05000286/LER-2012-002
| Indian Point 3 | |
| Event date: | 02-13-2012 |
|---|---|
| Report date: | 4-13-2012 |
| 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 |
| 2862012002R00 - NRC Website | |
Note: The Energy Industry Identification System Codes are identified within the brackets {}.
DESCRIPTION OF EVENT
On February 13, 2012, a review of NRC Information Notice (IN) 2012-01 (Seismic Considerations-Principally Issues Involving Tanks) determined there was a clarification in NRC's position regarding aligning non-seismic piping (PSP) to the seismically qualified Refueling Water Storage Tank (RWST) (BP} which impacted unit 3. The IN identified failures by licensees to recognize that aligning non-seismic piping to the RWST would require Technical Specification (TS) Limiting Condition of Operation (LCO) action statement entry or license amendments. Intentionally aligning the seismically qualified RWST piping to non-seismic Fuel Pool Purification System (FPPS) {DA} by opening a boundary valve (ISV) can cause the RWST to become inoperable. TS LCO 3.0.2 requires that upon discovery of a failure to meet an LCO, the required actions of the associated conditions must be met. TS LCO 3.0.2 does not allow applying compensatory measures such as manual actions in place of a closed boundary valve for periods longer than the TS completion time for restoring the RWST to operable unless the TS expressly permit such operation. TS 3.5.4 (Refueling Water Storage Tank) is applicable in Modes 1-4. RWST operability requirements are dictated by ECCS and containment Spray system operability which is required to be operable in Modes 1-4. TS 3.5.4 Condition C (RWST inoperable for reasons other than Condition A or B) required action is to restore RWST to operable status in ,one hour. Condition D (Required action and associated completion time not met) requires the plant to 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 Mode 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
Mode 5 (Cold Shutdown) is the Mode to which the RWST LCO no longer applies. Indian Point unit 3 had performed a safety evaluation based on IN 97-78 (Crediting of Operator Actions in Place of Automatic Actions and Modifications of Operator Actions, Including Response Times) that allowed operator action. IN 2012-01 clarifies that application of compensatory actions for periods longer than the TS completion time is not allowed unless the TS expressly permits operation under such measures or the licensee can demonstrate that the RWST can meet the TS definition of operability without reliance on compensatory measures. Unit 3 currently aligns RWST seismic piping to non-seismic piping of the FPPS for cleanup of RWST water.
An extent of condition review determined that unit 2 has piping that is identified as seismic.
The RWST purification loop is normally isolated (boundary isolation valves are locked shut) while the plant is above cold shutdown. There, are times that would require the RWST to be placed on purification. These activities when it is required are intermittent, infrequent and of limited duration. Required plant activities such as periodic Engineered Safety Features pump testing, Safety Injection Accumulator level adjustments, or RWST makeup may alter the boron concentration requiring RWST circulation for thorough mixing during adjustments or sampling. Additionally, in order to ensure the RWST water is as pure as possible to support refueling operations, it is desired to purify the RWST water via the Refueling Water Purification system which serves as an auxiliary sub-system of the Spent Fuel Pool Cooling system. These activities were previously recognized as part of the design and operation of the plant systems. During plant operation, the RWST can be purified by means of the RWST Purification System and if required the RWST can be isolated by closure of at least one manual valve on each end of the RWST purification loop (valves AC-727A and AC-727B).
The RWST is purified by pumping the water through the Spent Fuel Pit (SFP) demineralizer and the SFP filter before returning it to the RWST. The RWST purification process requires the non-qualified purification loop piping (Seismic Class III) to be connected to the safety related Seismic Class I piping of the RWST.
Cause of Event
The apparent cause was historical interpretation. Initially the issue was resolved by Nuclear Safety Evaluation (NSE) 99-3-035 SFPC Rev. 0 which stationed a dedicated operator at the RWST purification pump during its operation to ensure timely isolation of the flow path should its integrity be impacted. Subsequently, Revision 1 of the NSE was issued eliminating the need for a dedicated operator stationed locally using the NRC guidance of IN 97-78 for crediting operator manual actions and reclassification of the seismic boundary and qualification of a check valve. Subsequently, the NRC clarified that position described in IN 2012-01 which invalidated the previous evaluation which credited operator action to isolate the RWST flow path.
