ML19257D337
| ML19257D337 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 12/27/1979 |
| From: | Moody D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-26, NUDOCS 8002040137 | |
| Download: ML19257D337 (3) | |
Text
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4' VERMONT Y AN KEE NUCLEAR POWER CORPORATION
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SEVENTY SEVEN GROVE STREET B.4.1.1 RUTLAND, VE!D10NT 05701 WY 79-149 REPLY TO:
ENGINEERING OFFICE TURNPIKE RO AD December 27, 1979 WEST 50RO. M ASS ACHUSETTS 0158 8 T ELEPHO N E 417 35 6-90 t t United States Nuclear Regulatory Commission Office of Inspection and Enforcement Region I 631 Park Avenue King of Prussia, PA 19406 Attention: Office of Inspection and Enforcement Mr. Boyce H. Grier, Director
References:
(1) License No. DPR-28 (Docket No. 50-271)
(2) USNRC Letter to VYNPC dated Novecber 20, 1979; IE Bulletin 79-26
Dear Sir:
Subject:
Response to IE Bulletin 79-26; Boron Loss from BWR Control Blades As required by Reference (2), we are providing the following information.
Vermont Yankee has a program in place to monitor and replace high exposure control blades.
Data on blade exposures accumulated since Cycle 1 is monitored and used to predict blade exposures in future cycles.
Based en this data, predicted exposures for an upcoming cycle are calculated.
Any blade calculated to have an exposure at any time during the upcoming cycle which corresponds to > 34% B10 depletion average over the upper quarter of the blade is scheduled for replacement during the preceeding refueling outage.
This program results in having no blades in any operating cycles which exceed 34% B10 depletion.
Vermont Yankee is presently supplying to General Electric the tubes from our highest exposed blade for destructive examination.
The results of this examination should be fully responsive to Item 4 of the fbb/f
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referenced Bulletin.
Responses to specific questions are.
Item 1.
Thru the use of plant process computer, exposure histories for the top quarter of all control rods have been, and will continue to be, maintained and monitored.
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United States Nuclear Regulatory Commission December 27, 1979 Attention:
Mr. Boyce H. Grier, Director Page 2 Item 2.
As part of our present control blade lifetime program, blades which are predicted to reach 34% B10 depletion averaged over the upper one-fourth of the blade during a given cycle are replaced during the preceeding refueling outage.
This program was in effect this past year and resulted in replacing three control rod blades during a plant outage in March 1979 and six blades during the refueling outage in October 1979.
No blades in any cycle exceeded the 34% B10 depletion over the upper one-fourth of the blade.
VY will continue to adhere to this program.
Item 3.A.
As part of VY refueling surveillance, suboriticality is verified for each control rod withdrawn to the full out position in the fully loaded core prior to start-up for a given cycle.
This test was successfully performed for the current operating cycle in October, 1979 B.
As no blades are expected to exceed 34% B10 depletion during a given cycle, it will not be necessary to include additional margin to account for potential loss of boron in the Shutdown Margin Demonstration test.
Item 4.
As part of continuing the program with General Electric the highest exposure blade at VY, having an exposure that corresponds to 34% B10 depletion in the upper fourth of the blade, is scheduled for destructive examination.
At the present time, tubes from these rods are awaiting shipment to the G.E. hot cell for further examination.
We feel that our present control blade lifetime program is fully responsive to this Dulletin.
The results of the destructive examination by General Electric on our highest exposed blade will be forwarded to the NRC as soon as they are available.
Should you desire additional information, do not hesitate to call.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION
+4 D.
. Moody
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Manager of Operations RJW/dsp 1864 279