ML20151Z569

Safety Evaluation Supporting Amend 21 to License DPR-21

ML20151Z569
Person / Time
Site:	Millstone
Issue date:	08/19/1988
From:	Office of Nuclear Reactor Regulation
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ML20151Z546	List: ML20151Z543 ML20151Z554 ML20151Z569
References
NUDOCS 8808300022
Download: ML20151Z569 (3)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENOMENT NO. 21 TO FACILITY OPERATING LICENSE NO. DPR-21 NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.

MILLSTONE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-245

1.0 INTRODUCTION

By letter dated December 18, 1987, the Northeast Nuclear Energy Company (NNECO or licensee) submitted a request for changes to the Millstone Nuclear Power Station, Unit No.1.

The amendment will revise Technical Specification Section 3.7.A.3, "Primary Containment," and its associated Basis Section 3.7.A.1 by removing the permission to perform open vessel criticality and men vessel low power physics testing without containment integrity.

Also, by letter dated June 1,1987, the licensee proposed a change to Bases Section 3.5.C. "Isolation Condenser (IC) System." This change removes the i reference to a "special procedure" which provides instructions to the l cperators for mitigating a loss of feedwater transient at a reactor level less than 40% concurrent with an out-of-service IC. This reference is being deleted in deference to Off-Nonnal Procedures and/or Emergency Operating Procedures.

l 2.0 EVALUATION The accident at Chernobyl prompted the licensee to review a number of aspects of nuclear power operations. Among the issues considered is the matter of i administrative control and opportunities to bypass safety systems. These and other factors have prompted NNECO to initiate an evaluation of the merits of continuing to permit open vessel and open containment reactivity tests, as reflected in Technical Specification 3.7.A.3.

Standard practice in the early 1970s included perfonnance of open vessel cold critica11 ties and shutdown margin (SDM) tests without containment integrity.

Occasionally, problems such as inadvertent criticalities have occurred, including two such events at Millstone Unit No. 1 in the mid-1970s. In the case of Millstone Unit No.1 no physical damage occurred due to a scram based on nuclear instrumentation. Following the Chernobyl accident, a re-look by the licensee at whether such practices should be allowed to continue was undertaken 8800300022 800019 45 DR ADOCK 0500

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The proposed change will revise Technical Specification 3.7.A.3, "Primary Containment," and Basis 3.7.A.1 by removing the explicit permission to perform open vessel criticality and open vessel low power physics testing without containment integrity. The conceptual approach used by the licensee to evaluate the inerits of this proposed change was to consider potential risks and benefits. In summary, this amendirent request represents a case of balancing a low probability and low plant risk situation agair.st the low benefits associated with continuation of currently allowed evolutions. It is recognized that this change in the technical specifications does not diminish the likelihood of an inadvertent criticality. However, compliance with the proposed specification would prevent an inadvertent criticality from occurring without cuotainment system integrity.

If a complication during SOM testing were to occur, it wouM be due to an error involving core misloading, design error, manufacturing error, or a similar problem. Procedures and controls governing these activities make the i likelihood of this occurrence very low. Further, nuclear instrumentation is l designed to ensure a scram before criticality would be achieved. Hence, the l likelihood of concurrent events such as improper rod selection and bypass of nuclear instrumentation is low.

The benefit associated with continuing to allow reactivity tests with an open containtnent is also quite low. The principle benefit is an economic one, in that if a core loading or internals problem was identified during reactivity tests without containment integrity, the time required to remedy the problem woulo be less than if the vessel and containment were intact. While more difficult to quantify, the potential safety and economic implications of an l inadvertent criticality with the head off are also quite real. It is judged that the consequences for the latter outweigh any economic benefits of having the opportunity to conduct these tests conveniently.

l In addition, the licensee proposed to change Bases Section 3.5.E. "Isolation Condenser (IC) System, of the Hillstone Unit No.1 Technical Specifications.

As stated in 10 CFR 50.36, the bases are not a part of the Technical l Specifications; hence, a formal license amendment request is not necessary.

The bases for the IC System Technical Specifications refer to a special procedure which provides instructions to the operators for mitigating a loss of feedwater transient at a reactor power level less than 40% concurrent with an out-of-service IC. Current Off-Hormal procedures and/or Emergency Operating Procedures, which have been implemented since June 29, 1983, represent an improved procedural approach to accident mitigation, and more i

adequately address this particular event scenario in its entirety. As such, I the special procedure has previously been deleted by the licensee pursuant to I

the provisions of 10 CFR 50.59. NNECO proposed to delete the reference to this special procedure from the bases of the Technical Specifications.

The staff concurs with this change to the Bases, i

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3.0 ENVIRONMENTAL CONSIDERATION

This amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Connission has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public connent on such finding. Accordingly, the amendrnent meets the eligibilit criteria for categorical exclusion set forth in 10CFR951.22(y)(9).

c Pursuant to 10 CFR 951.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendinent.

4.0 CONCLUSION

We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Connission's regulations, and the issuance of the annendment will not be inimical to the connon defense and security or to the health and safety of the public.

Dated: August 19, 1988 Principal Contributor:

flichael L. Boyle