ML20009E304

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Safety Evaluation Accepting Containment Purging & Venting Sys During Normal Operation
ML20009E304
Person / Time
Site: Beaver Valley
Issue date: 07/15/1981
From:
Office of Nuclear Reactor Regulation
To:
Shared Package
ML20009E301 List:
References
NUDOCS 8107280022
Download: ML20009E304 (4)
v • d • e


Text

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SAFETY E'/ALUATION REPORT FOR CONTAINMENT PURGING / VENTING DURING NCPP.AL OPERATION BEAVER VALLEY POWER STATION, UNIT 1 DOCKET N0. 50-334 I.

INTRODUCTION 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 oceration. These events have raised concerns relative to potential failures affecting the purge / vent penetrations which could lead to a cegra-dation in containment integrity, and, for PWRs, a degradation in ECCS per-fo rmance. By letter, dated November 28, 1973, the Ccmmissien (NRC) re-quested all licensees of operating reactors to respond to certain generic concerns about containment purging or venting during normal plant operaticn.

The generic concerns were twofold:

(1)

Everts had ccurred.,here li:ensees overrode or bypassed tha sa fety actua:':n isolation signals to tne centainmen; isolation valves.

These events were datermined to be abnormal occurrences and were so characteri;ed in our Report to Congress in January 1979.

(E)

Recent licensing revie'.es have required tests or analyses to shcw that containrent purge or vent valves would shut withcut degrading contain-v ment integrity during the dynami: loads of a design basis icss of coolant ac:ident (:EA-LOCA).

The NRC cositi:n letter of "cvember 1973 requested that licensees caa^e purging (or vanting) of centairtaat or limit ? urging (or venting) to an ab-s olute m,inimum.

Licensees wno elected to ourge (cr vent) the containment

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% wece requested to demonstrate that the containme t n

design met the criteria outlined in the NRC St purge ;or vent) system 6.2.4, Revisien 1 and the associated Branch Tech iandard Rev n cal Position (BTP)

CSB 6-4 II.

DISCUSSION AND EVALUATION Seaver '! alley Pcwer Station, Unit i utilizes a subatmospheric containment design.

In addition, an iodine filtration system tainment, aids in removing airborne radio

, located inside the con-the reactor coolant system during normal opeactivity that ma ration.

purging or venting through the 42 i Therefore, containment not permitted by Technical Specifications duringnch 2, 3 and 4.

reactor Ocerating Modes 1, Beaver Valley, Unit i has had the cation of during Mcde a for evacuating tne containme t using a steam jet air n

to the prescribed str,0 spheric pressure.

The 3-inch butterfly isolation valves in th to be cpened under administrative c ntrols f e system were permitted The licensee has determined that this Optioor use of the Mode 4.

1 n is no longer necessary and has submitted a proposed change this procedural cotion.

..:n cal Specifications to renove We find the above described proposed chan tne 3-inen isolation valves to be acceptable e,

ge regarcing A mechaaical vacuum pump system is periodically used during ncreal plant co-erati:n to maintain the containment at the prescribed This sy3 tem utilizes 2-inch gate valves for sucate:spneric pressure.

containment isciation chanical vacuum pump system does not fall within the The me-tairment purge / vent cperaticns.

se:pe Of review for con-H:weser, we have reviewed :he isolation

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rctisions for the pene
raticns of this system and conclude that their iso-lation provisions comply with General Design Criteria 5" and 55. Moreover, the cencern over ability of the valves to cime during a LOCA transient does not apply to these small valves.

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Type C isolation valve tests in 10 CFR Part 50, Appendi>.J.

These tests wou?d be performed in addition to the quanti *ative Type C tests required by Appendix J and would not relieve the licensee of the responsibility to con-form to the requirements of Appendix J.

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