ML20117L194

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Provides Addl Info Re Insp on 960530-31 of RELAP5YA Implementation
ML20117L194
Person / Time
Site: Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date: 06/11/1996
From: Duffy J
VERMONT YANKEE NUCLEAR POWER CORP.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-96-77, NUDOCS 9606140043
Download: ML20117L194 (2)


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' VsRMONT YANKEE NUCLEAR POWER CORPORATION l

.- Ferry Road, Brattleboro, VT 05301-7002

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ENGINE R N OFFICE 580 MAIN STREET BOLToN. MA 01740 l (508) 779-6711 June 11,1996 BVY 96-77 l

United States Nuclear Regulatory Commission i ATFN: Document Control Desk Washington,DC 20555

References:

(a) License No. DPR-28 (Docket No. 50-271)

(b) Report," Vermont Yankee Loss-of-Coolant Accident Analysis," YAEC-1772, June 1993 (c) Letter, VYNPC to USNRC, BVY 95-141, dated December 29,1995 t

Subject:

Additional Information Requested at Inspection of Vermont Yankee RELAP5YA (BWR) Implementation l

The purpose of this letter is to provide information requested by the NRC during the subject inspection held at Yankee Atomic Electric Company on May 30 and May 31,1996. SpeciGcally, Vermont Yankee is providing the individual effects on peak clad temperature (PCT) of changes in our LOCA model as analyzed in our Cycle 17 and 18 LOCA calculations.

The limiting Cycle 17 single failure case with one core spray pump and one low pressure coolant l injection pump operable resulted in a maximum PCT of 1778.l'F under the old UNIX operating l system. Installation of the new UNIX operating system changed the results of this case to 1764.0 F, a decrease of 14.1 F. This decrease was due to the different time steps selected automatically by RELAP5YA with the new operating system. This change is consistent with the time step sensitivity study performed for Cycle 17 and documented in Reference (b).

The Cycle 18 core-specific changes in density, scram and doppler reactivity changed the results j of this case to 1788.9'F, an increase of 24.9 F above the UNIX only change.

The combination of operating system and Cycle 18 core-specific changes resulted in an increase of 10.8 F above the original maximum PCT for Cycle 17. Also, for Cycle 18, an error in the

- RELAP5YA fuel behavior model resulted in a PCT of 1778.1 F, a decrease of 10.8 F. These changes were reported to the NRC in Reference (c).

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9606140043 960611 PDR ADOCK 05000271 0 PDR 1 0

l VERMONT YANKEE NUCLEAR POWER CORI' ORATION Utfited States Nuclear Regulatory Commission June 11,1996 l Page 2 of 2 We trust that the information provided satisfies your request; however, should you have any l questions, please contact this office. l l

Sincerely, VERMONT YANKEE NUCLEAR POWER CORPORATION phM' ,

James J. Duffy Licensing Engineer l

- c: USNRC Region I Administrator USNRC Resident Inspector - VYNPS USNRC Project Manager - VYNPS i

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