ML20035A265
| ML20035A265 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/18/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20035A263 | List: |
| References | |
| NUDOCS 9303250069 | |
| Download: ML20035A265 (4) | |
Text
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UNITED STATES c, e
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NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 2055s-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 77 TO FACILITY OPEP,ATING LICENSE NO. OPR-80 AND AMENDMENT NO. 76 TO FACILITY OPEPsATING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT. UNITS 1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By letter of December 21, 1990, as supplemented on November 22, 1991 and i
October 26, 1992, Pacific Gas and Electric Company (or the licensee) submitted a request for changes to the Technical Specifications (TS). The proposed amendments would add a new TS, " Main Feedwater Regulating, Bypass and Isolation Valves," to the Diablo Canyon Power Plant (DCPP) TS. These amendments also increase the main feedwater regulating valve and bypass valve closure time limit from 5 to 7 seconds.
The amendment request is intended to improve control of the DCPP Main Feedwater Systems without implementation of design or hardware changes and to provide clarification concerning the Applicability and Action for an inoperable Main Feedwater System valve.
The November 22, 1991 and October 26, 1992, letters provided clarifications on the safety analysis, and more restrictive surveillance requirements and allowed outage times for the proposed TS that did not change the action noticed in the Federal Reaister on March 6,1991, and did not affect the initial proposed no significant hazards consideration determination.
2.0 EVALUATION The proposed license amendment would add TS 3/4.7.1.7, " Main Feedwater Regulating, Bypass and Isolation Valves," and the associated TS Bases. This proposed TS requires all Main feedwater Regulating Valves (MFRV), their associated Bypass Valves, and all Main Feedwater Isolation Valves (MFIVs) to be Operable during Modes 1, 2 and 3.
This applicability is consistent with the Applicability of TS 3/4.7.1.5, " Main Steam Isolation Valves" (MSIVs). We find a definite safety functional relationship between the MSIVs and the MFIVs.
These safety functions are to limit reactor coolant system cooldown and containment peak pressure. The main feedwater system valves and MSIVs would be expected to have similar requirements, therefore, we find the applicability of the proposed TS to be acceptable.
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9303250069 930318 PDR ADOCK 05000275 P
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With one Main feedwater Regulating, Bypass or Isolation Valve inoperable,- the required TS action would be to either restore or close the inoperable valve within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, or if the inoperable valve is a MFRV or MFRV bypass valve, isolate the inoperable valve with at least one closed valve within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
The intended safety function is met by closing or isolating an inoperable valve.
In the event that an inoperable valve is not restored to operable status or closed, the required Action would place the plant in Hot Standby i
within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Hot Shutdown within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. These i
allowed outage times are consistent with those specified for an inoperable MSIV and are acceptable.
i The surveillance requirements require that the MFIV, MFRV and MFRV bypass l
valves be tested to verify closure times in accordance with TS 4.0.5.,
consistent with the requirements for the MSIVs. Thus, the operability of each valve would be demonstrated at least each cold shutdown, but not more i
frequently than once per 92 days which the staff finds acceptable.
The closure time limit for the MFRVs and the MFRV bypass valves would be less than or equal to 7 seconds, not including instrumentation delays, consistent
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with a 2 second increase. The closure time limit for the MFIVs would remain i
at the present limit of 60 seconds, not including instrumentation delays.
Double isolation is provided with the MFRVs and MFRV bypass valves providing c
early isolation and the MFIVs in tandem with the feedwater pump trip providing the primary isolation function. As a result, the MFRVs and MFRV bypass valves i
are only relied upon for the first 60 seconds of a transient, after which the MFIVs are relied upon.
The safety functions of the MFRVs and MFRV bypass valves are to rapidly close on the following transients i
i 1.
A main steam line break, thereby limiting the reactor coolant system (RCS) cooldown and limiting the total energy release to the Centainment.
2.
An excessive heat removal due to a feedwater system malfunction, thereby
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terminating cooldown of the RCS.
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Although the feedwater system is primarily Design Class II, the feedwater control valves (MFRVs and MFRV bypass valves) are maintained as Design Class 1.
Although these valves are installed in Design Class II piping, situated about 40 feet from the MFIVs, both piping and valves have been seismically evaluated to ensure continued operation to support the accident mitigation requirement of the MFRVs and MFRV bypass valves which is early isolation of the main feedwater system to prevent continued feedwater flow into the steam generators.
In addition, Design Class I check valves are installed upstream i
of each MFIV. These valves ~ provide the pressure boundary for operation of the-i auxiliary feedwater system if the MFIV were to fail open. The pressure-retaining feedwater system valves, fittings, and piping conform, as a minimum i
design criteria, to the ANSI code for Pressure Piping B31.1 and B31.7 where applicable. The feed lines from the MFIVs to the steam generators are covered by the ASME Boiler and Pressure Vessel Code,Section I.
If the feedwater l
control valves fail _ to close, then the primary means of feeQater isolation would occur by feedwater pump trip actuated by a safety grade signal (terminates feedwater flow in about the same time frame as the MFRV closure) r,
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. and closure of the MFIV (60 second closure time).
In addition, the air operators on MFRVs and MFRV bypass valves fail in the closed position upon loss of air or loss of power.
The licensee proposed an increase of 2 seconds in the MFRVs and MFRV bypass l
valve closure time limit.
They requested the increase due to the difficulties experienced in meeting the 5 second time requirement at Diablo Canyon. The licensee performed a safety evaluation to address increasing the limit from 5 i
seconds to 7 seconds. As previously mentioned, the potentially affected accident analysis included feedwater system malfunction, main steam line break mass and energy release inside containment, and main steam line break core response. The licensee confirmed that the analysis met all acceptance criteria and fully supports a 7 second closure time. The staff reviewed the licensee's non-LOCA safety analysis feedwater isolation assumptions for Diablo Canyon, provided by letter dated November 22, 1991, and found them acceptable.
Based on the equivalent safety grade / Design Class I feedwater system components, the TS 4.0.5 surveillance requirements and the unique Diablo Canyon design providing a double main feedwater isolation function, the staff finds the licensee's proposed new TS and the increase of 2 seconds in the MFRVs and MFRVs bypass valve closure time limit to be acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, i
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 a proposed finding that the amendments involve no significant hazards considera-tion, and there has been no public comment on such finding (56 FR 9382).
Accordingly, the amendments meet 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 prepared in connection with the issuance of the amendments.
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 i
public will not be endangered by operation in the proposed manner, (2) such
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i activities will be conducted in compliance with the Comission's regulations, i
and (3) the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
S. Peterson i
Date:
March 18, 1993 I
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