ML061250442
| ML061250442 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/02/2006 |
| From: | Mahesh Chawla Plant Licensing Branch III-2 |
| To: | Vincent D Nuclear Management Co |
| Mahesh Chawla, LPL3-1, 415-8371 | |
| References | |
| TAC MC9272, TAC MC9273 | |
| Download: ML061250442 (2) | |
Text
From:
Mahesh Chawla To:
Dale.Vincent@nmcco.com Date:
5/2/06 1:17PM
Subject:
Extension of Integrated Leakage Rate Test Interval for Prairie Island, Unit 1 & 2
- MC9272/73 As the inservice inspection requirements mandated by 10 CFR 50.55a and the leak rate testing requirements of Option B of Appendix J complement each other in ensuring the leak-tight and structural integrity of the containment, the staff needs the following information to complete its review of the license amendment request. Please arrange a teleconference to discuss the following:
- 1. The approach used to assess the risk impact of the integrated leakage rate test interval extension considered only internal events risk. As stated in Section 2.2.4 of Regulatory Guide 1.174, the risk-acceptance guidelines (in this case, for large early release frequency (LERF))
are intended for comparison with a full-scope risk assessment, including internal and external events. Consistent with this guidance, and to the extent supportable by the available risk models for Prairie Island, provide an assessment of the impact of the requested change on delta LERF and total LERF (based on the Nuclear Energy Institute Interim Guidance Methodology) when external events are included within the assessment.
- 2. For the examination of seals and gaskets, and examination and testing of bolts associated with the primary containment pressure boundary (Examination Categories E-D, and E-G), you had requested relief from the requirements of the Code (Section 4.2.4.3 of Exhibit A of the Reference). As an alternative, you plan to examine them during the leak rate testing of the primary containment. With the flexibility provided in Option B of Appendix J for Type B and Type C testing (as per NEI 94-01 and RG 1.163), and the extension requested in this amendment for the Type A testing interval, please provide an examination schedule for examination and testing of seals, gaskets, and bolts (pressure seating and pressure unseating penetrations) that provides periodic assurance regarding the integrity of the containment pressure boundary.
3.Based on the review of Section 4.2.3.2 of Exhibit A of the Reference, the staff understands that you are using the 1992 Edition and the 1992 Addenda of Subsections IWE of the ASME Section XI Code for the examination of containment steel shell. Section 4.2.3.6 indicates that you perform VT-1 examinations for areas accessible from both sides, and perform ultrasonic thickness measurements for surface areas accessible from only one side. Please provide the locations of the containment surfaces where you have identified measurable degradation (other than coating irregularities), and a summary of findings of the examinations performed.
- 4. Section 4.2.3.3 of Exhibit A of the Reference indicates a number of areas exempt from the ISI examinations. Inspections of some steel containments have indicated degradation from the uninspectable (embedded) side of the primary containments. These degradations cannot be found by VT-3 or VT-1 examinations unless they are through the thickness of the shell. For the ellipsoidal bottom of the containment, it is not feasible to examine any part of it. Please provide information as to how potential leakages due to aging-related degradation of the primary containment areas, exempted from the ISI examinations, are factored into the risk assessment related to the ILRT interval extension.
CC:
Hansraj Ashar; James Pulsipher; Robert Palla Mail Envelope Properties (4457940D.1B5 : 2 : 35732)
Subject:
Extension of Integrated Leakage Rate Test Interval for Prairie Island, Unit 1 & 2 - MC9272/73 Creation Date:
5/2/06 1:17PM From:
Mahesh Chawla Created By:
MLC@nrc.gov Recipients Action Date & Time OWGWPO01.HQGWDO01 Delivered 05/02/06 1:17 PM HGA CC (Hansraj Ashar)
TWGWPO01.HQGWDO01 Delivered 05/02/06 1:17 PM JCP2 CC (James Pulsipher)
RLP3 CC (Robert Palla) nmcco.com Transferred 05/02/06 1:17 PM Dale.Vincent (Dale.Vincent@nmcco.com)
Post Office Delivered Route OWGWPO01.HQGWDO01 05/02/06 1:17 PM TWGWPO01.HQGWDO01 05/02/06 1:17 PM nmcco.com Files Size Date & Time MESSAGE 3936 05/02/06 01:17PM Options Auto Delete:
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