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 Entered dateSiteRegionReactor typeEvent description
ENS 5434021 October 2019 01:23:00Peach BottomNRC Region 1

While Unit 3 was shutting down for 3R22 refueling outage, the mode switch was taken to shutdown position which is a manual scram signal. The manual scram signal was not received from the mode switch. A subsequent manual scram was inserted with the use of the manual scram push buttons. The Unit 3 reactor is shutdown with all rods inserted. Unit 2 was unaffected by the event and remains in Mode 1 at 100 percent power. The licensee notified the NRC Resident Inspector, Pennsylvania and Maryland State Agencies, local government. A media press release is planned. Notified DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email), FEMA Region 3 Watch Office (email).

  • * * UPDATE AT 0316 EDT ON 10/21/19 FROM KEVIN GROMANN TO BETHANY CECERE * * *

Conditions no longer meet an Emergency Actuation Level and will not deteriorate. Unit 3 reactor is shutdown with all control rods fully inserted. The NOUE was terminated at 0230 EDT." The licensee notified the NRC Resident Inspector, Pennsylvania and Maryland State Agencies, local government. Notified the R1DO (Jackson), NRR EO (Miller), IRDMOC (Gott), R1RA (Lew via email), NRR (Nieh via email), DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email), FEMA Region 3 Watch Office (email).

ENS 5433015 October 2019 19:14:00Peach BottomNRC Region 1On 10/15/19 at 1210 (EDT) Peach Bottom discovered a degraded spring hanger (23DBN-H39) associated with Unit 3 High Pressure Coolant Injection (HPCI) system. The hanger is located downstream of MO-3-23-14 HPCI Steam Supply Valve before the HO-3-23-4513 Turbine Stop Valve. A review of the piping and support design analysis were performed and concluded the U3 HPCI turbine inlet nozzle would potentially exceed its allowable stresses. Following Engineering review, U3 HPCI was declared inoperable at 1743 (EDT). This report is being submitted pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified."
ENS 5393314 March 2019 17:08:00Peach BottomNRC Region 1A licensed employee was determined to be under the influence of alcohol during a random test. The employee's access to the plant has been suspended pending an investigation. The licensee notified the NRC Resident Inspector.
ENS 5363030 September 2018 15:29:00Peach BottomNRC Region 1On Sunday, September 30, 2018, at 1130 EDT, an automatic scram was received on U3 following a loss of two condensate pumps. Following the reactor scram, water level lowered from normal level of 23" to below 1" which resulted in automatic Group II and Group III isolations. Reactor water level lowered to -48" which resulted in initiation of the High Pressure Coolant Injection and Reactor Core Isolation Cooling systems. Reactor water level and reactor pressure have been restored to their normal bands. All systems responded properly to the event. Unit 3 remains in Mode 3 with reactor pressure being controlled on the turbine bypass valves. The cause and details of the event are under investigation. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B), and 10 CFR 50.72(b)(3)(iv)(A). All control rods inserted. Decay heat is being removed via the main condenser. The NRC Resident Inspector has been notified. A notification to the media and a press release were made. Unit 2 was unaffected and continues coastdown to refueling.
ENS 5359411 September 2018 17:14:00Peach BottomNRC Region 1On September 11, 2018 the Technical Support Center (TSC) ventilation was discovered to be non-functional during system testing. At 1310 EDT, an air leak was identified that prevented the modulating dampers to operate as designed to maintain required pressure. The air leak was not able to be repaired within a 60 minute period. This failure affected the ability of the TSC ventilation system to maintain adequate radiological habitability in the event of an emergency with an airborne radiological release. All other capabilities of the TSC are unaffected by this emergent condition. The air leak has been repaired and post maintenance testing was completed satisfactory at 1654 (EDT), restoring the TSC ventilation to a functional condition. This notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii) due to the potential loss of an emergency response facility because of the unavailability of the ventilation system. The NRC Resident Inspector has been notified.
ENS 5326515 March 2018 22:08:00Peach BottomNRC Region 1GE-4At 1524 (EDT) on Thursday, March 15, 2018, Operations was notified of a failure to meet Appendix R requirements for Peach Bottom Atomic Power Station (PBAPS) Unit 2 and Unit 3. Valves associated with the feedwater system for both units were not properly considered as Hi-Lo Pressure interface valves as required by the Appendix R program. This results in the susceptibility to a hot short condition that could open valves, diverting flow from the reactor, damage piping and prevent injection. U3 (Unit 3) Fire Safe Shutdown Credited Reactor Core Isolation Cooling (RCIC) System is affected. U2 (Unit 2) is affected by a potential leak path through the Reactor Water Cleanup system. This event is being reported as an occurrence of an event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety under 10 CFR 50.72(b)(3)(ii). The Station (PBAPS) is performing hourly fire watches for the impacted areas and is also evaluating this condition for corrective action. The licensee notified the NRC Resident Inspector.
ENS 5303123 October 2017 09:35:00Peach BottomNRC Region 1GE-4On Monday, October 23, 2017, with PBAPS (Peach Bottom Atomic Power Station) Unit 3 in Mode 3 at the beginning of a refueling outage, personnel entered the drywell to perform an inspection. At approximately 0400 (EDT), leakage was identified on a one-inch diameter instrument line socket weld for the 'B' recirculation pump. Because the leak was misting, the leakage rate could not be quantified. However, Unit 3 reactor coolant unidentified leakage prior to plant shutdown was 0.18 gpm. This line is considered part of the primary coolant pressure boundary. This event is being reported as an occurrence of an event or condition that results in the condition of the nuclear power plant, including its principal safety barriers being seriously degraded under 10 CFR 50.72(b)(3)(ii). The Station is preparing an evaluation and repair plan at this time. The NRC Resident Inspector has been notified.
ENS 5296111 September 2017 15:00:00Peach BottomNRC Region 1GE-4This report is being made as required by 10 CFR 50.73(a)(2)(iv)(A) to describe an automatic actuation of containment isolation valves in more than one system. Because the actuation was invalid, this 60-day telephone notification is being made instead of a written LER (Licensee Event Report), in accordance with 10 CFR 50.73(a)(1). On 07/14/17, at approximately 1453 hours (EDT), an electrical transient occurred due to an off-site lightning strike that de-energized one of the station's two qualified off-site power sources. This resulted in an automatic fast transfer of four 4 kV electrical buses to the alternate off-site source. The fast transfer occurred as designed without complications. The loss of power had numerous impacts on plant equipment that occurred in accordance with plant design, including a Group 2 primary containment isolation on both units. The Group 2 isolation affected multiple systems, including Reactor Water Cleanup, Instrument Nitrogen, and the Drywell Floor Drain. The fault on the off-site transmission line immediately cleared after the lightning strike and at 1457 hours (EDT) the transmission system operator gave the station permission to reclose the breaker to the off-site source. Following system restorations and equipment walkdowns, plant operators re-established normal connections to the off-site source on 7/14/17 at 2322 hours (EDT) in accordance with station procedures. The containment isolation occurred as a result of the loss of an off-site power source and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The NRC Resident Inspector has been informed of this notification.
ENS 5290916 August 2017 15:41:00Peach BottomNRC Region 1GE-4On 8/16/2017, at 1039 (EDT), an un-planned trip of the Peach Bottom Station Blackout Transformer 34.5 kV feeder breaker 1005 and a loss of the 191-00 line occurred causing a loss of power to Unit 1 and the TSC. Power was not restored to the TSC or the ventilation system within 1 hour. Power was subsequently restored to the TSC at 1207 hours (EDT) and the ventilation system was restored to available. This report is being submitted pursuant to 10CFR50.72(b)(3)(xiii) as a Major Loss of Emergency Preparedness Capabilities due to a reduction in the effectiveness of the Onsite Technical Support Center (TSC). The NRC Resident Inspector has been informed of this notification.
ENS 524789 January 2017 16:56:00Peach BottomNRC Region 1GE-4On January 9, 2017, during evaluation of protection for Technical Specification (TS) equipment from the damaging effects of tornado generated missiles, Peach Bottom Atomic Power Station identified a non-conforming condition in the plant design such that specific TS equipment is considered to not be adequately protected from tornado generated missiles. A tornado could generate multiple missiles that could strike one or more of the four emergency diesel generator (EDG) exhaust stacks. This could result in crimping of the stack, which could affect the ability of the EDG to perform its design function if such a tornado would occur. This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. This condition is being addressed in accordance with NRC enforcement guidance provided in EGM 15-002 and DSS-ISG-2016-01. Compensatory measures have been implemented in accordance with these documents. The NRC Resident Inspector has been informed of this notification.
ENS 524199 December 2016 05:29:00Peach BottomNRC Region 1GE-4

