05000277/LER-2015-001
| Peach Bottom Atomic Power Station Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2772015001R00 - NRC Website | |
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CONTINUATION SHEET
Peach Bottom Atomic Power Station 15 001 00 Unit Conditions Prior to the Event Unit 2 was operating in Mode 1 at 100% rated thermal power. There were no other structures, systems or components out of service that contributed to this event. On 9/16/15, the RSS was already considered inoperable since 9/4/15 due to the NRC determination that there existed insufficient testing of certain components associated with the RSS. Recently upgraded surveillance testing of the Remote Shutdown System (RSS) functions was in-progress when this event was discovered on 9/16/15.
Description of the Event
As a result of surveillance testing performed on 9/16/15, Licensed Operations personnel identified that the Reactor Core Isolation Cooling (RCIC) (EIIS: BN) system steam admission valve (M0-2-13- 131)(EllS: 20) would not open when manually operated from the Remote Shutdown System (RSS) panel (EllS: PL). Prompt troubleshooting performed by maintenance personnel on 9/16/15 identified that a wire within the RSS panel associated with the stop pushbutton (EIIS: HS) in the logic for the MO-2-13-131 valve was not connected. This disconnected wire did not impact the normal manual operation of the MO- 2-13-131 valve from the main control room, nor did it impact the automatic function of the MO-2-13-131 valve for licensed events. Only the manual open function of the valve from the RSS panel (located outside of the control room) was affected. The disconnected wire was promptly re-landed on 9/16/15 and the MO-2-13-131 was verified to operate properly from the RSS panel.
This LER is being submitted pursuant to 10CFR 50.73(a)(2)(i)(B) as a result of a condition prohibited by TS LCO 3.3.3.2, Remote Shutdown System. The NRC determined on 9/4/15 that insufficient Surveillance Requirement (SR) 3.3.3.2.1 testing was being performed for certain functions associated with the RSS as listed in TS Bases Table B3.3.3.2-1. Upon the determination on 9/4/15 of the missed surveillance of certain RSS functions, licensed operations personnel promptly declared the RSS inoperable and entered the associated Conditions and Required Actions of TS 3.3.3.2. Surveillance tests were upgraded and were being performed when the wiring condition was identified on 9/16/15. As specified by NUREG-1022, Rev. 3, Event Report Guidelines - 10 CFR 50.72 and 10 CFR 50.73, reporting is required if a late surveillance, once performed, indicates that the equipment was not capable of performing its function.
Analysis of the Event
There were no actual safety consequences associated with the event. There have been no actual plant conditions where the RSS was required to be used. The Unit 3 RSS was unaffected by this event.
Analysis of the Event, continued The RSS provides the control room operator with sufficient instrumentation and controls to maintain the plant in a safe shutdown condition from a location other than the control room. This capability is necessary to protect against the possibility of the control room becoming inaccessible for events other than a 10 CFR 50 Appendix R fire. For a 10CFR 50 Appendix R fire, the RSS is not used since other alternative control stations located in the plant exist to assure safe shutdown for a fire in which the control room becomes inaccessible. These alternative control stations used for a 10CFR 50 Appendix R fire event were unaffected by this event.
The RSS primary methods of maintaining safe shutdown in the event the control room becomes inaccessible is by having instrumentation on the RSS panel that can transfer control power and allow for control of equipment from the RSS, which is located outside of the control room. The plant is primarily maintained in a safe shutdown condition from the RSS by means of the RCIC system and Safety Relief Valves (SRVs). These systems ensure adequate reactor level and pressure control from outside the control room to allow for extended operation in Mode 3 (hot shutdown).
Had an event occurred which required use of the RSS, the consequences of the inability to manually open the MO-2-13-131 RCIC Steam Admission valve would not be significant. The RCIC automatic operation on reactor water low-low level was unaffected by this event and therefore, RCIC automatic initiation would allow for opening of the MO-2-13-131 valve automatically. RCIC would automatically cycle to maintain adequate water level from the RSS panel. The RCIC flow controller on the RSS was operable and could then be used to stabilize reactor water level. Additionally, the 10CFR 50 Appendix R safe shutdown alternative control panels (includes HPCI) located outside of the main control room were unaffected by this event and could be used as a backup for the RSS. Additional reactor level control systems including the automatic initiation of the High Pressure Coolant Injection (HPCI) and the usage of the Control Rod Drive system were unaffected by this event. Therefore, this event is considered to be of very low risk significance.
Cause of the Event
The historical cause of the wire being disconnected in the RSS panel affecting the manual opening of the RCIC MO-2-13-131 valve could not be identified. A search of the electronic work history of the stop pushbutton and the device from where the disconnected wire originated from (transfer / control switch for MO-2-13-131 on the RSS panel) was performed. No records of maintenance that would have lifted this wire were identified.
An underlying cause of the event was that the testing performed for TS Surveillance Requirement SR 3.3.3.2.1 was previously not extensive enough to detect this condition.
Further causal analysis is being performed in accordance with the station's corrective action program to further explore the cause(s) of this condition.
Corrective Actions
The disconnected wire in the RSS control circuit for the RCIC MO-2-13-131 valve was promptly reconnected. As a result of the NRC concern with the extent of RSS testing, surveillance testing had been recently upgraded. The first performance of the upgraded surveillance testing detected this condition with the MO-2-13-131 valve.
Surveillance tests for similar RSS related components were also recently upgraded for both Units 2 and 3. Although testing using these upgraded procedures did identify other minor equipment issues involving Units 2 and 3 RCIC valves, these conditions did not result in inoperability of the associated TS 3.3.3.2 RSS functions.
The Unit 2 RSS was declared operable on 9/18/15.
Additional corrective actions are being assessed as part of a causal analysis being performed in accordance with the station's corrective action program.
Previous Similar Occurrences There were no previous LERs identified involving inadequate testing of the RSS panel components.
4 kV circuit breaker associated with the 10CFR 50 Appendix R alternative shutdown requirements. It was determined that the testing of the transfer / isolation switch was not adequate to identify the broken wire. Extent-of-condition actions from LER 2-14-001 did not extend to the RSS and therefore, would not have been expected to identify concerns with the RSS.