ML19312C585

Suppl to BAW-1447, Oconee 1,Cycle 4 Reload Rept.

ML19312C585
Person / Time
Site:	Oconee
Issue date:	09/18/1977
From:	BABCOCK & WILCOX CO.
To:
Shared Package
ML19312C583	List: ML19312C582 ML19312C585
References
BAW-1447, NUDOCS 7912180892
Download: ML19312C585 (6)

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SUPPLEMENT TO BAW-1447 OCONEE 1, CYCLE 4 RELOAD REPORT SEPTEMBER, 1977 791218 0 [7 b

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Introduction and Summary This report supplements the Oconee 1, Cycle 4 Reload Report (BAW-1447, March 1977) to account for a modified Cycle 4 core loading. The modified core loading consists of the loading of four once burned Batch 2 fuel assemblies at core locations D-4, D-12, N-4 and N-12, originally intended to be loaded with four Batch 4 fuel assemblies. The replacement of the four Batch 4 fuel assemblies with the four Batch 2 assemblies was necessitated because of mechanical damage to one Batch 4 assembly while it was examined in the spent fuel pool. The modified core loading does not affect the results of the core safety analysis or limiting conditions of operation, as documented in BAW-1447.

The following paragraphs describe the four replacement fuel assemblies and provide evaluations of the impact of the modified core loading upon the orevious analyses.

Nuclcar Design The modified core loading consists of replacing 4 twice burned, 3.2 wt %

batch 4 fuel assemblies with 4 once burned, 2.1 wt % batch 2 fuel assemblies.

The batch 2 assemblies were selected to match the reactivity of the replaced batch 4 assemblies as closely as possible. BOC radial power distribution results for the revised core loading show that all fuel assembly powers are within 1% of the original Cycle 4 core loading,.except for the replacement location N-12, which has about 3.5% less power in the revised core loading.

A Cycle 4 PDQ depletion analysis was performed which showed that these differences become progressively smaller as the cycle is depleted. Figure 1 shows the revised core loading diagram for Oconee 1 Cycle 4 and Figure 2 is an eighth-core map showing the burnup and enrichment distribution at the beginning of Cycle 4 with the revised core loading.

Mechanical Design The replacement fuel assemblies have been evaluated for mechanical design adequacy and found to meet the criteria for ellowable cladding strain and irradiation swelling specified in the Reload Report. The creep collapse time was determined to be > 30,000 EFPH, which is greater than the maximum desigm life of 14,232 EFPH. Pertinent fuel design parameters for the 4 Batch 2 fuel assemblies are given in Table 1.

Thermal-Hydraulic Design The revised core loading has been evaluated for thermal-hydraulic design considerations and found not to affect the design presented in the Reload Report. The Mark B-2 replacement assemblies have a higher resistance to flow than the Mark B-3 assemblies being replaced. However, the hot assembly during Cycle 4 is either a Mark B-3 or B-4 assembly that is not in a core location where the replacement assemblies will be placed. Since the inser-tion of the higher resistance Mark B-2 assemblies will cause an increase in flow in the hot assembly, the thermal-hydraulic design presented in Section 6 of the Reload Report is conservative.

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4 3 Safety Analysis The system parameters important to safety analysis are not affected by the revised core loading, and the safety evaluation presented in the Reload Report therefore remains valid.

Technical Specifications The power peaking limits and the ejected and shutdown rod insertion limits have been verified acd found to be less limiting than the limits calculated previously. Based on hese results, the Technical Specificat_,ns previously submitted are valid for the modified loading and do not require revision.

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. Table 1. Fuel Design Parameters for Oconee 1 Cycle 4 Batch 2 Fuel

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Assemblies Fuel Assembly Type Mark-B2 No. of F.A.'s 4 235 U 2.13 Initial Fuel Enrichment, wt. %

Initial Fuel Density; % TD 93.5 Batch Burnup, BOC, MWD /MTU 12,630 Cladding Collapse Time, EFPH > 30,000 Fuel Pellet 0.D., in. 0.3700 Undens. Active Fuel Length, in. 144 Flexible Spacers, Type Corrugated Solid Spacer Material Zr02

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• • , Revised Enrichment and Burnup Distribution .or Oconec 1, Cycle 4

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R XXX Initial Enriennent XXXX BOC Burnup ( M0/MTU) e

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