ML20080G671
| ML20080G671 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 02/04/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19277F954 | List: |
| References | |
| TAC-53214, TAC-53215, NUDOCS 8402130567 | |
| Download: ML20080G671 (4) | |
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_SjFETY Ep,LUATIO!! REPORT UI ATED TO A!TUO"FNT N0. 28 TO FACIlli f OPFP.ATING LICE!'sr NPF-9 pl_Ty A[END!aEitT ila. 9 TO FACILITY CPEPATING LICENSE HPF-17
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l' UKE POWER C0MPAftY INTRODUCTION By letter dated November 18, (Ref.1) 1983, as supplemented by letters dated December 5 (Ref. 2) 6nd 8, (Ref. 31 1983, the Duke Power Company (licensee) requested amendments to Appendix A of Operating Licenses NPF-9 and NPF-17.
The proposed change involves Technical Specifications related to minimum reactor coolant systen (RCS) flow for Unit 2.
In addition, changes to the limits for safety system settings were proposed to accommodate the new RCS flow recuirements.
tinit 2 operation is restricted to 90% rated thermal power because the measured RCS flow does rot meet the existing Technical Specification flow requirenent for operation above 90%. Briefly, the proposed Technical Specification changes, primarily concerned with Unit 2, are (1) reduction by 2% of the reactor coolant system flow rate required for operation of Unit 2 at 100% power; (2) revision of the safety system setting limits to accommodate the RCS flow reduction; and (3) provision for a 2% reduction in power for each 1% reduction in the measured RCS flow below the flow requirement for 100% power.
EVALUATION Uith regard to the proposed Technical Specification amendment to allow plant operation of Unit 2 at 100% power with a reduced reactor coolant systen flow of 98% of the existing rated flow, the licensee has performed a safety analysis to determine the impact of the flow reduction. Since the RCS flow reduction will result in lower DNBR during the normal operation and anticipated trans-ients, the licensee has performed a sensitivity study on the rate of change of DNBR with respect to flow reduction, as described in a December 5,1983 letter (Ref. 2). The sensitivity study is performed with the approved THINC IV code for various state points representative of normal operating condition and transients including the DNBP, limiting loss of flow event. A DNBR sensitivity factor associated with each statepoint is calculated for both the typical cell and the thimble cell. The result of the analysis shows a maximum sensitivity factor of 1.6 obtained from the typical cell. This maximum sensitivity factor is used to assess the impact of flow reduction on DNBR even though the thimble cell is DNBR limiting. Using the sensitivity factor of 1.6, the DNBR reduction would be 3.2% for a 25 flow reduction. This DNBR reduction is comparable te the staff independent calculation using the sensitivity factor frem a Battelle Pacific Unrthwest Laboratories (PNL) study (Ref. 41.
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. The licensec has identificJ a 9.1': thermal mrgin due to the conservatisr 07d in the design analysis. A breakdown of the source of this thernal rarain is es follmes:
1.6% trun the use of the design linit DNBR cf 1.3 versus the allwable limit of 1.7h, 2.9% from the use of the grid spacing factor (K )
of 0.046 w rsus tbc allcwable 0.059, 1.2% from the use of the thermal diffusico coefficient of 0.033 versus the allowable 0.051, 1.7% from the use of a DNBR nultiplier of 0.86 versus the allowable 0.88, and 1.7% from the 17X17 rod bundle pitch reduction. This total margin ~of 9.1% is lower than the margin identified previously in the McGuire SER (Ref. 5) and is, therefore, conservative.
The licensee has used 6.9% of the thermal margin to compensate for the DNBR penalty due to fuel rod bowing.
The remaining 3.2% margin can, therefore, be used to compensate for the 3.2% DNBR penalty resulting from 2% RCS flow reduction.
Therefore, the proposed Technical Specification change to operate at 98%
of the current rated RCS flow will not result in the minimum DNBR falliry below the specified acceptable fuel design limit. This conclusion is applicable to DNBR liniting transients described in Chapter 15 of the Final Safety Analysis Report (FSAR).
Non-DNB-limited transients were also evaluated and the reults were determined to be within their respective limits.
