05000397/LER-2013-003
| Columbia Generating Station | |
| Event date: | 06-03-2013 |
|---|---|
| Report date: | 08-01-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3972013003R00 - NRC Website | |
Energy Industry Identification System (EllS) codes are identified in the text as [XX].
Introduction Initial Conditions At the time of the event, Columbia Generating Station (Columbia) was in Mode 5, at 0 percent of rated thermal power. The preferred source of offsite power from the 230 kV source through the startup transformer [XMFR) was inoperable. The Division 2 emergency diesel generator system [Etq was inoperable. The Division 2 emergency core cooling systems (ECCS) consisting of two trains of low pressure coolant injection (LPCI) [BO) were inoperable. The Division 1 emergency diesel generator and ECCS, consisting of one LPCI train and the low pressure core spray system IBM), were operable and protected.
Reportability Criteria Secondary containment [NO] operability was not maintained during an operation with a potential to drain the reactor vessel (OPDRV) activity and Required Action C.1 of Technical Specification (TS) 3.6.4.1 to immediately initiate actions to suspend OPDRV activities was not completed. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(1)(B) as an operation prohibited by the plant's TS.
Event Description
On June 3, 2013, with Columbia in a planned refueling outage and the reactor cavity flooded up (Mode 5), leakage past a closed isolation valve associated with one hydraulic control unit [HCll] on the control rod drive system [AA] was observed through a drain line. This leakage originated from the reactor vessel and constituted an operation with the potential to drain the reactor vessel (OPDRV). When the leakage was initially identified, it was not recognized as an OPDRV. The leakage rate was estimated to be less than 10 gallons per hour. This leakage persisted for 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> on June 3, 2013, from 0405 hours0.00469 days <br />0.113 hours <br />6.696429e-4 weeks <br />1.541025e-4 months <br /> to 1955 hours0.0226 days <br />0.543 hours <br />0.00323 weeks <br />7.438775e-4 months <br /> until the maintenance activities were completed and the drain line was isolated. The leakage was observed by Engineering personnel conducting a field walk down of the control rod drive system. A subsequent review of the issue by Licensing personnel determined that, although the leakage was minimal, It constituted an OPDRV under the plain language definition provided by Enforcement Guidance Memorandum (EGM) 11.003, "Enforcement Guidance Memorandum on Dispositioning Boiling Water Reactor Licensee Noncompliance with Technical Specification Requirements during Operations with a Potential for Draining the Reactor Vessel," dated October 4, 2011.
gvent Cause The cause determination is still in progress. The preliminary cause of this event is attributed to inadequate procedure guidance for actions to take when unexpected OPDRV conditions are encountered. The TS require that actions be initiated immediately to suspend the OPDRV activity. In this case, upon discovery of the leakage, the maintenance activity should have been stopped and a determination undertaken to identify the necessary actions to isolate the leakage while still preserving equipment and personnel safety. A supplement to this licensee event report will be submitted if the final cause determination is substantively different from the initial cause determination.
26158 R5 Columbia Generating Station 05000397 NRC FORM 3156A U.S. NUCLEAR REGULATORY COMMISSION
CONTINUATION SHEET
Safety Assessment The safety significance of this event is considered to be negligible. At the time of the event, Columbia was in Mode 5 with the reactor cavity flooded up. The leakage rate was small, on the order of 10 gallons per hour.
Approximately 500,000 gallons of water are added to flood up the reactor cavity; thus, this amount of water would be available to drain prior to reaching the top of active fuel. Additionally. the makeup capability of the ECCS far exceeded the observed leakage rate.
Corrective Actions
The following corrective actions were completed: A Night Order was issued to identify that when CRD-V- 126/2635 [V] is open, the known leakage past CAD-V-101/2635 requires this configuration be considered an OPDRV. Additionally, the Night Order reinforced the expectation that upon notification that leakage has been discovered that may constitute an OPDRV, action must be commenced immediately to allow isolation of the drain path in order to satisfy the TS requirements. These actions must be done in a controlled manner to ensure industrial, radiological, and nuclear safety is not jeopardized.
The corrective action plan is still being developed. The preliminary plan will revise procedure PPM 3.4.1 to incorporate the expectations from the Night Order, A supplement to this licensee event report will be submitted if the final corrective action plan is substantively different than that included here.
Previous Similar Events
During the refueling outage that was in progress during this event, a number of evolutions were properly classified as OPDRVs using the guidance in EGM 11-003. For these planned evolutions, the TS requirements were met. There are no previous similar events involving unplanned OPDRV activities.
26158 R5