ML20082P639
| ML20082P639 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 08/28/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082P637 | List: |
| References | |
| NUDOCS 9109100429 | |
| Download: ML20082P639 (3) | |
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'i; UNITED STATES i (
NUCLEAR REGULATORY COMMISSION h
WASHINGTON D.C. 20E66 g v[/
o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 74_TO FACILITY OPERATING LICENSE NO. NPF-43 DETROIT EDISON COMPANY FERMI-2 00CKET NO. 50-341
1.0 INTRODUCTION
By letter dated August 2, 1990, the Detroit Dison Company (DEt.o or the licensee) requested amendment to the Technical Specifications (TS) appended to Facility Operating License No. NPF-43 for Ferei-2.
The proposed amendment would revise the emergency core cooling 7
%m (ELCS) response time requirements for the low pressure core injm,9n (JCI) mode of the residual heat removal (RHR) system.
The new response time requirements eflect the results of a recalculation of the applicable accident analysis by General Eler,ti-ic that includes a five second time delay for re energizing the Swing Bus that was not specifically accounted for in the accident analysis.
While performing a modification change to enhance the LPCI Swing Bus to address a degraded voltage concern (this modification was the sub,)ect of the Fermi-2 Licensee Event Report 87-045-01, dated November 6, 1989), it was determined that a five second time delay in the re-energization of the LPCI Swing Bus, which is required in some accident situations, had not been specifically accounted for in the accident analysis.
The licensee stated that the original analysis at the time of the above determination contained enough conservatism to bound the five second Swing Bus time delay even though it did r.ot specifi-cally consider it.
The accident situation which is applicable to i
re-ener0 zation of the Swing Bus is discussed below.
In the event of a break or loss-of-coolant accident (LOCA) in one of the two reactor recirculation system loops, logic is provided to sense the broken loop and to inject full LPCI flow into the unbroken loop from both divisions of LPCI.
Thus, the flo,e from t.,o LPCI divisions are interconnected by valving and depend on individual valves J ose failure could completely inhibit LPCI flow.
Since electrical power to each LPCI Division is separated (Division I and II),
Fermi-2 has a LPCI Swing Bus arrangement which permits essential LPCI recir-culation system valves that c:: Id be disabled by a failure of a divisional electrical supply to be erergf"ed by either electrical division.
Under loss-of-offsite power (LOSI) con ;itions, the Swing Bus is normally re-energized from the Division II Emergency Diesel Generators (EDGs) without further time delay when this power source becomes available, 91091C7429 910920 PDR ADOCK 0500034.1 P
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. o However, if this power source is not available because of single failure, the logic to allow re-energization from the Division I EDGs has an inherent five second time delay.
Because this five second time delay was not specifically covered in the applicable analysis of record, Detroit Edison had General Electric recalculate the ECCS response time to allow for this additional time delay and to provide for additional margin, as described below.
The response time was also recalculated to verify that delaying LPCI would not exceed the accident consequences of the most limiting analysis of record.
A recalculation of the applicable analysis of tha LPCI mode of RHR was performed delaying LPCI for an additional 12 seconds to account for the loading time to re-energize the LPCI Swing Bus, as discussed above, and to justify an increase in the response time.
The revised analysis datermined that the limiting analysis of record was not exceeded by the additional time delay associated with LPCI.
The limiting anilysis of record is associated with a LPCI injection valve failure which completely disables all LPCI flow and relies on the core spray and high pressure coolant injection (HPCI) systems for core flooding.
2.0 EVALUATION Detroit Edison had General Electric recalculate the appropriate ECCS accident response calculations accounting for a longer (by 12 seconds) LPCI injection time which, conservatively, bounds the additional five seconds required for the Swing Bus to re-energize as previously described.
This calculation was done using an approved ECCS Evaluation Model in accordance with Appendix K to 10 CFR Part 50 to determine the peak cladding temperature (PCT) of the reactor fuel.
This PCT is compared to the acceptance criterion of 2200*F PCT specified in 10 CFR 50.46.
The previous worst-case PCT for events involving the response of the LPCI mode of RHR has increased from less than 1800*F to less than 1900 F when evaluated with a new response time of 55 seconds for the LOCA/LOSP event.
The most limiting PCT for the large break LOCA/LOSP still occurs for an event where the LPCI mode of RHR does not respond (LPCI injection valve failure).
This case is unaffected by the increased response times discussed above and thus the limiting PCT remains unchanged at 2084 F.
The other acceptance criteria of 10 CFR 50.46 are not affected by the increased response time since the limiting PCT remained unchanged.
The General Electric analysis also, conservatively, assumed that the last initiation signal (low water level 1) rather than the first initiation signal (high drywell pressure) initiates LPCI.
This assumption delays the initiation of LPCI more than the delay from the single failure which causes the Swing Bus transfer.
In summary, a margin of over 300 F remains between the new calculated PCT value for LPCI node of RHR and the 10 CFR 50.46 PCT criterion of 2200 F with the delayed response time.
Additionally, the limiting PCT (2084 F) remains unchanged.
For these reasons, we find the proposed change to be acceptable.
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6 3.0
SUMMARY
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We have reviewed the results of the analysis submitted by Detroit Edison
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Company for fermi-2 with a delayed LPCI response time. We find that acceptable methods (10 CFR Part 50, Appendix K) were utilized for the calculations and that the criteria of 10 CFR 50.46 have been satisfied.
For these reasons, te find the l
proposed change of 55 seconds instead of 43 seconds delay time to be acceptable.
4.0 STATE CONSULTATION
i In accordance with the Comission's regulations, the Michigan State official was notified of the proposed issuance of the amendment. The State official j
had no comments.
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5.0 ENVIRONMENTAL CONSIDERATION
j The amendment changes a requirement with respect to the installation or use of 5
a facility component located within the restricted area as defined in 10 CFR r
Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of i
any effluents which may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there-has been no public coment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical axclusion 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 amendment.
6.0 CONCLUSION
The Comrtission 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 a:tivities I
will be conducted in compliance with the Commission's regulations, and (3) the i
issuance of the amendment will not be inimical to the comon defense ano security or to the health and safety of the public.
Principal Contributor:
R. Frahm Date: August 28, 1991 l
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