strosnider, Chief Materials and Chemical Engineering Branch Division of Engineering

SUMMARY

OF MEETING WITH NUMARC AND PWR OWNERS GROUPS CONCERNING PRIMARY WATER STRESS CORROSION CRACKING (PWSCC) 0F CONTROL ROD DRIVE (CRD) PENETRATIONS AT REACTOR VESSEL HEAD On July 15, 1993, the staff met with representatives of NUMARC and PWR Owners Groups for an update of the status of the PWR Owners Groups's Inconel 600 (Alloy 600) program and a discussion of the proposed flaw acceptance criteria regarding the stress corrosion cracking (PWSCC) of control rod drive (CRD) penetrations at reactor vessel heads. The meeting was coordinated by NUMARC. Westinghouse made the presentation for the PWR Owners Groups. A list of meeting attendees and a copy of the presentation materials are attached. The presentation is summarized below: (1) Up-date of CRD Penetrations inspection Results Up to this date, a total of 1850 CRD penetrations were inspected at 37 overseas PWR plants. Axial indications were found in 59 penetrations. No leakage or circumferentially oriented indications were reported. (2) Crackina of J-aroove weld at Rinohals Unit 2 Boat samples were taken from the cracked J-groove weld of CRD penetration

1. 62 at Ringhals Unit 2.

Based on the examination of the boat samples, the cracks are multiple and small, and are not connected to form a single large crack. It appears that the cracking is the result of the original fabrication process. Effort to confirm the root cause of the cracking is continuing. (3) Allov 600 Crack Growth Testino Crack growth testing for a period of 800 hours has been completed on two heats of Alloy 600 materials (Sandvik heat 22 tube material and Standard Steel heat 43 forged bar material). Crack growth was observed in the heat 43 specimen. The constant load testing was performed at 325'C using a compact tension specimen. Currently, specimens from heats 75 and 151 are under testing. It is expected that 6 to 8 additional heats will be tested by the end of 1993, and a third chamber will be added to speed up the testing. The goal of this program is to test enough heats of materials to 9309150362 930908 3 ./ PDR REVGP ERGNUMRC / f PDR g%. ')7 ( C hf " Y) _14n00:1 [g pHper, yd n ,m,t t:.. ~ ~ wn y n

d s 3 ( ) J. Wiggins l P cover all operating plants. A report for the initial test results will be issued by the end of September, 1993. (4) Proposed Flaw Acceptance Criteria For flaws located below the penetration attachment weld, the criteria are designed to avoid the formation of loose parts since there is no concern i for structural integrity. For flaws located at and above the penetration attachment weld the criteria are designed to avoid potential primary ] pressure boundary leakage and to ensure structural integrity of the penetration. Flaws exceeding the proposed criteria must be repaired unless analytically justified for further service without repair. The owners groups wished to get NRC concurrence for the proposed flaw 1 acceptance criteria by the end of 1993 to support the spring 1994 l inspection. The staff stated that to simplify the crack growth calculations,and to provide adequate conservatism, a bounding crack growth i rate of 5x10' inch / hour should be used in the estimation of the acceptable service length since customized analysis and calculations would j significantly lengthen the staff's review time. !l t (5) NRC Ouestions to Owners Groups' Safety Evaluations 4 NRC's request for additional information on the owners groups' safety evaluations was faxed to NUMARC (Morris Schreim) on July 12, 1993. These-questions are also attached to this meeting summary. The owners groups indicated that a response to the questions will not be available until September 15, 1993. j 1 a (6) Non-Destructive Examination (NDE) Demonstration 4 l EPRI is coordinating the effort to develop a demonstration program for the i inspection of Alloy 600 CRD penetrations using eddy current and ultrasonic testing techniques. During the last meeting, the staff requested to have a meeting with EPRI and PWR Owners Groups to discuss how the demonstration ( program should be handled. During this meeting, the owners groups suggested such a meeting be held at the EPRI NDE Center some time in i October 1993. The staff preferred an earlier date for discussions of imbedded flaws. Subsequent to the meeting, the NRC staff agreed to visit j the EPRI NDE center on September 30, 1993. l J 3 i O Mw Jack R. Strosnider, Chief [ q Materials and Chemical Engineering Branch Division of Engineering i