On 12/08/16 at approximately 2237 (EST), the Unit 2 HPCI (High Pressure Coolant Injection) system failed to meet surveillance testing requirements for achieving rated flow at greater than or equal to a minimum test pressure established per the surveillance. Operations declared the HPCI system inoperable and entered Technical Specification 3.5.1 Condition C for HPCI being inoperable. Other standby systems (Reactor Core Isolation Cooling and low pressure emergency core cooling systems) are operable. HPCI is a single train system. Therefore, per NUREG-1022, this condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of the safety function of a system required to mitigate the consequences of a design event. This condition has been entered into the Corrective Action program (IR 3951006). Investigation of the exact failure condition is in progress so that repairs can be made. At the surveillance flow of 5,000 gpm, the system was approximately 80 psi below the required pressure of 1,278 psi. Technical Specification 3.5.1, Condition C, is a 14-day Limiting Condition of Operation. The NRC Resident Inspector will be notified.

  • * * RETRACTION AT 1440 EST ON 01/19/17 FROM ELMER KAUFFMAN TO S. SANDIN * * *

The licensee provided the following information as the basis for retracting this report: This is a retraction of an event notification made on 12/09/16 at 0529 EST (EN #52419). This event was initially reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as a condition that, at the time of discovery, was believed to have prevented the fulfillment of the High Pressure Coolant Injection (HPCI) system safety function. On 12/08/16 at 2237 EST, the Unit 2 HPCI system was declared inoperable due to failing to meet surveillance testing requirements for achieving rated flow at greater than or equal to a minimum test pressure established per the surveillance. Prompt troubleshooting was performed and it was determined that an adjustment to the HPCI turbine governor control system was required. This adjustment was performed and HPCI was returned to an operable status on 12/09/16. Subsequent to this occurrence, Engineering has completed an evaluation that concluded that HPCI was capable of fulfilling its safety function and that the associated Technical Specification (TS) Surveillance Requirement (SR) 3.5.1.8 was met. The evaluation concluded that HPCI was degraded, but met the threshold for TS operability. The NRC Senior Resident has been informed of this retraction." Notified R1DO (Kennedy).

ENS 5226427 September 2016 00:20:00Peach BottomNRC Region 1GE-4

On 9/26/16 at approximately 1845 EDT, investigation of an identified water leak on one of the two Unit 3 HPCI turbine exhaust drains to the drain pot determined that there was through wall leakage of approximately 2 drops per minute. Operations promptly declared the HPCI system inoperable and entered Technical Specification 3.5.1 Condition C for HPCI being inoperable. Other standby systems (Reactor Core Isolation Cooling and low pressure emergency core cooling systems) are operable. HPCI is a single train system. Therefore, per NUREG-1022, this condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of the safety function of a system required to mitigate the consequences of a design event. This condition has been entered into the corrective action program (IR 2720241). Investigation of the exact flaw location is in progress so that repairs can be made.

The NRC resident has been informed of this notification.

ENS 5196227 May 2016 09:22:00Peach BottomNRC Region 1GE-4

This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made pursuant to 10 CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of containment isolation valves in more than one system. On 3/28/16, at approximately 1320 (EDT), a loss of power occurred on the Unit 2 E124 480 volt load center due to an equipment operator inadvertently opening the main feed breaker during the process of applying a clearance to de-energize the E124-P-A motor control center for planned maintenance. Loss of the E124 load center resulted in Group II and Group III primary containment isolations due to an invalid ESF actuation signal. Systems impacted by the containment isolations included containment instrument nitrogen, containment atmospheric monitoring, reactor water cleanup, and secondary containment. Balance of plant impacts included partial loss of feedwater heating and a reduced condenser vacuum. Reactor power lowered to 86% as a result of the event and further decreased to approximately 80 percent when re-establishing the 3A, 4A and 5A feedwater heaters.

