ML20247K908
| ML20247K908 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 05/11/1998 |
| From: | Watford G GENERAL ELECTRIC CO. |
| To: | Joshua Wilson NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GAW-98-011, GAW-98-11, MFN-016-98, MFN-16-98, NUDOCS 9805220248 | |
| Download: ML20247K908 (4) | |
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GENuclear Energy GeneralEMtrk Conveny P. O. Box 700, %%rinrton NC 26402 May 11,1998 MFN-016-98
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GAW-98-011 Document Control Desk Nucle,ar Regulatory Commission, Washington, D. C. 20555-0001 Attention: James H. Wilson
Subject:
Summary of Channel Bow Status Attached is a summary discussion of the recent channel bow issue at Limerick Unit 1. The attachment discusses the preliminary root cause, operating experiencifor channels of the same and similar design, and a summary ofplants estimated to be currently operating with the potentially affected channels. The attachment also provide information that suppons applying a monitoring program only to those channels that have exceeded 45 GWd/MTU exposure.
Ifyou need further information, please contact Jim Rash, (910) 675-5612 or myself.
Sincerely, J />
len A. W rd, Manager Nuclear Fuel Engineering (910) 675-5446 Attachment u u v' W 'l
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I i-O 9805220248 980511 PDR ADOCK 05000352 P
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AfFN-016-98 Attachment Channel Bow Issue l
Scram time testing at Limerick I during Cycle 7 indicated a noticeably slower scram response in one cell. Although the technical specification scram time limit was not exceeded, the discrepant cell was investigated to determine the underlying cause. The underlying cause was determined to be an unusual, although unquantified at this time, amount of channel bow of a single high exposure Gell 100/65/50 mil thick-thin TSA (Thermal Size Anneal) channel.
Investigation of the possible cause of the unusual channel bow indicates the fabrication I
condition as the likely cause (differential irradiation growth caused by the residual partially cold worked - incompletely recrystallized - microstructure introduced during expansion sizing operations).
t Multiple channel bow measurement campaigns have been conducted on GE thick / thin TSA channels, extending to ~42 GWd/MTU bundle average exposure, demonstrating excellent performance. In addition, extensive reload fuel operating experience has been achieved with GE thick / thin TSA channels. Over 1,800100/65/50 mil thick / thin TSA channels have successfully completed their planned lifetime to peak bundle average exposures of up to ~43 GWd/MTU with no indication of a performance anomaly. Similarly, over 500120/75 mil l
thick / thin TSA channels have also successfully completed their planned lifetime to peak l
bundle average exposures of up to ~46 GWd/MTU with no indication of a performance
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anomaly. Additionally, the Limerick experience included 56 channels irradiated up to ~52 j
GWd/MTU. There were no other cells containing these high exposure channels that exhibited i
anomalous scram behavior. The bow in this single channel was apparent during a visual examinat;on, whereas the channels in the symmetric cells (from the same manufacturing lot) did not exhibit a similar visually apparent bow. For the Limerick channel that did experience unusual bow, the last normal scram thne result was obtained at ~46 GWd/MTU and the first anomalous scram time result was obtained at ~49 GWd/MTU Based on this combined experience, it is concluded that the risk of a shnilar condition as experienced at Limerick 1 is very low, especially for peak bundle average exposures 5 45 GWd/MTU.
At exposures above 45 GWd/MTU, although a sifallar occurrence is also judged to be unlikely, a monitoring program is recommended to provide early indications of channel / control blade interference. Fabrication process improvements introduced in early 1993 eliminated expansion sizing operations; thick / thin TSA channels fabricated after early 1993 are, therefore, unaffected. The channels currently in operation that were fabricated with the same processes as the unusually bowed Limerick I channel, and are therefore potentially affected, are summarized in Table 1. The information in Table 1 represents an estimate of the number of channels and exposure ranges for each of the potentially affected plants.
Table 1 identifies up to 1500 channels currently operating that are potentially affected. Of these 1500 potentially affected channels, the majority are planned to be discharged at exposures less than 45 GWd/MTU Up to 600 channels in a total of five plants are currently planned to be discharged beyond 45 GWd/MTU bundle average exposure.
o MFN-016-90 Attachment Table 1 Potentiahy Affected Channels Currently Estimated to be in Operation Estimated Estimated Estimated Exposure Estimated No. of Exposure g Discharge Discharge Plant Reload Channels 5/98 (GWd/MTU) (GWd/MTU)
Date Note Brunswick-1 8
3 35 42 Apr-00 1
Brunswick-2 9
24 40 42 Apr-99 10 6
35 42 Apr-99 Clinton 4
4 30 36 2
Fermi-2 3
182 35 41 Apr-00 3
40 25 45 Sep01 4
2 30 45 Apr-00 FitzPatrick 9
12 40 41 Oct-98 10 152 45 47 Oct-98 10 32 30 35 Oct-98 10 16 30 49 Oct-00 Hatch-1 14 3
40 45 Mar-99 Limerick-2 2
44 45 53 Apr 99 1R4 4
45 53 Apr-99 Millstone 1 13 187 20 2
l 14 5
10 Monticello 15 100 35 42 Sep-99 Nine Mile 12 144 35 45 Apr-99 Point-1 Nine Mile 3
14 33 42 May-00 3
Point-2 Peach 9
208 47 50 Sep-98 Bottom-2 Peach 9
138 45 53 Sep-99 Bottom-3 Perry 3
24 35 40 Apr-99 4
8 35 40 Apr-99 Pilgrim 9
88 35 43 Mar-99 9
52 35 46 Mar-01 Quad Cities-1 14 3
5 40-45 Oct-02 Notes:
- 1. Plant currently in outage. Current estimated number of potentially affected channels in reload.
- 2. Plant startup information not available at this time.
- 3. Plant currently in outage. Number of channels reloaded is dependent on core configuration due to identified fuelleaker.