9 _ g S *66 i + J. Wiggins > i I

Enclosures:

l (1) A List of Meeting Attendees i (2) A Copy of Presentation Materials (3) A Copy of NRC's Request for Additional Informat'.on cc: i T. Murley W. T. Russel J. Partlow' F. Miraglia B. D. Liaw C. Hinson C. Serpan W. Rosin /NUMARC S. Burns /WOG J. Taylor /B&WOG L. A. Walsh/WOG J. Hutchinson/CEOG M. Schriem/NUMARC G:\\K00\\PWSCC-7.WHK i e 1 l 1 4 4 ^ d i i I i l i 1 l d w

.~.. . ~.. SU c o 63 t J. Wiggins l

Enclosures:

(1) A List of Meeting Attendees (2) A Copy of Presentation Materials (3) A Copy of NRC's Request for Additional Information d i cc: T. Murley W. T. Russel J. Partlow F. Miraglia B. D. Liaw C. Hinson C. Serpan W. Rosin /NUMARC S. Burns /WOG J. Taylor /B&WOG L. A. Walsh/WOG J. Hutchinson/CE0G } M. Schriem/NUMARC i i l 9 DIS 1RIBUTION l l l NRC & Local PDRS 1 8 Docket & Central Files EMCB RF DET RF l WHKoo d RHermann l JRStrosnider i a $)1lhC]0Y / DE;EMg E:EMCB DE:EMCB WHKdb RHermann JRStros der W /3:/y ; 9/P/93 9/7193 0FFICIAL RECORD COPY DOCUMENT NAME: G:\\K00\\PWSCC-7.WHK 1 3 1 a i l 5

r ENCLOSURE 1 LIST OF ATTENDEES AT A JULY 15, 1993 MEETING WITH NUMARC AND PWR OWNERS GROUPS CONCERNING PRIMARY WATER STRESS CORROSION CRACKING OF CONTROL ROD DRIVE PENETRATIONS AT REACTOR VESSEL HEAD NAME POSITION ORGANIZATION D. S. Brinkman Ssr. Project Manager NRC/NRR/PDI-l Theresa Meisenheimer Lisencing Engineer Bechtel John Galembush Sr. Engineer Westinghouse Craig Protaero Sr. Engineer-Nuclear Westinghouse Phil Richardson CEOG Project Office ABB-CE T. Satyan Sharma Principal Engineer AEPSC Steve Brewer Group Manager AEPSC Ken Yoon Advisory Engineer B&W Nuclear Technology Dick Cyboron Manager, Inconel 600 ABB-CE Steve Hunt Principal Engineer Dominion Engineers Steve Fyfitch Lead Engineer, CRDM Proj. B&W Nuclear Tech Mel Arey Sr. Engineer Duke Power Comp. Geoff Hornseth Materials Engr. NRC/NRR/DE/EMCB Duke Wheeler Technical Assistant NRC/0EDO Charles Lashkari System Engineer PSE&G Ed Hackett Sr. Matls Engr. NRC/NRR/DE/EMCB Laney Bisbee Associate Structural Integrity A. W. Robinson Progm Manager BWNT William H. Koo Sr. Matls Engr. NRC/NRR/DE/EMCB Robert Hermann Section Chief NRC/NRR/DE/EMCB Mike Melton Sr. Engr. APS/CE0G David Whitaker Nuclear engr. Duke Power /BWOG Tom Spry Welding & Matls Eng. Commonwealth Edison Sid Burns Sr. Prof. Engr. Southern Nuclear Raj Pathania Project Manager EPRI Robert A. Capra Director PDI-l NRC/NRR/DRPE Morris Schreim Sr. Proj. Mangar NUMARC

Michael McNeil Metalluragist NRC/RES/DE/MEB David Boyle Primary Components /Mgr Westinghouse L. Zerr Sr. Licensing Engr.

STS/EPRI Y. Kim Sr. Elec. Engr. NUS Warren Bamford Fellow Engr. Westinghouse

f 9 l REACTOR VESSEL HEAD PENETRATION INDUSTRY /NRC MEETING JULY 15,1993 AGENDA o INTRODUCTION NUMARC ao INDUSTRY ACCEPTANCE CRITERIA W o DATA EXCHANGE INSPECTION UPDATE W CRACK GROWTH RESULT UPDATE W o NRC QUESTIONS ALL o FUTURE ACTIONS NRC CONCURRENCE ON INDUSTRY ACCEPTANCE CRITERIA EPRI NDE CENTER VISIT ) i

4 REACTOR VESSEL ALLOY 600 y, BACKGROUND J Head Penetration Leak Found at Bugey 3 - Sept.1991 Through Wall Crack in Alloy 600 Tube s Cause Determined To Be PWSCC ] Inspections Performed To Date Piant Plants [ Tota! Peneradons ""?f"

