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Explosion occurred in a non-safety related transformer at 1908 EST 0n 01/13/04. The transformer became deenergized as a result of the explosion. Licensee declared an Unusual Event at 1921 EST on 01/13/04 due to an explosion resulting in visible damage to a non-safety related transformer in the Turbine Enclosure building. There was no fire or injured personnel, and the site did not require any off site assistance. The transformer explosion resulted in the loss of power to some 480 VAC non-safety related loads (most significant was a non-safeguard DC battery charger). The explosion has not severely impacted Unit 1 operations. The transformer has been inspected, and it appears that the explosion was internal to the transformer and due to an electrical malfunction. Security personnel conducted thorough walk downs of all areas and had no concerns. NRC Management determined that this event did not require entry into the Monitoring Phase of Normal Mode of Incident Response at 2040 on 01/13/04. The licensee notified the state and local emergency management agencies and notified the NRC Resident Inspector.

• * * UPDATE FROM PETE ORPHANOS (VIA FACSIMILE) TO HOWIE CROUCH @ 0221 EST ON 1/14/04 * * *

Notification of reduction in classification status from Unusual Event. Failure of non-safeguards electrical supply determined to be due to cable fault. Plant remains stable at 100% power. No additional equipment damage identified. Blocking and repair planning in progress. The unusual event was terminated by the licensee at 2151 hrs. EST on 1/13/04. The licensee has notified the NRC Resident Inspector and State and County authorities. A media press release will be issued in the morning.

Notified DHS (Beal) and FEMA (Caldwell).

Limerick has completed the 10CFR Part 21 evaluation of the failure of the spring charging function on an Asea Brown Boveri (ABB) Model HK circuit breaker. The investigation determined that the primary contributor to the failure was the replacement of ABB latch reset torsion spring number 195205A00 with a weaker spring that was supplied with the breaker overhaul kit number 716656T104. Secondary contributors to the failure were normal wear on additional parts in the operating mechanism. ABB supplied a six-turn latch reset torsion spring and a five-turn latch reset torsion spring under spring part number 195205A00 and overhaul kit number 716656T104. The spring of concern is a six-turn spring that does not provide as much force as the original six-turn or five-turn spring. When informally tested during the investigation the six-turn spring provided approximately 66 ounces of force and the five-turn spring provided approximately 102 ounces of force. The original six-turn spring provided a force of 88 ounces. Limerick's evaluation concluded that installation of the replacement six-turn latch reset torsion spring could create a substantial safety hazard depending on the breaker's application. Therefore, this notification is being submitted pursuant to the requirements of 10CFR21.21(d)(3)(i). The required 10CFR21.21(d)(3)(ii) 30-day written notification will provide more detail when submitted. ABB evaluation of this issue is still in progress. The licensee notified the NRC Resident Inspector.

• * * RETRACTION ON 6/30/04 @ 1451 HRS. EDT FROM GAMBLE TO CROUCH * * *

This is a retraction of the Part 21 initial notification made per 10CFR21.21(d)(3)(i) on 6/3/04 at 12:47 EDT (EN# 40788). The issue involved an in-service malfunction of the closing spring charging function of an Asea Brown Boveri (ABB) Model HK circuit breaker following replacement of the latch reset torsion spring (ABB number 195205A00) during breaker maintenance. The spring was supplied with ABB overhaul kit number 716656T104. Upon further review of the Part 21 reporting requirements it has been determined that this issue does not require reporting. NUREG-1022 Rev.2 'Event Reporting Guidelines 10CFR50.72 and 50.73' provides guidance for Part 21 reporting in section 5.1.8. The NUREG section references a federal register notice (56 FR 36081, July 31, 1991) in footnote 18, which provided notification of an amendment to 10CFR Parts 21 and 50. The amendment was intended to reduce duplicate reporting of defects. The notice provides the following guidance for components that have been installed in operating plants: Operating license holders can reduce duplicate evaluation and reporting effort by evaluating deviations in basic components installed in operating plants which produce events which could meet the criteria of 50.72 and 50.73. If the evaluation of events using the criteria of 50.72 and 50.73 results in a finding that the event is reportable and the event is reported via these sections, then as indicated in 21.2(c), the evaluation, notification, recordkeeping, and reporting obligations of part 21 are met. If the event is determined not to be reportable under 50.72 or 50.73, then the obligations of part 21 are met by the evaluation. The evaluation using the criteria of 50.72 and 50.73 resulted in a finding that the event was not reportable. There was no reasonable expectation of preventing fulfillment of a safety function, no equipment was declared inoperable, and the principle safety barriers were not seriously degraded. Therefore, this event is not reportable using the criteria of 50.72 and 50.73 and the Part 21 evaluation obligation is met. The licensee has notified the NRC Resident Inspector of this retraction. The Headquarters Operations officer notified R1DO (Barkley), R2DO (Evans), R3DO (Gardner), R4DO (Whitten), and NRR (Dennig).

