ML20133Q239
| ML20133Q239 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 10/28/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20133Q235 | List: |
| References | |
| NUDOCS 8511010452 | |
| Download: ML20133Q239 (3) | |
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UNITED STATES
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9 E W ASHINGTON, D. C. 20555 t
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%s,, *.... f SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 91 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271
1.0 INTRODUCTION
By letter dated January 15, 1985, Vermont Yankee Nuclear Power Corporation (the licensee /VYNPC) proposed a change to Sections-3.6, 4.6, and 4.7 of the Technical Specifications for the Vermont Yankee Nuclear Power Station. The proposed change would provide spike limit for the reactor coolant concentration of iodine and limit the opening of purge and vent valves V16-19-7 and V16-19-7a to no more than 50 degrees while the reactor is operating.
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2.0 EVALUATION 2.1 Iodine Spike Limit The evaluation of the radiological consequences of a LOCA while purging requires that an assessment be performed with "a pre-existing iodine spike." This " pre-existing iodine spike" is the maximum value during transient reactor operation (as well as steady state operation) pemitted by the Technical Specifications. Exceeding this value would require plant shutdown. The licensee has proposed a Technical Specification limit on primary coolant dose equivalent iodine of 4 ci/gm. The licensee's analysis assumes a LOCA coincident with purging, a coolant concentration of dose equivalent iodine of 4 ci/gm, a decontamination factor of 2, primary coolant mass release of 2400 pounds of contaminated steam through an 18" purge valve assuming choked flow, and a ground level release with no filtration. The purge valve closure time is estimated at 10.5 seconds, and the release is assumed to be a rapid pressure surge that destroys piping downstream of the safety isolation valve. The staff did an independent dose analysis using the above assumptions with the exception of the decontamination factor (DF). The staff assumed a DF of 1 in its analysis of the purge contribution. The calculated purge dose contribution at the Exclusion Area Boundary (EAB) for the thyroid was calculated to be 9 rem and the Low Population Zone (LPZ) dose contribution for the thyroid was calculated to be 8 rem.
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Inthestaff'sSafetyEvaluationReport(SER)datedJune1,1971 l'
accompanying the review of Vermont Yankee for an operating license, the EAB LOCA dose for the thyroid was calculated to be 148 rem, and the LPZ thyroid 0511010452 851028 1
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1 1 dose was calculated to be 113 rem. The addition of the purge doses to the SER LOCA doses result in the raising of the estimated EAB thyroid dose to 157 rem and the LPZ thyroid dose to 121 rem. The whole body doses for the purge contribution are negligible (less than 1) and would not result in a significant change in the previously calculated whole body doses reported in the operating license SER. Based on these estimated total EAB and LPZ doses, the staff concludes that the revised dose estimates are within the 10 CFR Part 100 dose guidelines, and are acceptable.
2.2 Purae and Vent Valve Opening By letter dated May 22, 1984, the NRC staff concluded that the licensee had demonstrated the ability of the Vermont Yankee containment purge and vent valves to close against the buildup of containment pressure in the event of a DBA/LOCA. This conclusion was based on valves V16-19-7 and V16-19-7a being blocked at 50 degrees open, and the licensee was requested to propose Technical Specifications limiting the opening of these valves to 50 degrees.
The licensee has added limit stops to valves V16-19-7 and V16-19-7a so that they are blocked at 50 degrees open. The licensee proposes to modify Table 4.7.2a of the Technical Specifications, listing primary containment isolation valves, to require that valves V16-19-7 and V16-19-7a remain blocked to limit opening to 50 degrees or less.
The licensee's proposed Technical Specification change of January 15, 1985 pertaining to purge and vent valve opening is fully responsive to the NRC staff's requests of May 22, 1984, and is acceptable.
3.0
SUMMARY
Based on the infomation provided by the licensee, we have concluded that the proposed changes to limit the spike reactor coolant iodine concentration and to limit the opening of valves V16-19-7 and V16-19-7a are acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
S This amendment involves changes in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements. The staff has determined that the amendment involves no significant increase in the amounts, and no i
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 Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
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5.0 CONCLUSION
i We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) i 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 tht health and safety of the public.
Principal Contributors:
L. Bell, R. Wright, and V. Rooney Dated:
October 28, 1985 i
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