ML20081K018
| ML20081K018 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 03/16/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20081K013 | List: |
| References | |
| NUDOCS 9503280360 | |
| Download: ML20081K018 (4) | |
Text
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UNITED STATES j
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' NUCLEAR REGULATORY COMMISSION l
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WASMGTON, D.C. 25H000 is,a, SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED'TO AMEN 0 MENT NOS. 164 AND.145 TO FACILITY-0PERATING LICENSE NOS. DPR-70 AND DPR-75 PUBLIC SERVICE ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC' COMPANY SALEM NUCLEAR GENERATING STATION. UNIT NOS. 1 AND 2 I
DOCKET NOS. 50-272 AND 50-311 t
1.0 INTRODUCTION
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By letter dated April 16, 1993, the Public Service Electric & Gas Company (the licensee) requested staff approval of a proposed change.to the Salem Nuclear j
Generating Station, Units 1 and 2, Updated Final Safety Analysis Report 1
(UFSAR). The proposed UFSAR change would add an exception to a general statement in the containment isolation system description. The general statament -is that automatic containment isolation' valves that receive signals to close, fail closed on loss of air or power. The proposed exception would
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apply to the outboard isolation valves for the control air system. These four i
valves (11,12, 21 and 22CA330, collectively identified as CA-330) fail closed on loss of air but fail as-is upon loss of the vital 125 VDC power supply to their solenoid control valves.
2.0 D.LSCMS_IDN
2.1 DESCRIPTION
0,F SALEM CONTROL AIR SYSTEM The Salem Control Air System consists of two headers.
Each header has a 2-inch penetration through each containment by which control air is supplied J
to_ equipment in the containments. An emergency control air compressor (ECAC) is provided for each header.
Each ECAC operates automatically in the event of failure of the normal supply of air from the non-safety-grade station service i
air system. The ECAC and portions of the control air system are safety-grade.
The control air headers can be manually cross-connected if desired. The ECACs are not subject to Technical Specifications. However, the licensee has administrative controls that preclude ECAC preventative maintenance if the other ECAC is unavailable. The station air system which provides the normal air supply to the control air systems has three 100% capacity air compressors.
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2.2 DESCRIPTION
OF SALEM 1 & 2 COMPRESSED AIR LINE CONTAINMENT ISOLATION PROVISIONS j
i Each of the 2-inch control air header containment penetrations has two isolation valves: (1) a check valve (CA-360) located inside containment and, (2) an air-diaphragm operated, solenoid-controlled valve (CA-330) located outside containment. The design of CA-330 is such that it will open when air pressure is applied to its air operator. When the air pressure is released, it will close under spring action. Application of air pressure to, or venting of air pressure from each CA-330 operator is controlled by a pilot solenoid valve. The solenoid valves are energized from a panel that is powered from a 125 VDC vital power bus.
The air supply for each CA-330 air operator is taken from its associated air header.
The CA-330 valves are designed to close on a Phase A containment isolation signal.
Control air is not required in containment to mitigate a design basis accident (DBA) as the equipment using control air will fail to the accident position on loss of control air.
The solenoid valves that control the CA-330 air operators are three-way valves, each having two 125 VDC coils. One coil, when energized (the normal condition), causes control air pressure to be applied to the associated CA-330 air operator in the open direction. The other coil, when energized, causes the solenoid to vent the air operator allowing the valve to close.
If neither coil is energized, the solenoid valve ports are sealed and the isolation valve is locked in its current position. Should a DBA occur, the Phase A isolation signal resulting from high containment pressure will apply 125 VDC power to the close coil which shifts the solenoid valve to the position that vents air from CA-330 air operator diaphram.
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. 2.3 REGULATORY CRITERIA REGARDING FAILURE POSITION OF CONTAINMENT ISOLATION VALVES Section 6.2.4 of the Standard Review Plan (SRP) specifies.he regulatory criteria for containment isolation systems. The SRP states, In the event of power failure to a valve operator, the valve p:sition should be the position of greater safety,.which is normally the postaccident position. However, special cases may arise and these will be considered on an individual basis in determining the acceptability of the prescribed valve positions.
3.0 EVALUATION The staff has examined the design of the isolation system for the control air header piping penetration. r'itn the exception of the failure position for valve CA-330 on loss of its 125 VDC power supply, the design meets all applicable criteria.
Failure of the 125 VDC power supply results in a slight degradation in containment isolation reliability. Upon failure of the 125 VDC power supply, the valve m.
remain in the "as is" position.
Since the valve is normally open, this means that the valve will stay open and will not close on an isolation signal.
For all other single failures, the valve will automatically close upon either loss of air or w isolction signal.
The staff has evaluated the conditions for the "as is" failure and finds that the reduction in safety margin due to this condition is acceptably small.
First of all, there is a check valve in series with the air operated valve so that containment integrity is maintained at all times.
Secondly, the probability of loss of air pressure is quite low since the normal air supply is backed up with a safety grade supply which is activated automatically upon sensing low air pressure. With an operable air supply, the penetration is not a containment leak path since the air pressure is greater than the peak calculated containment pressure.
Although the valve does not fail in the position of greater safety (an SRP 6.2.4 criterion) for a loss of 125 VDC power supply, the staff finds the degradation acceptably small for the reasons provided above.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the New Jersey State official was notified of the proposed issuance of the amendments.
The State official had nc comments.
5.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental assessment and finding of no significant impact have been prepared and published (60 FR 10617) in the Federal Register on February 27, 1995. Accordingly, based upon the environmental assessment, the staff has determined that issuance of the amendment will not have a significant effect on the quality of the human environment.
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5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, i
that:
(1) there is reasonable assurance that the health and safety of the i
public will not be endangered by operation in the proposed manner, (2) such activities will ha conducted in compliance with the Commission's regulations, and (3) the issuance of the avendments will not be inimical to the common l
defense and security cr t:: the health and safety of the public.
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Principal Contributor:
W. Long l
Date: thrch 16,1995 i
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