The notification is being made pursuant to Unit 2 Operating License for potential non-compliance of the Fire Protection Program. At 12:55 on January 18, 2005 following the review of Operating Experience for Wolf Creek (ENS 41327), it was discovered that the pilot lines to the manual pneumatic actuator pilot lines on the Halon bottles for the Halon System for the Auxiliary Equipment Room were incorrectly piped. In accordance with TRM 3.7.6.4 a continuous fire watch was established in the area. This event resulted in a condition that could have rendered the Halon System for the Unit 2 Auxiliary Equipment Room inoperable during a fire. The Unit 1 Auxiliary Equipment Room Halon System was not affected and remained operable. At this time the cause of this condition is not currently known, and an investigation is ongoing. NRC Resident Inspector was notified of this event by the licensee. HOO NOTE: See Ens # 41326 and 41327 for similar reports.

• * * UPDATE AT 1059 ON 02/16/05 FROM MARK CRIM TO W. GOTT * * *

The notification is being made to retract the ENS 41346 Rev 0 reported on 1/19/05 pursuant to Unit 2 Operating License for a potential noncompliance of the Fire Protection Program. At 12:55 on January 18, 2005 following the review of Operating Experience for Wolf Crook (ENS 41327), it was discovered that the pilot lines to the manual pneumatic actuator on the main and reserve Halon cylinders for the Unit 2 Auxiliary Equipment Room Under Floor Halon System were incorrectly piped. In accordance with TRM 3.7.6.4, a continuous fire watch was established in the area.. Immediately following the event, it was believed that the condition could have rendered the Unit 2 Auxiliary Equipment Room Under Floor Halon System inoperable during a fire. On January 19, 2005 Limerick corrected the piping to meet the vendor design for the manual-pneumatic actuators associated with the Unit 2 Auxiliary Equipment Room Under Floor Halon System. On January 26, 2005 Chemetron performed a functional test of the Halon System for Callaway with the incorrect pilot line piping and discovered that Halon injected properly with a 2 second delay (See IEN 2005-001). Callaway had a similar Halon system configuration as Limerick Unit 2 Auxiliary Equipment Room Under Floor Halon System (same make and model number manual-pneumatic actuators and cylinder heads). An evaluation of the test report concluded that the Limerick Unit 2 Auxiliary Equipment Room Under Floor Halon System would have actuated in the event of a fire. In conclusion, despite the pilot line piping error, the Unit 2 Auxiliary Equipment Room Under Floor Halon System would have remained operable and would have completed it's suppression function during a fire. Therefore, there was no violation of the Unit 2 Operating License Section 2.C.(3) for the Fire Protection. The licensee will notify the NRC Resident Inspector. Notified R1DO (E. Coby).

During performance of the quarterly HPCI valve stroke test the HV-55-2F006, HPCI pump discharge isolation valve to Core Spray failed to open within the maximum allowed time. The HV-55-2F006 valve is a motor operated valve and the maximum allowed opening time is 17.25 seconds. The valve was given an open signal via the hand switch as required by the test but did not initially respond. Several minutes later the valve went full open. HPCI was declared inoperable at 0315 on 6/21/2007. Cause for valve stroke time failure is not known at this time. As a result, the licensee is in a 14 day shutdown LCO. The licensee notified the NRC Resident Inspector.

