ML20042A233

Technical Evaluation Rept for Containment Purging & Venting During Normal Operation of Fort Calhoun Station.

ML20042A233
Person / Time
Site:	Fort Calhoun
Issue date:	02/28/1982
From:	Laudenbach D EG&G, INC.
To:	NRC
Shared Package
ML20042A229	List: ML20042A228 ML20042A233
References
NUDOCS 8203230231
Download: ML20042A233 (3)

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February 1982 t

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TECHNICAL EVALUATION REPORT .

FOR CONTAINMENT PURGING AND VENTING DURING NORMAL OPERATION OF -

THE FORT CALHOUN STATION (Docket Number 50-285) by D. H. Laudenbach EG&G, Inc.

Energy Measurements Group San Ramon Operations -

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TECHNICAL EVALUATION REPORT FOR CONTAINMENT PURGING AND VENTING DURING NORMAL'CPERATION OF THE FORT CALHOUN STATION (Docket No. 50-285)

1. INTRODUCTION P

A number of events have occurred over the past several years which directly relate to the practice of containment purging and venting during normal plant operation. These events have raised concerns relative to potential failures affecting the purge penetrations which could lead to degradation in containment integrity, and, for PWRs, a degradation in ECCS performance. By letter, dated November 28, 1978, the Commission (NRC) requested all licensees of operating reactors to respond to certain generic concerns about containment purging or venting during normal plant opera-tion. The generic concerns were twofold: '.

(1) Events had occurred where licensees overrode or by-passed the safety actuation isolation signals to the cor.tainment isolation valves. These events were -

determined to be abnormal occurrences and were so characterized in our report to Congress in January 1979.

(2) Recent licensing reviews have required +,ests or an-alyses to show that containment purge or vent valves would shut without degrading containment 'ntegrity i

during the dynamic loads of a design basis loss of coolant accident (DBA-LOCA). -

The NRC position of the November 1978 letter requested licensees to cease purging (or venting) of containment or limit purging (or venting) to an absolute minimum. Licensees wno elected to purge (or vent) the con-tainment were requested to demonstrate that the containment purge (or vent) system design met the criteria outlined in the NRC Standard Review Plan (SRP) 6.2.4, Revision 1, and the associated Branch Technical Position (BTP)

CSB 6-4, Revision 1.

II. DISCUSSION AND EVALOATION The containment purge system'at the Fort Calhoun Nuclear Station consists of a 42-inch intake line, a 42-inch exhaust line, and a 2-inch vent (pressure relief) line. The purge system is a separate part of the containment air cooling and ventilation system (ACVS), and is designed to provide a means for l reducing atmospneric activity (including noble gases)

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to allowipersonnel access to the containment and to alleviate containment pressure increases resulting from temperature transients and equipment air leakage.

The licensee responded to the NRC position letter of November 1978, by stating that they plan to justify unlimited purging and, pending completion of the commission's review,Jould limit use of the 42-inch lines to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year during powar opyracion, but indicated that the use of the 2-inch vent line to maintain containment pressure within technical i specification limits cannot be limited to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year. The licensee indicated tnat operating experience at fcrt Calhoun Station has indicated a

need to frequently purge the containment.>

0uring 1976, Fogt Calhoun purged containment via the 42-inch isolation valves for a period of 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> in

" Hot Standby" and 189 hours0.00219 days <br />0.0525 hours <br />3.125e-4 weeks <br />7.19145e-5 months <br /> in " Power Operation." ,The licensee indicated that during the period from January 1977 through September 1979, the 42-inch valves were not utilized in containment. purging in either " Hot Stand-

'- by" or " Power Operation".

Subsequently, in a letter dated October 2,. 1981 the licensee

. indicated that they had dacided not to pursue qualification of the 42-inch purge valves during normal plant operations and will limit the use of these valves to the refueling and _ cold shuf.down modes. Tne licensee- plans to evaluate th'e installation of an 8-inch (or ' smaller) fully-qualified saini-purge system which can operate during'all modes of operation, and indicated that appropriate Technical Specificatio9, ctianges/ additions would be sub-mitted when the mini-purge system is installed.

The licensee committeo to propose a Technical Specification change by November 1,1981, which is to include the requirement for leakage integrity tests of tne 42-inch purge isolation valves at least once every six months. , ,

III. CONCLUSIONS 1 We agree with the licensee's view that limiting the use of the 42-inch purge valves to the refur.iing and cold shutdown modes of operation resolves the NRC staff's concerns associated with the 42-inch diameter purge isolation valves. However, we recommend that the licensee be re-quested to submit a Technical Specification requiring that the 42-inch purge isolation vcives De maintained locked-clc3ed during operational modes 1 through 4, as 'definec; in SRP 6.2.4 -(Item II. ht ) . These valves mul_t be verified' to be locked-crosed at least every N *tvs, Further, ws recommend that tN o. & avalified mini-purge system proposed by' the licensee meet the requ rw Si the NRC Standard Review Plan (SRP) 6.g.4 and the' associated Bunch lecipical position (BTP) CSB

, 6-4.

Subjer,t to implementation of the above recommendations, we find the purge / vent ' system design and operating practices for Fort Calhoun Station to be' acceptable.

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