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"'S 'h*[ T'm Peneratons inspected ind nons ~rarce CPO j 6 l 80 90 595-593 390 J 3G4 19 CP( l 8 30-80 ' 552 520 l 459 20 1300MW 10 l 25-50 l 589-597 770 l 469 10 Sweden l 3 Loop l 3 l 75-115 580-606 l 195 l 190 l 8 Switzer!andl 2 Loop l 2 l 155 575 l 72 l 49 j 2 _!apan l 2 Loop l 3 l 105-108 l 590-599 j 1 23 j 107 l 0 i l 99 l 610 l 62 l 57 l 0 3 Loop 1 l 4 Loop l 1 l 46 l 593 l 74 l 62 l 0 Schium j 3 Loop { 2 l 60-120 l 596-603 l 133 l 133 } O Spain l 3 Loop l 1 l 65 610 65 20 l 0 TOTALS l l 37 l 2404 l 1850 l 59 e ANYD W IM D N .,y

O -80DE dF CRACKING AT RINGHALS UNIT 2, PERETRATION 62 1. LARGEST OBSERVED CRACKED REGION IS 30 PERCENT OF i CIRCUMFERENCE. 2. CRACKS ARE MULTIPLE AND SMALL (.5MM), NOT ALIGNED TO FORM A SINGLE LARGE CRACK, AS SEEN IN THE BOAT SAMPLES TO DATE. 3. UT RESULTS SHOW A SINGLE FLAW BECAUSE OF PROXIMITY, BUT THE CRACKS ARE NOT CONNECTED. l 4. CRACKING IS THE RESULT OF THE ORTGINAL FABRICATION PROCESS.

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Q STATUS OF AL_0Y 600 CRACK GROWTH TESTIbG i

JULY, 1993 o MATERIALS o SPECIMENS AND LOADINGS l

0 RESULTS TO DATE o FUTURE PLANS

1 TEST MATERIALS RT YIELD PRODUCT SPECIMEN FABRICATOR (KSI) C FORM DESIGNATOR SANOVIK 51.1 0.055 TUBE 22 i STANDARD STEEL 54.5 0.069 FORGED BAR 43 FRANCE 48 0.033 FORGED BAR 147 FRANCE 64 0.029 FORGED BAR 151 B&W TUBULAR PROD. 47.7 0.031 TUBE 62 B&W TUBULAR PROD. 39.7 0.053 TUBE 69 B&W TUBULAR PROD. 43.1 0.028 BAR 03 i i HUNTINGTON 41.5 0.068 TUBE 75 HUNTINGDON 36.0 0.10 TUBE 20 HUNTINGDON 35.5 0.06 TUBE 46 I i i N

4 SPECIMEMS AND LOADINGS SPECIMENS: 0.5T CT TEMPERATURE: 3250C LOADING: CONSTANT LOAD MONITOR.ING: LOAD TEMPERATURE DC POTENTIAL FOR CRACK LENGTH OPEN CIRCUIT CORROSION POTENTIAL ]

RESULTS TO DATE o 2 CHAMBERS IN USE 0 HEATS 22 AND 43 HAVE BEEN TESTED: NO CRACKING IN HEAT 22 AFTER 800 HRS. CRACK GROWTH IN HEAT 43 o HEATS 75, 151 IN TEST o CRACKING APPEARS TO BE OCCURRING IN BOTH SPECIMENS, BUT RATES ARE NOT YET AVAILABLE o STATUS REPORT PUBLISHED 4-30-93 e

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O ~ FUTURE PLANS o FINAL REPORT FOR PRESENT PROGRAM TO r BE ISSUED 9-30-93, WITH 4 l MICR0 STRUCTURES AND CRACK GROWTH RESULTS ] o PROGRAM EXTENSION ADD A THIRD CHAMBER CONSIDER ALL 8-10 HEATS WELD BEHAVIOR TEMPERATURE EFFECTS G0AL IS TO C0VER ALL OPERATING PLANTS 1

