ML19309A934
| ML19309A934 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/23/1976 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19309A927 | List: |
| References | |
| NUDOCS 8004010688 | |
| Download: ML19309A934 (2) | |
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UNITED STATES 3"
'a NUCLEAR REGULATORY COMMISSION
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g WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 8 TO LICENSE NO. DPR-54 SACRAMENTO MUNICIPAL UTILITY DISTRICT RANCHO SECO NUCLEAR GENERATING S1ATION DOCKET NO. 50-312 Introduction By letter dated October 4,1976, the Sacramento Municipal Utility District (the licensed proposed a Technical Specification change modifying the limits affecting control rod insertion and core power imbalance.
The reason for the proposed change was that during an unplanned outage for generator repair a rod interchange was perfonied. At that time the burnup was 168 effective full power days (EFPD's) instead of the planned burnup at rod interchange of 200 EFPD's used in the loss o#
coolant accident (LOCA) calculations. With this interchange the present Technical Specification limits would become nonconservative in early January.
Evaluation The proposed Technical Specifications are based on a more accurate l
operating history for the Rancho Seco core than used in the existing i
Technical Specifications.
In addition to correcting for the revised rod interchange time, the licensee has allowed for more adverse operating conditions thereby introducing additional conservatism.
1 The calculations on which the existing Technical Specifications are based assumed that the plant would be operated at er near optimum j
imbalance conditions. The assumption on which the proposed curves are based is that the plant is placed in a bad offset condition but still within the imbalance limits and reactor protective system limits.
Therefore, the ifcensw has proposed that more conservative curves for the rod position limits (Figure 3.5.2-1) and the operational power imbalance envelope (Figure 3.5.2-2) be implemented than are presently in effect.
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o 2-Use of the proposed rod position limits curve (Figure 3.5.2-1) will require operation in a more restricted window. Above 92% of rated power the plant must be operated with the rods inserted 2.2%. The effect of the rod insertion is to reduce the operating imbalance (Figure 3.5.2-2) in the upper half of the core. Thus, peaking is reduced in the upper part of the core. The operational limits proposed are conservative with respect to both those currently specified and the LOCA peaking limits and are acceptable.
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 ignificant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 551.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (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: December 23, 1976 l
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