Following direction from the control room, the E124 main feed breaker was promptly re-closed by equipment operators. Affected equipment was restored to its normal or planned configuration and containment isolations were reset at 1406. The containment isolation signal was generated as a result of the loss of power to the E124 load center and was not due to actual plant conditions or parameters meeting design criteria for containment isolation. Therefore, this is considered to be an invalid actuation. The licensee has notified the NRC Resident Inspector.

ENS 5163031 December 2015 13:15:00Peach BottomNRC Region 1GE-4

On 12/31/15, at approximately 0630 hours (EST), during shift turnover panel walk-downs, a licensed Unit 3 reactor operator identified that the High Pressure Coolant Injection (HPCI) flow controller output indicated a downscale condition. The controller was in automatic with the set point at 5000 gpm, which would typically indicate a controller output value of 100%. HPCI was not in operation and is a standby system. Operations promptly declared the HPCI system inoperable and entered Technical Specification Condition C for HPCI being inoperable. Other standby systems (Reactor Core Isolation Cooling and low pressure emergency core cooling systems) are OPERABLE. HPCI is a single train system. Therefore, per NUREG-1022, this condition is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of the safety function of a system required to mitigate the consequences of a design event. This condition has been entered into the Corrective Action program (IR 2606215). Maintenance troubleshooting of the flow controller loop has identified a failed component and repair activities are in progress.

The NRC Resident Inspector has been informed of this notification.

ENS 5057129 October 2014 12:50:00Peach BottomNRC Region 1GE-4This notification is to report a condition involving higher than allowable through-seat leakage of two redundant feedwater system check valves (28A and 96A). Unit 2 is currently shut down and primary containment is not required to be operable. Therefore, there is currently no safety impact due to this discovered condition. This leakage was identified as a result of planned local leak rate testing of the feedwater primary containment isolation valves for the 'A' feedwater line being performed during the current P2R20 refueling outage. At approximately 1100 EDT, Engineering determined that the primary containment penetration pathway leakage through the redundant check valves resulted in a condition where the maximum allowable primary containment leakage rate (La) was exceeded. In accordance with NUREG-1022, Rev. 3, Event Report Guidelines 10 CFR 50.72 and 50.73, Section 3.2.4, this occurrence is an example of a reportable condition. Therefore, this notification is being made pursuant to 10CFR 50.72(b)(3)(ii)(A). This condition has been entered in the plant corrective action program (IR 2402909). The NRC Resident Inspector has been informed of this notification.
ENS 5039523 August 2014 20:19:00Peach BottomNRC Region 1GE-4At 13:00 (EDT) on Saturday, August 23, 2014, both trains of the Peach Bottom Atomic Power Station (PBAPS) Emergency Service Water (ESW) System were declared inoperable on Unit 2 and Unit 3, due to a pin-hole, through wall piping leak. In accordance with 10CFR 50.72(b)(3)(v), this event is being reported as an event or condition that could have prevented the fulfillment of the safety function of systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, remove residual heat and mitigate the consequences of an accident. At 19:22 (EDT), the station received verbal approval of a Notice of Enforcement Discretion (NOED) request. Simultaneously, the station is preparing an evaluation to support an emergent-relief request. The NRC Resident Inspector has been notified.
ENS 5018510 June 2014 19:38:00Peach BottomNRC Region 1GE-4At 1600 EDT on June 10, 2014, a non-work related on-site fatality as a result of natural causes occurred at the Peach Bottom Atomic Power Station. The fatality was not related to the health and safety of the public or on-site personnel. Specifically, a contract truck driver was found non-responsive in a truck in the parking lot. The individual was outside of the Radiological Controlled Area and no radioactive material or contamination was involved. The location of the parking lot is outside of the Protected Area but within the owner controlled area. An Event of Potential Public Interest has been completed. Peach Bottom Atomic Power Station will make notifications due to a fatality on-site. This ENS notification is in response to a notification to another government agency in accordance with 10CFR50.72(b)(2)(xi). The licensee notified the NRC Resident Inspector. The licensee notified the Emergency Management Agencies in Pennsylvania and Maryland, the Pennsylvania State Police, as well as the surrounding counties.
ENS 5012821 May 2014 17:39:00Peach BottomNRC Region 1GE-4This notification is to report a condition involving degraded control power wiring that resulted in an adverse impact on the ability to perform Fire Safe Shutdown for a postulated fire in the Main Control Room / Cable Spreading Room (MCR/CSR) complex. Therefore, this notification is being made pursuant to 10CFR 50.72(b)(3)(ii)(B). At approximately 1100 hours (EDT), based on inspections being performed as part of an extent-of-condition review, Engineering personnel concluded that a degradation existed involving transfer / isolation switches that potentially impacted the ability to mitigate an Appendix R fire postulated to occur in the MCR/CSR complex. During scheduled maintenance outage windows on March 6, 2014 and May 5, 2014, broken wires were identified and repaired while the associated systems were out of service. Based on completion of the extent of condition walkdowns today, an additional location was identified, raising the potential that this condition existed for a longer period of time. The wiring degradation is limited to the capability of using Shutdown Method 'D' as described in the Peach Bottom Atomic Power Station Fire Protection Program. Shutdown Methods 'A', 'B' and 'C' used for other postulated fire areas were not affected by this condition. The postulated fire would have had to cause the normal control power fuses to fail for the issue to impact the safe shutdown function. Compensatory measures have been established until the condition is corrected. The NRC Resident Inspector has been informed of this notification. In the event of fire resulting in a loss of control power, compensatory measures will allow restoration of control power by replacing blown fuses. The compensatory measures are detailed in a temporary change to the MCR/CSR complex fire response procedure. The condition will be repaired during future equipment outages at the earliest opportunity.
ENS 500896 May 2014 12:50:00Peach BottomNRC Region 1GE-4

This 60-day report, as allowed by 10CFR 50.73(a)(1), is being made pursuant to 10CFR 50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of an emergency service water system. On 3/9/14, at approximately 1536 EST, the E2 Emergency Diesel Generator (EDG) was started for a post maintenance operability test. The 'A' safety-related Emergency Service Water (ESW) pump was being used to provide cooling to the EDG. At approximately 1613 EST and 1622 EST, unexpected automatic starts of the 'B' ESW pump and the non-safety related single train Emergency Cooling Water (ECW) pump occurred. The EDG run was terminated at 1622 EST to investigate the cause of the unexpected starts.

