ML20149E725
| ML20149E725 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 01/29/1988 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML19341D909 | List: |
| References | |
| SL-4065, NUDOCS 8802110254 | |
| Download: ML20149E725 (7) | |
Text
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Atlanta, Georgia 30308
-l Telephone 404 526-6526 f
ox 545 Atlanta, Georgia 30302 b
Georgia Power L. T. Gucwa Ine sourhern etctro system Manager Nuclear Safety and Licensing SL-4065 0752m X7GJ17-V410 January 29, 1988 U. S. Nuclear Regulatory. Commission ATTN: Document Control Desk Hashington, D.C.
20555 PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 OPERATING LICENSE NPF-68 TEMPORARY EXEMPTION FOR COMPLIANCE HITH 10 CFR 50.46 Gentlemen:
On January 27, 1988, Hestinghouse Electric Corporation (Hestinghouse) informed Georgia Power Company (GPC) of new information affecting the FSAR large break LOCA analysis for Plant Vogtle.
This information is related to the effect of the Containment Spray System (CSS) flowrates upon the Peak Clad Temperature (PCT) and, while not presenting any safety concern, does require the performance of additional confirmatory analyses to provide plant specific margin for Plant Vogtle compliance with the PCT criteria of 10CFR50.46(b)(1).
Evaluations performed by Westinghouse demonstrate that adequate margins exist and that there are no safety concerns.
GPC hereby
- requests, in accordance with 10CFR50.12, a
temporary exemption from certain provisions of 10CFR50.46(a)(1) to allow startup and operations of Plant Vogtle Unit 1 at full power with administrative restrictions as described below.
The current large break LOCA analysis for Plant Vogtle Units 1 and 2 was performed in April 1983.
That analysis assumed a CSS flowrate of 6400 gpm.
However, projected CSS flow, as determined using plant startup tests, is 6569 gpm.
This represents an increase of 169 gpm in the CSS flowrate.
Since higher CSS flowrates result in a reduction in computed containment backpressure and lower containment backpressure is a penalty for. large break ECCS analyses, the current analysis reported in the Vogtle Final Safety Analysis Report (FSAR) is impacted in the non-conservative direction.
The large break LOCA analysis, which currently forms the licensing basis for Plant Vogtle Unit 1, has very little margin to the 22000F PCT i
specified in 10CFR50.46(b)(1).
The limiting case, not considering the subject increase
'n CSS flowrate, has a PCT of 21720F at an overall peaking factor (Fg) of 2.30 for the limiting discharge coefficient
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(C ) of 0.6, as computed using the 1981 version of the large break D
Hestinghouse Evaluation Model.
The effect of containment purging as hgg2Qggggggj241 M3 N
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. Georgia Power A U. S. Nuclear Regulatory Commission January 29, 1988 Page Two reported in chapter 6.2.1.5 of the FSAR increased the PCT by 100F.
A safety evaluation performed by Westinghouse which considered the effect of thimble tube modelling and chamfered fuel pellets resulted in an 80F increase in the PCT.
Therefore, the overall PCT that serves as the current licensing basis, for the limiting case, is 21900F.
The increase of 169 gpm in the CSS flowrate would result in a PCT of 22150F which is slightly above the 22000F criterion specified in 10CFR50.46(b)(1).
Results of calculations. performed using the current NRC-approved Hestinghouse ECCS BART Evaluation Model (BART) have shown significant reductions in calculated PCT when compared to the results obtained using i
earlier Westinghouse evaluation models such as the NRC-approved 1981 ECCS Evaluation Model (1981 Model) used in the licensing basis for Plant Vogtle Unit 1.
Westinghouse has per 'ormed generic fuel studies for 4-loop plants using the 1981 Model with BART.
The computations were made using the Plant Vogtle Unit 1 and 2 inputs with modifications for a different fuel type, Vantage 5.
The results of these computations exhibit a PCT of 21940F at an FQ of 2.50 for the same limiting CD of 0.6.
Studies have shown the sensitivity of the PCT to FQ changes to be approximately 100F per 0.01 change in F.
