ML20195K353

Correction to Safety Evaluation Supporting Amend 129 to License NPF-30.Page 3 of SE Contained Editorial Error & Two Clarifications

ML20195K353
Person / Time
Site:	Callaway
Issue date:	06/15/1999
From:	NRC (Affiliation Not Assigned)
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ML20195K359	List: ML20195K353
References
NUDOCS 9906220068
Download: ML20195K353 (1)

Text

3 flooded with unbnrated water must not exceed 0.95. The maximum calculated reactMty must include a margin for uncertainties in reactMty calculations and in manpfacturing tolerances such that the true k, will not exceed 0.95 at a 95% probability,95% confidence (95/95) level (Reference " Guidance on the Regulatory Requirements for Criticality Analysis of Fuel Storage at Light-Water Reactor Power Plants," Memo from L Kopp to T. Collins, dated August 19, i

1998).-

The Econsee's criticality analyses were performed with several conservative assumptions which tend to maximize the rack reactMty. These include:

(1) unborated pool water at the temperature yielding the highest reactMty (4'C) over the expected range of water temperatures, (2) an infinite array of storage cells in the lateral direction (except for the assessment of peripheral effects and certain abnormal conditions where neutron leakage is inherent),

and i

(3) neutron absorption effect of minor structural materialis neglected.

Since the Callaway Plant, Unit 1 contains Westinghouse Standard (STD), Vantage 5H (V5H) i

and Optimized (OFA) fuel designs, the licensee performed calculations for each of these fuel types. The OFA fuel exhibited the higt.est reactivity at zero bumup. Therefore, the design basis fuel assembly was a Westinghouse OFA with a 17x17 array of fuel rods containing

• uranium oxide (UO2) at a maximum initial enrichment of 5.0 weight percent (w/o) U-235, with

_ 25 fuel rods replaced by 24 control rod guide tubes and one instrument thimble. At higher bumups, the V5H assembly type is the more reactive and, therefore, for the bumup dependent Regions 2 and 3, reactivities equivalent to the V5H sssembly were used.

~ The staff concludes that the licensee made appropriate conservative assumptions.

Spent fuel storage is designated into regions based on administrative controls. Region 1 is designed to accommodate new (fresh) fuel with a maximum nominal enrichment of 4.6 w/o U-235. To enable the storage of fuel assemblies with nominal enrichments greater than 4.6 w/o U-235, the licensee utilized the concept of reactMty equivalencing. In this technique, which has been previously approvad by the NRC, credit is taken for the reactMty decrease due to the j

integral fuel bumable absorber (IFBA) material coated on the outside of the UO2 pellet. Region 2 and Region 3 are designed to accommodate fuel of up to 5.0 w/o U-235 initial enrichments which has accumulated minimum irradiation levels within the acceptable bumup domain depicted in the proposed TS Figure 3.91.

The licensee proposes to use a

• Mixed-Zone Three-Region * (MZTR) configuration and/or a checkerboard configuration for storage of fuel assemblies in the spent fuel pool. In a MZTR

' configuration, Region 1 cells are only located along the outside periphery of the rack modules and must be separated by one or more Region 2 storage cells. Region 1 storage cells may be located directly across from one another when separated by a water gap. The outer rows of altamating Region 1 and 2 storage cells must be further separated from the intomal Region 3 storage cells by one_ or more Region 2 cells. Fresh assemblies with enrichment greater than l

4.6 w/o U 235 and without IFBA rods must be stored in any peripheral Region i storage cou

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