ENS 46317
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ENS Event | |
|---|---|
17:15 Oct 7, 2010 | |
| Title | Feedwater Isolation Inadvertently Disabled |
| Event Description | At about 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br /> EDT on October 7, 2010, with the unit in Mode 3 and operators performing recovery actions following a reactor trip that had occurred at 0013 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> (see EN#46313), it was discovered that actions that had been performed to restore the main feedwater system had inadvertently resulted in disabling the feedwater isolation function. The feedwater isolation function, as described in Technical Specifications Section 3.3.2, Table 3.3.2 1, Function 5, requires that the feedwater isolation function be operable in Modes 1, 2, and 3, when the feedwater system is not isolated by the main feedwater isolation valves, main feedwater regulating valves, and bypass valves or by a closed manual valve. At approximately 1018 hours0.0118 days <br />0.283 hours <br />0.00168 weeks <br />3.87349e-4 months <br />, during actions being taken to restore operation of the main feedwater system, the feedwater isolation key switches for the three steam generators, A, B, and C, were placed in the override/reset position. Although it was not realized at that time, this action was contrary to the Technical Specifications Section 3.3.2 operability requirements for the feedwater isolation function. This inoperability of the feedwater isolation function would have prevented the automatic feedwater isolation function described in the basis of Technical Specifications Section 3.3.2, which states that the primary function of the feedwater isolation signal is to stop excessive flow of feedwater into the steam generators. It also states that this function is necessary to mitigate the effects of overfeeding the steam generators, which could result in overcooling of the primary system. This function is actuated by a safety injection signal. There is no Technical Specifications allowed condition for both trains of the feedwater isolation function to be inoperable. Therefore, Technical Specifications Limiting Condition for Operation (LCO) 3.0.3 was applicable from the time the feedwater isolation switches were placed in the override/reset position, until the feedwater isolation function operability was restored at approximately 1329 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.056845e-4 months <br />. The LCO 3.0.3 completion time to be in Mode 4 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> was not exceeded. This condition is reportable in accordance with 10 CFR 50.72(b)(3)(v)(D), any event or condition that at the time of discovery could have prevented the fulfillment of a safety function.
The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Robinson  South Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+0.88 h0.0367 days <br />0.00524 weeks <br />0.00121 months <br />) | |
| Opened: | Garrett Sanders 18:08 Oct 7, 2010 |
| NRC Officer: | Charles Teal |
| Last Updated: | Oct 7, 2010 |
| 46317 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Standby (0 %) |
| After | Hot Standby (0 %) |
Robinson with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 507782015-01-29T00:57:00029 January 2015 00:57:00
[Table view]Other Unspec Reqmnt, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Safety System Will Not Function as Required ENS 477482012-03-16T08:00:00016 March 2012 08:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Refueling Water Storage Tank Connected to an Unqualified System ENS 480112011-05-04T17:25:0004 May 2011 17:25:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Refueling Water Storage Tank Connected to Non-Seismically Qualified System ENS 463172010-10-07T17:15:0007 October 2010 17:15:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Feedwater Isolation Inadvertently Disabled ENS 460452010-06-24T18:34:00024 June 2010 18:34:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Instrument Buses 3 and 8 Failed Causing Closure of Rhr Valves ENS 406172004-03-28T15:26:00028 March 2004 15:26:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Both Trains of High Pressure Safety Injection Inoperable for 25 Minutes 2015-01-29T00:57:00 | |
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