ML19345C772
| ML19345C772 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 11/10/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19345C769 | List: |
| References | |
| NUDOCS 8012080326 | |
| Download: ML19345C772 (2) | |
Text
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UNITED STATES y
q (,g NUCLEAR REGULATORY COMMISSION qg}g.'I. [/ C Q
WASHINGTON, D. C. 20555 t
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 59 TO LICENSE NO. OPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION DOCKET NO. 50-271 VERMONT YANKEE NUCLEAR POWER STATION
1.0 INTRODUCTION
By letter dated November 6,1980, Vermont Yankee Nuclear Power Corpor-ation (the licensee) requested an amendment to the Technical Specifica-tions for the Vermont Yankee Nuclear Power' Station. The effect of the amendment would be to allow the count rate in the Source Range Monitor (SRM) channels to drop below 3 counts per second (cps) when the entire reactor core is being removed or replaced. The present Technical Specifications require that a count rate of at least 3 cps be main-tained whenever one or more fuel assen.blies are present in the core.
2.0 DISCUSSION The impetus for this Technical Specification change is the necessity to completely unload the core. Under these circumstances, the present requirement of a count rate of 3 counts per second in the source range monitors cannot be met during the complete unloading. Similarly, such a count rate cannot be met during the initial stages of the reload.
A method is, therefore, sought to assure that the core remains sub-critical during these operations. The spiral unloading and loading procedure meets the need.
In spiral unloading, the fuel assemblies are removed from the outer boundary of the core in a " spiral" fashion until the core is empty.
i In this manner, the occurrence of " flux traps" in the core is avoided and the core reactivity is not increased above its initial value.
Vermont Yankee proposes to reload the core by performing the steps in precisely the reverse direction with the exception that two " burned" fuel assemblies will be placed diagonally next to each of the four source range monitor channels (SRM's) as the first step in the loading.
This will assure continuous monitcring of the SRMs.
Such loading and uninading procedures have been previously approved for other BWR plants { e.g., Duane Arnold, see letter dated February 15, 1980 from T. Ippolito (NRC) to Mr. Duane Arnold (Iowa Electric)}.
3.0 EVALUATION Based on our review, we find the proposed spiral unloading and reload-kg of the Vermont Yankee core acceptable and conclude that the l
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l 2-proposed Technical Specifications permit these operations to be conducted safely. These findings are based on the following considerations:
1.
The spiral nature of the unloading procedure assures that the core reactivity is not increased during the process.
1 2.
The-reverse process used in the reload will have the same reactivity at each stage of the procedure as occurred at the same stage during the downloading.
3.
Added protection will be provided during both phases by the continuous monitoring of the operability of the SRM's.
4.0
SUMMARY
7 We have examined the safety issues and found the proposed amendment to be acceptable provided that the spiral reload consists of 50%
previously exposed fuel as required by proposed Technical Specifica-i tion 3.12.3d.
5.0 ENVIRONMENTAL CONSIDERATION
S We have determined that the amen &nent does not authorize a change in effluent types or total amounts nor an increase in power level and-will not result in any significant environmental impact. Having made i
this determination, we have further concluded that the amendment involves an action wnich is insignificant from'the standpoint of environmental impact, and pursuant to 10 CFR Section Sl.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 the amendment.
6.0 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.
l
~ 0ated November 10, 1980
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