ML20056A349
| ML20056A349 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/03/1990 |
| From: | Eddy J CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-90-002, IEB-90-2, NUDOCS 9008070084 | |
| Download: ML20056A349 (5) | |
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1 Consumers Power rowsmne
. AMBNGAN5 Nt0GRE55' oeneral offices: 1945 West PerneH Road, Jackson. MI 49201 * (517) 788-0550
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g Nuclear Regulatory Commission le in Document Control Desk
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' H DOCKET 50-155 - LICENSE DPR BIG ROCR POINT PLANT -
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UPDATE TO BULLETIN 90-02 RESPONSE - LOSS OF THERMAL
~ MARGIN DUE TO CHANNEL BOW H[
-NRC Bu11ctin 90-02 entitled, " Loss of Thermal Margin Caused by Channel Box.
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'_ Bow," dated March 20,1990, ~ requested Consumers Power Company to verify that i
the current Minimum Critical Power Ration (MCPR) Technical Specification "f
' 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 applicable plants account for the effects of channel box bow in analysis supporting the next refueling outage..By letter dated April 20, 1990, Consumers Power Company provided the required 30-day Bulletin response and committed to providing the NRC with the results of an analysis evaluating the effects 1of channel box bow upon MCPR at Big Rock Point prior to the start of the next fuel cycle. This. letter provides the results of that analysis.
. 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".
LThe fuel assemblies and channel assemblies are not attached as in-modern BWRs. Channels are positioned-and captured in place in the vessel with a grid l system of hold down bars and remain in place when fuel is moved during refueling. The fuel assemblies are moved independently of the channels.
Because each channel assemblies are tracked separately from fuel exposure.
Individual channel assemblies are currently replaced when the exposure reaches approximately 35-40 GWD/ST.
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Core Configuration - Cycle 24 shows the exposures of the
' 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.
Assemblies which remain in low power areas receive small exposures each operating cycle.
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Bi'g-Rock Point' Plant Update to IEB 90-02. Response
. August 3; 1990 Methods to Account for the Effects of Channel Bow An Engineering Analysis has been done to determine the change in critical power _ ratio due to' channel' bow.
Calculations show that Big Rock Point Plant'.
fuel channels bow only 1/5 the amount of modern BWR plants given the same exposure. This is.due to the fact'that Big Rock Point Plant channels are 1/2 the length _and wider-than modern BWR plant channels-(Ref.-Attachment 2).
The maximum amount a fuel channel ', e ws was determined' f rom actual mea sured -
da t a'.
From EPRI Report NP4225M, 1985, it was determined that the bow for channels with up to 40 GWD/ST exposure was.less,than 4.3 mm at a 2 o confidence level. This conclusion was well supported in SM Stoller Cornoration BWR Channel Reuse Seminar, November 11, 1989.
In the Stoller
'eport, measurements of approximately 1800; fuel channels, the maximum bow for ihannels with up to 40 GWD/ST exposure was less than 4.3 mm.
The measured i
bow found on channels by the name manufacturer as Big Rock Point (Cartech) was a maximum of 2.4 mm with an. average bow of 1.2 mm.
Therefore, using the conservative maximum bow of '4.3 mm for 12 f t. channels, Big Rock Point Plant's 6 foot channels maximum bow would be 1/5 of 4.3 mm or 0.9 mm for a typical channel' lifetime.
A channel bow of.9mm results in-a maximum change in critical power ratio of 0.030 for a typical core loading. The table in Attechment 3 shows the relationship 'between bowed end non-bowed channels throughout one fuel cycle, j:
The current limit for minimum critical power ratio (MCPR)'at Big Rock Point Plant is 1.763 including uncertainty. In order to insure compliance with the Technical Specification limit for MCPR of 1.763. the fuel assemblies in the cycle design physics package identified as having MCPR's of 5 1.793 will have new channels installed during core loading. This will insure that no fuel
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assemblies will exceed the MCPR limit of 1.763 due to channel bow during future fuel cycles.
l J Daniel Eddy Plant Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector - Big Rock Point Attachments t
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BOC Exposures'(GWD/ST) d"-
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A WACl! MENT! 1 C:re CrafigAratico - Cyc13 21,
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a' FUEL CHANNELS AND THEI,' DISP 6SITION IN THE REACTOR g'
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ATTACHMENT 2
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BIG ROCK POINT CHANNEL BOW VS TYPICAL BWR CHANNEL BOW s
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. length compared to standard.
i M =-1/5 6.5/5.3 = Big Rock Point channel width compared 'to standard.-
-Max expected' bow of standard 162" channels = 4.3mm.
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Max expected bow of Big Rock Point Plant 80" channels 1
4.3mm x 1/5'=.9mm f
==
Conclusion:==
Since' channel bow is caused by a difference in growth of opposite sides of a
. channel, a shorter and wider channel such as used at Big Rock Point Plant can L
be expected to bow 1/5 as much.
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.s l1 Referencet EPRI Document NP-2483,1982 H a t 8. M **W ***W t
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ATTACEMENT 3 FFFECTS OF CHANNEL BOW ON MCPR FOR FUEL CYCLE 24 AT BIG RO I
i Difference of Max Difference Cycle 24 MCPR MCPR Most Limiting Other Than Exposure CWD/ST N No Bow 4 Bow Bundle __
Outer Two Rows *
'1.
0.035 2.387 2.404 0.017 0.030
~2.
0.164 2.277 2.294 0.017 0.017 3.
0.286 2.047 2.061 0.014 0.020 4.
0.403 1.961 1.973 0.012 0.014 5.
0.803 1.905 1.916 0.011 0.014 6.
1.254 1.858 1.870 0.012 0.011 7.
1.701 1.858 1.875 0.017 0.012 8,
2.230 1.845 1.858 0.013 0.025 9.
2.655 1.899 1.909 0.010 0,022
'10.
3.119 1.982 1.997 0.015 0.015 11.
3.539 1.951 1.966 0.015 0.016 12.
4.030 2.059 2.075 0.016 0.022 s
13.
4.535 2.125 2.122 0.003 0.013 1
- Fuel assemblies in the outer two rows are not MCPR limiting during fuel l
cycles. The minimum MCPR for the outer two rows is 2.00.
This is 0.23 greater than the Technical Specification limit. Therefore, the outer two l
rows can be excluded when determining a change in MCPR due to channel bow.
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.IC0650-0261A-BT01 l
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