• * * RETRACTION FROM ARNOSKY TO HUFFMAN AT 0807 EDT ON 8/01/07 * * *

This is a retraction of the event notification made on 6/21/07 at 04:05 hours EDT. This event (#43436) was initially reported as a condition that at the time of discovery could have prevented the fulfillment of the High Pressure Coolant Injection (HPCI) system safety function under the requirement of 10CFR50.72(b)(3)(v)(D). The Unit 2 HPCI system was declared inoperable due to failure of the HPCI pump discharge isolation valve to Core Spray to open within the maximum allowed time during surveillance testing. The valve was required to open within 17.25 seconds but opened several minutes after the open signal was initiated. The open contactor was replaced and the valve was successfully tested. The affected valve was declared operable on 6/22/07 at 04:07 hours. The HPCI system was restored to operable on 6/23/07 at 04:07 hours following completion of maintenance and testing activities. An evaluation determined that HPCI was capable of injecting sufficient flow to complete its safety function through the unaffected operable injection flow path to the feedwater header. The achievable flow rate would have exceeded the leakage from a one-inch liquid line break. Also, HPCI operation remained capable of being terminated by operator action during an ATWS event. Therefore, HPCI remained capable of fulfilling its safety function while the injection flow path to Core Spray was unavailable. A condition did not exist at the time of discovery that could have prevented the fulfillment of the HPCI safety function. The licensee notified the NRC Resident Inspector. R1DO (White) notified.

The D/C power supply for the Unit 1 High Pressure Coolant Injection (HPCI) system instrumentation has failed resulting in the inability of HPCI to meet its requirement to support safely shutting down the reactor during a Station Blackout (Complete Loss of A/C Power) situation. The Emergency Core Cooling System (ECCS) function of HPCI is still available with the alternate A/C power supply. The licensee is actively troubleshooting the power supply. The HPCI unavailability places the licensee in a 14-day Limiting Condition for Operation action statement. The licensee has notified the NRC Resident Inspector.

* * * RETRACTION FROM D. SEMETER TO P. SNYDER ON 3/27/08 AT 1300 * * * 

This is a retraction of the event notification made on 1/29/08 at 21:50 EST hours. This event (#43942) was initially reported as a safety system functional failure under the requirement of 10 CFR 50.72(b)(3)(v)(A). The notification stated that the D.C. power supply for the Unit 1 High Pressure Coolant Injection (HPCI) system instrumentation failed resulting in the inability of HPCI to meet its requirement to support safely shutting down the reactor during a Station Blackout (SBO) (Complete Loss of A/C Power) situation. The Emergency Core Cooling System (ECCS) function of HPCI is still available with the alternate A/C power supply. A review of the station's current licensing basis determined that HPCI is not credited with a safety function during a Station Blackout (SBO) event. Operating procedures direct securing HPCI early in an SBO event to minimize the discharge rate on the Class 1E batteries. The Reactor Core Isolation Cooling (RCIC) system is credited with maintaining reactor inventory during a SBO event. HPCI remained capable of completing its safety function to inject coolant into the reactor pressure vessel during a loss of coolant accident (LOCA) concurrent with loss of offsite power (LOOP) event. The Division 2 automatic initiation logic was inoperable but the Division 4 automatic initiation logic was unaffected by the Division 2 instrument power supply failure. Division 2 instrument power is required for HPCI automatic flow control and would not have been initially available during a LOOP event. However, the Division 2 instrument power would have been restored when the 480 VAC load center is re-energized approximately 13 seconds into the event. The 13 second delay in HPCl injection is offset by existing margin in HPCI's capability to meet the Technical Specification response time of 60 seconds. Therefore, a condition did not exist at the time of discovery that could have prevented the fulfillment of the HPCI safety function. The licensee notified the NRC Resident Inspector. Notified R1DO (Bellamy).

The Emergency Notification System (ENS), Health Physics Network (HPN), site commercial telephone lines and Emergency Response Data System (ERDS) have been taken out of service for a planned maintenance outage. The outage is scheduled for a duration of six hours. The plant radio system, plant page system, and Prelude phone system are unaffected by the maintenance. The licensee notified the NRC Resident Inspector.

* * * UPDATE AT 1534 ON 2/17/08 FROM NED DENNIN TO JEFF ROTTON * * * 

All phones are back in service and operable. The licensee will notify the NRC Resident Inspector. Notified R1DO (Dentel).

On June 10, 2008, at 2255 hours it was determined that 54 of the 165 Limerick Generating Station's Emergency Offsite Sirens were inoperable due to a loss of power. The loss was a result of heavy storms which passed through the area resulting in power outages throughout the region. Efforts are underway to restore power to the affected sirens. The licensee notified the NRC Resident Inspector

• * * UPDATE FROM BRANDON SHULTZ TO HOWIE CROUCH AT 1709 EDT ON 6/11/08 * * *

On June 11, 2008 at 1645 restoration efforts have recovered 44 of the 54 sirens rendered inoperable by the storm. The remaining 10 inoperable sirens no longer represents a major loss of emergency preparedness capabilities. Restoration of power to the remaining inoperable sirens continues under normal prioritization and using routine siren operating and maintenance procedures. No completion time was provided concerning repair of the remaining sirens. The licensee will be notifying the NRC Resident Inspector. Notified R1DO (Summers).

