05000445/LER-2016-001

LER-2016-001, Safety Chiller Inoperable For Longer Than Allowed By Technical Specifications

Comanche Peak
Event date:	6-22-2016
Report date:	8-22-2016
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4452016001R00 - NRC Website

LER 16-001-00 for Comanche Peak Nuclear Power Plant, Unit 1, Regarding Safety Chiller Inoperable For Longer Than Allowed By Technical Specifications

ML16245A232
Person / Time
Site:	Comanche Peak
Issue date:	08/22/2016
From:	McCool T P Luminant Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CP-201600797, TXX-16093 LER 16-001-00
Download: ML16245A232 (6)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000- NUMBER NO.

., 001 00 Comanche Peak 445 16 -

A. REPORTABLE EVENT CLASSIFICATION

10CFR50.73(a)(2)(i)(B) "Any operation or condition which was prohibited by the plant's Technical Specifications" as a result of the Unit 1, Train A Safety Chiller exceeding its LCO completion times, for entering Mode 4 with an inoperable chiller, and for subsequently entering Modes 3, 2, and 1 with an inoperable safety chiller in violation of Technical Specification (TS) 3.7.19.

B. PLANT CONDITION PRIOR TO EVENT

On June 22, 2016, Comanche Peak Nuclear Power Plant (CPNPP) Unit 1 was operating in Mode 1, at or near 100% power.

INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT

There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.

D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES

On May 10, 2016, during a Unit 1 refueling outage Maintenance personnel (Utility, Non-Licensed) completed dashpot overload relay testing and re-installed the relays into the Unit 1, Train A Safety Chiller Motor Starter Panel [El IS:(KM) (CHU)(DPT)(MSTR)]. The Maintenance personnel then re-terminated the Phase A, B, and C upper and lower cables to their respective dashpot overload relays, and should have torqued the bolted connections in accordance with the applicable Maintenance procedure.

On May 15, 2016, at 1625 the Unit 1, Train A Safety Chiller Technical Specification acceptance criteria was satisfactorily met and approved by the U1 Supervisor (Utility, Licensed) and the chiller was declared operable.

On May 28, 2016 at 0330 Unit 1 entered Mode 4, and per TS 3.7.19 the Unit 1, Train A Safety Chiller was required to be operable.

On June 9, 2016, at 1005 it was discovered during the performance of routine periodic predictive maintenance thermography by Engineering personnel (Utility, Non-Licensed) on the Unit 1, Train A Safety Chiller Motor Starter Panel that the Phase 'A' cable termination on the dashpot overcurrent relay had a significantly higher temperature reading than expected (950°F as opposed to a typical reading of about 90°F). The Unit 1, Train A Safety Chiller was shut down per the direction of the Shift Manager (Utility, Licensed) and the chiller was declared inoperable.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000- NUMBER NO.

_001 00 Comanche Peak 445 16 - On June 22, 2016, an evaluation was completed that determined the Unit 1, Train A Safety Chiller had been inoperable from May 28, 2016 to June 9, 2016.

ERROR

During routine periodic predictive maintenance thermography activities, Engineering personnel (Utility, Non-Licensed) identified that the 'A' phase connection to the Unit 1, Train A Safety Chiller was at an elevated temperature.

A. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE

Not Applicable — No other component or system failures were identified that contributed to this event.

B. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT

Not Applicable — No component or system failures were identified during this event.

MULTIPLE FUNCTIONS

Not Applicable — No component or system failures were identified during this event.

D. FAILED COMPONENT INFORMATION

Not Applicable — No component or system failures were identified during this event.

A. SAFETY SYSTEM RESPONSES THAT OCCURRED

Not Applicable — No safety system responses occurred as a result of this event.

B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY

The Unit 1, Train A Safety Chiller was inoperable per Technical Specification 3.17.9 from May 28, 2016 to June 9, 2016 (approximately 222.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />).

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000- NUMBER NO.

001 00 Comanche Peak 445 16 _ -

C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT

The Unit 1, Train A Safety Chiller was inoperable per Technical Specification 3.17.9 from May 28, 2016 to June 9, 2016.

During that time, the Unit 1, Train A Safety Chiller ran without any indication of abnormal performance or degraded function and the Train B Safety Chilled Water System was operable.

The safety significance of the identified condition is low, since the Train B Safety Chiller cooling function remained available during the subject period from May 28, 2016 to June 9, 2016, and no interim actions were required during the planned evolutions to reduce the effect on nuclear safety.

A probabilistic risk assessment of the inoperability of the Unit 1, Train A Safety Chiller found a non-risk significant effect on core damage frequency and large early release frequency. Based on the above considerations, this event had very low safety significance and there was no adverse effect on plant safety or on the health and safety of the public.

IV. CAUSE OF THE EVENT

The cause of this event was the restoration and post work activities by Maintenance personnel during a Unit 1 refueling outage did not ensure that the Unit 1, Train A Safety Chiller was properly configured per procedure and ready to be turned over to Operations. The improper torque resulted in one of the terminations experiencing significantly elevated temperatures once the equipment was returned to service and resulted in the Unit 1, Train A Safety Chiller being declared inoperable. Procedures and work practices contributed to this event. The Maintenance workers inadequately performed a procedure step directly after the termination torque performances directing them to ensure there were no loose electrical connections in the panel. The Maintenance procedure also currently only provides one sign-off step for the performance of six QIV termination torques. There were no training, communication, supervision, human-system interface, fitness for duty, or time/situational pressures associated with this event.

V. CORRECTIVE ACTIONS

The other three Safety Chillers were verified to have no thermal abnormalities. The Phase 'A' cable and dashpot relay were replaced and the Phase 'B' and 'C' dashpot relay terminations were retorqured. The applicable Maintenance procedure will be revised before the next scheduled performance to have the equipment specific thermography inspection performed as a part of the maintenance restoration/post work activities so that an improper torque will be identified and corrected before the equipment is turned over to Operations. The applicable Maintenance procedure will also be revised to include six component verification sign-off steps to verify each of the three line side and three load side terminations are torqued.

VI. PREVIOUS SIMILAR EVENTS

than allowed by Technical Specifications. However, the cause of the 2014 event was due to a different cause than this event.