05000280/LER-1979-045, Updated LER 79-045/01X-1:on 791228,air Would Not Flow Through Filters If Consequence Limiting Safeguards hi-hi Signal Removed from Control Circuit of Safeguards Area Exhaust Ventilation Dampers.Caused by Design Deficiency

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Updated LER 79-045/01X-1:on 791228,air Would Not Flow Through Filters If Consequence Limiting Safeguards hi-hi Signal Removed from Control Circuit of Safeguards Area Exhaust Ventilation Dampers.Caused by Design Deficiency
ML20055B721
Person / Time
Site: Surry Dominion icon.png
Issue date: 07/15/1982
From: Joshua Wilson
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20055B719 List:
References
LER-79-045-01X, LER-79-45-1X, NUDOCS 8207230188
Download: ML20055B721 (3)
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LER-2079-045, Updated LER 79-045/01X-1:on 791228,air Would Not Flow Through Filters If Consequence Limiting Safeguards hi-hi Signal Removed from Control Circuit of Safeguards Area Exhaust Ventilation Dampers.Caused by Design Deficiency
Event date:
Report date:
2802079045R00 - NRC Website
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" UPDATE REPORT - PREVIOUS REPGAT DATE 01-10-30" ATTACHMENT 1 SURRY POWER STATION, UNIT 50. 1 DOCKET NO: 50-280 REPORT NO: 79-045/0lX-1 EVENT DATE: 12-28-79 TITLE OF THE EVENT: Discrepancy in Safecuards Area Exhaust Vent _ilation Fans Operation (1-VS-F-40A, B 6 2-VS-F-40A, B)

1. DESCRIPTION OF EVENT:

During a recent analysis, a non-conservative feature was found that is contrary to a FSAR commitment. The design deficiency concerned a discrepancy in the operation of the Safeguards Area Exhaust Ventilation Dampers for Units 1 and 2.

The event is reportable in accordance with Technical Specification 6.6.2.a.9.

2. PROBABLE CONSEQUENCES / STATUS of REDUNDA?TT SYSTEMS:

The analysis revealed that when a Consequence-Limiting Safeguards Hi-Hi signal is removed (CLS Hi-Hi Reset) from the control circuit of the Safeguards Area Exhaust Ventilation Fans (1-VS-F-40A, B 6 2-VS-F-40A, 3), the filter damper will close preventing the flow of air from passing through the filters. If a radioactivity source remained in the Safeguards Area following the resetting of the CLS Hi-Hi circuitry, contaminated air may be released to the atmosphere.

Existing procedures require the damper control switch to be placed in the " Divert to Filter" position prior to resetting the CLS Hi-Hi signal; therefore, the health and safety of the public would not have been affected. -

3. CAUSE:

The non-conservative feature of the Safeguards Area Exhaust Ventilation Damper operation was caused by an improper initial design concept.

4. IM'IEDIATE CORRECTIVE-ACTIONS:

A review of station procedures was initiated upon the discovery of the non-conservative operation of the Safeguards Area Exhaust Ventilation Dampers.

It was determined that existing procedures insure that prior to the resetting of the CLS Hi-Hi signal, the damper control switch is placed in the " Divert to Filter" position.

5. SUBSEQUENT CORRECTIVE ACTIONS:

A detailed analysis was initiated to verify that the control circuits of all Engineered Safeguards equipment operate in a conservative manner.

" UPDATE REPORT - PREVIOUS REPORT DATE 01-10-80" Page.2 Report ::o. 79-045/0lX-1

6. ACTION TAKEN TO PREVENT RECURREiCE:

A detailed analysis to verify that the control circuits of all engineered Safeguards equipocr.t operate in a conservative canner has been completed.

The findings have been forwarded to the NRC in the VEPCO letter Serial No. 346 dated March 6, 1981.

The control circuit of the Safeguards area exhaust ventilation system has been modified such that the resetting of the ESF actuation signal will not return the dampers to a non emergency position.

7. CENERIC IMPLICATIONS:

This event was a Stone & Webster identified generic item.

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