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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 50871 | 7 March 2015 13:30:00 | Non | Limiting Condition for Operation Not Met Due to Emergency Sump Pump Inoperable | On March 7, 2015, at 0830 EST, the NCNR (NIST Center for Neutron Research) discovered a probable violation of the Limiting Condition for Operations of the TR-5 Technical Specifications (TS), 3.3.2, Specification (1), while performing maintenance during the scheduled reactor shutdown period. This initial report is being made in accordance with TR-5 TS 6.7.2.d. The TS is as follows: TS 3.3.2 Emergency Core Cooling; Specification: The reactor shall not be operated unless: (1) The D2O (deuterium oxide) emergency core cooling system is operable, and (2) A source of makeup water to the D2O emergency cooling tank is available. The discovery was made at 0830 EST on March 7, 2015, that the local disconnect switch for the emergency sump pump was in the disconnect position. The last time that it was verified operable was on July 2, 2014, when the annual surveillance of operability was performed. There was no maintenance performed on the emergency sump pump, nor is there any other known reason that the switch would have been placed in the disconnect position since July 2, 2014. After the discovery the sump pump disconnect switch was immediately placed in the connect position. The emergency core cooling system, in the event of loss of core coolant, provides sufficient D2O, to passively provide adequate coolant for ~ 2.5 hours to cool the fuel and protect against the release of fission products. That part of the emergency core cooling system was and remains operable and is not part of this violation. The emergency core cooling system employs one sump pump to return spilled coolant to the overhead storage tank. There is only enough D2O in the overhead storage tank to provide cooling for 2.5 hours on a once through basis. Because there is only one sump pump, it must be operational whenever the reactor is operational (TS 3.3.2 (1)). In the event that that pump fails or is inoperable and the D2O supply in the overhead storage tank is exhausted, domestic water or a suitable alternative would be used to furnish water for once through cooling (TS 3.3.2 (2)). A source of makeup water to the D2O emergency cooling tank was and remains available and is not part of this violation. The violation that is the subject of this report is that the sump pump was discovered inoperable and may have been inoperable since July 2, 2014, which includes periods of reactor operation. That is a violation of TS 3.3.2 (1). The licensee is conducting an investigation into this event. | Emergency Core Cooling System | |
| ENS 47466 | 21 November 2011 22:00:00 | Non | Confinement Not Maintained as Required by Technical Specifications | Yesterday afternoon, while performing retests on replacement control shim arm switches, reactor operators placed the reactor in a condition that would allow more than one shim control rod to be withdrawn. This violated Technical Specification 3.4.1, "Operations that require confinement." The reactor facility did not have full confinement in place at that time. The specific language of Technical Specification 3.4.1 is "Confinement shall be maintained when changes of components or equipment within the confines of the thermal shield, other than rod drop tests or movement of experiments, are being made which could cause a significant change in reactivity." Although the shim control rods were not withdrawn and the rod bottom lights never cleared, the circumstances, in the licensee's opinion, were that they could have caused a significant change in reactivity, allowing more than one control rod to be withdrawn when the reactor was not in full confinement. The licensee notified the NRC Reactor Inspector. | Control Rod |