ML20237D528

Safety Evaluation Re Proposed Increase in Sf Pool Heat Loads for Plant

ML20237D528
Person / Time
Site:	South Texas
Issue date:	08/21/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20237D526	List: ML20237D524 ML20237D528
References
NUDOCS 9808260263
Download: ML20237D528 (2)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION BELATED TO PROPOSED INCREASE IN SPENT FUEL POOL HEAT LOADS FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 STP NUCLEAR OPERATING COMPANY DOCKET NOS. 50-498 AND 50-499 {

SOUTH TEXAS PROJECT. UNITS 1 AND 2

1.0 INTRODUCTION

By letter dated May 30,1995, as revised by letter dated February 8,1996, and supplemented by letter dated May 1,1996, STP Nuclear Operating Company (STPNOC) proposed a license amendment to revise the Updated Final Safety Analysis Report regarding an increase in spent fuel pool heat loads. The application states that the purpose of the proposed change is to revise the spent fuel pool heat load licensing basis to provi:le greater flexibility for normal refueling practices. The application also states that the current refueling practice at STP is to remove the entire core and place it in the spent fuel pool.

2.0 EVALUATION The Nuclear Regulatory Commission (NRC) staff has reviewed the application. The staff position on the current licensing basis for planned refueling outages at STP, assuming a single failure, is that the spent fuel pool temperature will not exceed 150.7*F with one train of spent fuel pool cooling in operation. The other train of spent fuel pool cooling is assumed to be failed.

This is consistent with 10 CFR Part 50, Appendix A, General Design Criterion 44.

STPNOC's proposal for a planned refueling outage, assuming a single failure, results in a spent fuel pool temperature to 200.0*F for the normal operating condition. However,200.0*F exceeds the analyzed design temperature of the spent fuel pool structure of 155'F for the normal operating condition as indicated in STPNOC's letter dated May 1,1996. To increase the operating temperature of the spent fuel pool structure beyond its analyzed value of 155'F, the licensee would need to demonstrate that the spent fuel pool structure has additional

capacity to perform its safety functions at higher temperatures consistent with the approved design basis criteria. In addition, the staff would need additional details on makeup systems to the spent fuel pool to ensure that make-up water could be supplied to the pool before the pool

> begins to boil, should a complete loss of cooling occur at this temperature.

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SUMMARY

Accordingly, the staff finds that the analyzed design temperature of the spent fuel pool structure is inconsistent with the proposed increase in spent fuel pool temperature. The analysis of the pool structure assumes a maximum spent fuel pool temperature of 155'F under normal operating conditions. Cases evaluated in the application indicate that under refueling operations with a full-core offload and assuming a single failure, which is considered a normal operating condition, the pool temperature could reach 200*F.

Principal Contributors: C. Gratton H. Ashar T. Alexion Date: August 21, 1998 i

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