05000261/LER-2012-002

LER-2012-002, Unplanned LCO 3.5.4 Entry Due to RWST alignment to Purification

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
2612012002R00 - NRC Website

I. DESCRIPTION OF EVENT

The Refueling Water Storage Tank (RWST) [TK] was placed on purification in accordance with OP-913, Refueling Water Purification Pump [P] Operation, as directed from OP-301-1, Chemical and Volume Control System (Infrequent Operation), at 04:00 on March 16, 2012, to support make up of level to the RWST. The Plant was in MODE 4 with the Reactor Coolant System at approximately 285 degrees Fahrenheit. This configuration, connection of the Refueling Water Purification (RWP) to the RWST, is not currently allowed based on unresolved seismic concerns. This was later discovered during a log review at 05:45, and operators were immediately directed to remove the RWST from purification. Technical Specification (TS) 3.5.4 was applied from 04:00 based on when it was determined that this condition had been entered. TS 3.5.4 was exited at 06:22 when the RWST was removed from purification.

TS Limiting Condition for Operation (LCO) 3.5.4 has an Applicability of MODES 1, 2, 3 and 4. Condition B of the LCO states that the RWST inoperable for reasons other than Condition A, restore the RWST to OPERABLE status in one hour. This was not accomplished. Condition C of the LCO states that if the Required Action and associated Completion Time is not met, be in MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and be in MODE 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The total time the RWST was inoperable was approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 22 minutes.

(Condition A pertains to inoperability of the RWST associated with born concentration and temperature limits.)

II. CAUSE OF EVENT

This event was investigated using the HBRSEP, Unit No. 2, Corrective Action Program (CAP) and is documented in Condition Report (CR) 524619. The investigation in CR 524619 was approved on April 30, 2012.

The CR 524619 investigation concluded to be a result of ineffective implementation of previous corrective actions. Several contributors were identified that relate to Human Performance. No Pre-Job Brief, Heavy Work load, failure to effectively use human performance tools, habits and patterns, assumptions, inaccurate risk perception are several of the identified contributors. However, the one Human Performance tool identified that was a repetitive and significant contributor to many of the inappropriate actions was procedure use and adherence. Procedure use and adherence during the procedure revision process could have resulted in a more effective procedure revision and prevented this event. Procedure use and adherence on the part of the Senior Reactor Operator (SRO) controlling the evolution or the operator performing the field operations could have prevented this event.

Fundamentally focus on doing the job right the first time was lost in the magnitude of activity associated with plant startup and the desire plan for moving into the next sequential Mode and producing power.

III. ANALYSIS OF EVENT

The HBRSEP, Unit No. 2, original plant design included a RWP loop, consisting of a refueling water purification pump, filter, and demineralizer. The loop can be aligned to filter and demineralize either the spent fuel pool or the RWST. The RWP loop is not seismically qualified and is normally isolated from the RWST by manual isolation valves which are within the seismically qualified boundary of the RWST.

As stated in Condition Report 524619, there were numerous contributing factors influencing activities on the March 15th night shift. It is the culmination of actions taken in response to the May 2011 event and these influencing factors that resulted in a repeat event.

IV. SAFETY SIGNIFICANCE

Safety Significance as determined in HBRSEP, Unit No. 2 LER 2011-001-00 remains valid and bounds this event. The risk impact of having the RWST aligned for purification has been evaluated and determined to be of low risk impact ( internal flooding due to a pipe break, as well as the increase in risk due to a seismic event. The result of the analysis was based on having the non-seismic purification loop in service aligned to the RWST with the plant on-line for a conservative estimate of approximately 5000 hours0.0579 days <br />1.389 hours <br />0.00827 weeks <br />0.0019 months <br /> per year. The duration of the event documented in this LER was 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 22 minutes. The analysis conservatively assumed that the purification path will fail and drain the RWST under a range of seismic events. Also, operator actions are conservatively not credited after a break in the purification flow path. Even with these conservative assumptions, having the RWST in recirculation mode while the plant is at power results in a very small increase in risk due to seismic events.

It has been previously concluded that aligning the purification loop to the RWST created an inoperable condition for the RWST; however, the RWST was available and capable of providing the RWST inventory during a design basis event. Providing the required fluid inventory during the design basis event is a safety related function of the RWST. No components were deemed failed during this alignment configuration. It has previously been concluded that aligning a non-seismic and non-safety related purification system to the RWST creates an in-operable condition for the RWST, but this alignment does not create a condition where RWST is not available if needed. In order for a failure to occur a seismic event would have to occur. During the time frame when the purification loop was aligned no seismic event took place; therefore, there was no unavailability nor was there a functional failure of a safety significant component that occurred during this alignment.

V. CORRECTIVE ACTIONS

Completed Corrective Actions:

• Operating procedures associated with placing the non-seismic RWP system in service on seismic systems were suspended.

• Caution tags (CTs) on SFPC-805A [ISV], RWP Pump Suction from RWST, and SFPC-805B [ISV], RWST Return were replaced with Danger Tags which state "DO NOT OPERATE.

Planned Corrective Actions:

• Applicable Operations procedures will be revised to correctly apply TS implications into procedural step as required by administrative procedures. These procedural changes may be removed upon completion of the seismic qualification of the RWP and remove TS implications.

• Perform seismic qualification of RWP to allow alignment to the RWST without affecting operability.

VI. PREVIOUS SIMILAR EVENTS:

Licensee Event Reports (LERs) for HBRSEP, Unit No. 2, were reviewed from the past 5 years. LER 2011-001-00, Condition Prohibited by Technical Specifications When Non-Seismic System was Aligned to Refueling Water Storage Tank due to Regulatory Requirements not Adequately Incorporated in Plant Documentation, documented the historical use of the purification loop to mix and clean up the volume of the RWST.