ML20084K750
| ML20084K750 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/30/1995 |
| From: | Stetz J CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2299, NUDOCS 9506070003 | |
| Download: ML20084K750 (2) | |
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4 CENTE8 HOR ENERGY 300 Madison Avenue John P. Stetz foiedo, OH 43652@01 Vice President Nuclear 419-249-2300 povis Besse Docket Number 50-346 License Number NPF-3 Serial Number 2299 l
May 30, 1995 l
United States Nuclear Regulatory Commission
{
Document Control Desk Vashington, D. C.
20555 Subj ec t :
Report of Error in the Emergency Core Cooling System Evaluation Model [10CFR50.46(a)(3)(ii)]
Gentlemen:
On April 27, 1995, Toledo Edison (TE) determined, based upon information from B&V Nuclear Technologies (BVNT), that the Nuclear b egulatory Commission (NRC) approved Version 9.3 of THETAl-B computer code used in Emergency Core Cooling System (ECCS) evaluation model for B&V fuel designs was in error. The error in the current ECCS evaluation model results in calculated Peak Cladding Temperature (PCT) reduction of over 50"F at some locations within the core. This report is being submitted in accordance 10CFR50.46(a)(3)(ii) as a significant change or error in an acceptable evaluation model.
While performing an analysis for a new fuel design, BVNT discovered an error in the THETAl-B computer code which is part of the approved 10CFR50, Appendix K ECCS evaluation model. The effect is cor. fined to the post-rupture gap dimension in any unruptured, plastic-deformed cladding j
segment and results in a conservative error of 150" to 200"F for these segments.
Specific details of the errors in the evaluation model vere provided to the NRC by BVNT in a letter dated May 26, 1995.
Toledo Edison has reviewed the implication of the error discovered by BVNT for the fuel design for the Davis-Besse Nuclear Power Station (DBNPS). The resulting PCT for the ruptured nodes are not affected by the error and the PCTs for unruptured nodes are reduced by the amounts 9506070003 950530 PDR ADOCK 05000346 P
PDR f
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Dockat Number 50-346 Licensa Number NPF-3 Serial Number 2299 Page 2 mentioned above. Given the conservatism of the error, the DBNPS operating limits remain valid and bounding for the fuel designs currently in use.
Therefore, no changes or additions to operational limits need to be imposed by TE.
Additional operating margin is not presently requ.' red for the unruptured node segments. Theref, ore, Toledo Edison intends te ensure that the THETA 1-B error is documented, but will not pursue revision to the existing evaluation model.
The existing evaluation podel is in the process of being replaced by a RELAP-5 based evaluation model. A topical report (BAV-10192) describing the new evaluation model was submitted for NRC review in February 1994. The new model does not utilize the THETA 1-B code.
Therefore, it does not contain the same conservative error as the the existing evaluation model.
Should you have~any questions or require additional information, please contact Mr. Villiam T. O'Connor, Manager - Regulatory Affairs, at (419) 249-2366.
Very truly yours, GAB / eld cc:
L. L. Gundrum, NFC Project Manager J. B. Hartin, Regional Administrator, NRC Region III S. Stasek, DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board i
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