ML20040B193

Final Deficiency Rept Re Quality of Spent Fuel Pool Heat Exchanger Matls,Originally Reported on 800902.Heat Exchangers to Be Returned to Vendor for Heat Treatment to Relieve Potential Residual Weld Stresses

ML20040B193
Person / Time
Site:	Nine Mile Point
Issue date:	12/31/1981
From:	Rhode G NIAGARA MOHAWK POWER CORP.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8201250257
Download: ML20040B193 (3)

Text

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hj V NIAGARA huMOHAWK

' ' IIII' W I ' 474 I NIAGAR A MOH AWK POWIR CORPOR ATION

• Decenber 31, 1981 Office of Inspection and Enforcement Region I -

Attention: f1r. R.11. Starostecki, Director

- 7' 7 ., /j f, X 4, Division of Resident and Project Inspection '

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U. S. Iluclear Regulatory Connission p 631 Park Avenue -vj;,-

King of Prussia, PA 19406

r Re: fline fiile Point Unit 2 -

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Docket flo. 50-410 ,f/

Dear f1r. Starostecki:

EW Enclosed is a final report in accordance with 10 CFR 50.55(e). This reportable deficiency regards the quality of certain spent fuel pool heat exchanger naterials. This was originally reported to fir. R. Feil of your staff on September 2,1980, as a potentially reportable deficiency.

Very truly yours, HIAGARA f10HAWV POWER CORPORATI0f1

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wGerald K. hode Vice Presid nt#

Systen Project flanagement PEF:Ja xc: Director of Inspection and Enforcenent U. S. lluclear Regulatory Connission Washington, D. C. 20555 8201250257 811231 PDR ADOCK 05000410 S PDR "I L - -- - - - - - - - - - - - - - - - _ - - - - d

NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT UNIT 2 DOCKET NO. 50-410 FINAL REPORT FOR A REPORTABLE DEFICIENCY UNDER 10CFR50.55(e)

REGARDING SPENT FUEL POOL HEAT EXCHANGERS D_escription of the Deficiency The deficiency was discovered during a review of the documentation package for the spent fuel pool cooling water heat exchangers.

l The inpact test data for several heat exchanger shell naterials do not contain sufficient infornation to deternine whether or not the purchase specification inpact test acceptance criteria have hee' net. Although inpact testing for Class 3 heat exchangers is not a nandatory requirement of the ASME code, it was required by our procurenent specification to ensure that the heat exchanger naterials were of adeouate toughness. The heat exchangers successfully passed a shop hydrostatic test and were ASME III, Class 3 i stamped. However, the specified acceptance criteria in the procurement l specification are based on a test specimen parameter called nils lateral expansion (MLE). For the heat exchanger carbon steel shell end plates, nozzles, nozzle reinforcing pads, and cradle supports, the inpact test data included in the certified material test reports do not report this paraneter.

Furthernore, the impact test data that are reported for the suspect naterials indicate that the material used nay be deficient for inpact values.

It has been confirned that the infornation to obtain nils lateral expansion parameter is not available, and that the test specimens were not retained by the testing laboratory, thus precluding additional testing. The heat exchanger vendor, Anerican Standard, was therefore requested to show by Ltilizing the available test data, that the stresses in the suspect materials are lower than that required to initiate brittle fracture.

An analysis was perforned which indicates that, with heat treatment, the

brittle fracture is not a credible failure node for these heat exchangers.

The analysis deternined that the stress intensity factor for the material resulting from actual stresses under operating conditions is less than the critical stress intensity factor required to initiate brittle fracture, based on aaterial inpact properties. The materials analyzed included the shell end ,

j plate, nozzle reinforcing pads, cradle, and cradle support. The analysis assuned that the naterial was stress relieved by heat treatment.

The shell nozzles were not included in the analysis.

The toughness properties of this material are considered acceptable, based on the original test performed at 100 F by the vendor. The test results provide assurance that had the appropriate parameters been neasured during the testing (nils lateral expansion), the results would have satisfied the specification acceptance c riteria.

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Analysis of Safety Inplications The potential brittle fracture of the spent fuel pool cooling water heat exchangers could have an adverse inpact on the safe operation of the nuclear power plant. However, it is believed that this potential failure would have minimal inpact on the protection provided to the public. This is because that even under naxinun spent fuel pool heat load gonditions, it would take several hours before the spent fuel pool would beat up -to the point where the capability of the pool to perforn its safety function would he jeopardized.

During that time, alternate actions to ni,tigate .the consequences of the loss of both spent fuel pool gooling heat exchangers can he taken. A detailed analysis of the safety inplications was not perforned since the required corrective action as outlined below is being taken.

Corrective Action The heat exchangers will he returned to the vendor for heat treatnent to relieve potential residual veld stresses.

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