(The licensee experienced) a loss of the ability to send ERDS data to the NRC for greater than 60 minutes due to a computer problem. The HPN and ENS communications systems were not affected and remained available through a commercial communication line. SPDS also remained in service and remained available during this period. The ERDS system was restored to service after 109 minutes. The licensee notified the NRC Resident Inspector.

• * * UPDATE AT 1240 EDT ON 06/22/09 FROM MARK ARNOSKY TO VINCE KLCO * * *

06-22-2009 Update to clarify the above statement: The HPN and ENS communications systems were affected by the computer problem, however, they remained available for use through an alternate and unaffected commercial communication line. Notified R1DO (Burritt).

Non-conservative Tech Spec setpoints were discovered that affected Steam Leak Detection for Unit 1 and Unit 2 (High Pressure Coolant Injection) HPCI room high differential temperatures. During a steam leak detection system design basis leak, the present temperature setpoint would not isolate the HPCI steam supply piping. A calculation has been performed by engineering which demonstrates that, with both room coolers secured, a design basis steam leak will result in the room ventilation differential temperature exceeding the present Tech Spec setpoints. At this time, the room unit coolers have been secured and HPCI and the associated steam leak detection system remain operable. Calculations are in-progress by engineering for changes to the high differential temperature steam leak detection setpoint. The licensee notified the NRC Resident Inspector.

* * * RETRACTION FROM J. BROILET TO P. SNYDER ON 10/20/09 AT 1154 EDT * * * 

This is a retraction of the event notification made on 8/28/09 at 0113 EDT. This event (#45307) was initially reported as a condition that could have prevented fulfillment of a safety function under the requirement of 10 CFR 50.72 (b)(3)(v)(c). A follow-up review of the HPCI equipment room steam leak detection system calculations determined that other HPCI equipment room ambient high temperature instruments would have automatically actuated a HPCI steam line isolation during a 25 gpm design basis HPCI steam line leak event. Therefore, a condition did not exist at the time of discovery that could have prevented the fulfillment of the HPCI steam line isolation safety function. The licensee notified the NRC Resident Inspector. Notified R1DO (Doerflein).

On Thursday, February 11, 2010, the Limerick Technical Support Center (TSC) emergency ventilation system will be removed from service for planned preventative maintenance activities on the damper flow controller and air filtration charcoal system. During the maintenance, the non-emergency ventilation system will be functional. The TSC air filtration fan and dampers will be non-functional, rendering the TSC HVAC accident mode non-functional. This maintenance is scheduled to minimize out of service time. The planned TSC ventilation outage is scheduled to be completed within 12 hours. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing EP (Emergency Planning) procedures and checklists. 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 applicable site procedures. The licensee has notified the NRC Resident Inspector.

• * * UPDATE FROM BRANDON SHULTZ TO DONG PARK ON 2/11/10 AT 1721 EST * * *

The maintenance on the Limerick Technical Support Center (TSC) emergency ventilation system has been completed and the TSC is available. The licensee has notified the NRC Resident Inspector. Notified R1DO (Powell)

On June 14, 2010 at 0300 hours, Limerick Generating Station will apply a clearance to inspect and repair Fire Suppression Equipment associated with the Onsite Technical Support Center (TSC) Emergency Ventilation System and perform corrective maintenance associated with MD-1 (Outside Air Damper). During the time that the clearance is applied, the TSC Ventilation System will not be available to be restored in a time period required to staff and activate the TSC Emergency Response Organization. This work is expected to be completed on June 16, 2010. If an emergency is declared requiring TSC activation, the TSC will be staffed and activated using emergency planning procedures unless the TSC becomes uninhabitable due to ambient temperature. Radiological or other conditions. If relocation becomes necessary, the Station Emergency Director will relocate the TSC staff to an alternate TSC location in accordance with applicable Site procedures. This notification is being made in accordance with 10CFR50.72(b)(3)(xiii) due to the Loss of an Emergency Response Facility (ERF) because of the Unavailability of the Emergency Ventilation System. The NRC Resident Inspector has been informed.

• * * UPDATE FROM BROILLET TO HUFFMAN AT 2206 EDT ON 6/14/10 * * *

The TSC Emergency Ventilation System was returned to service at 2150 EDT on 6/14/10. The licensee has informed the NRC Resident Inspector. R1DO (Holody) notified.