ML18142A698
| ML18142A698 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 05/22/1978 |
| From: | White L Rochester Gas & Electric Corp |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18142A698 (11) | |
Text
REGULATORY INFORI'lATION DISTRIBUTION SYSTEN (RIDS)
DISTRIBUTION FOR INCOMING I"NTERIAL 50-244 REC:
ZIENANN 9 L NRC ORG:
WHITE L D PORTLAND GEN ELEC DOCDATE: 05/22/78 DATE RCVD: 05/25/78
'O LETTER NOTARIZED:
NO COPIES RECEIVED
SUBJECT:
LTR 1
ENCL 1
FORWARDING INFO CONSISTING OF ANALYSIS OF THE EFFECT OF UPPER PLENUM INJECTION ON THE PEAK CLAD TENPERATURES OF EXXON FUEL FOR SUBJECT FACILITY.
PLANT NANE: RE GINNA UNIT 1
REVIEWER INITIAL:
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(DISTRIBUTION CODF A001)
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ITAtt ROCHESTER GAS AND ELECTRIC CORPORATION D 89 EAST AVENUE, ROCHESTER, N.Y. 14649 LEON D. WHITE, JR.
VICE PRESIDENT TELEPHONE AREA CODE 7IS 546.2700 May 22, 1978 Director of Nuclear Reactor Regulation ATTN:
Mr. Dennis L. Ziemann, Chief Operating Reactors Branch No.
2 U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Ziemann:
Xn a letter dated April 25, 1978 Rochester Gas and Electric agreed to obtain from Exxon Nuclear Company, and submit to you within 30 days, an analysis of the effect of upper plenum injec-tion on the peak clad temperatures of Exxon fuel.
That analysis is provided in attachment A.
The analysis results confirm that the effect of injecting low head ECC water into the upper head instead of into the cold legs is not significant and demonstrate continued compliance with 10 CFR 50.46 and Appendix K to 10 CFR Part 50.
Sincerely yours, L.D. Whit, Jr.
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ATTACHMENT A ECCS ANALYSIS FOR R. E.
GINNA INCLUDING THE EFFECTS OF UPPER PLENUM INJECTION In December
- 1977, Exxon Nuclear Company (ENC) performed a
large break spectrum ECCS analysis for the R. E. Ginna Reactor.
The results of this analysis were reported in XN-NF-77-SS (1)
The analyses were performed using the ENC WREM-II PWR ECCS Evaluation Model.
For this analysis, the assumption was made, as in previous NSSS vendor analyses, that the ECC water from the Low Pressure Safety Injection (LPSI) system could be conservatively modeled as injecting into the reactor vessel downcomer region.
For Westinghouse two-loop PWRs, the LPSI system is actually piped directly to the upper plenum region of the reactor vessel.
In December 1977, the United States Nuclear Regulatory Commission (NRC) reevaluated the acceptability of this modeling approach and on December 16, 1977, issued a letter to the owners and operators of Westinghouse-designed two-loop PWRs with upper plenum LPSI injection (UPI).
This letter required additional analyses which account for the LPSI into the reactor vessel upper plenum to be performed in support of continued operation of the reactor plants.
Enclosed with the letter were two Safety Evaluation Reports (SERs).
One was prepared by the Analysis Branch of the Division of System Safety (DSS) and concerned the ECCS model and the second provided Staff conclusions regarding continued safe operation.
The DSS SER described an NRC "Staff Model" which could be used on an interim basis to provide an
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analysis supporting continued operation until a long-term solu-tion was developed.
The following discussion presents the results of a similar interim UPI analysis performed by Exxon Nuclear Company for the R. E. Ginna reactor.
UPI MODEL To perform the interim UPI analysis, ENC adopted the approach presented in the DSS SER "Safety Evaluation Report. on ECCS Evalua-tion Model for Westinghouse Two-Loop Plants" The computer program representing the NRC Staff model was obtained and verified against the NRC Staff sample results.
The program was then modified as required to represent the R. E. Ginna reactor and incorporate the base ENC ECCS analysis results.
Modifications to the Staff model include the following:
(1)
The capability to use time-varying data from the base ENC ECCS analysis was added for the containment pressure, satura-tion temperature, decay power, reflood rate, and low pressure safety injection (LPSI) flow parameters.
The analysis values used are those reported in ZN-NF-77-58 (2)
The carryover rate fraction value used was 0.7 (3)
An upper plenum structures heat transfer conduction model was incorporated into the program.
(4)
The clad temperature rise versus flooding rate curve, Figure 24 in Reference 2,
was replaced with the updated data provided on Figure 2 from Reference 3.
The updated curve is more representative of the peak rod power, initial rod temperature, reflood subcooling, and system pressure for a two-loop PWR.
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The horizontal entrainment was taken as a constant fraction of the LPSI injection flow (1.6%)
(6)
The core flow area was changed as appropriate to reflect ENC fuel in the R. E. Ginna reactor.
RESULTS Applying the above model to the R. E. Ginna reactor with Exxon Nuclear fuel gives the following results for the limiting break:
Current ENC Analysis R. E. Ginna 0.4 DECLG Break Revised Analysis with UPI F
Peak Claddin Tem erature F
Peak Claddin Tem erature 2.32 1922oF 2.32 1906 F
These results show continued compliance with 10 CFR 50.46 and Appendix K to 10 CFR Part 50, and are considered conservative since the adverse effects of UPI steam generation have been con-sidered in reducing reflood rates, while the benefits of UPI steam generation i'n reducing core temperatures have been neglected.
(1)
"ECCS Analysis for the R. E. Ginna Reactor with ENC WREM-2 PWR Evaluation Model," XN-NF-77-58, December
- 1977, Exxon Nuclear
- Company, Inc.
(2)
"Safety Evaluation Report on ECCS Evaluation Model for Westinghouse Two-Loop Plants," U.S.N.R.C., Analysis Branch, Division of Systems Safety, Office of Nuclear Reactor Regulations, November.1977.
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(3)
Letter from Keith W. Amish to Director of Nuclear Reactor Regulation, February 15, 1978.
(4)
"Safety Evaluation Report on Interim ECCS Evaluation Model for Westinghouse Two-Loop Plants," U.S.N.R.C.,
March 1978.