ENS Event | |
|---|---|
18:15 Sep 29, 2010 | |
| Title | Discovery of Microtherm Insulation in Containment Which Could Impact Sump Strainer Performance |
| Event Description | On September 12, North Anna Power Station Unit 1 entered a scheduled refueling outage. During the outage while performing reviews for a design change, it was determined that some uncontrolled plant drawings indicated that Microtherm insulation may have been installed on some piping locations inside the containment. The Microtherm insulation impacts the new containment sump strainers installed to address NRC GSI-191 requirements. It was subsequently confirmed via walk downs that the Unit 1 containment contained some Microtherm insulation.
Based on conflicting information on the possible installation of Microtherm inside Unit 2 containment and the identification of Microtherm insulation on Unit 1, a conservative decision was made to shutdown Unit 2 on September 29, and the Unit was cooled down to Mode 5 to allow a detailed inspection to be performed. The areas where the Microtherm insulation was potentially installed could not be inspected with the Unit at power. Subsequent inspections have confirmed that the Microtherm insulation was installed in some areas of the Unit 2 containment. These locations include the reactor vessel nozzles and reactor coolant pump casings. Plans are being developed to remove this insulation on both units. The overall impact of the Microtherm insulation on the containment sump operation is being evaluated by engineering. The licensee has notified the NRC Resident Inspector and the Louisa County Administrator. |
| Where | |
|---|---|
North Anna  Virginia (NRC Region 2) | |
| Reporting | |
| Information Only | |
| Time - Person (Reporting Time:+21.35 h0.89 days <br />0.127 weeks <br />0.0292 months <br />) | |
| Opened: | Paige Kemp 15:36 Sep 30, 2010 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Sep 30, 2010 |
| 46294 - NRC Website
Loading map... | |
Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 462942010-09-29T18:15:00029 September 2010 18:15:00
[Table view]Information Only Discovery of Microtherm Insulation in Containment Which Could Impact Sump Strainer Performance ENS 443932008-08-07T20:00:0007 August 2008 20:00:00 Information Only Civil Disturbance at the North Anna Nuclear Information Center ENS 403792003-12-09T20:59:0009 December 2003 20:59:00 Information Only Information Only - Seismic Activity Felt at North Anna Power Station 2010-09-29T18:15:00 | |