ML20010H350
| ML20010H350 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/19/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-79-12, NUDOCS 8109240374 | |
| Download: ML20010H350 (2) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE 37dolli!R C ~-F : 1-2:~
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,b Mr. James P. O'Reilly, Director
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Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission fh IO -
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Dear Mr. O'Reilly:
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0FFICE OF INSPECTION AND ENFORCEMENT BULLETIN 79 RII:JPO 50-259, -260, -296 - BROWNS FERRY NUCLEAR PLANT My letter to you dated July 30, 1979 provided TVA's response to the subjed bulletin. Enclosed is a supplemental response to item 3 of the subject bulletin based on further evaluations of rod withdrawal sequences.
If you have any questions, please call Jim Domer at FTS 857-2014 Very truly yours, TENNESS VALLEY UTHORITY 0
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. M. Mi is, Manager i
Nuclear egulation and afety Enclosure cct Office of Inspection and Enforcement (Enclosure)
Division of Reactor Operations Inspection U.S. Nuclear Regalatory Commission Washington, DC 20555
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.. ;s' ENCLOSURE OIE BULLETIN 70-12 SUPPLEMENTAL RESPONSE BR0tNS FERRY NUCLEAR PLANT (50-250, -260, -296)
Item 3 of the subject bulletin requices licensees to " review and evaluate your control rod withdrawal sequences tc assure that they minimize the notch worth of individual control rods, especially those withdrawn inmediately at the point of criticality.
" In response to this item we have further evaluated rod withdrawal sequences, comparing notch worths-of control rods. We have found that-the notch worths are minimized by withdrawing the rods in RWM
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groups 1 through 4 in spiral sequence from the core periphery to the center. This withdrawal sequence is currently being used for the units at Browns Ferry since these notch worths were found to be less than those for the sequence with bank withdrawal of RWM groups' 3 and 4 between position 04 and 12.
We continuously evaluate our withdrawal sequence for each unit and cycle to ensure that notch worths are acceptable.
Additionally, the results of each sequence analysis are used to id6ntify rods which have potentially high relative worths.
Notch-step withdrawai is then specified for these rods during the approach to critical.
This modified sequence has been coordinated with General Electric Company, and they are in agreement with this approach to minimize notch worths for the Browns Ferry units. We intenti to continue to evaluate the rod withdrawal sequences for each specific unit and cyc19 to ensure that the notch worths remain acceptable.
Presently the rame sequence is being used on all the Browns Ferry units; however, future reload cores could dictate modification of the withdrawal sequence for one or more units in order to maintain low notch worths. We believe that this cycle-specific approach is better than specifying a permanent generic withdrawal sequence for mi.iinizing notch worths.
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