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| Report date | Site | Event description | |
|---|---|---|---|
| 05000458/LER-2015-003, Operations Prohibited by Technical Specifications and Loss of Safety Function Due to Inoperability of Division 2 Containment Penetration Leakage Control System | 9 July 2015 | River Bend | (LSV) subsystem was found out of position. Subsequent investigation concluded that this condition had existed since before the plant was started up from a refueling outage on March 26, 2015, causing that subsystem to be inoperable for a period greater than the 30-day allowable outage time in Technical Specifications. The valve (SWP-V912) is in the service water supply to the air compressor on that determined that, during the intervening period, there were two short planned outages of the Division 1 subsystem. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as operations prohibited by Technical Specifications, as well as 10 CFR 50.73(a)(2)(v)(C) as a loss of the LSV safety function during those periods when the Division 1 subsystem was out of service. The two periods during which the Division 1 LSV subsystem was inoperable totaled approximately 7.5 hours. Otherwise, it was capable at all other times to perform the design safety function. At no time during the period from plant startup on March 26 until the Division 2 subsystem was restored to an operable status was there an actual demand for the system to operate. This event was thus of minimal significance to the health and safety of the public. |
| 05000458/LER-2015-001, Operations Prohibited by Technical Specifications Due to Deficient Local Leak Rate Test Procedures Containing Erroneous Valve Alignments | 16 April 2015 | River Bend | On February 18, 2015, while the plant was operating at approximately 98% power, it was discovered that four local leak rate procedure erroneously required the closure of the respective motor-operated valve in the packing leak-off line for the outboard main steam isolation valve (MSIV) being tested, when the proper test configuration would require the valve to be open. The net effect of the error was to partially negate the effectiveness of a surveillance test required by Technical Specifications. This condition had existed since the procedures were revised in 1992 to add valve lineup checklists. The incorrect valve position for the subject test procedures was caused by lack of attention to detail when the procedures were developed. An assessment of the effects of the procedure error was conducted, and reasonable assurance was established that the safety function of the outboard MSIVs was not compromised by this condition. The procedures were corrected, and the tests were successfully conducted in the recent refueling outage. This condition is being reported in accordance with 10CFR50.73(a)(2)(i)(B) as operations prohibited by Technical Specifications. |
| 05000458/LER-2015-002, Operations Prohibited by Technical Specifications Due to Deficient Local Leak Rate Test Procedures Containing Erroneous Valve Alignments | 16 April 2015 | River Bend | On March 7, 2015, at 9:40 p.m., while the plant was in cold shutdown, power from the reserve station service line no. 2 to the Division 2 onsite electrical distribution system was lost. The Division 2 diesel generator (EDG) received an automatic start signal due the under-voltage condition on the 4160v bus, but did not start since it was out of service for scheduled maintenance. The Division 2 standby service water pumps were operating at the time for scheduled testing, and subsequently shut down when power was lost. The cabinet on the reserve station service transformer "D". The apparent cause of this event was inadequate work practices on the part of the electricians, in that they did not take all available precautions prior to performing the voltage check. The workers recognized the adverse conditions, but did not recognize the need to put into place any robust barriers. The electricians' successful past performance of this type of task likely led to overconfidence. Reviewers of the work package didn't challenge the potential risks or identify a most error-likely task. The EDG start logic responded as designed to the loss of power on the Division 2 electrical systems. This event did not involve any interruption of the shutdown cooling function. This event was, thus, of minimal safety significance with respect to the health and safety of the public. This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as a valid actuation of the EDG starting logic. |
| 05000458/LER-2014-005 | 26 September 2014 | River Bend | On August 1, 2014, at approximately 9:42 p.m. CDT, with the plant operating at 100 percent power, the high pressure core spray (HPCS) system was declared to be inoperable as a result of an engineering evaluation of an apparent leakage path through a part of the system. The evaluation determined that, should the HPCS system be initiated in response to a design basis event, the leakage path through a pump test return line to the condensate storage tank (the symptoms of which were first seen on July 12) could potentially cause the suppression pool inventory to be depleted to the extent that the pool would not support its 30-day mission time assumed in the station's accident analysis. Operators closed the HPCS pump suction valve at the suppression pool on August 1, resulting in the inoperability of the system. This event is being reported in accordance with 10 CFR 50.73(a)(2)(v) as a condition that defeated the safety function of the the HPCS system. A subsequent evaluation confirmed that, had the HPCS system actuated in response to a design basis event, the leakage through the pump test return line would have depleted the suppression pool inventory before the completion of its 30-day mission time. Regarding the suppression pool, this event constituted operations prohibited by Technical Specifications (10 CFR 50.73 (a)(2)(i)(b)), as well as a condition that defeated the safety function of the suppression pool (10 CFR 50.73 (a)(2)(v)). A blind flange was installed in the pump test return line to the condensate storage tank in order to isolate the leakage path, and the 1-IPCS system was restored to an operable status on August 5. Repairs on the test return line isolation valves are scheduled. |
| 05000458/LER-2014-004 | 26 September 2014 | River Bend | On July 30, 2014, with the plant operating at 100% power, a review of an engineering analysis of the ultimate heat sink (UHS) determined that the UHS was in an unanalyzed condition that degraded plant safety. This condition was the result of a design basis deficiency for the UHS that did not account for the adverse effects of system leakage on compliance with the 30-day inventory required by Regulatory Guide 1.27. The system design basis requires that 30-day inventory be maintained, with the assumption that no replenishment of the UHS inventory occurs for the entire duration of the postulated event. In support of the development of the engineering analysis, compensatory measures have been implemented which provide adequate assurance that the UHS will perform its design safety function. Corrective actions to restore full compliance with design basis requirements are in development. This event is being reported in accordance with 10 CFR 50.73 (a)(2)(ii) as an unanalyzed condition that degrades the safety function of the UHS. |