Corrective Actions
The following corrective actions will be performed under Entergy's Corrective Action Program to address the cause:
- System operating procedure 3-SOP-SI-003 will be revised to prevent aligning the RWST to the FPPS during the applicable Modes until the issue is resolved.
- A license amendment will be evaluated for feasibility to request an allowance for operator action.
- An assessment of FPPS piping will be performed to determine if an upgrade to seismic is feasible.
Event Analysis
The event is reportable under 10CFR50.73(a)(2)(i)(B). The licensee shall report any operation or condition which was prohibited by the plant TS. TS 3.5.4 (Refueling Water Storage Tank) Condition C (RWST inoperable for reasons other than Condition A or B), requires restoration of the RWST to operable within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or per Condition D, 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 Mode 5 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. As a result of intentionally aligning the seismically qualified RWST piping to the non-seismic fuel pool purification system (FPPS) by opening .a boundary valve caused the RWST to become inoperable based on the information provided in IN 2012-01. Per IN 2012-01 applying compensatory measures for TS required equipment in lieu of meeting the requirements of the LCO could constitute a change to the TS, which is prohibited without prior NRC review and approval. During past operation, the non-seismic purification piping was connected to the RWST to perform cleanup of refueling water. In accordance with IN 2012-01 the manual actions in place of a closed boundary valve isolating the RWST piping from non-seismic FPPS piping rendered the RWST inoperable. The inoperable condition during past operation exceeded the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> allowed completion time for TS 3.5.4 Condition C and Condition D actions were not performed. The condition was not a safety system functional failure reportable under 10CFR50.73(a)(2)(v)(D) as the condition was mitigated by the actions identified in NSE 99-3-035 SFPC Rev. 1. The actions served to assure RWST required TS inventory was maintained at all times following a seismic event, but these actions relied on manual operator action.
Past Similar Events
A review was performed of Licensee Event Reports (LERs) for the past three years for any events reporting TS prohibited conditions due to inappropriately crediting operator actions. The review included any LERs reporting seismic conditions that were not adequate. No LERS were identified.
Safety Significance
This event had no effect on the health and safety of the public. There were no actual safety consequences for the condition because there were no seismic events that impacted the non-seismic FPPS piping. Had an event occurred, the actions implemented in accordance with Nuclear Safety Evaluation (NSE) 99-3-035 SFPC would have mitigated the event. To permit the use of the RWST purification loop while the plant Tavg is above 200 degrees F (Modes 1-4), administrative controls were implemented to protect the RWST's minimum required stored volume of borated water should the non-qualified piping connecting the RWST to the purification loop catastrophically fail while the purification loop is in service.
� Administrative controls (procedure SOP-SI-3, ARP-7, EOP-RO-1) in effect ensure that sufficient RWST inventory is maintained above the minimum TS level whenever loop isolation valves are opened. These controls include procedural requirements to promptly isolate the RWST purification loop for specified conditions/events. Prior to initiation of the RWST purification process, the RWST would have its level raised to maximum (overflow) which provides the maximum volume prior to reaching the minimum TS level thereby providing increased operator response time. The Control Room operators have RWST level instrumentation and alarms per the Critical Functions Monitoring System (CFMS) that would alert operators to take action to isolate the RWST. Administrative controls include RWST isolation initiation on RWST low level (RWST Level instruments, CFMS alarm, Seismic Event Occurred alarm, suspected seismic motion detected by Control Room personnel, SI signal actuation, loss of power to RWST purification pump (pump strips off bus in a SI), loss of area lighting at the RWST purification pump or in the SI pump room (lights strip off bus in a SI), local area floor flooding (potential pipe break). The administrative controls ensured that the TS RWST minimum inventory requirement is maintained and available for accident mitigation.