ML20207S493

Safety Evaluation Supporting Util 870213 Request to Allow Temporary Transfer of Fuel Assemblies During Ultrasonic Fuel Insp in Spent Fuel Pool

ML20207S493
Person / Time
Site:	Fort Calhoun
Issue date:	03/12/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20207S489	List: ML20207S488 ML20207S493
References
TAC-64713, NUDOCS 8703190547
Download: ML20207S493 (2)

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1. $  %, UNITED STATES

. 8 g NUCLEAR REGULATORY COMMISSION g a wasHmaTom o.c.zooss SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATON OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION, UNIT NO. 1 DOCKET NO. 50-285 ULTRASONIC FUEL INSPECTION IN SPENT FUEL POOL

1.0 INTRODUCTION

By letter dated February 13, 1987, Omaha Public Power District (OPPD) requested a revision to Section 2.1.4 of the staff's September 9, 1983 Safety Evaluation (SE) supporting Amendment No. 75 to Operating License DPR-40. This section of that SE prescribes that the Fort Calhoun refueling machine be interlocked to prevent movement directly into Region 2 of the spent fuel pool during refueling operations. This revision would allow the temporary transfer of fuel assemblies in and out of Region 2 of the Fort Calhoun spent fuel pool during refueling outages for the purpose of inspection of spent fuel assemblies. The request is due to the Fort Calhoun fuel integrity program which necessitates fuel inspections to be conducted in the cask loading area (Region 2) of the spent fuel pool due to test equipment requirements.

2.0 EVALUATION In order to support the movement of fuel directly into Region 2 during refueling operations, Pickard, Lowe and Garrick (PLG) performed a supplementary criticality analysis of the Fort Calhoun spent fuel pool with the proposed ultrasonic test rig located in the cask laydown area. An analysis of the spent  ;

fuel pool in the absence of the test rig had been performed previously by PLG and approved by the staff.

Both Combustion Engineering (CE) and Advanced Nuclear Fuels Corp. (ANF) fuel are stored in the pool. However, since criticality analyses have indicated that the ANF fuel is more reactive than the CE fuel at the limiting enrichment of 4.0 weight percent U-235, the ANF fuel design was used in these analyses.

The test rig is rectangular in shape with dimensions of approximately 3 ft by 4 ft. No more than two fuel assemblies may be in the test rig at any time and a minimum center-to-center separation distance of 17 inches between assemblies

is mechanically assured. During refueling, the charging system is locked out.

l Therefore, a boron dilution event is not feasible. However, water may escape from the test facility and, therefore, PLG has investigated the criticality effects of both a water density decrease and a water temperature increase (due t

to the increased heating arising from a water height decrease).

The results of these analyses, which were performed with the approved LEOPARD computer program and which used appropriately conservative input assumptions,

= 0.8020) for the showcase worst that configuration.

the test rig willThe be staff, at least 20% subcritical therefore, finds the(K'Niticality effects l of any normal or abnormal test rig configuration to be acceptable. In l addition, the staff agrees that any permanently discharged fuel assemblies may l be placed in the Region 2 racks directly from the test rig provided that the l required burnup verification has been performed.

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3. 0 CONCLUSION Based on the above evaluation, the staff finds that the OPPD request to allow the refueling machine interlock to be bypassed for the temporary transfer of discharged fuel assemblies to the test equipment in the cask loading area in Region 2 for inspection during refueling outages is acceptable. In addition, fuel assemblies being permanently discharged may remain in the Region 2 spent fuel racks provided that the required burnup verification has been performed.

Date: March 12,1987 Principal Contributor:

L. Kopp 4

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