ML20137Q976

Informs That as-found LOCA & Life Testing & Analysis Does Not Provide Acceptable Approach for Demonstrating Qualification at Accident Temp Higher than 340F,per 970110 TAR

ML20137Q976
Person / Time
Site:	Pilgrim
Issue date:	03/31/1997
From:	Milano P NRC (Affiliation Not Assigned)
To:	Hehl C NRC (Affiliation Not Assigned)
References
TAC-M96294, NUDOCS 9704110189
Download: ML20137Q976 (5)

Text

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.. March 31, 1997-t

' MEMORANDUM TO: Charles W.'Hehl, Director  ?

Division of Reactor Projects FROM: Patrick D.,Milano, Acting Director  !

Project' Directorate I-3 ,

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-. Division of Reactor; Projects - I/II ,

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SUBJECT:

, x REQUEST FOR TECHNICAL ASSISTANCE REGARDING THE PILGRIM r

ENVIRONMENTAL-QUALIFICATION OF ELECTRICAL PENETRATIONS (TAC '

N0fM96294),7 ,

i By letter dated' January 10,1997, 'you' requested NRR assistance in evaluating the acceptability, of the Boston 1 Edison Companyx(BEco) use of thermogravimetric i analysis l methodology to, qualify in-containment' electrical penetration. This

• is to. inform (you; that'we have completed our review and concluded that the as- 3 found loss-of-coolant, accident.-(LOCA) plus life' testing and analysis does not  !

provide an acceptable approach for demonstrating qualification at accident  ;

temperatures higher.than 340 *Ft However,,the additional LOCA test results '6 (340 *F with conductors energized), subsequently provided in response to the NRC inspector's request, envelop peak ~LOCA temperature (334 *F) with margin,  :

and are consistent with requirements defined in paragraph (f) of 10CFR50.49.

Therefore, it is considered 'an acceptable approach for ensuring that the penetration is qualified for the new accident peak temperature of 379 'F (334 *F plus 45 *F to. account- for temperature rise due to energized power l cables). Our evaluation. is attached. ,

Attachment:

As stated orir,inal signed by P.Milano cc w/att: L. Reyes, RII A. B. Beach, RIII E. Merschoff, RIV i

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Contact:

Alan Wang 415-1445 Distribution Docket File JKnox PUBLIC- ' SBloom (e-mail only)

PDI-3 RF SVarga MBoyle (e-mail only)

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~ March 31, 1997 g*****

MEMORANDUM.TO:- - Charles W. Hehl, Director Division of Reactor Projects FROM: Patrick D. Milano, Acting Directo h N '

Project' Directorate I-3 Division of Reactor Projects .1/II

SUBJECT:

REQUEST FOR TECHNICAL ASSISTANCE REGARDING THE PILGRIM ENVIRONMENTAL QUALIFICATION OF-ELECTRlCAL PENETRATIONS (TAC NO. M96294)

By letter dated January 10, 1997, you reouested NRR assistance in evaluating the acceptability of the Boston Edison Company (BEco) use of thermogravimetric analysis methodology to qualify in-containment electrical penetration. .This is to inform you that we have completed our review and concluded that the as-found loss-of-coolant accident (LOCA)'plus life testing and analysis does not provide an acceptable approach for demonstrating qualification at accident temperatures higher than 340 *F. However, the additional LOCA test results (340 *F with conductors energized),. subsequently provided in response to the NRC inspector's request, envelop peak LOCA temperature (334 *F) with margin, and are consistent with requirements defined in paragraph (f) of 10CFR50.49.

Therefore, it is considered an acceptable approach for ensuring that the

. penetration is qualified for the new accident peak temperature of 379 'F (334 *F plus 45 *F to account for temperature rise due to energized power cables) . Our evaluation is attached.

Attachment:

As stated cc w/att: L. Reyes, RII A. B. Beach, RIII

E. Merschoff, RIV

Contact:

Alan Wang 415-1445

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REGION I TIA REGARDING THE PILGRIM ENVIRONMENTAL QUALIFICATION OF FLECTRICAL PENETRATIONS [

BACKGROUND Due to a service water temperature increase from 65 *F to 75 *F at the Pilgrim' Nuclear Power Station, the Boston Edison Company (BEco) contracted with  !

I General Electric (GE) to perform an analysis to establish the resulting new *

' post-design basis accident (DBA) containment temperature profile. The resulting new profile consisted of an increased post-DBA peak-temperature (4 'F from 330 *F to 334 *F) for a longer duration. Because of.the resulting new profile, BECo also implemented a program (in accordance with license '

requirements) to assure that documentation associated with the affected in-containment equipment continued to demonstrate. qualification (i.e., the t

. capability of equipment to perform.its required safety function when subject to the higher temperature following a DBA). The results of the program i indicated that most in-containment equipment (which included containment electric penetrations) could be considered qualified through the use of  ;

additional data from other existing environmental qualification-(EQ) test reports. [

To establish the adequacy of BEco's program for assuring qualification, the  :

NPC initiated a special inspection at the Pilgrim plant site. As part of this  !

inspection, three EQ documentation packages were selected for review. EQ  !'

packages selected were: (1) GE electrical penetrations, (2) Limitorque MOV components, and (3) safety-relief valve flow monitor. From the package on GE  ;

electrical penetrations, the NRC inspector noted the following:  ;

Original qualification, using a lant accident requirement's profile having a peak temperature of 330 *F, was ased on a test profile of 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at 352 'F  :

plus 23.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at 309 'F plus 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at 135 'F.  !

