ML083090404

RAI Regarding a Revision to the Minimum Critical Power Ratio

ML083090404
Person / Time
Site:	Browns Ferry
Issue date:	11/06/2008
From:	Ellen Brown Plant Licensing Branch II
To:	Campbell W Tennessee Valley Authority
Brown Eva, NRR/DORL, 415-2315
References
TAC MD9255
Download: ML083090404 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 6,2008 Mr. William R. Campbell, Jr.

Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TI\J 37402-2801 SUB..IECT: BROWNS FERRY NUCLEAR PLANT, UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION REGARDING SAFETY LIMIT MINIMUM CRITICAL POWER RATIO (TAC NO. MD9255) (TS-446)

Dear Mr. Campbell:

By letter dated July 18, 2008, Tennessee Valley Authority submitted a request to revise Technical Specifications (TS) 2.1.1.2 to decrease the safety limit minimum critical power ratio from 1.11 to 1.09 for single recirculation loop operation and from 1.09 to 1.07 for double recirculation loop operation.

Based on our review of your submittal, the U. S. Nuclear Regulatory Commission staff finds that a response to the enclosed request for additional information is needed before we can complete the review.

This request was discussed with Mr. James Emens of your staff on November 3,2008, and it was agreed that a response would be provided by December 2, 2008.

If you have any questions, please contact me at (301) 415-2315.

Sincerely, IRA!

Eva A. Brown, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-259

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION SAFETY LIMIT MINIMUM CRITICAL POWER RATIO TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-259

1. Provide the number of months Unit 1 operated during Cycle-7, and the number of months expected for Cycle-8. Describe the key differences in core design and/or any other important difference between the Cycles 7 and 8 that support permitting Cycle-8 to be operated at a lower safety limit minimum critical power ratio (SLMCPR) value.

2. Although Cycle-8 SLMCPR analysis was performed assuming approval of extended power uprate (EPU), the EPU may not be approved. Address the number of months at current licensed thermal power Unit 1 is capable of operating before changes to the operating strategy (i.e. major control rod pattern adjustments, core flow, etc.) would be required.

3. Should Unit 1 operate during Cycle-8 at less than EPU conditions for a prolonged period, changes in control rod pattern and core flow could change the core power distribution and result in an increase in the SLMCPR. Increases in SLMCPR would be possible through extended changes in operating strategy in two ways:

Insertion of additional control rods could cause the axial power shape of individual rods and bundles to become more outlet-peaked, and Reduction of power at the center of the core could result in a flatter radial power distribution, placing more fuel rods near boiling transition in the limiting SLMCPR scenario.

It is stated in Section 2.4 of Enclosure 3 of the submittal that the limiting power shapes were not found in Cycle-8 and, therefore, no power shape penalties were applied to the calculated Cycle 8 SLMCPR values. Justify why no power shape penalties will be required should a different operating strategy be necessary.

4. Clarify whether the SLMCPR values of 1.07 for double loop operation (TLO) and 1.09 for single-loop operation (SLO) already include the EPU penalty of 0.02, approved in the NRC staff safety evaluation dated February 6,2007, or whether the penalty is added on top of the proposed values of SLMCPR.

5. Provide the exposure dependent SLMCPR values for the limiting fuel bundle. Address which fuel type (GE13 or GE14) is limiting for Cycles 7 and 8.

Enclosure

-2

6. The current Technical Specification surveillance requirement (SR) 3.3.1.1.7 requires that local power range monitors (LPRMs) be calibrated at an interval of 1000 megawatt day per ton of average core exposure. Provide the following additional information:

a. Clarify whether the LPRM calibration interval will be changed from the current requirements.

b. If the LPRM calibration interval will be increased from the current requirement, then explain any changes needed to the SLMCPR calculation to account for increased LPRM uncertainty.

November 6, 2008 Mr. William R. Campbell, Jr.

Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

BROWNS FERRY NUCLEAR PLANT, UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION REGARDING SAFETY LIMIT MINIMUM CRITICAL POWER RATIO (TAC NO. I\I1D9255) (TS-446)

Dear Mr. Campbell:

By letter dated July 18, 2008, Tennessee Valley Authority submitted a request to revise Technical Specifications (TS) 2.1 .1 .2 to decrease the safety limit minimum critical power ratio from 1.11 to 1.09 for single recirculation loop operation and from 1.09 to 1.07 for double recirculation loop operation.

Based on our review of your submittal, the U. S. Nuclear Regulatory Commission staff finds that a response to the enclosed request for additional information is needed before we can complete the review.

This request was discussed with Mr. James Emens of your staff on November 3, 2008, and it was agreed that a response would be provided by December 2, 2008.

If you have any questions, please contact me at (301) 415-2315.

Sincerely, IRA!

Eva A. Brown, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-259

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv Distribution:

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