ML17325A175
| ML17325A175 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 06/12/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17325A174 | List: |
| References | |
| NUDOCS 8706240363 | |
| Download: ML17325A175 (3) | |
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UNITEDSTATES NUCLEAR REGULATORYCOMMISSION WASHINGTON, O. C. 20555 SAFETY EVALUATION BY THE OFFICE. OF NUCLEAR REACTOR REGULATION NY By letter dated January 29, 1987, the Indiana and Hichigan Electric Company submitted RevisiorI 2 to XN-NF-85-115 (P) and Revision 2 to XN-NF-85-115(NP) which are the proprietary and non-proprietary versions of the large break loss-of-coolant accident (LOCA) analysis for D.C. Cook Unit 1.
These analyses support the limiting normalized power peaking factor vs. height curve K(Z) for Exxon Nuclear Company (ENC) fuel.
The K(Z) curve is contained within the D.C.
Cook Unit 1 Technical Specifications.
The LOCA analyses were originally performed as described in XN-NF-85-115 Rev.
0 dated February 21, 1986.
Since that time, the Exxon ECCS Evaluation model has been modified to include rev1sed reflood correlations from the Fuel Cooling Test Facility and to correct minor errors in the model.
The revised reflood models were approved by the staff as described in Reference 1.
In Reference 2,
ENC described a number of minor modifications to the evaluation model.
The impact of these modifications resulted in increases in peak cladding temperature of less than 20'F.
These modifications were included in the large-brcak LOCA analyses described in Revision 2 to XN-NF-85-115(P) and XN-NF-85-115 ( NP ).
The purpose of re-establishing the K(Z) limit curve with ENC fuel is essentially confirmatory to show that the current curve in the Technical Specifications provides an adequate margin of safety when the revised Exxon ECCS model is utilized.
Currently, only about one-third of the fuel in D.C.
Cook Unit 1 has been provided by ENC and that is scheduled to be removed at the end of the current cycle.
All the ENC fuel now in the core has a burnup of greater than 20,000 HMD/HTH.
The LOCA analyses were performed assuming much lower burnup than that of the fuel currently in the core.
The amount of burnup assumed in the. analysis was conservatively selected to maximize the amount of stored energy in the core and,
- hence, maximize the calculated peak cladding temperature.
The analyses assumed an initial reactoI power of 3315 HWt which includes 2X power uncertainty.
The core was assumed to contain a full loading of ENC 15X15 fuel.
The calculations were made for the double-ended cold leg split break with a discharge coefficient of 1.0 which has been previously determined to be the most limiting break.
One percent of the steam generator tubes were assumed to be plugged.
The axial dependence of the peaking factor limit K(Z) is defined as K(Z)
FQ(Z)/Hax FQ where FQ(Z) is the maximum power peaking factor allowed at any elevation Z.
Confirmation of the axial dependence was based on use of limiting power shapes which are a top skewed distribution at the beginning of life and a
chopped cosine distribution typical of the end of an operating cycle.
The maximum local power for each distribution was set at the appropriate value from the K(Z) curve.
The resulting calculated peak cladding temperatures were 1853'F for the top skewed power shape -and 1918'F for the chopped cosine power shape.
Since the 87php4p363 87pba2 PDR ADDCg PSOOO3a5 P
calculated peak cladding temperatures are less than the limit of 2200'F set by 10 CFR 50.46, the staff concludes that the limiting peaking factors used in the calculations and specified by the K(Z) curve in the Technical Specifications are acceptable for D.C.
Cook Unit 1 when fueled with ENC fuel.
References:
l.
Oennis Crutchfield, NRC, letter to Gary Ward, ENC.
Sub)ect:
"Safety Evaluation of Exxon Nuclear Company's Large Brcak ECCS Evaluation Model EXEH/PWR and Acceptance for Referencing of Related Licensing Topical Reports", July 8, 1986.
2.
G. Ward, ENC, letter to J. Lyons, NRC, November 18, 1986.
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