It was determined that a failed angle drive adaptor resulted in invalid input to the speed switch, which resulted in the unplanned starts of the 'B' ESW pump and the ECW pump. Except for the failure of the angle drive adaptor, all systems and equipment operated as expected. The NRC resident has been informed of this notification.

ENS 498641 March 2014 14:19:00Peach BottomNRC Region 1GE-4At 1125 (EST) on Saturday, March 1st, 2014, the Peach Bottom Atomic Power Station Main Stack Wide Range Radiation monitor was declared inoperable due to a loss of sample flow. This event is being reported as a loss of emergency assessment capability in accordance with 10 CFR 50.72(b)(3)(xiii). The inoperability would impact the ability to declare an Emergency Action Level at a level of an Alert or higher based on Main Stack radiation release. The NRC Resident Inspector has been notified.
ENS 498109 February 2014 08:10:00Peach BottomNRC Region 1GE-4On 02/09/2014, at 0100 (EST), a major portion of Peach Bottom Atomic Power Station's (PBAPS) offsite communication capability was discovered to be non-functional due to an offsite communications equipment failure outside the control of PBAPS. Peach Bottom continues to investigate and resolve the cause of this loss of offsite communications. Peach Bottom Main Control Room ENS and offsite communication lines have been restored and are currently available. The Technical Support Center is limited to satellite phones for offsite communications. On-site communications were not affected. This report is being submitted pursuant to 10CFR 50.72(b)(3)(xiii) as a result of a major loss of offsite communications capability. The NRC (Resident Inspector) has been informed of this notification.
ENS 4948029 October 2013 05:01:00Peach BottomNRC Region 1GE-4

At 0500 (EDT) Tuesday, October 29, the Peach Bottom Atomic Power Station (PBAPS) main stack radiation monitors will be removed from service for planned preventative maintenance activities on the flow elements. This maintenance is scheduled to be worked continuously until completion to minimize out of service time. The planned main stack radiation monitor outage is scheduled to be completed within 13 hours. Periodic gas sampling will be performed in accordance with the offsite dose calculation manual while the monitors are out of service. The NRC Resident Inspector has been notified. There are no follow-up written reports required for this event.

  • * * UPDATE ON 10/30/13 AT 0216 EDT FROM BOB RAUCCI TO DONG PARK * * *

This is an update to notification #49480. The out of service duration has been extended from the original estimated 13 hours due to work scope taking longer than expected with fatigue rule compliance requirements. The radiation monitor maintenance has been completed and the components have been restored to service, however, the post maintenance testing will be delayed until this morning (10/30/13) when the necessary component expert resource is next available. Periodic gas sampling remains in effect in accordance with the Off Site Dose Calculation Manual. The licensee will notify the NRC Resident Inspector. Notified R1DO (Krohn).

ENS 494001 October 2013 14:11:00Peach BottomNRC Region 1GE-4Exelon Generation has successfully tested the new emergency warning sirens installed in the 10-mile radius surrounding Peach Bottom Atomic Power Station. With approval from the Federal Emergency Management Agency (FEMA), Exelon Generation began transitioning to the new sirens on 10/1/13. At 11:31 am EDT, during the transition, a vendor technician inadvertently actuated the York County emergency warning sirens. The Sirens went through a full sounding of three minutes and then stopped alarming. The alarming sirens were not due to any condition at Peach Bottom. Exelon and York County have investigated the issue and found that the system worked properly. The cause of the inadvertent actuation was that a test signal was not given sufficient time to clear prior to putting the system in service after testing. The NRC Resident Inspector has been informed. The licensee will issue a press release.
ENS 4845530 October 2012 03:20:00Peach BottomNRC Region 1GE-4

Peach Bottom Atomic Power Station Control Room was notified of a loss of greater than 25% of sirens after severe storms in the area associated with Hurricane Sandy. Thirty-one (31) of 97 Emergency Planning Zone (EPZ) sirens are currently unavailable in Lancaster, York, Cecil and Harford Counties. Actions are currently being taken to restore unavailable sirens. The licensee notified the NRC Resident Inspector.

  • * * UPDATE AT 0515 EDT ON 10/31/12 FROM SCOTT RUCKER TO S. SANDIN * * *

Currently 12 of 97 sirens remain inoperable. The licensee will inform state and local agencies and the NRC Resident Inspector. Notified R1DO (Caruso).

