ML103280015
| ML103280015 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/19/2010 |
| From: | Virginia Electric & Power Co (VEPCO), Dominion |
| To: | Cotton K Plant Licensing Branch II |
| Cotton K, NRR/DLPM, 301-415-1438 | |
| References | |
| Download: ML103280015 (5) | |
Text
Page 1 of 5 Provided in an email to Surry NRC Project Manager Karen Cotton on November 19, 2010 NRC Request for Additional Information Relief Requests SPT-004, Rev. 2 and SPT-003, Rev. 2 for Surry Power Station Units 1 and 2, respectively During a conference call between the NRC and Dominion on November 18, 2010, Dominion discussed the recently approved Surry Units 1 and 2 Relief Requests SPT-004, Rev. 2 and SPT-003, Rev. 2, respectively, associated with inservice inspection of the reactor pressure vessel (RPV) bottom mounted instrumentation (BMI) penetrations. Dominions concern was the statement in the NRCs Safety Evaluation Report (SER) included in the NRC letter dated October 26, 2010, which indicated the RPV bottom head VT-2 inspections conducted each refueling outage (RFO) would be bare-metal inspections, as opposed to outside the insulation inspection (i.e., the bottom head insulation would be inspected for indication of boric acid leakage without being removed). Dominions intent is to perform the VT-2 inspection without removing the insulation as allowed by ASME Section XI. As a result of the discussion, the NRC requested additional information. The NRCs questions, provided in an email from the Surry NRC Project Manager Karen Cotton on November 19, 2010 to Gary Miller of Dominion, and Dominions responses are provided as follows:
NRC Question No.1 Describe the insulation configuration and the ability to see the annulus region of the nozzles even with the insulation in place.
Dominion Response The insulation at the bottom of the reactor vessel consists of reflective metal insulation (RMI) that conforms to the shape of the reactor vessel. The RMI has holes where each of the guide tubes exit the bottom of the reactor vessel. The insulation at the very bottom of the reactor vessel is one circular piece approximately six and half feet in diameter that can be dropped when a direct visual inspection of the reactor vessel bottom is required. The RMI is not a tight fit around each of the guide tubes and the size of the gaps around the guide tubes vary. (See Fig. 1 below.)
In accordance with ASME Section XI, IWA-5242 Insulated Components, which allows for the conduct of a pressure test inspection without removal of insulation, the VT-2 examiners inspect the accessible and exposed surfaces and joints of the RMI. Though a direct visual inspection of the bottom of the reactor vessel is not possible with the RMI in place, should any leakage have occurred at a BMI penetration during the operating cycle, the leakage would likely travel down the BMI guide tubes that extend through the insulation penetration gaps around the guide tubes, as well as to the low points of the insulation and through the insulation seams, where it would be identified by the examiners. (See Figs. 1 and 2 below.) The VT-2 examiners also thoroughly investigate surrounding areas around the bottom of the reactor vessel for evidence of leakage and other areas to which such leakage may be channeled. This VT-2 examination, in
Page 2 of 5 Provided in an email to Surry NRC Project Manager Karen Cotton on November 19, 2010 conjunction with the bare-metal Visual Examination (VE) of the RPV bottom head BMI penetrations that will be performed every other RFO would provide adequate assurance that any leakage in this area would identified.
In addition, the three previous bare metal VT-2 visual inspections that were performed on Surry Unit 1 in 2006, 2007 and 2009, and the four previous bare metal VT-2 visual inspections that were performed on Surry Unit 2 in 2005, 2006, 2008 and 2009 did not identify any BMI penetration area leakage.
NRC Question No.2 Explain the hardship associated with removing the insulation (i.e., dose, planning delays, etc.).
Dominion Response Requiring the performance of a bare metal VT-2 inspection of the BMI penetrations would require the removal and reinstallation of the RPV bottom head insulation. This effort incrementally increases the wear and tear on the RMI insulation. Removal and reinstallation of the RPV bottom head insulation would also result in the accumulation of additional personnel dose. The previously performed bare-metal inspections of the RPV BMI penetrations were reviewed to determine the dose that was incurred for the removal and reinstallation of the RPV bottom head insulation. It was determined that, on average, a dose of approximately 0.7 Rem was required to accomplish this task.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), the increased wear and tear on the RPV bottom head insulation and the additional personnel dose that would be incurred due to insulation removal and reinstallation is considered an unnecessary hardship without a compensating increase in the level of quality and safety because: 1) as noted in the response to Question 1 above, the RPV bottom head BMI penetration area can be adequately inspected for signs of boric acid leakage with the RPV bottom head insulation in place, and 2) a bare-metal VE visual inspection will be performed every other RFO pursuant to Code requirements.
Precedents Pursuant to 10 CFR 50.55a(a)(3)(ii), similar alternatives, which did not include the performance of the VE bare-metal RPV bottom head BMI inspection every other RFO or require a bare-metal VT-2 inspection, were previously approved by the NRC for both North Anna and Surry Units 1 and 2 as listed below:
- North Anna Unit 1 (Relief Request SPT-1) for the third inspection interval by NRC letter dated April 25, 2000 (TAC No. MA5750) and for the fourth inspection interval by NRC letter dated April 14, 2009 (TAC NO. MD9956);
Page 3 of 5 Provided in an email to Surry NRC Project Manager Karen Cotton on November 19, 2010
- North Anna Unit 2 (Relief Request SPT-005) for the third inspection interval by NRC letter dated June 12, 2002 (TAC NO. MB2280); and
- Surry Units 1 and 2 (Relief Requests RR-14 and RR18, respectively) for the third inspection interval by NRC letter dated August 1, 2001 (TAC NOS. MB1083 and MB1084).
Page 4 of 5 Provided in an email to Surry NRC Project Manager Karen Cotton on November 19, 2010 Figure 1 Surry RPV Bottom Head Insulation
Page 5 of 5 Provided in an email to Surry NRC Project Manager Karen Cotton on November 19, 2010 Figure 2 Surry RVH Bottom Head Showing BMI Penetrations and Guide Tubes