Current qualification, using the new plant requirement's profile having a peak temperature of 379"F (334*F to account for the higher ambient plus 45'F to l account for temperature rise due to energized power cables) was based on a  !

, test profile of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> at 340*F and 10 days at 281*F and a life test which  :'

showed a 10% loss of weight after a duration c.' 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at a temperature of 392*F.

t Because life tests of epoxy at 392*F did not specifically address questions relating to the mechanical strength and capability of the penetration's epoxy sealant to withstand DBA containment pressure conditions at the higher temperature, it was unclear (based on information supplied in the EQ

~ documentation package) that the GE electrical penetrations were adequately  !

qualified for the higher taprature. Thus, the NP.C inspector (1) requested  !'

- BECo to explain why life tests are acceptable for justifying a higher temperature during an accident and (2) by an NRC internal memorandum dated August 1,1996, requested the NRC Office of Nuclear Reactor Regulation (NRR) to determine whether the life tests are acceptable for justifying the higher

temperature during accident conditions.

i ENCLOSURE l

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t In response to the inspector's request, NRR initiated a review to establish- '

the acceptability of life tests for justifying the higher temperature during accident conditions, the adequacy of qualification documentation, and .

environmental qualification of electrical penetrations. As part of this i review, BEco provided responses to a number of questions. These questions and responses have been added to EELB's HyperNews Homepage on NRC's internet at http://irm25.nrc. gov /NRR/jlk/eq-home. hts under the Environmental Qualification >

(EQ) Discussion Topic file folder entitled " Pilgrim: Environmental ,

Qualification of Electrical Penetrations." l EVALUATION i Wyle Report No. 47066-PEN-1.1, Qualification Verification Report on General  !

Electric Electrical Penetrations No. 238X600NLG1 for use in Pilgrim 1 Nuclear  !

Power Station, Revision F, dated March 20, 1996, indicated the following: i Linear slopes comparison analysis (which utilized Arrhenius methodology and a  !

conservative activation energy of 1.13 eV) shows that the original qualification test profile (i.e., 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at 352 *F plus 23.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at l t

309 *F plus 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at 135 *F) causes less thermal degradation than the new l 1 required plant accident profile (i.e., analysis results indicated thermal  :

degradation at 18929.01 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from the original qualification test profile while the new required plant accident profile was at 34457.64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br />). Using another test profile (340 *F for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and 281 *F for 10 days on the same type of penetration epoxy), linear slopes comparison analysis showed greater I

thermal degradation than the new required plant accident profile (i.e., l 2

analysis results indicated thermal degradation at 68933.37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> from the new l qualification test profile while the new required plant accident profile was '

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, at 34457.64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br />).

I The test peak temperature of 352 *F is less than the required accident peak i temperature of 379 *F (334 *F to account for the higher ambient plus 45 *F to '

account for temperature rise due to energized power cables). Additional l testing on a test sample of the same epoxy was performed at a higher j temperature. The test sample lost 10% of its weight after a duration of 2.3 ,

' hours at a temperature of 392 'F. Another test sample lost approximately 9% 1 of its weight during 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> testing at 338 *F. Based on these additional 4 tests, BECo concluded that the epoxy has demonstrated capability for withstanding the peak temperature requirement of 379 *F.

4 Subsequently, in response to the NRC inspector's request to explain why life tests are acceptable for justifying a higher temperature during an accident, BEco provided the results of additional LOCA testing which verified that the penetration's epoxy will not breakdown at the peak temperature expected at PNPS. This additional LOCA testing was conducted at a maximum ambient ]

temperature of 340 *F with the penetration conductors energized at their maximum derated valuo for 30 to 60 minutes during the qualification testing.

Based on this additional LOCA testing, BECo confirmed the penetration's capability for withstanding higher temperature.

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.i CONCLUSION l 1

The licensee's justification was based on a test of the penetration's epoxy  !

for 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at 392 *F, a linear slopes comparison analysis (which utilized )

Arrhenius methodology), and the same premise (a 10 percent weight loss) that  !

was apparently used to justify qualification of the penetration for its stated qualified life of 40 years. The licensee concluded that if (1) a 392 'F temperature for 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> causes a 10 percent weight loss of the. penetration's epoxy, (2) linear slopes comparison analysis demonstrates a 2-to-1 thermal degradation (weight loss) ratio between test and accident profiles, and (3) a penetration with similar epoxy is qualified after a weight loss of 10 percent.

One should be able to reasonably conclude that the penetration can survive the pressure conditions at the higher temperatures during a LOCA. However, the use of Arrhenius methodology to accurately project aging (or weight loss) during transient conditions, which will exist during a LOCA environment, has not been validated by either operating experience or research test results.

Thus, the weight loss comparison between test and accident profiles may not accurately project the 2-to-1 ratio stated in the qualification report.

Based on the above, the' staff concluded that the as-found LOCA plus life testing and analysis does not provide an acceptable approach for demonstrating qualification at accident temperatures higher than 340 *F. However, the additional LOCA test results (340 *F with conductors energized), subsequently provided in response to the NRC inspector's request, envelop peak LOCA temperature (334 'F) with margin, and are consistent with requirements defined in paragraph (f) of 10 CFR 50.49. Therefore, it is considered an acceptable approach for ensuring that the penetration is qualified for the new accident peak temperature of 379 'F (334 *F plus 45 *F to account for temperature rise due to energized power cables).

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