ENS 483764 October 2012 16:37:00Peach BottomNRC Region 1GE-4The 'A' Main Control Room Emergency Ventilation System (MCREV) fan failed to automatically start when placed in service at 0959 EDT on 10/4/12. The `B' fan was available at the time of the initiation, but was inoperable due to E-42 Emergency 4kV Bus outage. Both MCREV fans inoperable is an entry into Technical Specification 3.7.4 Condition E which requires Unit 3 to be Mode 3 in 12 hours. Unit 2 was not in a mode of applicability at the time of the event (Unit 2 is defueled). This issue is being reported under 10 CFR 50.72(b)(3)(v)(D) for an event that could have prevented the fulfillment of a safety function - mitigate the consequences of an accident. The 'A' MCREV fan was restored to an operable status at 1237 EDT on 10/4/12 and the Technical Specification Action was exited. The NRC Resident Inspector has been notified.
ENS 4829711 September 2012 11:11:00Peach BottomNRC Region 1GE-4This ENS (report) is being voluntarily issued to notify the NRC that voluntary communications were made to offsite agencies this morning between 0700 and 0830 (EDT) due to an event of potential public interest. At approximately 1 a.m. on September 1, 2012, Peach Bottom outage workers on the Unit 2 refuel floor were disassembling the reactor head vent when steam discharged from the flange, causing a small but detectable amount of airborne contamination that was contained in the building. All workers were wearing the proper protective equipment and no significant personal (personnel) exposure has been reported. As a precaution, employees were asked to temporarily leave the area for onsite evaluation while radiation protection technicians investigated. Approximately 50 workers were impacted by the radiological airborne event at Peach Bottom and had to stay over shift for radiological monitoring. In accordance with station Radiological procedures, affected personnel are being monitored and as required bioassay is being conducted. Radiation monitors in the reactor building initially detected the airborne contamination, but all have returned to normal levels. This event resulted in no significant impact to the health and safety of our workers or the public. The station made voluntary notifications to the NRC Senior Resident, the State Bureau of Radiation Protection and state and local stakeholders. This issue has been entered into the site Corrective Action Program for evaluation and implementation of further corrective actions.
ENS 479078 May 2012 12:33:00Peach BottomNRC Region 1GE-4This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Unit 2 Primary Containment Isolation System (PCIS). On 3/13/12, at approximately 1604 hours, Unit 2 experienced an invalid PCIS partial isolation. An equipment operator was in the process of making an adjustment to the Reactor Protection System (RPS) MG Set output voltage during daily rounds. As the rheostat was beginning to be rotated to increase the voltage, output voltage quickly dropped below the MG Set undervoltage trip setpoint. The BC757B and BC757D MG Set output breakers opened, resulting in the loss of the 2B RPS bus causing a half scram. The half scram signal resulted in closure of the instrument nitrogen primary containment isolation valve, secondary containment normal ventilation isolation valves and start of the 'B' Standby Gas Treatment supply fan. The invalid PCIS isolation was a result of the failure of the voltage adjustment rheostat for the MG Set output voltage. This issue has been entered into the site Corrective Action Program (AR 1340452) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification.
ENS 4778629 March 2012 04:04:00Peach BottomNRC Region 1GE-4

At 0400 (EDT) on Thursday March 29th, the Peach Bottom Atomic Power Station (PBAPS) Technical Support Center (TSC) supply and exhaust fans will be removed from service for planned preventative maintenance activities on the exhaust fan. This maintenance is scheduled to be worked continuously until completion to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 14 hours. If TSC staffing is required, it will take a maximum of 4 hours to return the ventilation system back to an operable status. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM JEREMY HITE TO CHARLES TEAL ON 3/29/12 AT 1949 EDT * * *

The planned maintenance is complete and the TSC was restored back to service at 1530 EDT. The NRC Resident Inspector has been informed. Notified R1DO (Newport).

ENS 4758110 January 2012 00:55:00Peach BottomNRC Region 1GE-4

On January 09, 2012 the Technical Support Center(TSC) ventilation was discovered to be non-functional during system testing. At 1722 hours (EST), it was identified that control power was lost to four motor operated dampers. Investigation revealed that a control power fuse was blown. In addition, the TSC ventilation Supply Fan (AHU-1) was identified to have one of two fan belts failed. The fuses were replaced at 19:45 (EST) and the system was restored to service. However, the system has been removed from service this evening to replace the fan belts. An update will be provided when the system is restored to full functionality. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE AT 1744 EST ON 1/10/12 FROM JEFF MOORE TO HUFFMAN * * *

Maintenance personnel installed two new belts on AHU-1 and aligned the motor/fan sheaves to ensure correct operation. TSC ventilation has been restored to the normal condition. The licensee will notify the NRC Resident Inspector. R1DO (Trapp) notified.

ENS 4744215 November 2011 22:19:00Peach BottomNRC Region 1GE-4On 11/15/2011 at 1952 (EST), while performing a Fire Protection Program review, it was determined that one of the 'Multiple Spurious Operation' (MSO) modifications implemented during the P3R18 refueling outage adversely impacted Peach Bottom's fire safe shutdown analysis conclusions. New cabling that was routed for the Unit 3 High Pressure Coolant Injection (HPCI) system steam supply valve lacks appropriate fire barrier protection in the event of a postulated fire-induced damage to this cable. This cable is routed through a fire area in which the only credited and protected method of reactor level control for a fire in this area is HPCI. Postulated fire-induced damage in the cable could prevent the steam supply valve from opening, thereby causing the HPCI pump to be unavailable for an Appendix R fire. An hourly fire watch has been established as a compensatory action. The licensee has notified the NRC Resident Inspector.
ENS 4728621 September 2011 22:48:00Peach BottomNRC Region 1GE-4On 9/21/11 at 10:20 a.m. during the performance of a simulated loss of offsite power testing off the E33 4KV emergency bus, an unplanned start of the E3 Emergency Diesel Generator (EDG) occurred due to a valid bus under voltage signal caused by a relay malfunction. The bus being tested was inoperable in support of the test and was not carrying any required safety system loads at the time of the event. The EDG was secured and troubleshooting initiated. The initial determination was the EDG actuation was from an invalid signal but following further review it was determined that the relay malfunction had caused an untimely bus transfer that resulted in a valid 4KV bus under voltage condition. The NRC Resident Inspector has been notified.
ENS 4727318 September 2011 08:52:00Peach BottomNRC Region 1GE-4A worker was transported to an off-site medical facility due to a work-related hand injury. The individual was not contaminated. The individual's left hand work glove was found to be contaminated. The individual remains under the care of physicians and all contaminated material was safely collected and is being transported back to Peach Bottom Atomic Power Station as required. A licensee health physics employee accompanied the worker to the hospital. There was no spread of contamination in the ambulance or at the hospital. The licensee notified the NRC Resident Inspector and will be notifying the Pennsylvania Emergency Management Agency and local authorities.
ENS 4721128 August 2011 06:35:00Peach BottomNRC Region 1GE-4PBAPS (Peach Bottom Atomic Power Station) Control Room was notified of a loss of greater than 25% of sirens after severe storms in the area associated with Hurricane Irene. 51 of 97 Emergency Plan Zone (EPZ) sirens are unavailable in York County and Hartford County. Actions are currently being taken to restore unavailable sirens. The licensee notified Pennsylvania and Maryland Emergency Management and York and Harford Counties. The licensee notified the NRC Resident Inspector.
ENS 4718323 August 2011 14:50:00Peach BottomNRC Region 1GE-4