Therefore, these studies indicate that a Q
reanalysis of the Plant Vogtle large break LOCA using BART would result in an increase in the margin to the regulated limit of 22000F PCT of approximately 1000F (the Vantage 5 fuel has been shown to be worth 1000F LOCA benefit with the BART model; i.e.,
(100F) / (0.01 Fg) 30.X (0.2 Fo) - (1000F) = 1000F ) at the current licensed Fg of 2.
Although these scoping analyses assumed the CSS flowrate value of 6400 gpm, the noted 169 gpm increase in actual flow would not increase the PCT by 2000F, Thus, increased margins to the 22000F Limit are available which are more than sufficient to accommodate the PCT increase due to a 169 gpm increase in the CSS flowrate, and i
therefore, no safety concern exists, and restart and operation at full l
power of Plant Vogtle Unit 1 is justified.
l To provide further assurance that the intent of 10CFR50.46 is met, GPC will limit Fg by administrative controls to a value of 2.28, a reduction of 0.02 in Fg units. PCT of approximately 200F. g will This decrease in F result in a reduction in calculated These results are based upon studies performed by Hestinghouse with the 1981 model, and demonstrate compliance with the 22000F criteria for Unit 1 full power operation with an increased CSS flowrate of 6569 gpm and an Fg of 2.28.
A detailed discussion and safety evaluation performed by Westinghouse is provided as l to this letter.
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GeorgiaPowerA U. S. Nuclear Regulatory Commission January 29, 1988 Page Three As previously discussed, the use of 'the BART model would, with its improvements in the modeling of heat transfer during the reflood portion of the transient, increase calculated margins to PCT and eliminate the need for a 0.02 reduction in F.
GPC will, through ~ reevaluation, Q
demonstrate the acceptability of full power operations with a CSS flowrate which reflects actual plant conditions.and an FQ of 2.30 prior to restart from the refueling outage currently expected to begin the first week of September,- 1988.
The modeling techniques and codes may include use of BART.
It is possible that, due to considerations beyond the scope of this issue, the evaluation may -be based on the 1981 Model and the reanalysis using BART deferred pending integration with other core design issues.
The evaluation will be submitted to the NRC.
Upon NRC acceptance of the evaluation, aFQ of 2.30 w111 again be used for Unit 1.
Since.the assurance of operation at full power with a PCT of less than 22000F through reduction in Fo is based upon the 1981 Model cited in the FSAR and associated 1987 Model sensitivity studies, and since there may be a question as to whether this satisfies the administrative provision of 10CFR50.46(a)(1) that ECCS model evaluations must be performed with values specifically applicable to the unit in question, GPC hereby requests a one time temporary exemption from 10CFR50.46(a)(1) to allow startup and full power operation of Plant Vogtle Unit 1 until reevaluation of the PCT at increased CSS flowrates is complete.
This request for temporary exemption meets the requirements of 10CFR50.12(a)(1) and (2).
This temporary exemption meets the criteria of 10CFR50.12(a)(1) in that it is authorized by law, will not present undue risk to the public health and safety, and is consistent with the common defense and security.
Additionally, the following special circumstances are present which authorize the Commission to grant this temporary exemption.
(1)
Application of the regulation in the particular circumstances is
- not necessary to achieve the enderlying purpose of the rule.
As noted
- above, evaluations performed by Westinghouse demonstrate that adequate safety margin exists and that there are no safety concerns with Unit I startup and full power operation at a lower Fo of 2.28 and a CSS flowrate of 6569.
While an ECCS evaluation with an FQ value of 2.28 and a CSS flowrate of 6569 has not specifically been calculated for Unit 1 at this time, Westinghouse sensitivity studies demonstrate compliance to the PCT criterion for rwm
W GeorgiaPower A U. S. Nuclear Regulatory Commission January 29, 1988 Page Four' Unit 1 full
)ower operation under these conditions.
Since. the PCT cr\\terion would be met as discussed in Enclosure 1, there is no safety Contern in allowing full power operation of Unit I pending completion of the reevaluation and the underlying purpose of 10CFR50.46(a)(1) will be met.
(2)
Compliance with the rule would result in undue hardship and other costs that is significantly in excess of those contemplated when the regulation was adopted.