These transients were:
- Control Rod Withdrawal From A Subcritical Condition
- Boron Dilution
- Loss of Load
- Loss of Normal Feedwater/ Station Blackout
- Steanline Break
- Rupture of a Main Feedwater Line
- Locked Rotor
- Control Rod Ejection
- LOCA Analysis Operation under this aspect of the proposed amendments would not involve a significant increase in the consequences of accidents previously evaluated.
With regard to the change to the Unit 2 Technical Specification to allow operation below 100% but above 95% of the rated RCS flow, the licensee proposes a 2 to 1 power / flow tradeoff, i.e., the reactor power will be reduced by 2% for every 1% reduction in measured flow above 95% of the full flow.
A similar amendment has previously been approved for McGuire Unit I where operation of 9E% flow in conjunction with 90% power level is acceptable.
The licensee has provided a sensitivity study showing that for every 1% flow reduction, a 0.088% power reduction is required in order to maintain the same thermal margin to DNB.
i The staff independent calculation using the PML sensitivity study results has shcwn comparable results.
Therefore, the proposed Technical Specification change to allow operation at reduced RCS flow with 2 to 1 pover/ flow tradeoff is conservative and acceptable.
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. In cc ution with the reader creration n reduccd RCS flow, the Technicci Speci; < r tions reg #ing the i ~c*or cco o afety limit and the thn mcl over torper a aro AT t. ip scQ oint a a revised :: ensure rmetor operaticn withN the DNS dc :ign L%cs and the hot leg boiling limit. The revision is donc et'.np the Mcstir 9 0use standard methedology describcd in WCAP-8745 (Ref. 6).
The licensee has deternined that the currcnt s'etpoint equation for the overter..pera-ture AT trip is adecuate with a slight modification in the Fi (a I) function.
This modification is shown in Table 2.2-1 of the proposed Technical Specification revision. Since WCAP-8745 contains the standard methodology used for over-temperature trip design bases, we conclude that the revised core safety limit and overtemperature aT trip setpoint are acceptable.
In sunnary, we have reviewed the safety analysis performed by the licensee to justify the proposed Technical Specification change for operation at reduced RCS flow. The review included sensitivity studies on the impact on the flow reduction on DNB thernal nargin, the DNBR limiting transients, and control rod withdrawal and ejection transients. We have found that there is enough thermal margin to compensate for the DNBR penalty resulting from 2% flow reduction, and that the proposed 2 to 1 power / flow tradeoff for operation above 95% flow is also acceptable. We have also concluded that the non-DNB-linited transient analyses in Chapter 15 of the FSAR renain valid.
ENVIRONMENTAL CONSIDERATION We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environnental impact. Having nade this determination, we have further concluded that the amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 951.5(d)(4),
that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of these amendri,ents.
CONCLUSION The Comnission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal Register (49 FR 529) on January 4, 1984, and consulted with the state of North Carolina.
No public comments were received, and the state of F rth Carolina did not have any comments.
We have concluded, based on the consideration 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 regulation and the issuance of these amendnents will not be inimical to the common defense and security or to the health and safety of the public.
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REFERENCES:
1.
Letter fron H. B. Tucker (Duke Power Company) to H. R. Denton (URC), "McGuire Nuclear Station, Docket Nos. 50-369 and 50-370, Unvember 18, 1983.
2.
Letter from H. B. Tucker (Duke Power Co.) to H. R. Denton (NRC),
"McGuire Nuclear Station, Docket No. 50-370,"' December 5, 1983.
3.
Letter from H. B. Tucker (Duke Power Co.) to H. R. Denton (NRC),
"McGuire Nuclear Station, Docket Nos. 50-369 and 50-370,"
December 8, 1983.
4 G. M. Hesson and J. M. Cuta, " Analysis of the Sensitivity of Calculated MDNBR to Eight Selected DNB Parameters, " FATE-70-101, Battelle Pacific Northwest Laboratories, March 1979.
5.
NtIREG-0422, "Sefety Evaluation Report Related to Operation of McGuire Nuclear Station, Units 1 and 2," March 1,1978.
6.
WCAP-8745, " Design Bases for the Thermal Overpower AT and Thermal Overtemperature AT Trip Functions," March 1977.
Principal Contributors:
Ralph Birkel, Licensing Branch No. 4, DL Y. Hsii, Core Performance Branch, DSI E. Throm, Reactor Systems Branch, DSI Dated: February 4, 1984 i
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