PBAPS (Peach Bottom Atomic Power Station) Units 2 and 3 experienced a seismic event which was felt in the control room in conjunction with a seismic trigger alarm set a 0.01G acceleration. The operating basis earthquake alarm of 0.05G was not received. 'Both units continue to operate at pre-event levels. Currently there is no indication of damage at the site. Initial plant walkdowns indicate no plant damage and walkdowns are continuing. There were no personnel injuries. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM BRAD KIRKMON TO HOWIE CROUCH AT 1800 EDT ON 8/23/11 * * *

At 1750 hrs. EDT, Peach Bottom terminated the Unusual Event that was declared at 1401 today due to a seismic event that occurred at the station. Both Unit 2 and 3 operational walk downs of the site have been completed. There are no issues related to the seismic event which would impact continued safe operation of either unit. The licensee has made state and local notifications as well as notifying the NRC Resident Inspector. Notified R1 IRC (Dentil), IRD (Gott), DHS, FEMA, HHS, USDA.

ENS 4698726 June 2011 05:25:00Peach BottomNRC Region 1GE-4

On 06/26/11, at 0030 (hrs. EDT), Peach Bottom Atomic Power Station Unit 3 declared the High Pressure Coolant Injection (HPCI) system inoperable for an ASME class 2 exempt piping leak found during operator rounds. Piping on the steam line pressure indication sensing line downstream of a sensing line root valve had an approximate 5 drop per minute leak. The leak has been isolated and the Unit 3 HPCI system was restored to an operable condition as of 0347 on 06/26/11. This report is being submitted pursuant to 10CFR 50.72(b)(3)(v)(D).

The licensee notified the NRC Resident Inspector.

  • * * RETRACTION ON 08/08/2011 AT 1432 EDT FROM DAVE FOSS TO RYAN ALEXANDER * * *

The purpose of this notification is to retract a previous report made on 06/26/11 at 0525 (EDT) (EN# 46987). Notification of this event to the NRC was initially made as a result of declaring the Unit 3 High Pressure Coolant Injection (HPCI) system inoperable on 06/26/11 at 0030 (EDT) when a small leak on an instrument sensing line was found during performance of routine operator rounds. Specifically, it was observed that the 1/2 inch instrument piping for the non-safety related HPCI steam supply pressure indicator was leaking at approximately 5 drops per minute. The location of the leak was downstream of the instrument line root valve. The leak was isolated and the Unit 3 HPCI system was considered operable at approximately 0347 (EDT) on 06/26/11. The ENS report on 06/26/11 was originally submitted to report a potential loss of safety function involving the Unit 3 HPCI system due to this leak. Since the initial report, engineering has determined that HPCI was capable of performing its safety function at the time the instrument sensing line was leaking. The evaluation determined that the small sensing line leak would not have resulted in any significant equipment qualification, internal flooding or other equipment concerns that could have affected the HPCI system capability during any postulated design basis events. The pressure indicating instrument supplied by the sensing line is not safety related and is not required for any HPCI function or HPCI operability. Therefore, HPCI was determined to have maintained its operability during the time period that the HPCI sensing line was leaking. The NRC resident has been informed of the retraction. Notified R1DO (Powell).

ENS 4667717 March 2011 00:01:00Peach BottomNRC Region 1GE-4On 03/16/11, at 1647 (EST), Peach Bottom Atomic Power Station Unit 2 declared the High Pressure Coolant Injection system inoperable for a condition found during testing which could cause the system to malfunction when swapping suction sources. While lined up to the suppression pool suction flow path, unsatisfactory results were obtained while venting for system fill verification, indicating potential voiding of a portion of the pump discharge piping. Unit 2 HPCI remains available while aligned to its normal suction, the condensate storage tank. This report is being submitted pursuant to 10CFR 50.72(b)(3)(v)(D). The NRC resident has been informed of this notification.
ENS 4656524 January 2011 11:39:00Peach BottomNRC Region 1GE-4

On 01/24/2011, at 0900 EST, Peach Bottom Atomic Power Station had a spill and release of Sodium Hypochlorite from our water treatment plant's Sodium Hypochlorite tank. The quantity (rate) of release has been estimated at approximately 1 gpm to the surrounding soil area. The leak was into a moat surrounding the tank but it appears it has subsequently leaked from the moat. The leak was identified on 01/24/11 and was quantified as reportable at approximately 0900 EST. The leak is currently in progress with actions being taken to mitigate and control leakage to the area storm drain. This is a release of CERCLA (Comprehensive Environmental Response Compensation and Liability Act) reportable quantity of substance. The release impacted or potentially impacted the Susquehanna River due to release through a storm drain and additional impact to the surrounding soil. Additional measures being taken include installing additional barriers to release. Lewis Environmental Hazard Mat team has been contacted and is responding to the site. In addition a truck has been dispatched to the site to pump out the moat. This report is being submitted pursuant to 10CFR 50.72(b)(2)(xi) as a result of a notification of other government agencies. The licensee has notified the NRC Resident Inspector, and state and local government agencies.

  • * * UPDATE FROM PHILIP PAUTLER TO VINCE KLCO ON 1/25/2011 AT 1340 EST * * *

As of 2200 (EST) last night, the leaking tank and moat area have been drained, and all standing liquid has been removed. Hourly water samples were collected from the discharge canal and tested. These samples confirmed that no release in excess of the station's NPDES (National Pollutant Discharge Elimination System) permit occurred. Notified the R1DO (Newport).

