ML19289C508
| ML19289C508 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 01/09/1979 |
| From: | Andognini G BOSTON EDISON CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| 79-22, NUDOCS 7901170212 | |
| Download: ML19289C508 (2) | |
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DOSTON EDISON COMPANY GENERAL oFFICCW 000 GOYLaTON STREET B O sT O N. M AssAcNusETTs 02199
- 0. CARL ANDOGNING MANAGER NUCLEAR OPERATIONS DEPARTMENT January 9, 1979 BECo. Ltr. #79-22 Mr. Thomas A.
Ippolito, Chief Operating Reactors Branch #3 Division of Operating Reactors Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C.
20555 License No. DPR-35 Docket No. 50-293 Ccntainmen, Purging During Normal Plant Operation
Dear Sir:
This letter responds to your letter of November 29, 1978 concerning contain-ment purging during normal plant operation.
The results of our review of our override circuitry is presented.
A schedule for completio.
.f our evaluation justifying continuation of unlimited purging during power opera ion is given.
We believe the present Technical Specifications appropriately prots-t the heal.h and safety of the public and suggest no modification to these Technical Specifications be made at this time.
Review of Circuitry Our review of the override circuitry involved examining the control circuit logic for containment isolation valves associated with venting and purging the drywell and suppression chamber during power operation.
The results of this review indicate that all the valves receive a signal to go closed upon receipt of a containment isolation signal.
All valves will close upon receipt of a containment isolation signal even if initially in an open position.
Thece are two instances where the isolation signal can be overriden.
These are the two isolation valves in series in a two inch line venting the suppres-sion chamber and two isolation "alves in series in a two inch line venting the drywell to the Standby Gas Treatment System.
The control logic for these valves allows an override of the containment isolation signal if the key lock control switch for these valves is in the emergency locked open position. The keys are administratively controlled.
Schedule for Completion of Evg]uation (h
The scope of this evaluation will be consistant with Item (3) Page 3 of your
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letter (justify unlimited purging).
The schedule for completion of this evalu-g ation is May 1, 1979. However, certain aspects of this evaluation are currently
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g gDSTON EDISON COMPANY Mr. Thomas A. Ippolito, Chief January 9, 1979 Page 2 already available. First there should be no impact on ECCS performance due to containment purging since the Appendix K ECCS analysis assumes a constant 14.7 psig backpressure (see General Electric Company Report
" Analytical Model for Loss-of-Coolant Analysis in accordance with 10CFR50 Appendix K" NED0-20566).
The closure times of the containment purge isola-tion valves are such that the containment pressure will not be reduced to below 14.7 psig.
Second all coatainment isolation valves are subject to local leak rate testing and on integrated leak rate test in accordance to 10CTR50 Appendix J.
Existinj Technical Specifications Technical Specification 3.7.A.S.b (page 157a) permits deinerting twenty-four hours prior to a shutdown and allows twenty-four hours after startup to in-ert.
The purge isolation valves a e used during these periods.
The Bases for this Technical Specification indicates the benefit gained f rom access to the drywell for leak inspections during these periods is added plant safety without significantly reducing the margin of safety.
This basis will con-tinue to be valid throughout the life of the plant.
Hence no change to this Technical Specification is recommended.
Technical Specification 3.8.B.6 permits purging through the Standby Gas Treatment System during power operation. Technical Specification 3.7.A.1.2 requires that a differential pressure between the drywell and suppression chamber of 1.5 psid or greater be maintained. The only practical way of maintaining this differe_tial pressure requires that the two inch suppression pool exchange purge isolation valves be left open.
These valves do close upon receipt of a containment isolation signal.
The benefit gained by maintaining this 1.5 psid differential pressure enhances plant safety without significantly reducing the margin of safety. Hence no change to these Technical Specifications are recommended.
In conclusion we feel this letter is responsive to your letter of November 29, 1978.
Should any further information be required please contact us at your convenience.
Very truly yours, 1
WG