ML051520070
| ML051520070 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/31/2005 |
| From: | Alexion T NRC/NRR/ADPT |
| To: | Sharon Bennett Entergy Operations |
| References | |
| Download: ML051520070 (3) | |
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Thomas Alexion - FOLLOW-UP RAI: ANO-1 SG 1SI REPORT FOR 1 R18 - Docket 50-313 Page 1A.
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Thomas Alexion STEVE A BENNETT 5/31/05 9:49AM FOLLOW-UP RAI: ANO-1 SG ISI REPORT FOR 1 R18 - Docket 50-313
- Steve, See the attached.
Tom
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FOLLOW-UP RAI: ANO-1 SG ISI REPORT FOR IR18 - Docket 50-313 5/31/05 9:49AM Thomas Alexion TWA@nrc.gov Recipients entergy.com SBENNE2 (STEVE A BENNETT)
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Size 491 10934 Date & Time 05/31/05 09:49AM 05/31/05 09:46AM No None Yes Standard No None No Standard Immediate Delivered & Opened
FOLLOW-UP REQUEST FOR ADDITIONAL INFORMATION SPRING 2004 ONCE-THROUGH STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT ARKANSAS NUCLEAR ONE, UNIT 1 (ANO-1)
DOCKET NO. 50-313 The August 3, 2004, report (ADAMS Accession No. ML042240207) provided the results for the calculated total best-estimate large-break loss-of-coolant accident (LBLOCA) leakage during the ANO-1 eighteenth refueling outage (1 R1 8). The calculated total best-estimate LBLOCA leakage for Cycle 18 was estimated to be 2.57 gallons-per-minute (gpm) for the initial two minutes and 1.49 gpm for the remaining 30 days. In Question 5 of the NRC staff's request for additional information (see e-mail at ADAMS Accession No. ML051450289), the licensee was asked to provide a summary of the flaws used in the evaluation and to discuss their individual contributions to the leak rate. In their draft response (see e-mail at ADAMS Accession No. ML051450296), the licensee discovered that there were flaws that had been classified as being in the pressure boundary during the original calculation, but were in fact outside the pressure boundary. When the licensee re-calculated the total best estimate LBLOCA leakage for Cycle 18, the estimate was revised downward. The revised best estimate LBLOCA leakage was estimated to be 1.29 gpm for the initial two minutes and 0.02 gpm for the remaining 30 days.
The staff notes that the licensee's LBLOCA leakage estimate during the previous refueling outage (1 R17) considered the potential leakage of all circumferential cracks found during the inspection, including those above the re-roll repairs, because of the possibility that a leak path could exist around the roll or re-roll joints.
- 1.
Discuss why the flaws in question were classified as being inside the pressure boundary for the original LBLOCA leakage estimate for Cycle 18, and discuss the basis for re-classifying the flaws as being outside of the pressure boundary. Include in your discussion the reasons why you concluded that the flaws in question should not be included in the LBLOCA leakage estimate and why the revised leakage estimate is conservative.
- 2.
Discuss whether the LBLOCA leakage estimate methodology (i.e., not considering cracks above original rolls or re-roll repairs in the leakage estimate) has changed since the previous outage. If the LBLOCA leakage estimate methodology has changed, provide a technical basis. Include in your discussion the reasons why the leakage of flaws above the original rolls or re-roll repairs during a LBLOCA is no longer important in your assessment.