ENS 48237
ENS Event | |
|---|---|
17:00 Aug 27, 2012 | |
| Title | Both Emergency Diesel Generators Declared Inoperable |
| Event Description | At 12:00 CDT maintenance personnel identified a pinhole leak from the Division 1 Service Water System piping in the Service Water Pump Room. Division 1 Service Water [SW] was declared inoperable and LCO 3.7.2 Condition A was entered due to a potential loss of structural integrity. This directs entry into LCO 3.8.1 for Diesel Generator #1 made inoperable by SW. DG 2 was previously made inoperable at 05:39 CDT on 8/25/2012 due to an unrelated issue regarding rain water inleakage into the DG 2 Room. Control Room Emergency Filtration system [CREFs] is aligned to Div 1 power. LCO 3.7.4 Condition A is applicable, requiring restoration of CREFs to operable status within 7 days. TRM LCO 3.6.1 condition A and B also apply, requiring (A) Restoration of containment spray subsystem A to OPERABLE status within 7 days and (B) Restore one RHR containment spray subsystem to operable status within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
DG 1 and DG 2 comprise the onsite emergency power systems. Both DGs inoperable is reportable per 10CFR50.72(b)(3)(v)(D) as a condition that could prevent fulfillment of the safety function of structures or systems needed to mitigate the consequences of an accident. Actions were taken to expedite repairs of the DG 2 roof leak and to further characterize the Division 1 SW piping leak. LCO 3.8.1 Condition E allows 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to restore one DG to operable status or enter Condition F, to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, which was entered at 14:00. Repairs to the roof leak on the DG 2 room were completed, after which DG 2 was declared Operable at 18:30. LCO 3.8.1 Conditions E and F required shutdown were exited at this time. LCO 3.8.1 Condition B for DG 1, and 3.7.2 for SW Loop A, continue to be active. Planning to repair the SW piping pinhole leak is continuing. There were no adverse grid conditions during the period both DGs were inoperable. The NRC Resident has been informed of the condition. No media or press release is planned at this time.
This notification is being made to retract Event Notification EN#48237 which reported a loss of safety function due to both onsite Emergency Diesel Generators (DGs) being simultaneously INOPERABLE. On 8/25/12 at 0539 CDT, DG#2 was declared INOPERABLE due to rain water in-leakage into the DG#2 room. Condition B of LCO 3.8.1 was entered. and Required Actions were being taken to restore the INOPERABLE DG within 7 days. Subsequently, on 8/27/12 at 1200 CDT Maintenance personnel identified a pinhole leak from the Division I Service Water System piping in the Service Water Pump Room. Division I Service Water was declared INOPERABLE and LCO 3.7.2 Condition A was entered due to a potential loss of structural integrity. This prompted entry into LCO 3.8.1 Conditions E and F which require shutdown, because DG#1 was made INOPERABLE by SW. Both DG's INOPERABLE is reportable per 10CFR50.72.b.3.v.D as a condition that could prevent fulfillment of a safety function of structures or systems needed to mitigate the consequences of an accident. Repairs to the roof leak on the DG#2 room were completed, after which DG#2 was declared Operable at 1830 CDT on 8/27/2012. LCO 3.8.1 Conditions E and F were exited at the time. LCO 3.8.1 Condition B for DG#1, and 3.7.2 for SW Loop A, continued to be active, and planning to repair the pin-hole leak continued. Subsequent investigation and UT examinations provided data which enabled SW Division 1 and DG#1 to be declared OPERABLE on 8/30/2012 at 0528 CDT. An evaluation of this condition concluded that further characterization of the SW Piping Pin-Hole leak enabled ASME Code Case N-513-3 to be applied to determine piping structural integrity was maintained. SW ability to supply required flows to its loads is not adversely diminished, because the flaw is small. Water leaking from the flaw will not adversely affect any other equipment important to safety by spray or flooding. The piping is compliant with ASME code. Based on this evaluation, the Division 1 SW system can perform its safety function and is OPERABLE. With Division 1 SW subsystem capable of fulfilling its safety function, DG#1 was therefore also capable of fulfilling its safety function during the period of SW subsystem INOPERABILITY. Consequently, during the period of DG#2 INOPERABILITY, DG#1 was capable of fulfilling the safety function of the onsite emergency power system. NPPD therefore retracts Event Notification EN 48237. The NRC Resident has been informed of this retraction. Notified R4DO (Azua). |
| Where | |
|---|---|
Cooper  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.8 h0.158 days <br />0.0226 weeks <br />0.00521 months <br />) | |
| Opened: | John Myers 20:48 Aug 27, 2012 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Aug 31, 2012 |
| 48237 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |