ML20199J091

Requests Technical Assistance Supplement 1,in Determining If Util Interpretation Re Reactor & Turbine Bldgs Blowout Panels,Per 10CFR50.59 SE Requirements

ML20199J091
Person / Time
Site:	Nine Mile Point
Issue date:	05/01/1996
From:	Cooper R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:	Varga S NRC (Affiliation Not Assigned)
Shared Package
ML20199J065	List: ML20199J059 ML20199J084 ML20199J091 ML20199J097 ML20199J104
References
FOIA-97-375 NUDOCS 9711280053
Download: ML20199J091 (2)

Text

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+ UNITEo STATES E -g NUCLEAR REGULATORY COMMISSION ti. r j REGION I o, 4 ' 475 ALLENDALE ROAD KING OF PRUSSIA. PENNSYLVANIA 19406 1416

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May 1, 1996 MEMORANDUM _T0: -Steven A.-Varga, Director Division of Reactor Projects-1/II Office of Nuclear Reactor Regulation i Richard W. Cooper, II, Director [/

FROM:

Division of Reactor Projects, K (oA y .

N

SUBJECT:

REQUEST FOR TECHNICAL ASSISTANCE ON NINE MILE POINT 1 REACTOR AND TURBINE BUILDING BLOWOUT PANELS - SUPPLEMENT 1 Our-previous memorandum of March 13, 1996 reqLested your assistance to determine the-technical adequacy of Niagara Mohawk Power Corporation's (NMPC) revised design calculations for the reactor ar;d turbine building blowout panels. The.;e calculations are related to an event (LER 50-220/95-05) that identifie) the existence of an initial construction deficiency and a subsequent 1993 error in design assumptions. At an Enforcement Conference held on April 12, 1996, two additional concerns were identified that require NRR's assistance about which NRR staff agreed to review with a supplement to the original task interface agreement (TIA).

The additional concerns are both related to the 10 CFR 50.59 safety evaluation requirements and are associated with the calculations currently being reviewed by NRR.

First, in October 1993, NMPC erroneously determined that the relief panels would relieve at piessures in excess of the design relief pressure of 45 psf but less than the design pressura of 80 psf. The UFSAR specifies both design values and it states that pressure relief of the structures through the blowout panels will prevent excessive internal pressure on the superstructure walls, roof and their supports, which would fail at an internal pressure in excess of 80 psf. Specifically, the blowout panels for the reactor and turbine building would relieve at 53 asf and 60 psf, respectively. During the Enforcement Conference, NMFC agreed t1at NMPC violated 10 CFR 50.59 by not completing a safety evaluation when they identified that the actual configuration was different from that described in the UFSAR. However, NMPC took the position that the safety margin was not reduced because the actual blowout value (if not in error, which it was) was still under 80 psf and the safety ,nargin is the differential between the 80 psf and actual failure pressure (estimated to be about 110 - 149 psf). NMPC's interpretation appears to be consistent with NSAC 125, which the NRC staff has not endorsed. . We acknowledge the _ safety margin is at least 80 psf to failure pressure but we believe that the safety margin' also includes the range of 45 to 80 psf since the licensee's-stated design relief pressure is 45 psf. We request your -

assistance in determining _if the NHPC interpretation is consistent with current staff guidance.

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,4 l1 l t Steven A. Varga 2 Please; note that the enforcement action is proceeding because of the

-calcu'3tional error and the failure to evaluate a condition different than that described in the UFSAR.

Secondly, in March 1995, NMPC' modified the reactor and turbine building blowout panels by removing every other (oversized) fastener,- to Themeet the commitments with the UFSAR design relief pressures _of 45 psf.

calculations to suppert this modification were provided to NRR as part of the original TIA. Although the size and spacing of the blowout panel fasteners are not descrioed in the UFSAR in either words or drawings, the plant was modified from a non-conservative condition to a condition in_ compliance with the UFSAR.

NMPC took the position that they did not have to do a 10 CFR 50.59 since they were restoring the commitment or safety condition as stated in the UFSAR. We believe the 50.59 evaluation should be done to confirm We have that the decided ne' commitment or safety condition was indeed being restored.

to issue enforcement action regarding this 1995 failure to do a safety evaluation pending your review.- We request yo"- assistance in determining if a 10 CFR 50.59 safety evaluation should have W completed prior to the impleinentation of this modification.

These. additional questions were discussed with Susan Shanks.an of your staff.

We would appreciate that the review of these additional questions be included in your response to the uriginal TIA.

cc:

T. Martin, ORA R. Conte, RI/DRP M. Modos, RI/DRS H. Eichenholz, RI/DRP B. Norris, RI/DRP S. Shankman, NRR/PD I-I J. Lieberman, OE D. Holody, ORA E. McKenna, NRR D. Hood, NRR/PD I-l M. Oprendek, RI/DRP1 R. Gallo, RI/DRP J. Wiggins, RI/DRS R. Blough, RI/DRS E. Merchoff, RII

'W. Axelson, RIII J. Dyer, RIV C. Anderson, RI RI/DRP Branch Chiefs