05000482/LER-2015-001, Personnel Error Causes Two Inoperable Residual Heat Removal Trains
| Wolf Creek Generating Station | |
| Event date: | 1-28-2015 |
|---|---|
| Report date: | 03-25-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat |
| Initial Reporting | |
| ENS 50772 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat |
| 4822015001R00 - NRC Website | |
PLANT CONDITIONS PRIOR TO THE EVENT
Mode 1 Power - 100% There were no systems, structure or components (SSC) that were inoperable at the start of the event and contributed to the event.
DESCRIPTION
In December 2014, clearance orders were prepared to support planned maintenance on valves EJFCV0610, Residual Heat Removal (RHR) pump A miniflow valve [EEIS Code: BP-V], and BNHV8812, Refueling Water Storage Tank (RWST) to RHR pump A suction valve [EEIS Code: BP-V]. The clearance orders support isolating all possible flow paths and were prepared by a non-licensed individual. The clearance orders as prepared close valve EJHV8809A, RHR cold leg injection loops 1 and 2 [EEIS Code:
BP-V], and valve EJHV8716A, RHR discharge cross-tie [EEIS Code: BP-V], resulting in isolation of the flow path to two of the four cold leg injection nozzles for the RHR System [EEIS Code: BP]. The Technical Specification (TS) 3.5.2 Bases, Limiting Condition for Operation (LCO) Section, specifies that during an event requiring Emergency Core Cooling System (ECCS) actuation, a flow path is required to provide an abundant supply of water from the RWST to the Reactor Coolant System (RCS) via the ECCS pumps (RHR is a subsystem of the ECCS) and their respective supply headers to each of the four cold leg injection nozzles. On January 8, 2015, the senior license operator performing the tagging authority review of the clearance orders failed to ensure that the clearance orders would not adversely impact the plant.
On January 27, 2015, it was identified by the on-shift work control center (WCC) senior licensed operator reviewing the upcoming schedule that the on-shift operations crew would be hanging the clearance orders for taking the 'A' RHR train out of service for planned maintenance starting at 0500 hours on January 28, 2015. During the evening, the WCC senior licensed operator reviewed the clearance orders, referencing the drawings in the clearance order detail page and TS 3.5.2. During this review, the WCC senior licensed operator did not recognize that both trains of RHR would be rendered inoperable with the clearance orders place. The WCC senior licensed operator approved for issuing clearance orders at approximately 0310 hours on January 28, 2015.
On January 28, 2015, an extra licensed operator was assigned to hang the applicable clearance order tags that were located on the control boards in the control room. The licensed operator compared each tag to the tag hang list and compared the nomenclature on each valve to the hand switches ensuring the correct tag was placed on the correct component. On hand switch EJHIS8716A [EEIS Code: BP-LIS], the licensed operator compared the nomenclature on the tag to the hand switch, and the tag hang list. The components were then repositioned to obtain the desired configuration for the clearance order. While signing the clearance order tags in electronic clearance order database, the licensed operator identified information in the electronic data base and questioned the Control Room Supervisor (CRS) regarding the acceptability of closing valve EJHV8716A. The CRS reviewed procedure AP 26C-004, "Operability Determination and Functionality Assessment," Section A.16 of Attachment A, determined that closure of valve EJHV8716A results in the entry into LCO 3.0.3.
At 0534 hours on January 28, 2015, Condition C of LCO 3.5.2 was entered upon determining that less than 100% of the ECCS flow equivalent to a single OPERABLE ECCS train was available with valve EJHV8716A closed. Entry into LCO 3.0.3 in accordance with Required Action C.1 was made at 0535 hours. Actions were taken to restore valve EJHV8716A to the open position. LCO 3.0.3 was exited at 0550 hours. A review of Nuclear Plant Information System (NPIS) data determined that EJHV8716A was closed for 41 minutes.
Further review of this event by the WCC senior licensed operator identified that valve EJHV8809A was included in procedure AP 26C-004, Section A.16 of Attachment A and that closure of this valve results in entry into LCO 3.0.3. Entry into LCO 3.0.3 in accordance with Required Action C.1 was made at 0635 hours. Actions were taken to restore valve EJHV8809A to the open position. LCO 3.0.3 was exited at 0650 hours. A review of NPIS data determined that valve EJHV88809A was closed for 1 hour and 42 minutes.
REPORTABILITY
With less than 100% of the ECCS flow equivalent to a single OPERABLE ECCS train available, the plant is in a condition outside of the accident analysis. With both RHR trains inoperable, the plant was in a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. As such, this event is reportable under 10 CFR 50.73(a)(2)(v)(B).
The event was reported (EN #50772) under 10 CFR 50.72(b)(3)(v)(B) for an event that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.
CAUSE
The licensed operators involved with the preparation and implementation of the clearance orders did not recognize that current plant conditions could not support the proposed activity.
CORRECTIVE ACTIONS
The individuals involved with this event had their qualifications removed until remediation occurred. On January 29, 2015, WCGS Standing Order 36, Revision 0, "Tagging Authority Duties," was issued that specified guidance for clearance orders that affect equipment OPERABILITY.
On February 10, 2015, the electronic clearance order database was modified to identify the valves in procedure AP 26C-004, Section A.16 that can cause an entry into LCO 3.0.3.
On February 19, 2015, procedure AP 21D-003, "Control of Tagging Information," was revised to identify the use of red switch boxes for the valves in procedure AP 26C-004, Section A.16 that can cause an entry into LCO 3.0.3. Red switch boxes have been placed on the control boards in the control room on the valves in procedure AP 26C-004, Section A.16 that can cause an entry into LCO 3.0.3. The placement of the red switch boxes provides an awareness to the operator of the significance of the valve.
SAFETY SIGNIFICANCE
The event is of low safety significance due to the amount of times the valves were out of their required position and the low probability of an event occurring during this period that would require the RHR System. The WCGS Probabilistic Risk Assessment model only requires injection into one RCS cold leg.
The 'B' RHR train was capable of injecting into two RCS cold legs.
OPERATING EXPERIENCE/PREVIOUS EVENTS
None.