ML062560134
| ML062560134 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 08/25/2006 |
| From: | Mahesh Chawla NRC/NRR/ADRO/DORL/LPLIII-1 |
| To: | Vincent D Nuclear Management Co |
| M. Chawla LPL3-1 | |
| References | |
| Download: ML062560134 (2) | |
Text
From:
Mahesh Chawla To:
dALE.Vincent@nmcco.com Date:
08/25/2006 11:32:56 AM
Subject:
SG Inspection Report By letters dated June 8, 2005 (ML051650318), June 22, 2005 (ML051740093), and September 8, 2005 (ML052560345), Nuclear Management Company, LLC, submitted information summarizing the results of the 2005 steam generator tube inspections at Prairie Island Unit 2.
In addition to these reports, the U.S. Nuclear Regulatory Commission staff summarized additional information concerning the 2005 steam generator tube inspections at Prairie Island Unit 2 in a letter dated July 19, 2005, (ML052020002).
In order for the NRC staff to complete its review of the licensee=s reports, the staff is requesting that the licensee provide responses to the enclosed questions. Please let me know if you would like to set up a teleconference to discuss this request for additional information (RAI).
- 1. In Table III of your September 8, 2005 letter, several tubes were plugged for indications at the cold-leg tube support plates (presumably attributed to cold-leg thinning). The depth of the degradation for several of these indications increased significantly when compared to the last outage. For example, one indication grew from 25-to 44-percent through-wall (steam generator 21, row 45, column 41); another indication grew from no reported degradation to 56-percent through-wall (steam generator 22, row 44, column 34); and another indication grew from 26-to 46-percent through-wall (steam generator 22, row 42, column 60). Assuming these indications are attributed to cold-leg thinning, the growth rates appear high. Please discuss any insights you have on the growth rates for the cold-leg thinning indications at Prairie Island Unit 2.
Please include in your response historic growth rates for cold-leg thinning (average growth rates and maximum growth rates) and the implications of these apparently high growth rates on future inspection intervals.
2.Please discuss the nature of the single volumetric indications that were plugged during the outage.
3.Please discuss whether the extent (number of tubes affected) and the severity of the dents at the uppermost tube support plates is similar to what has historically been observed at Prairie Island Unit 2 (i.e., is the denting Astable@).
4.Please discuss the final results of your foreign object search and retrieval in steam generator
- 21. The staff notes that at the time of the conference call in May 2005, the inspections were still ongoing. If any loose parts (foreign objects) were left in service, please discuss whether an analysis was performed to confirm that tube integrity would be maintained (with the part in the steam generator) until the next scheduled tube inspection.
CC:
Kenneth Karwoski Mail Envelope Properties (44EF1828.C74 : 2 : 35476)
Subject:
SG Inspection Report Creation Date 08/25/2006 11:32:56 AM
From:
Mahesh Chawla Created By:
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