10CFR50,12(a)(2)(iii).
GPC believes that to prevent startup and full power operation of Plant Vogtle Unit 1 pending resolution of an. issue wh' ch involves no safety concern would be an application of 10CFR50.46 w dch would not serve the underlying purpose of the rule, and wo'ld result in an undue hardship and cost in excess of u
those contemplated when 10CFR50.46 was adopted.
(3)
The exemption would provide only temporary relief from the rule and the 'icensee has made good faith efforts to comply with the rule.
The analysis provided in the FSAR was aerformed to comply with the "Acceptance Criteria for Emergency Core Cooling Systems for Light Water Cooled Nuclear Power Reactors",10CFR50.46 and Appendix K of 10CFR50.
This evaluation resulted in an acceptable peak cladding temperature of 21720F (21900F with penalties for containment purging and modeling assumptions noted previously) based on a peaking factor Fo of 2.30 and a CSS flowrate of 6400 gpm.
During evaluation of actual CSS flowrate, as determined during the startup testing program, it was determined that the PCT limits were exceeded slightly. Upon notification of this circumstance, GPC directed Westinghouse to perform sensitivity studies and a safety evaluation for operation with a reduced FQ an increased CSS flow.
These evaluations provided justification for operation at full power.
Promptly following notification of these circumstances, GPC notified the NRC and is hereby proposing a resolution to this problem.
GPC will provide the results of a reevaluation of PCT with FQ of 2.30 and CSS flowrate at actual as-built values prior to startup from the refueling outage scheduled to begin in September 1988.
These efforts demonstrate GPC's good faith effort to meet the requirements of 10CFR50.46 and, therefore, meet the special circumstance of 10CFR50.12(a)(2)(v).
Since there is no safety concern, this temporary exemption request does not involve a
significant increase in the probability or consequences of an accident previously evaluated, does not create the possibility of a new or different kind of accident from any accident previously evaluated, and does not involve a s'gnificant reduction in a margin of safety.
- "5
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- GeorgiaPower A
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U. S.' Nuclear Regulatory Commission January 29, 1988 Page Five
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GPC believes that this exemption will not ~ affect the environmental analysis in the FSAR, nor the environmental report, since the temporary exemption would involve no significant increase in the amounts, and no significant -change in the types, of effluents that may be released offsite.
Further, there is no significant increase in individual-or cumulative _ occupational radiation exposure.
Therefore, there are no unreviewed environmental questions involved.
The ' Plant Vogtle Plant Review Board and the GPC Safety Review Board have reviewed this letter and its enclosure and concur in its conclusions and request for exemption.
A Payment of the filing fee in the amount of one hundred and fifty dollars'is enclosed.
If you have any questions, regarding this request, please contact this office.
Sincerely,
^
4% 4L-A L. T. Gucwa HEB/Im
Enclosure:
1.
Westinghouse Sensitivity Study and Safety Evaluation 2.
Filing Fee - $150.00 c:
(see next page) r
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- Georgia Power A -
h U. S. Nuclear Regulatory Commission January 29, 1988-Page Six c: fdpraia Power Comoany -
.Mr. J.'P. O'Reilly Mr. P.
D.~ Rice Mr. G. Bockhold, Jr.
Mr. C. H. Hayes Mr. J. E. Swartzwelder GO-NORMS Southern Comoany Services Mr. R. A. Thomas Mr. J. A. Bailey Shaw. Pittman. Potts & Trowbridae Mr. B. H. Churchill, Attorney-at-Law Troutman. Sanders. Lockerman & Ashmore Hr. A. H. Domby, Attorney-at-Law U. S. Nuclear Reaulatory Commission Dr. J. N. Grace,~ Regional Administrator Mr. J. B. Hopkins, Licensing Project Manager, NRR (2 copies)
Mr. J. F. Rogge, Senior Resident Inspector-Operations, Vogtle 0752m norn
GeorgiaPower d ENCLOSURE 1 PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 OPERATIllG LICENSE NPF-68 HESTINGHOUSE SENSITIVITY STUDY AND SAFETY EVALUATION s