ML20207N899
| ML20207N899 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/07/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20207N848 | List: |
| References | |
| TAC-60833, TAC-60834, NUDOCS 8701140481 | |
| Download: ML20207N899 (5) | |
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NUCLEAR REGULATORY COMMISSION o
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 11 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT NO. 9 TO FACILITY OPERATING 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 INTRODUCTION By letter dated February 14,1986 (Ref.11, the licensee proposed the following changes to the facility Technical Specifications:
1.
Revise Technical Specification 3.6.2.3 to assure that two, instead of the current three, containment fan cooler units are available, assumino a single failure; 2.
Revise Technical Specification 3.6.1.4 and its Bases to specify a maximum positive containment internal pressure of 1.2 psig, instead of the current 0.3 psig, and a maximum positive containment internal pressure of 46.65 psig, instead of the current 46.91 psig in the event of a loss of coolant accident (LOCA); and 3.
Revise Basis 3/4.6.1.6 to specify a maximum containment pressure of 46.65 psig, instead of the current 46.91 psig in the event of a LOCA.
EVALUATION The containment fan cooler system (CFCS) for Unit I and Unit 2 of the Diablo Canyon Nuclear Power Plant consists of five fan cooler units each, also called fan coolers,' cooling fans or fans. The five fan cooler units are divided into three independent groups, each group powered from a separate electrical bus (Buses F, G and H). Two groups (Bus F and Bus G) have two fan units each; the third group (Bus H) has a single fan unit. lne current Technical Specifications require all three groups with all five fan cooler units to be operable. A single failure with the loss of one fan places the CFCS into an action statement mode.
Thus, three fan coolers would be operable, as a minimum, assuming the single failure to be the loss of a group with two fan cooler units.
8701140481 870107 PDR ADOCK 05000275 P
-2 The proposed revised Technical Specifications would require either one fan cooler unit in each of the three groups or two fan cooler units in two groups to be operable, before the loss of a fan cooler unit would place the CFCS into an action statement mode. This revision would greatly enhance the operational capability of the CFCS. Two fan coolers would be operable, as.a minimum, to provide the required cooling capability as discussed below. ~The staff concludes that the proposed revision with respect to the three independent electrical power sources is acceptable.
The staff also considered the proposed changes in the Technical Specifications with respect to the necessary redundancy in capability for heat removal from the fan cooler units via the component cooling water (CCW) system and auxiliary saltwater (ASW) system to the ocean as the ultimate heat sink. The CCW system had been evaluated in detail with respect to its redundancy and heat renoval capability under accident conditions as discussed in Supplement No.16 to the Safety Evaluation Report (SSER-16, August 1983). That evaluation determined the system to be adequate in all aspects; it does not change as a result of the proposed changes in the Technical Specifications.
(The acceptability of two fan coolers as compared to three fan coolers required for safe shutdown under emergency conditions is discussed below). The ASW system consists of two, 100 percent capacity loops, one each connected to each of the two CCW system heat exchangers. The two ASW loops are cross-connected similar to the cross-l connection between the two vital CCW loops. Based on its evaluation of the CCW and ASW system, the staff has determined that adequate cooling capability is provided to the fan coolers under emergency conditions assuming a single failure.
The staff concludes that the proposed changes in Technical Specifications are acceptable with respect to heat reeval capability from the fan cooler units.
To support the proposed changes to the Technical Specifications, the licensee performed a reanalysis of the containment pressure and temperature response to the design basis LOCA, that is, a dcuble-ended break of the reactor coolant pump suction (cold leg) piping. The licensee's reanalysis, performed by l
Westinghouse, shows that the peak containment pressure does not exceed the l
containment design pressure of 47 psig.
For the analysis the licensee increased the assumed initial containment pressure from the current 0.3 psig to 1.2 psig, assumed two instead of three containment fan cooler units to be operable following a single failure, and took credit for containment heat sinks that had not been I
included in the previous analysis. The heat sinks act as a passive heat removal l
system and, in conjunction with the containment spray system, provide most of the heat removal from the containment atmosphere early in the transient.
The additional heat sinks consist of items that have traditionally been ignored in containment analyses as unnecessary, but which have always been present inside the containment. The additional items are the accumulators, reactor coolant punp motors, fan coolers, steam generator snubbers, and large bore pipe supports.