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SUMMARY

OF CRACK GROWTH RESULTS LABORATORY AND FIELD DATA

4 C) BACKGROUND AND TECHNICAL BASIS FOR PWR REACTOR VESSEL UPPER HEAD PENETRATION FLAW ACCEPTANCE CRITERIA Acceptance criteria have been developed for indications found during inspection of reactor vessel upper head penetrations. These criteria were developed as part of an industry program coordinated by NUMARC. Such criteria are normally found in Section XI of the ASME Code, but Section XI does not require inservice inspection of these regions and therefore acceptance criteria are not available. In developing the enclosed acceptance enteria, the approach used was very similar to that used by Section XI, in that an industry consensus was reached using input from both operating utility technical staff and each of the three PWR vendors The criteria developed are applicable to all plant designs. The cntena which are presented herein are limits on flaw sizes which are acceptable. Tne criteria are to be applied to inspection results. It should be noted that determination of the future service during which the critena are satisfied is plant-specific and dependent on flaw geometry and loading conditions. It has been previously demonstrated by each of the owners groups that head penetration cracking is not an immediate safety issue The safety evaluations document that the penetrations are very tolerant cf flaws and there is only a small likelihood of flaw extension to large sizes. Tnerefore, it was concluded that complete fracture of the penetration is highly unlikely and, therefore, protection against leakage during service is the priority. The approach used here is more conservative than that used in Section XI applications where the acceptable flaw size is calculated by putting a margin on the cntical flaw size in this case, the critical flaw size is far too large to allow a practical application of this approach so protection against leakage is the key element. The acceptance enteria apply to all flaw types regardless of orientation and shape. The same approach is used by Section XI where flaws are charactenzed according to established rules and then compared with acceptance critena. Flaw Characterization Flaws detected must be characterized by length and preferably depth. If only the length is determined, assume the depth is half the length based on expenence with the shape of flaws reported. The proximity rules of Section XI for considering flaws as separate, may be used directly (Section XI, Figure IWA 3400-1). This figure is reproduced here as Figure 1. When a flaw is found, its projections in both the axial and circumferential directions must be determined. The location of the flaw relative to both the top and bottom of the partial penetration attachment weld must be determined since a potential leak path exists when 6

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1 ) i l 1 i t i l Table 1: Summary of R.V. Head Penetration Acceptance Criteria l l 1 1 i l i LOCATION AXIAL CIRC I l l l O k O k f f i t no limit t .75 circ i BELOW WELD i i j: i AT AND ABOVE WELD 0.75t no limit 0.75t .50 circ i, i i { a = FLAW DEPTH AS DEFINED IN IWB 3600 g l l k = FLAW LENGTH t = WALL THICKNESS l 1 i a i a 4 1 i i i l i I l l l l i I i T l 1 1 l 1 I s 1 \\ l I i a I I.

i INTRODUCTION ~ 1 i I l l O ACCEPTANCE CRITERIA DEVELOPED JOINTLY BY THE THREE OWNERS' GROUPS AND EPRI, AS THE AHAC SUBGROUP ON HEAD PENETRATION INTEGRITY i t i O INSPECTION GUIDELINES: EACH OWNERS' GROUP 1 l HAS PUBLISHED OR IS IN THE PROCESS OF 2 PUBLISHING INSPECTION GUIDELINES i 4 jO REPAIRS: TO BE MADE TO APPLICABLE SECTIONS OF l ASME SECTION XI AND 10CFR50.59 AS APPROPRIATE i I i l ) I j l l

~ GENERAL APPROACH o DEVELOP CRITERIA GENERALLY APPLICABLE TO ALL PLANT DESIGNS 1 Io PENETRATION FRACTURE IS NOT A CONCERN S0 LEAKAGE PROTECTION IS THE PRIORITY l l i o CONSIDER ALL FLAW TYPES lo DEVELOP A TECHNICAL BASIS FOR EACH ELEMENT OF THE CRITERIA o ALLOW ADDITIONAL EVALUATION IF THE l CRITERIA ARE NOT MET i l l

i '4 \\ i j a l 1 1 i i i I f40ZZLE l'l J I RV HEAD i I 1 -t l TOP OF WELD i N-f i i l I i 3 1 l I BOTTOM I OF - ( 7 j 1 WELD S i, l a = ~ l i t I i i i 1 i i f i 4 b 1 l l

