ML20042E647
| ML20042E647 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/20/1990 |
| From: | Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-90-002, IEB-90-2, NUDOCS 9004260332 | |
| Download: ML20042E647 (5) | |
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Consumers Power POWERING i
niKN8GAN'E NEGGRE55
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General Office.1 1946 West Pernall Road, Jackson, MI 49201 * (617) 7ss-obb0 l
April 20, 1990 s
Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 l
DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT -
RESPONSE TO BULLETIN 90 LOSS OF THERMAL MARGIN CAUSED BY CHANNEL BOX BOW NRC Bulletin 90-02 entitled, " Loss of Thermal Margin Caused by Channel Box Bow," dated March 20, 1990, requested Consumers Power Company to verify that the current Minimum Critical Power Ratio (MCPR) Technical Specification operating and safety limits for Big Rock Point are being met while accounting for the effect of channel box bow.
The Bulletin also requested that applica-ble plants account for the effects of channel box bow in, analysis supporting the next refueling outage. This letter provides Consumers Power Company's 30-day response to the Bulletin.
General Description of Fuel and, Channel Configuration The Big Rock Point reactor has a small core rated at 240 MWT and contains 84 fuel assemblies.
Each fuel assembly is in an 11 x 11 array with a cross section of approximately 6-1/2" x 6-1/2" and an active fuel length of 70".
The fuel assemblies and channel assembides are not attached as in modern BWRs.
l; Channels are positioned and captured in place in the vessel with a grid system of hold down bars and remain in place when fuel is moved during refueling.
g The fuel assemblies are moved independently of the channels. Because each 00 fuel assembly and channel assembly is not an integral unit, exposures for 8N channel assemblies are tracked separately from fuel exposure.
Individual
- O channel assemblies are currently replaced when the exposure reaches approxi-
.bb mately 35-40 GWD/ST.
oso Figure 1: Core Configuration - Cycle 24 (attached) shows the exposures of the coo channel assemblies at the beginning of the current operating cycle. Also shown are the number of operating cycles each channel has been in the core.
y Assemblies which remain in low power areas receive small exposures each
-gg operating cycle.
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Big Rock Point Plant Response to Bulletin 90-02 April 20, 1990 Discussion 3
Big Rock Point does not presently account for the change in moderation and localized peaking contribution to critical power ratio by channel box bow.
Other conservatisms have been large enough to preclude dryout conditions caused by this-phenomenon. There have been no fuel failures at Big Rock Point L
for the last three operating cycles. Fuel failures in a previous-cycle were investigated to determine if any correlation existed between fuel failures and channel exposure. A correlation between these was not found.
The current operating cycle from the present to the end of cycle is not MCPR limiting. The minimum margin to the Technical Specification limit (including uncertainty) 16 8.1% and increases to 29.6% by all rods out exposure. _ Table 1 (attached) summarizes the MCPR for various exposures from the current status to all rods out. The percent margin to the Technical Specification limit is well in excess of the loss of CPR margin expected from channel box bow.
Conc 1 unions Big Rock Point channels are approximately one-half the length of channels used in modern BWRs and the magnitude of bowing expected by our channels is less than expected for the longer channels. The remainder of the current cycle is not MCPR limiting and has adequate margin to preclude dryout from channel box bow. Big Rock Point has not experienced any fuel failures during.the past three operating cycles. Based upon these facts, it is concluded that compli-ance with Technical Specifications CPR limits is assured.
Analyses evaluating the effect of channel box bow upon MCPR at Big Rock Point are being performed.
The results and any actions necessary to preclude the effects of channel box bow vill be submitted prior l to the start of the next.
l cycle.
6 h
L Kenneth W Berry Director, Nuc' lear Licensing CC Administrator, Region III, USNRC NRC Resident Inspector - Big Rock Point Attachment
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n (GWD/ST)
-MCPR T.S' Limit
- i% Marstin 4
0 3.53 11.906:
- 1. 763 ;--
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CONSIMERS POWER COMPAhT Big Rock Point Plant Docket 50-155 License DPR-6 NRC Bulletin 90-02.
At'the request of the Commission and. pursuant to the Atomic Energy Act of.1954' and.the Energy Reorganization Act of 1974. - as amended, and the Commission's' Rules and Regulations thereunder, Consumers Power Company submits our response to NRC Bulletin 90-02, dated March 20, 1990,' - entitled, " Loss of Thermal Margin Caused by Channel Box Box."
Consumers Power Company's response is dated April 20, 1990.
CONSIMERS POWER COMPAhT 4
To the best of my knowledge, information and belief, the contents of this Technical Specification Change Request are truthful and complete.
By
).
W-David P lloffman, Vic 1 e ident Nuclear Operation Sworn and subscribed to before me this 20th day of Apr11l1990.
..U E3aine-E Buehrer, Notary Public Jackson Iounty. Michigan My commission expires October 11, 1993 OC0490-0324-NLO4-I