Except for these changes, the reanalysis is the same as the analysis previously presented by the licensee (Refs. ? and 3) and reviewed and approved by the staff (Ref. 4).
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Using these assumptions the licensee calculated a peak containment pressure of 46.65 psig. The staff performed a confirmatory analysis using its CONTEMPT-LT/28 computer code, based on two operable fan cooler units, an initial containment pressure of 1.2 psig, and the original heat sinks (i.e., the staff's calculation did not account for the additional heat sinks mentioned above). This resulted in a calculated peak containment pressure of 47 psig, which is slightly higher than the licensee's calculated pressure.
However, considering information gained by the earlier confirmatory analysis performed by the staff in Reference 4 and considering the additional heat sinks which the licensee included in its calculation, the staff finds that the licensee's calculated value of 46.65 psig is reasonable. Therefore, the staff concludes that the licensee's analysis is acceptable.
An additional acceptance criterion of the Standard Review Plan (SRP), Section 6.2.1.1.A. is that the calculated containment pressure should decrease to less than 50% of the peak calculated pressure within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the onset of an accident. This is based on General Design Criterion 38, which requires that the containment heat removal systems shall be capable of rapidly reducing-the containment pressure following a LOCA and maintaining it at an acceptably low level. Although the licensee has not addressed this criterion in the license amendment request (Ref.1), the licensee's earlier analysis (Refs. 2 and 3) shows that the criterion would be met in less than 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. at which time containment pressure would be less than 20 psig. Although in the current analysis by the licensee the containment heat removal capacity is reduced by one-third (i.e., decreasing the number of operable fan coolers from three to two) and the initial containment pressure is increased by 0.9 psig, the staff concludes that the containment pressure would be reduced to less than 23.3 psig (i.e., 50% of peak calculated pressure) in approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or less, that is, less than the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> maximum set forth in the SRP. Therefore, the staff concludes that General Design Criterion 38 and the cited acceptance criterion of SRP 6.2.1.1.A are satisfied.
Based on the above, the proposed changes to the Technical Specifications are found to be acceptable, as they would not result in the containment design pressure of 47 psig being exceeded in the event of a LOCA, and the requirements of General Design Criteria 38, as provided for in SRP 6.2.1.1.A, are satisfied.
l The revised Technical Specifications as approved by the staff are not verbatim the changes proposed by the licensee.
In order to maintain greater consistency between the Diablo Canyon Technical Specifications and the Westinghouse Standard Specifications, the staff changed some of the wording proposed by the licensee.
These alterations, however, do not change the intent of the changes proposed by the licensee.
ENVIRONMENTAL CONSIDERATION These amendments involve a change in the use of the facilities components located within the restricted areas as defined in 10 CFR 20. The staff has determined that these amendments involve 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 occupaticaal radiation exposure. The Commission has previously i
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. issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding.
Accordingly, these 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 statenent or environmental assessment need be prepared in connection with the issuance of these amendments.
CONCLUSIONS The staff concludes, based on its evaluation of the licensee's submittal and its own confirmatory analysis as discussed above, that the proposed changes to the Technical Specifications involve no significant hazards consideration and are acceptable. The staff further concludes, 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, and (?) such activities will ba conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the commnn defense and security or to the health and safety of the public.
s Dated: January 7, 1987 PRINCIPAL CONTRIBUTOR:
J. Pulsipher C. Moon H. Schierling e
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REFERENCES:
1.
Letter DCL 86-035 from J. D. Shiffer (PG&E) to H. R. Denton (NRC),
Subject:
LAR 86-03, Containment Internal Pressure and Fan Cooler Operability Technical Specification Changes, dated February 14, 1986.
2.
Letter from J. O. Schuyler (PG&E) to H. R. Denton (NRC),
Subject:
Containment Spray Timing, dated June 23, 1983.
3.
Letter from J. O. Schuyler (PG&E) to H. R. Denton (NRC),
Subject:
Additional Information.on Containment Spray Timing - LAR 83-06, dated i
July 26, 1983.
4.
U.S.. Nuclear Regulatory Commission, Amendment No. 7 to Facility Operating License No. DPR-76, letter from G. W. Knighton, (NRC) to P. A. Crane (PG&E),datedNovember 10, 1983.
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