ML20106D934
| ML20106D934 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 10/02/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20106D932 | List: |
| References | |
| NUDOCS 9210160128 | |
| Download: ML20106D934 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF-NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. - 65 TO FACILITY OPERATING LICENSE NO. NPF-47 MLF STATES UTILITIES COMPANY RIVER BEND STATION. UNIT 1 DOCKET NO. 50-458
1.0 INTRODUCTION
The automatic depressurization system (ADS) is a safety related system:used to depressurize the primary _ system in the event of a small loss-of-coolant.-
accident-(LOCA) combined with the failure of the high pressure core spray system.
Depressurization of the primary system by opening 7'of the 16 safety relief-valves (SRVs) permits injection _. by either-the low pressure. core spray-system or the low pressure coolant injection system.
Each -SRV is a spring loaded valve-capable of being operated by_ either an externally attached p.ieumatic operating cylinder or-by direct steam pressure in opposition to spring compression. The normal air supply for the SRVs is-from the non-safety main steam system air compressors.
These compressors supply air at approximately 17 SCFM at.175 psig..In addition, the seven SRVs that -provide the ADS-function-have -a safety related accumulator and check
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valve to ensure the ability to hold the _ valve open if:the_ air compressors are lost.
Following a-LOCA,:it-is= assumed that off-site power will--be unavailable.
which would result in the loss of the air compressors to the SRVs..Long-term operation of the'SRVs will rely on the safety-related penetration valve leakage control system (PVLCS). - However, the PVLCS is manually loaded on the
' diesel generators and availability, as discussed:in the staff's Safety-Evaluation ~ Report (NUREG-0989), is nct assumed until 25 minutes after the LOCA.. Therefore, short-term pneumatic operation of the-ADS SRVs-is-dependent on-the SRV accumulators.
On January 31, 1991, an enforcement conference'was held in the Region IV Office regarding the rcrted inoperability of: the: ADS Nhich was caused:by the!
-inoperability of the normal supply; air compressors. Specifically, on January 4,1991 with the f.cility operating in Mode l', the licensee declared -
the. ADS. inoperable becausa of the indeterminate status of the _ capability of
'the ADS SRV.; to meet their design basis functions due to = apparent -inadequate i
air presrure in the.SRV accumulators. The apparent inoperability existed for approximately: 27-hours, which exceeded the technical specification limit of 12-hours. However, based on further analysis, it' was determined that sufficient air' pressure remained in the SRV accumulators such that the-ADS remained operable and would have been capable of performing-its intended function.
During the enforcement conference, the' licensee committed t o ~ submit a technical specification change t'o define the operability requirements of the ADS SRVs.
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'PDR-'ADOCK 05000458e P.
. In fulfilling the above commitment, the licensee's letter of ebruary 5, 1992 requested an amendment to facility Oper. ing License O. NPF 47.
The proposed amendment would add a surveillance raquirement to technical specification 3/4.5.1, " Emergency Core Cooling Systems - Operating," to verify a minimum SRV accumulator pressure of 131 psig once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
2.0 EVALVATIM The Standard Review Plan (NUREG-0800) does not recommend specific requirements for the ADS SRV accumulator size or pressure. General Electric design specifications list the minimum operating pressure for the ADS SRV air supply as 150 psig.
In addition, these design specifications state that for the ADS function, 50 gallons of accumulator volume for each ADS valve is required to provide two actuations with the drywell at 70 percent of drywell design p assure. While only one actuation of the ADS would be sufficient to perform its intended function, two actuations provide for additional margin.
In the River Bend Final Safety Analysis Report, the licensee stated that the accumulators were 60-gal'an capacity and designed to provide two actuations of the AOS at 70 percent of drywell design piecsure, which is equivalent to four to five actuations at atmospheric pressurr The staff accepted these values and included them in the Safety Evaluation Remrt.
Therefore, this has become the regu?atory basis for sizing the SRV accumulators.
The River Bend accumulators provide an actual pressurized volume of 66 gallens (including the piping volume between the accumulator and the air valve on the SRV actuator). With a larger volume than that specified by General Electric, accumulator pressure could be less than 150 psig and still be capable of meeting the FSAR commitments.
Engineering calculations performed by the licensee determined that a minimu.n accumulator pressure of 126.3 psig would be-necessary to provide for two actuations at 70 percent drywell design pressure.
Similarly, a minimum accumulator pressure of 130.4-psig would be necessary to provide for four actuations with the drywell at atmospheric pressure. Based on this information, the licensee determined that verification of a minimum-SRV accumulator pressure of 131 psig would be sufficient to demonstrate operability.
Pressure indication and low pressure alarm cnanrals are provirted in the' Main Control Room for both ADS SRV accumulator air supply headers.
The staff has reviewed the licensee's submittal and has concluded that a minimum SRV accumulator pressure of 131 psig will satisfy the licensing requirements for safe operation. Control Room indication and alarms are available to alert plant operators if pressure falls to unacceptable levels.
Based on our review, we conclude that the proposed change to require periodic verification of the SRV accumulator pressure is accaptable and that the l
licensee has met the comitment made in the January 31, 1991 enforcement conference previously discussed.
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'I 3.01: STATE CONSULTATION In accordance with the Commission's regulations, the Louisiana-State official:
was notified of the proposed: issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
. The amendment changes surveillance requirements. The NRC' staff has determined-that the amendment involves no significant increase in the amounts, and no-
- significant change in the. types, of any effluents that may be released
. offsite, and that there is no'significant increase in individual or cumulative occupational-radiation exposure.
The Commission-has previously issued aL proposed finding that the amendment involves no ~significant hazards-consideration, and there has been no public comment on such finding (57:FR 9414). Accordingly, the amendment meets the eligibility criteria for-categorical exclusion set forth in 10 CFR 51.22(c)(9)'.
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be
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prepared in connection with the issuance of the amendmer.t.
5.0 CONCLUSION
The Commission has' concluded, based on the considerations discussed above, that:- (1) there is-reasonable assurance'that the health and safety of the public will not be endangered by operation in the proposed manner,-(2) such-activities' will be conducted in compliance with the Commission's.rtgulations, and (3) the issuance'of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Douglas Pickett Date: October 2, 1992
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