FLAW CHARACTERIZATIOV 1. FLAWS DETECTED MUST BE CHARACTERIZED BY LENGTH AND PREFERABLY DEPTH 2. IF ONLY FLAW LENGTH IS CHARACTERIZED, ASSUME A = 0.5 X LENGTH 4 3. FLAWS SHALL BE CONSIDERED SINGLE FLAWS PROVIDED THE SEPARATION DISTANCE BETWEEN FLAWS IS EQUAL TO OR LESS THAN THE DIMENSION S, WHERE S IS DETERMINED AS SHOWN IN SECTION XI, 3 e 1 l 4. FLAW LOCATION RELATIVE TO BOTH THE TOP AND BOTTOM OF THE PARTIAL PENETRATION ATTACHMENT WELD TO THE VESSEL HEAD SHALL BE DETERMINED. (SEE FIGURE 1) 1 4 5. FLAW PROJECTIONS SHOULD BE MADE IN BOTH THE AXIAL AND CIRCUMFERENTIAL DIRECTIONS IF THE FLAW IS ORIENTED AT AN ANGLE.

l t m (a) Esnow Linear Fis's (b) Estem Curvilanmar Flow s < t /2 n f - E z' M f L I \\ l / E:Pw y l 9 -A f_ lf+ l/ ~ 4 F 3 1 +E+ +- 02 '"*' i 3 S ' 'I2 *^- s<t,--*- p , g (c) Atsened Lmeer Flows (d) Nonocerlappeng Fnswa E#b E*E 1 3 2 E~ f'~ p-G* s c 1/2 in. 3, 3 77,,, t T I_ y Y l ' ',f i Ts /f' s 1 +G+ 1 WE* 3 3 'g Q s < 1/2 in. tel Deertaseeng Pratnel Fhs-s ggy % y % J i .= g w. E s < 1/2 in. - [3 + ~E * } 3 3 < 1/2.n. T A A '+-E-+ l 1 1 1 s < t/2 ' ~** E2 j'- d s < t, - -+., 3 s__ .- 0 -*"' i 2 j (s) Nonalenad Parallel Fkses (h)M epm F% E>I i 2 c FLAW PROXIMITY RULES FROM SECTION XI (FIGURE IWA 3400-1) l

FLAW ACCEPTANCE CRITERIA 1. MAXIMUM ALLOWABLE DEPTH AT OR ABOVE WELD IS A/T = 0.75 FOR BOTH AXIAL AND CIRCUMFERENTIAL

FLAWS, WHERE A = FLAW DEPTH AND T=

PENETRATION THICKNESS. THIS DEPTH IS Ap AS DEFINED IN IWB 3600. 2. AXIAL FLAWS FOUND BELOW THE WELD ARE ACCEPTABLE REGARDLESS OF DEPTH, PROVIDED THEIR UPPER END DOES NOT REACH THE BOTTOM OF THE WELD DURING THE PERIOD OF SERVICE UNTIL THE NEXT INSPECTION. AXIAL FLAWS ABOVE THE BOTTOM OF THE WELD ARE SUBJECT TO ITEM 1. A d 3. CIRCUMFERENTIAL FLAWS FOUND BELOW THE WELD ARE ACCEPTABLE REGARDLESS OF DEPTH, PROVIDED THE LENGTH IS LESS THAN 75% OF THE CIRCUMFERENCE.

4. AXIAL FLAWS EXTENDING THROUGH AND/OR ABOVE THE WELD REGION ARE NOT LIMITED IN LENGTH BUT DEPTH IS LIMITED BY ITEM 1. l 4 5. CIRCUMFERENTIAL FLAWS AT AND ABOVE THE WELD ARE LIMITED TO A MEASURED LENGTH OF 50 PERCENT OF THE CIRCUMFERENCE AND THE DEPTH IS LIMITED BY ITEM 1. 6. FLAWS WHICH EXCEED THESE CRITERIA MUST BE

REPAIRED, UNLESS ANALYTICALLY JUSTIFIED FOR FURTHER SERVICE WITHOUT REPAIR.

THIS ANALYSIS SHALL BE SUBMITTED TO THE REGULATORY AUTHORITY HAVING JURISDICTION AT THE PLTNT SITE. t l J l

• 15,3.

NOZZLE RV HEAD TOP OF [ BOTTOM mO N b movatwan=7"s \\ l 1 'L

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------------ ~- - ~ ~

t ~ j d I i 4 .75t 1 I v NOZZLE 1 l RV HEAD s , -t TOP OF WELD i 1 N i .l b N M i 1 BOTTOM l OF - WELD j i 4 .s 1 1 LIMITING ALLOWABLE FLAW DEPTHS CRDM HEAD PENETRATIONS i l I i )

1. +

I I I 4 l, Summary of R.V. Ilead Penetration Acceptance Criteria I l Location Axial Circ l a I a, G t Below Weld T x T .75 cire, i At and Above Weld 0.75T x 0.75T .50 cire. l l a, ; Flaw depth as defined in IWB 3600 f f: Flaw length 1 T: Wall thickness l l l l 1 i 1

