05000266/LER-2016-002

LER-2016-002, Operation or Condition Prohibited by Technical Specifications

Point Beach Nuclear Plant Unit 1
Event date:	04-01-2016
Report date:	05-31-2016
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2662016002R00 - NRC Website

LER 16-002-00 for Point Beach, Unit 1, Regarding Operation or Condition Prohibited by Technical Specifications

ML16152A094
Person / Time
Site:	Point Beach
Issue date:	05/31/2016
From:	Coffey B Point Beach
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC 2016-0024 LER 16-002-00
Download: ML16152A094 (4)

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 Internet 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.

Description of the Event:

At 1132 On April 1, 2016 the 345/13.8kV high voltage station auxiliary transformer (1X-03) tripped on a differential current relay (1-87A/X-03) actuation. Review of this event determined that there were three instances over the past three years when the required action completion time for not satisfying the Limiting Conditions For Operation of Technical Specification 3.8.1 (AC Sources — Operating) and 3.8.2 (AC Sources — Shutdown) would have been exceeded with the latent error present.

This 60 day licensee event report is being submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B).

Cause of the Event:

The cause of the operation or condition prohibited by technical specifications has been determined to be a wiring error introduced on April 3, 2013.

Analysis of the Event:

The 345/13.8kV high voltage station auxiliary transformer (1X-03) tripped on a differential current relay (1-87A/X-03) actuation while starting a Reactor Coolant Pump motor. The actuation triggered a 1X-03 lockout. During the event, an automatic fast bus transfer occurred as designed powering the 13.8kV/4.16kV low voltage station auxiliary transformer (1X-04) from offsite power through the opposite unit 345/13.8kV high voltage station auxiliary transformer (2X-03). An under voltage condition was not detected on the downstream 4.16kV safeguard bus switchgear (1A-05 or 1A-06) that would have started the emergency diesel generators. Operations promptly restored equipment affected by the 1X-03 lock out, including station battery chargers (D-07 and D-108) within four minutes. The 1X-04 transformer was returned to service through the 1X-03 transformer at 2342 on April 1, 2016.

An event investigation team determined the cause of the event to be a wiring error associated with the differential current relay. With the wiring error present, actuation of the relay was dependent upon the loading of the transformer.

As transformer load would increase, the relay would get closer to its actuation. If the relay actuated, the 1X-03 transformer would lock out and remove the circuit from the offsite transmission network. This is what occurred during the April 1, 2016 event.

Technical Specification 3.8.1 requires the associated unit X-03 transformer to be operable. Technical Specification 3.8.2 requires an offsite circuit to be operable. Analysis of the 1X-03 transformer load data for the past three years determined there were three instances when the required action completion time for not satisfying the Limiting Conditions For Operation of Technical Specification 3.8.1 and 3.8.2 would have been exceeded.

Safety Significance:

The condition was determined to be of very low safety significance. If the condition would have presented itself, Operations would have promptly restored equipment affected by the 1X-03 lock out. If an under voltage condition would have been detected on the downstream 1A-05 or 1A-06, the emergency diesel generators would have started and powered safety systems, structures or components needed to shut down the reactor, maintain safe shutdown conditions, remove residual heat, control the release of radioactive material or mitigate the consequences of an accident. There was no impact on the health and safety of the public as a result of this condition.

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 internet 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.

3. LER NUMBER

2016 002 - 00

Corrective Actions:

The 1X-03 transformer differential current relay wiring error has been corrected. A corrective action has been created from the extent of condition review of work performed by contractors to enhance the contractor training on the proper use of plant processes for lifting and landing wires/leads on equipment.

Similar Events:

There have not been similar events of this condition prohibited by technical specifications reported in the past three years.

Component Failure Data:

None