05000388/LER-2017-008

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LER-2017-008, 1 OF 3
Susquehanna Steam Electric Station Unit 2
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3882017008R01 - NRC Website
LER 17-008-00 for Susquehanna, Unit 2, Regarding Condition Prohibited by Technical Specifications Due to a Loose Terminal Block Associated with a Primary Containment Isolation Valve
ML17261B257
Person / Time
Site: Susquehanna Talen Energy icon.png
Issue date: 09/18/2017
From: Berryman B
Susquehanna, Talen Energy
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7638
Download: ML17261B257 (5)


comments regarding burden estimate to the Information Services Branch (T-2 F43), 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.

Susquehanna Steam Electric Station Unit 2 05000-0388 2017

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, approximately 100 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.

EVENT DESCRIPTION

On July 19, 2017 at approximately 02:25, while performing a control room panel walk down, Operations observed amber and red indication for Primary Containment Isolation Valves (PCIVs) HV21313 and HV21314 (Reactor Building Closed Cooling Water Outboard Isolation Valves) [EIIS System/Component Identifier: CC/ISV] extinguished (should have been showing red indication with valves open). The red LED indicating lamp was changed with a known good bulb and the red indication briefly returned along with a dim amber indication while the bulb was being changed. Locally, an operator found normal indication at HV21313, but no indication for HV21314. The operator replaced the red and amber indicating lamps at the local panel with no return of indication. During the process of changing the bulb at the local panel, the red indication in the control room briefly displayed a dim indication but extinguished after approximately one minute. The operator verified Breaker 26236092 [EIIS Component Identifier: BKR] to HV21314 closed and the valve itself open. Additionally, no Bypass Indication System (BIS) alarms were indicated for a loss of power to a containment isolation indicating the issue was with indication only and not control power.

Technical Specification 3.3.3.1, Condition A was entered for loss of remote position indication for HV21313 and HV21314.

During troubleshooting, an open neutral was identified, and on July 19, 2017 at approximately 10:49, investigation of the condition concluded that the loss of continuity revealed that the isolation circuit for HV21314 was affected and the valve would not close if called upon to do so. Technical Specification 3.6.1.3, Condition A was entered. The investigation identified a loose terminal block in 2B236092 due to not being seated properly. The block was subsequently securely snapped back into the seat and the mounting screw was tightened.

On July 19, 2017 at approximately 13:56, Technical Specification 3.3.3.1, Condition A and Technical Specification 3.6.1.3, Condition A were exited.

Further investigation identified the following timeline:

On April 21, 2013, a new bucket was installed into Breaker 2B236092.

On May 21, 2013, the post-maintenance testing (PMT) for the new bucket was completed.

comments regarding burden estimate to the Information Services Branch (T-2 F43), 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.

U.S. NUCLEAR REGULATORY COMMISSION 05000-0388

3. LER NUMBER

2017 -01 The terminal block affects HV21314 as well as the control room indication for both HV21313 and HV21314.

The loose terminal block was caused by improper seating during installation on April 21, 2013. Seismic evaluation concluded that the installed configuration (i.e., not properly seated) is not a dynamically qualified configuration and that operability in this condition is therefore indeterminate. Based on this information, HV21314 as well as the control room indication for both HV21313 and HV21314 are considered to have been inoperable since installation of the new bucket in April 2013 when the terminal block was not properly seated. Since the amount of time between the installation and restoration of operability was greater than allowed by Technical Specifications, this is a condition prohibited by Technical Specifications and is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B). Although the event date is listed as April 21, 2013, the discovery date is considered to be July 19, 2017.

CAUSE OF EVENT

The cause was determined to be a loose terminal block caused by a human performance error during installation in 2013.

ANALYSIS/SAFETY SIGNIFICANCE

PCIV HV21314 would not have been able to electrically close with the identified condition. HV21314 is the outboard containment isolation valve. The inboard containment isolation valve, HV21346, was operable and would have provided the required isolation of the containment penetration. The containment design and testing only requires one containment isolation valve in each penetration to close for successful isolation. All containment leakage rates and all containment isolation requirements would have been met.

In addition, no inoperability of control room indication associated with the redundant PCIVs was identified during the period of inoperability based on review of Technical Specification logs.

CORRECTIVE ACTIONS

Key corrective actions include the following:

1. Applicable electricians will be required to complete a read and sign regarding how to verify proper seating of terminal blocks.

2. A step will be added to applicable procedures regarding how to verify proper seating of terminal blocks.

COMPONENT FAILURE INFORMATION

Terminal Block, Pull Apart, 8 Pole 11330 Series manufactured by USD.

PREVIOUS SIMILAR EVENTS

No previous similar events were identified.