ML20041A751

LER 82-002/01T-0:on 820129,NRC Inspector Discovered That Primary Containment Following DBA LOCA May Not Be Vented Using Operating Procedure Due to Inaccessibility of Reactor Bldg.Combustible Gas Control Sys Will Be Installed

ML20041A751
Person / Time
Site:	Nine Mile Point
Issue date:	02/10/1982
From:	Patrou N NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20041A748	List: ML20041A747 ML20041A751
References
RTR-REGGD-01.007, RTR-REGGD-1.007 LER-82-002-01T, LER-82-2-1T, NUDOCS 8202220466
Download: ML20041A751 (2)

Text

NRC FORM 366 U. S. NUCLEAR REGULATOY CMON (7 77)

LICENSEE EVENT REPORT CONTROL BLOCK: l i

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) i 0 1 ti 3 lN lYLICENSEE lN lM CODE lP l1 l@l0 14 IS l 0l- l 0 l LICENSE Ol 0lNUMBEH0l 0 l -l 0 l 0 l@l 25 4 l 1LICENSE 26 l 1 l TYPE1 l 130 lhl5 7 LATl 58 l@

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! ? l1 lOl8l2lh DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h j o l2l l Upon review by the NRC Resident Inspector, it was discovered that the Operating i jol3l l Procedure describing the steps to be taken to vent the Primary Containment following l

[o [4 l l the DBA LOCA required personnel to enter the Reactor Building. Since the Reactor l

[o j s; [ Building may not be accessible at that time, the containment may not be able to be l l o I r> l l vented using this procedure. l lol71l l I

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l i [ o l l In response to Safety Guide 7 (now Regulatory Guide 1.7) Niagara Mohawk Power Corpora-l i i l tion committed to installing a combustible gas control system. This committment was 1 i , l made voluntarily during the Full Term Operating Licensing process (1972-1974 time periodp.

iij3; l Installation of the system proceeded af ter issuance of the Full Term Operating Licensel.

g i i4 ; l The system becam operational on November 21, 1977, about one year (see attached) l 7 8 9 80 ST S  % POWER OTHE R ST ATUS ISCOV F DISCOVEHY DESCRIPTION lil3l { @ l0l9l9l@l NA l l D l@l NRC Review l A TIVITY CO TENT RE LE ASE D OF RE LE ASE AMOUNT OF ACTIVITY LOC ATICN OF RELE ASE 7

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e to LICENSEE EVENT REPORT 82-02 (Cont'd) before the effective date of 10 CFR 50.44.

Shortly af ter the effective date of 10 CFR 50.44 (late 1978), the event at Three Mile Island occurred (early 1979). Considering that:

1. Emphasis to both the Niagara Mohawk Power Corporation and the Nuclear Regulatory Commission shifted to deal with numerous repercussions that evolved as a result of TMI.

2. Purging equipment existed at Nine Mile Point Unit #1 to meet the intent of 10 CFR 50.44; and

, 3. 10 CFR 50.44(g) allows a repressurization system provided pressure does not exceed 50% of containment design pressure, and the Nine Mile Point Unit #1 Final Safety Analysis Report states that pressure should not exceed 20 psig, which is only 32%.of dryvell design pressure, only 48% of torus test pressure, but 57% of torus design.

pressure of 35 psig (which is also DBA containment pressure).

A detailed review of the system with respect to 10 CFR 50.44 was just recently completed with the following findings:

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1. A redundant N supply existed.

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2. A redundant H2-02 m nitoring system existed.

3. Prior to January 29, 1982, a post LOCA containment venting procedure ~

existed but required entry into the Reactor Building for implementarion.

A procedure change was made on January 29 to allow venting without Reactor Building entry.

4. On February 5 another procedural change was made to establish a redun-dant purge path.

As' stated in the January 29, 1982, letter to Mr. Dominick B. Vassallo, Chief, Operating Reactors Branch #2, U.S. NRC, a system modification will be installed during the spring 1983 refueling outage. This modification will be designed in compliance with 10 CFR 50.44.

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