ML20096D100
| ML20096D100 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 08/28/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20096D096 | List: |
| References | |
| NUDOCS 8409050553 | |
| Download: ML20096D100 (3) | |
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NUCLEAR REGULATORY COMMISSION tj-WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 77.T0 FACILITY OPERATING LICENSE NO. DPR-35 BOSTON EDISON COMPANY PILGRIM NUCLEAR POWER STATION, UNIT 1 DOCKET N0. 50-293 1.0 Introduction By letter dated March 20, 1984 (Ref. 1) the Eoston Edison Company (BECo) requested permission to extend the operational envelope for the Pilgrim Nuclear Power Station.
The proposed power / flow map shown in Figure 1-1 of Reference 2 shows an increase in core flow to operate within the region i
bounded by 100% power,100% core flow and 100% power,107.5% core flow throughout C Cycle (E0C) ycle 6. Reference 3 supports proposed operation at End of 6 and for exposure beyond E0C 6 with increased core flow.
The conditions evaluated were 100% power operation beyond the standard E0C 6 conditions with a 43'F reduction in feedwater temperature followed by a natural reactivity coastdown to 80% power under conditions bounded by 112.5%~ core flow.
The evaluation also includes. continued operation in the region of the operating map bounded by the cons 4 ant core flow line between 80% power, 112.5% core flow and 50% power, 112.5% core flow.
l 2.0 Evaluation The limiting abnormal operational transients previously(analyzed for rated l
flow operation as well as the loss of coolant accident LOCA), fuel loading error accident, rod drop accident, and rod withdrawal error event were reevaluated for increased core flow operation. These events were also l
reevaluated for End of Cycle operation with increased core flow and the l
last stage feedwater heaters valved out.
The results show that the current Technical Specifications with incorporation of the minimum critical power ratio (MCPR) limits of Table 2-3 (Ref. 2) are adequate to preclude the violation of any safety limits during operation of Pilgrim within the proposed operating map for C The critical power ratios (CPRs)ycle 6 and for exposures beyond E0C 6.
and the MCPR operating limits are given in Tables 2-2 and 2-3 of Reference 2.
The MCPR limits.must, however, be raised from 1.46 (8x8) and 1.49 (P8x8R) to the appropriate values given in l
Table 2-3.
At core flows greater than 100% rated, the rod withdrawal error becomes the limiting transient.
However, by installing a constant 107% trip at flows greater than 100% rated, the flow dependence of the rod block trip is removed and the effects of this transient are mitigated.
The proposed constant 107% power rod block trip is more conservative than the present flow-biased setpoint for flows greater than 100% rated.
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~2-We have reviewed the effect of increased pressure differences due to increased core flow on the_ reactor internal components, fuel channels, and fuel bundles and find. that the design limi,ts will not be exceeded.
The effect of the increased flow rate on the flow-induced vibration response of the reactor internals was also evaluated. Based on the results, we conclude that the reactor internals response to flow-induced vibration would be within acceptable limits for plant operation in the increased core flow region.
The increase in the feedwater nozzle usage factor due to the feedwater temperature reduction was evaluated for coastdown.
The results show that the average additional fatigue usage due to rapid cycling that will occur on the feedwater nozzle would produce a usage factor greater than.1.0 in 36 to 37 years assuming 13-year refurbishment intervals.
This refurbishment period can be reduced to 12 years in order to keep the 40-year usage factor below I 0.
The thermal-hydraulic stability was evaluated for increased flow operation with the last stage feedwater heaters valved out-of-service.
The overall results indicate that the thermal-hydraulic stability is acceptable for feedwater temperature reduction and increased core flow.
The impact of feedwater temperature reduction and increased core flow operation on the containment LOCA response was analyzed.
The current containment LOCA response analyses results were found to be adequate for these extended operating conditions-3.0 Summary We find that approved thermal hydraulic methods have been used and that the results of the analyses support the proposed limit MCPRs, which avoid violation of the safety limit MCPR-for design transients.
We, therefore, conclude that the core flow increase beyond the rated flow will not adversely affect the licensee's capability to operate Pilgrim safely during extended flow operation.
Based on our review, we conclude that clipping the Rod Block Monitor at 1077,of rated power will permit the plant to be operated within the limits shown on Technical Specification Figure 3.11-9.
The proposed change in footnote 2 of Table 3.2.C requires this clipping.
We therefore find that the proposed changes in the Technical Specifications are acceptable.
4.0 Environmental Consideration This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined that the amendment involves no significant increase
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. 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 e The Commission has previously issued a proposed finding Yhat thi,xposure.
s amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, this 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 prepared in connection with the issuance of this amendment.
5.0 Conclusion
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We have 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, and (2) such activ-ities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
6.0 References 1.
Letter from W. D. Harrington, BECo, to D. B. Vassallo, NRC, dated March 20,1984, " Proposed Technical Specif4 cation Change to Allow Increased Core Flow."
2.
" Safety Review of Pilgrim Nuclear Power Station, Unit No. I at Core Flow Conditions Above Rated Flow Throughout Cycle 6," NED0-30242, August 1983.
3.
" Safety Review of Pilgrim Nuclear Power Station, Unit No. I at Core Flow Conditions Above Rated Flow Throughout Cycle 6," NED0-30242, Supplement 1, September 1983.
Principal Contributor:
L. Kopp Dated:
August 28, 1984
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