ENS 4649320 December 2010 05:15:00Peach BottomNRC Region 1GE-4On 12/20/10, at 0700, planned maintenance is being performed on the Onsite Technical Support Center (TSC) Ventilation System. Air handling unit #1 for the TSC supply ventilation is undergoing its 5 year PM. The TSC ventilation system will be tested following maintenance and returned to normal in service lineup. The system is expected to be out of service for a total time of 8 hours. This report is being submitted pursuant to 10CFR50.72(b)(3)(xiii) as a result of a reduction in the effectiveness of the Onsite Technical Support Center. The licensee notified the NRC Resident Inspector.
ENS 464451 December 2010 17:40:00Peach BottomNRC Region 1GE-4

On 12/01/10, at 1359 EST, Peach Bottom Atomic Power Station reported a petroleum product spill in the discharge canal. Total quantity of substance is less than 1 quart. Lewis Environmental agency has been contacted to aid in containment and cleanup of the spill. This report is being submitted pursuant to 10 CFR 50.72(b)(2)(xi) and 10 CFR 72.75(b)(2). The spill did not reach Comprehensive Environmental Response Compensation and Liability Act (CERCLA) reportable quantities. The licensee notified the Pennsylvania Department of Environmental Protection, United States Coast Guard, and EPA Region 3. The NRC Resident Inspector has been notified.

  • * * RETRACTION FROM E. WRIGHT TO V. KLCO ON 12/2/10 AT 1354 EST * * *

The licensee is retracting the event due to the quantity of substance released to the environment is less than the reportable quantity. The licensee will notify the NRC Resident Inspector. Notified R1DO (Schmidt).

ENS 4637327 October 2010 16:25:00Peach BottomNRC Region 1GE-4On 10/27/10, at 1107 (EDT), troubleshooting of Independent Spent Fuel Storage Installation (ISFSI) Cask TN-68-01 identified that a helium leak exists in the cask lid sealing area at a leak rate greater than allowed by ISFSI Cask Technical Specification Section 3.1.3, Cask Helium Leak Rate. TS 3.1.3 limits the Cask Helium Leak Rate to 1.0 E-O5 ref-cc/sec. The cask was in LOADING OPERATIONS and is currently located within the (Peach Bottom Atomic Power Station) PBAPS Unit 2 containment building. Preliminary review indicates that a leak exists in the Cask Main Lid Outer Closure Seal. The cask will be repaired and tested prior to returning the cask to the Independent Spent Fuel Storage Installation (ISFSI). No release of radiation occurred as a result of this issue. This report is being submitted pursuant to 10CFR 72.75(c)(2) as a result of a reduction in the effectiveness of the cask confinement system. The Certificate of Compliance for this cask is 1027 (Amendment 0). The NRC Resident Inspector has been informed.
ENS 4635322 October 2010 16:52:00Peach BottomNRC Region 1GE-4

On 10/22/10, at 1058 EDT, a troubleshooting of Independent Spent Fuel Storage Installation (ISFSI) Cask TN-50-A indicated that a leak existed in the cask lid sealing area at a rate greater than allowed by ISFSI Cask Technical Specification (TS) Section 3.1.3, Cask Helium Leak Rate. TS 3.1.3 limits the Cask Helium Leak Rate to 1.0 E-05 ref-cc/sec. The cask is currently in unloading operations and is located within the Peach Bottom Atomic Power Station Unit 3 containment building. Preliminary review indicates that a leak exists at the weld plug that provides sealing of the drilled interseal passageway associated with the drain port penetration of the cask lid. This leak effectively provides a bypass of the main lid outer confinement seal. This report if being submitted pursuant to 10CFR72.75(c)(1) as a result of a material defect in a weld in the cask main lid. This report is also being submitted pursuant to 10CFR72.75 (c) (2) as a result of a resolution in the effectiveness of the cask confinement system. The Certificate of Compliance for this cask is 1027 (Amendment 1). The NRC Resident Inspector has been informed of this notification.

  • * * UPDATE AT 1515 EDT ON 10/27/10 FROM JEREMY HITE TO DONG PARK * * *

On 10/27/10, at 1107 (EDT), troubleshooting of Independent Spent Fuel Storage Installation (ISFSI) Cask TN-68-01 identified that a helium leak exists in the cask lid sealing area at a leak rate greater than allowed by ISFSI Cask Technical Specification Section 3.1.3, Cask Helium Leak Rate. TS 3.1.3 limits the Cask Helium Leak Rate to 1.0 E-O5 ref-cc/sec. The cask was in LOADING OPERATIONS and is currently located within the (Peach Bottom Atomic Power Station) PBAPS Unit 2 containment building. Preliminary review indicates that a leak exists in the Cask Main Lid Outer Closure Seal. The cask will be repaired and tested prior to returning the cask to the Independent Spent Fuel Storage Installation (ISFSI). No release of radiation occurred as a result of this issue. This report is being submitted pursuant to 10CFR 72.75(c)(2) as a result of a reduction in the effectiveness of the cask confinement system. The Certificate of Compliance for this cask is 1027 (Amendment 0). The NRC Resident Inspector has been informed. Notified R1DO (Caruso), NRR EO (Thorp), NMSS EO (Lorson), and IRD (Grant).

