ML20076K735
| ML20076K735 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 10/26/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20076K734 | List: |
| References | |
| NUDOCS 9411020040 | |
| Download: ML20076K735 (3) | |
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NUCLEAR REGULATORY COMMISSION l
e WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
RELATED TO AMENDMENT N0.141 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 December 6, 1993, the Vermont Yankee Nuclear Power Corporation (the licensee) submitted a request for changes to the Vermont Yankee Nuclear Power Station Technical roecifications (TSs).
The requested changes would remove the requirement to perform jet pump integrity and operability surveillance for pumps in the idle loop during operation with only one recirculation loop.
2.0 EVALUATION Jet pumps are part of the Reactor Coolant Recirculation System and are designed to provide forced circulation through the core to remove heat from the fuel. The jet pumps are located in the annular region between the core shroud and the vessel inner wall. Each reactor coolant recirculation loop contains ten jet pumps.
Recirculated coolant passes down the annulus between the reactor vessel wall and the core shroud. A portion of the coolant flows from the vessel, through the two external recirculation loops, nd becomes the driving flow for the jet pumps.
Each of the two external recirculation loops discharges high-pressure flow into an external manifold from which individual recirculation inlet lines are routed to the jet pump risers within the reactor vessel. The remaining portion of the coolant mixture in the annulus becomes the suction flow for the jet pumps.
This flow enters the jet pumps at suction inlets and is accelerated by the drive flow.
The drive flow and suction flow are mixed in the jet pump throat section. The total flow then passes through the jet pumps diffuser section into the area below the core (lower plenum),
gaining sufficient head in the process to drive the required flow upward through the core.
The proposed change will remove the surveillance requirement for operability and integrity of idle loop jet pumps during single loop operation (SLO). The licensee states that this surveillance, which is intended to check jet pump integrity and operability, is not required during SLO due to the low flow rates.
These low flow rates make it prohibitive to determine established flow patterns and then calculate a 10% variance in these patterns.
During low flow conditions, jet pump ncise approaches the threshold response of the associated flow instrumentation and precludes the collection of repeatable and meaningful data.
l 9411020040 941026 PDR ADOCK 05000271 P
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. The inactive loop jet pumps are under much less stress; therefore, if they are l
intact before entering SLO, they are not likely to degrade during operation with one recirculation loop. Also proposed are some administrative changes j
within the Bases.
The proposed revisions will not compromise the integrity of jet pump operation. The Standard Technical Specifications (STSs) indicate that a surveillance requirement is required to be performed only when the loop has forced recirculation flow since surveillance checks and measurements can only be performed during jet pump operation. According to the STSs, surveillance is not to be performed on a jet pump until 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the associated recirculation loop is in operation, since these checks can only be performed during jet pump operation.
The 4-hour time period is used to establish conditions appropriate for data collection and evaluation.
4 The NRC staff finds the proposed change removing the requirement to perform jet pump integrity and operability surveillances in the idle loop during operation with one recirculation pump to be acceptable.
The additional changes are administrative in nature and provide clarity and consistency.- The staff finds them acceptable.
3.0 STATE CONSVLTATION In accordance with the Commission's regulations, the Vermont State official was notified of the proposed issuance of the amendment.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC 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 Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (59 FR 29637). Accordingly, the 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 the amendment.
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5.0 CONCLUSION
The Commission has 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, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
K. Cotton Date: October 26, 1994 l
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