ML20078E723
| ML20078E723 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 09/23/1983 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20078E715 | List: |
| References | |
| NUDOCS 8310060071 | |
| Download: ML20078E723 (3) | |
Text
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h UNITED STATES f
k"j NUCLEAR REGULATORY COMMISSION g,
E WASHINGTON, D. C. 20555 9 +...
,o SAFETY EVALUATION AMENDMENT NO. 11 TO NPF-13 GRAND GULF NUCLEAR STATION, UNIT 1 DOCKET NO. 50-416 Introduction Section 3 of Attachment 1 to Grand Gulf Unit 1 License NPF-13 contains a condition that prior to exceeding 1 percent power, the licensee shall complete to the satisfaction of the NRC, a control room envelope leak tightness test.
On March 8,1983, in test CZ51PT01, Revision 1, MP&L performed a control room leak test in which the leakage at 1/8" water gauge pressure was measured to be 435 cfm. This leakage was substantially higher than the 263 cfm assumed for the FSAR analysis.
By letter dated June 16, 1983, MP&L presented control room doses for an assumed 590 cfm leak rate calculated using doses assessment methodology as described therein. The NRC staff by letter dated August 1, 1983, found the analytical bases for these doses unacceptable and met with MP&L on August 4, 1983, to discuss NRC staff concerns. At that meeting, MP&L contended that several conservatisms in the NRC staff's computation of control room accident doses should be reduced, and that these reductions would permit the Grand Gulf control room to meet General Design Criterion (GDC) 19 with the higher proposed control room leak rate. The largest factor by which the NRC staff and licensee differ is the atmoshperic dispersion to be expected of releases from the containment prior to arrival at the control room intake. The NRC staff requested that MP&L have scale model tests performed to establish a reliable basis for estimating this atmospheric dilution, and it was estimated that such tests could be performed and the results reviewed within six months.
Following that meeting, MP&L submitted additional analytical data on August 18, 1983.
8310060071 830923 PDR ADOCK 05000416 P
2.
. Evaluation The August 18, 1983 submittal reported the results of this recalculation of the control room operator doses, which used the same meteorological parameters as in both the FSAR and SER, but which assumed control room and tested containment leak rates of 590 cfm and 0.072%/ day, respectively. The NRC staff has reviewed this submittal and confirms that the control room doses obtained by this calculation meet the SRP Section 6.4 criteria.
MP&L has also committed to supply additional information within six months.
Specifically, in an August 23, 1983 letter, MP&L stated that it will i
conduct plant-specific wind tunnel tests to establish an appropriate value for the concentration coefficient (K) used in obtaining X/Q values in the meteorological model for calculating doses. Also, as discussed in its August 23, 1983 letter, MP&L will perform other analyses in support of a control room leakage on the order of that measured in the March 8,1983 test.
It is the NRC staff's position that in the absence of a demonstrated basis for lesser consequences, a conservative estimate must show compliance to the GDC. The containment leak rate of 0.35%/ day was used in the SER computation of Grand Gulf accident consequences in order to assure that degradaticn of the containment over its life-time will not lead to excessive accident consequences. The MP&L data indicates that containment leakage does not increase rapidly, and has generally remained at its original value during the early years of a plant's operation. While it would be inappropriate to assume that the Grand Gulf containment leak rate would remain at its present tested level of 0.072%/ day for the life of the plant, it can be expected to remain at a low value for the next six months. This period of time would permit MP&L to demonstrate a firm basis for greater atmospheric dilution of containment leakage specifically applicable to the Grand Gulf building configuration.
On the basis of the results of the recalculation of the control room operator doses, MP&L proposed that interim operation of Grand Gulf Unit 1 be permitted at the higher control room leakage rate of 590 cfm for six months pending final resolution of other factors used in judging compliance with General Design Criterion 19.
The NRC staff concludes that an appropriate basis has been established, as indicated above, for operation during the six month period.
.m Accordingly, pending submittal and approval of the additional information identified in MP&L August 18 and 23, 1983 letters, the NRC staff finds that MP&L has satisfied the conditions of Section 3 of Attachment 1 to NPF-13 through February 1984. We consider this to be an extension of our review necessary for full power operation, resulting from the fact that the values initially assumed prior to plant completion required validation and/or reconsideration based on as-built plant conditions as actually measured.
In addition to the tests and analysis described above, the NRC staff believes that efforts be continued by MP&L to identify and seal leakage paths to the control room. Such action would provide margin to offset potential long term degradation of the containment and control room pressure boundaries and minimize reliance on the results of the above planned tests and analyses.
Environmental Consideration The Commission has determined that the issuance of this amendment will not result in any environmental impacts other than those evaluated in the Final Environmental Statement since the activity authorized by the amendment is encompassed by the overall action evaluated in the Final Environmental Statement dated September 1981.
Conclusion We have concluded, based on the considerat' ions discussed above, that: (1) this amendment results as part of the review for the full power operating license (43 FR 32903), (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) 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: September 23, 1983
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