ENS 462991 October 2010 07:23:00Peach BottomNRC Region 1GE-4At 0340 EDT on Friday, October 1, 2010, the turbine building was evacuated as a precaution while station employees investigated the presence of a chemical odor. The source of the odor was identified as paint fumes from planned outage activities and air samples confirmed that no safety hazard existed. Workers were returned to the building approximately 45 minutes later. An Event of Potential Public Interest was issued to outside agencies. State and local agencies were notified. The NRC Resident Inspector has been notified.
ENS 4626922 September 2010 20:23:00Peach BottomNRC Region 1GE-4During a thunder storm that extended across southern Pennsylvania and northern Maryland, 21 emergency sirens lost power in York County Pennsylvania and 8 emergency sirens lost power in Harford County Maryland. Exelon is communicating to the appropriate utilities to make emergent repairs to restore these sirens. In accordance with Peach Bottom plant specific procedures because greater than 25% of sirens were unavailable, the licensee contacted the following: Pennsylvania and Maryland Emergency Management; Harford and Cecil counties in Maryland and Lancaster, Chester and York counties in Pennsylvania. The licensee notified the NRC Resident Inspector.
ENS 4611120 July 2010 23:37:00Peach BottomNRC Region 1GE-4Exelon Nuclear Peach Bottom Atomic Power Station received notification from the Harford and Cecil County 911 centers that Harford County emergency sirens were intentionally activated due to a potential tornado in the area. The siren activation was due to the tornado and is in no way related to the operation of Exelon Nuclear Peach Bottom Atomic Power Station. The licensee notified the NRC Resident Inspector.
ENS 4569915 February 2010 15:28:00Peach BottomNRC Region 1GE-4A non-licensed, non-supervisory employee was found in possession of alcohol inside the protected area. For-cause fitness-for-duty testing was conducted with negative results. The individual's unescorted access has been prohibited pending further investigation. Contact the Headquarters Operations Officer for additional details.
ENS 4534814 September 2009 01:49:00Peach BottomNRC Region 1GE-4During the scheduled shutdown to commence the Peach Bottom Unit 3 refueling outage, Unit 3 was manually shutdown using the mode switch in accordance with GP-3, 'Normal Plant Shutdown,' when reactor period lowered below 50 seconds as indicated on the WRNM (Wide Range Nuclear Monitoring) system. The Feedwater Startup Level Controller was in automatic set at 23" when a small addition of cold water added enough positive reactivity to cause reactor period to be less than 50 seconds. The shortest period observed was 44 seconds. The WRNM system RPS (Reactor Protective System) automatic SCRAM setpoint is 19 seconds. All control rods inserted into the core. Decay heat is being removed by shutdown cooling. The plant is continuing into its scheduled refueling outage. The licensee notified the NRC Resident Inspector.
ENS 4528924 August 2009 21:21:00Peach BottomNRC Region 1GE-4This event is being reported pursuant to the requirements of 10 CFR 50.72(b)(3)(v) as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of systems supplied by the station safety-grade pneumatic supply. The systems affected include the primary containment isolation valves (i.e., large primary containment isolation valve boot seals) and the reactor-building to suppression pool vacuum breakers. On 8/24/09 at 1330, while troubleshooting the receipt of unexpected alarms during containment valve stroking the previous week, Exelon personnel discovered a valve closed instead of the expected open position. Licensed personnel concluded at 1415 that the out of position valve was restricting the Containment Atmospheric Dilution tank from supplying operating nitrogen to the Safety Grade Instrument Gas (SGIG) system headers for Peach Bottom Units 2 and 3. The valve was re-opened at 1445 (within the one hour action time required by Technical Specifications) and other system valves were verified to be in the required positions. The licensee notified the NRC Resident Inspector.
ENS 4519310 July 2009 13:40:00Peach BottomNRC Region 1GE-4Exelon has issued a news release due to elevated levels of tritium found in an on-site exploratory well at the Peach Bottom Atomic Power Station. The elevated levels of tritium were found in an area adjacent to the Peach Bottom Unit 3 Turbine Building. Tritium levels were measured as 123,000 picoCuries per liter. The licensee notified the NRC Resident Inspector, Pennsylvania Emergency Management Agency, Maryland Emergency Management Agency, and the counties of York, Cecil, Lancaster, and Chester.
ENS 4507618 May 2009 05:06:00Peach BottomNRC Region 1GE-4

At 0450 on Monday, May 18, 2009, power was removed to the Peach Bottom Atomic Power Station (PBAPS) Technical Support Center (TSC) ventilation system for planned preventative maintenance activities on the Unit 1 480VAC Load Center 10B014. During the 10B014 bus outage work activities, temporary power will be supplied to maintain all TSC facility equipment functional with the exception of TSC Normal and Emergency Ventilation. The TSC Supply, Exhaust and HEPA Filter fans will be de-energized, rendering the TSC HVAC non-functional while planned maintenance activities are in progress. This maintenance is scheduled to be worked continuously until completion to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 48 hours, including a total of 5 hours to establish and remove the clearances. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing EP procedures and checklists. It will take no more than 4 hours to return the Ventilation system back to an operable status, dependent on the stage of the work at the time the emergency occurs. If radiological conditions require TSC facility evacuation during ventilation system restoration, the Station Emergency Director will evacuate and relocate the TSC staff in accordance with, EP-AA-112-200-F-01. The NRC Resident Inspector has been notified.

  • * * UPDATE FROM BRAD KIRKMON TO HOWIE CROUCH @ 0400 EDT ON 5/20/09 * * *

This is a follow-up courtesy notification to EN# 45076. All scheduled work to the Unit 1 480VAC Load Center 10B014 is complete, with (the) exception of relay trip testing. Bus restoration has been delayed due to differences between the newly installed transformer and the old transformer, which required changes to the clearance. TSC facility restoration to normal power, including Normal and Emergency Ventilation system operation, is scheduled to occur on 5/20/09 day shift. The (NRC) Resident Inspector has been notified. Notified R1DO (Jackson).

ENS 4494027 March 2009 08:40:00Peach BottomNRC Region 1GE-4This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Unit 3 Primary Containment Isolation System (PCIS). On 3/2/09, at approximately 1155 hours, Unit 3 experienced an invalid PCIS partial isolation. Associated with the momentary shorting of a terminal lead during maintenance, a fuse was blown and power was lost to nine Primary Containment Isolation Valves (PCIVs). This resulted in two of the PCIVs re-positioning to the closed position. The re-positioned PCIVs were the AO-3-07B-3509 (Inner Drywell Exhaust Valve) and the AO-3-16-5235 (Instrument Nitrogen System Suction Valve). Closure of these valves affected the Containment Atmospheric Control (CAC), Containment Atmospheric Dilution (CAD) and Containment Instrument Nitrogen systems. Closure of these valves was the expected response for loss of power to this portion of the PCIS control circuitry. The fuse was replaced and the valves were restored to an operable condition by 1235 hours on 3/2/09. The invalid PCIS isolation was a result of the momentary shorting of an energized terminal lead associated with preventive maintenance to replace a pressure switch associated with PCIV AO-3-07B-3519 (Nitrogen Supply Purge Valve). This issue has been entered into the site Corrective Action Program (CR 887441) for evaluation and implementation of further corrective actions. The NRC resident has been informed of this notification.