BVY-93-114, Submits Results of 930823 Telcon on Behalf of Licensee Re Treatment of Varying Axial Power Distribution Effects in Reload Analyses

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Submits Results of 930823 Telcon on Behalf of Licensee Re Treatment of Varying Axial Power Distribution Effects in Reload Analyses
ML20057F646
Person / Time
Site: Vermont Yankee Entergy icon.png
Issue date: 10/08/1993
From: Tremblay L
VERMONT YANKEE NUCLEAR POWER CORP.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-93-114, NUDOCS 9310180300
Download: ML20057F646 (2)


Text

VERMONT ANKEE NUCLEAR POWER CORPORATION

  • A Ferry Road, Brattleboro. VT 05301-7002 , ,

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b ENGINEERING OFFICE 6M- ' 80 M AIN STREET B01 TON. u A c1740

.s (508) 779 6711 October 8,1993 BVY 93 - 114 United States Nuclear Regulatory Commission A'ITN: Document Control Desk Washington, DC 20555

References:

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

Subject:

Treatment of Varying Axial Power Distribution Effects in Reload Analyses

Dear Sir:

The purpose of this letter is to document, as requested by your staff, the results of a telephone conversation held on August 23,1993 between members of NRC staff and staff members of Yankee Atomic Electric Company (YAEC) on behalf of Vermont Yankee Nuclear Power Corporation (VYNPC). (Participants in this telephone conversation are listed at the end of this letter.)

During the NRC's review of the FROSSTEY 11 fuel performance code, the NRC raised questions regarding the treatment of transient power distribution effects in YAEC's Irload analysis methods in support of Vermont Yankee Nuclear Power Station (VYNPS). The questions were directed at whether the method used to generate the MCPR operating limits accounted for the effects of axial power distribution changes during the transient. The current approved method ,

assumes a changing axial power shape in the core wide analysis but a fixed axial power shape in '

the hot channel analysis.

YAEC performed a sensitivity study to evaluate the impact on both Cycle 16, which was operating at the time, and the upcoming Cycle 17, assaming various exposures, transients and initial axial power shapes. The results showed that varying the axial power shape in the hot channel analysis does affect the MCPR for the pressurization transients. However, for Cycle 16, the MCPR limits bounded the MCPR results from the study. For Cycle 17, the MCPR limits were adjusted to account for this change in method.

In future reload analyses in support of VYNPS, YAEC intends to continue to treat the axial power shape in the hot channel analysis, as described above. Based on the August 23rd telecon, it is our understanding that no funher documentation of the revised method is required and that NRC finds our approach acceptable.

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.j y vu<uou vrsun Necuan Pownn connmanos United States Nuclear Regulatory Commission October S,1993 Page 2 If you should have any funher questions, please contact this office.

Very truly yours,

. VERMONT YANKEE NUCLEAR POWER CORPORATION cnOWh , MW[ dot, , h ,

Leonard A. Tremblay, Tr.

SeniorLicensing Engineer

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cc: USNRC Region I Administrator USNRC Resident Inspector- VYNPS USNRC Project Manager- VYNPS Telephone conference participants:

NRC/NRR W. Butler D. Dorntu S. Liang-Wu YAECJVYNPC P. Bergeron B.Slifer M. Sironen L.Tremblay

-I

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