(_. i I BASIC ASSUMPTIONS i 1) USE P. SCOTT CRACK GROWTH LAW AT 330*C L f 2) TEMPERATURE CORRECTION BASED ON ACTIVATION ENERGY = 33 KCAL/ MOLE \\ i 3) THRESHOLD FOR CRACK GROWTH - USE GROWTH RATE FROM 1 i

1) AT K = 9MPa v'm I

i i 4) STRESS INTENSITY FACTOR CALCULATED BY RECOMMENDED j PROCEDURE OF APPENDIX A OF SECTION XI(LATEST DRAFT). [ OTHER APPROACHES ARE ACCEPTABLE WITH JUSTIFICATION i i 9 l I l l l i a i 4 ) i a

6 ga arcc,,,'o i UMIT ED STATES ~, $~ NUCLE AR REGULATORY COMMISSION 3., ; wasmNGTON D. C. 20555 o %+ / Please Deliver to: Name: Mnrris schreim Entity: NUMARC Phone: 202-872-1280 Message: Morris Enclosed are the auestions to support the 7/15/93 meetina. We will formally send you these cuestions with a letter transmittina Bob Hermann NUMARC Fax 202-785-1898 1 l 4 i i l l From: Robert A. Hermann Phone: 301-504 2768 Fax: (301) 504-2444 l Date: Room: 7D24 This is Page 1, with page(s) to follow. s:\\faxform s l n

i ,6 s Requer,t for 2dditional information: [ i s 4 (1) The crack growth at the reactor vessel CRDM penetrations is dominated by the residual stresses as a result of welding. Please provide the field data of measured ovality and bending fron, CRDM penetrations in your PWRs and compare to that reported from oversea; PWRS with degraded CRDM penetrations. e (2) Were your finite element stress analysis results bench marked against the ovality and bending measured from the subject penetrations in your PWRs. If f yes, please provide the details. -If no, what assurance do you have that your i stress analysis model is conservative, i l (3) What is the stress distribution on the outside surface of the penetration j under steady state operation condition? Please discuss the potential for circumferential cracking at those locations where the ratio of axial stress { over hoop stress is larger than one. In the B&W SER that situation did exist, however, no discussion was provided. i l (4) At the locations where the above mentioned stress ratio is larger than 1 I { one, the potential for PWSCC or IGSCC in the circumferential orientation J exists when the axial cracking initiated from the penetration inside surface ] has propagated through wall. Please evaluate the growth rate of such cracking and its safety consequences. j (5) As the growth of the through wall axial crack -is slow, the resulting i leakage from the cracked penetration would be small. The reported leak rate at Bugey 3 was about 0.003gpm. How would your leakage surveillence program or I l i ....m..

i o i j procedures including the walkdown inspection capable of discovering such a i j small leak? i. l (6) Dicuss the feasibility of performing an enhanced visual inspection or the need to develope a more sensitive leakage detection instrument or device which l is not commercially availabe so that a small leak can be detected with confidence. (7) Your inspection window is calculated from the CE mockup test results with the implicit assumption that the leakage (less than 0.2 gpm) would be detected as soon as it had occurred. As the timely detection of such a small leak is l questionable, how would you justify inat your calculated inspection window is i l conservative when there is no assurance that a small leak from the CRUM l 1 l penetrations would be detected? l i (B) Is an acoustic emission technique available for domestic PWRs to detect l q the leakage from CRDM penetrations during hydrostatic or system leakage test? 1 t Please discuss the availability of any other leak detection instruments, i devices or methods that can be used for leakage detection during hydrostatic and system leakage test or during normal operation. i (9) How would the aerated condition resulting from through wall cracking I affect your crack growth evaluation particularly for penetration outside i - f surface cracking (IGSCC vs PWSCC)? j l (10) Evaluate the extent of damage that would occur on the surrounding i penetrations as a result of the ejection of a CRDM penetration and assess its ] l l r A

t I i O i s e safet; consequences? j l 4 (11) Discuss the following two items as reported from the overseas PWRs and access its potential safety consequences for your PWRs: (i) Circcmferential cracking found on the outside surface of CRDM t e penetration #54 at Bugey 3. (2) Circumferential cracking found at the "a groove" weld of CRDM f i peaetration #62 at Rhingal 2. .a l l 5 i l l i N l i i 4 I t o i l 4 l ) i i .i I i a I l I -}}