ML20081L474
| ML20081L474 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/03/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20081L456 | List: |
| References | |
| NUDOCS 8311160275 | |
| Download: ML20081L474 (4) | |
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4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 64 TO FACILITY OPERATING LICENSE NO. NPF-3 TOLEDO EDISON COMPANY AND CLEVELAND ELECTRIC ILLUMINATING COMPANY DAVIS-BESSE NUCLEAR POWER STATION, UNIT 1 DOCKET NO. 50-346 1.
Introduction By letter dated February 11, 1980 (Ref. 1), ToTedo Edison (the licensee) proposed a Technical Specification (TS) amendment regarding Limiting Condition for Operation (LCO) 3.2.5.
The current Technical Specification 3.2.5 specifies that with any of the reactor coolant (RC) hot leg temperature, RC pressure or RC flow rate outside its limits during mode 1 operation, action is required to restore the parameter to within its limit within two hours or reduce the thermal power to less than 5% of the rated themal power within the next four hours. The proposed Technical Specification change would retain the same action when either
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the RC hot leg temperature or RC pressure exceeds its limit. With regard to the RC flow rate outside its limit, the action would require either (1) restoring the RC flow to within its limit within two hours; or (2) within the next four hours, reducing the thermal power at least 1
2% rated thermal power for each 1% RC flow is below the specified limit for three-pump operation. This Technical Specification amendment request was not granted for lack of basis.
By letter dated July 10, 1981 (Ref. 2), the licensee provided a revised Safety Evaluation for the proposed Technical Specification amendment.
This SE addresses the staff evaluation of the proposed Technical Specification change and the related safety analysis.
2.
Evaluation The purpose of the Technical Specification LCO 3.2.5 is to ensure that the departure from nucleate boiling ratio (DNBR) safety limit is not violated during normal operation and anticipated operational occurrences.
The current Technical Specification requires that the' measured RC flow,
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after compensating for a 2.5% measurement uncertainty, be greater than or equal' to 396,800 gpm with four pumps operating and 297,340 gpm with three pumps operating. The proposed amendment is to relax the j,
action statement to require a power reduction of 2% rated thermal power for each 1% flow is below its specified four-pump limit and a i
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12-3 power reduction of 2% of 75% rated thennal power for each 1% the flow is below its specified three-pump limit. The licensee provided I
the result of Babcock & Wilcox calculations showing a.DNBR margin gain from the proposed flow and power tradeoff, i.e., an increase in DNBR margin results from the power decrease per. the proposed action statement when RC flow is below its limit. The licensee, in response to NRC staff questions, provided a more detailed description (Ref. 3) of the analysis for both four-and three-RC pump operations. The-CHATA (Ref 4) and TEMP (Ref. 5) computer codes were used for the core flow distribution and detailed DNBR analysis respectively_of the limiting fuel assembly. The analysis was performed using the maximum design overpower conditions with conservative assemptions and varying RC flow and thermal power according to the proposed modified action statement. The results show increased DNBR margin with decreasing
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flow and power reduction at the steady state conditions. Since the initial DNBR margin tends to be carried through to the transient minimum DNBR, the consequences of the existing transient analyses remain bounding by preserving the initial conditions of the. transients.
The licensee, in response to an NRC staff question, provided a list of review results (Ref. 3) on the impact of the proposed flow and power-i reduction on the Final Safety Analysis-Report (FSAR) Chapter 15, analyses of all anticipated operational occurrences and accidents.
l These results show that the anticipated operational occurrences and accidents with reduced flow and power initial conditions are all bounded by the original FSAR analyses.
l The NRC staff has also performed an independent audit calculation-using the sensitivity factors'(Ref. 6) of the change of DNBR with respect to the RC flow and power for the B&W-2 critical heat flux correlation.
The result shows that a 1% RC flow reduction requires a 1.05% reduction in power in order to preserve the same DNBR. Therefore, the proposed Technical Specification change of 2% power reduction per 1% RC flow reduction is conservative. Based on our review of'the licensee's l
proposed Technical Specification amendment on LCO 3.2.5, we have-j concluded that the proposed change will not result in a reduction of the DNBR margin during normal operation, and the safety analyses j
of the anticipated operational occurrences and accidents are still bounded by the original analyses provided in FSAR Chapter 15.
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Therefore, we have concluded that the proposed Technical Specification change poses no significant safety concern and is acceptable..
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Environmental Consideration We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the stand 4
envirnnmental impact and, pursuant to 10 CFR 551.5(d)(4) point of tha t - an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
4.
Conclusion 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 activities 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.
Dated: November 3, 1983 This Safety Evaluation was prepared by Y. Hsii of NRR.
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References 1.
Letter', R. P. Crouse (Toledo Edison) to NRC, Docket No. 50-346, License No. NPR-3, Serial No. 590, February 11, 1980.
2.
Letter, R. P. Crouse (Toledo Edison) to J. p. Stolz (NRC), Doc: et No. 50-346, License No. NPF-3, Serial No. 731, July 10,1981.
3.
Letter, R. P. Crouse (Toledo Edison) to J. F. Stolz (NRC)
Docket No. 50-346, License No. NPF-3, Serial No. 923, March 21,1983.
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4.
BAW-10110. "CHATA-Core Hydraulic and Thermal Analysis," Babcock & Wilcox Company, January 1976.
5.
BAW-10021, " TEMP-Thermal Enthalpy Mixing Program," Babcock & Wilcox Company, April 1970.
6.
FATE-79-101, G. M. Hesson and J. M. Cuta, " Analysis of the Sensitivity of Calculated MDNBR to Eight Selected DNB Parameters," Battelle Pacific Northwest Laboratories, Richland, Washington, March 1979.
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