05000219/LER-2013-001

LER-2013-001,

Event date:	10-03-2013
Report date:	2-6-2014
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2192013001R01 - NRC Website

10. POWER LEVEL

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FACILITY NAME

Michael McKenna, Regulatory Assurance Manager TELEPHONE NUMBER Ontiodo Aram Cods) (609) 971-4389 'reildiba ii COWILETE

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Y N/A N/A N/A N/A N/A X IG RI 6090 is. $MOLISONAL 0 YES (If yes. complete 15. EXPECTED lbACIE6 IL. EXAM= lle SUBMISSION DATE) NO DAY lleON TE MONTH ' DAY YEAR N/A N/A N/A ABSTRACT (Limit to 1400 spaces, i.e.. apprainstoc 4 singl

• -spaced typewritten ghee) On 10/3/13 at 0643 EDT, during reactor startup, with the reactor critical and power in the intermediate range, an automatic reactor scram occurred due to an invalid (noise) intermediate range monitor (IRM) scram signal processed on both RPS trip systems. The SCRAM was caused by both Reactor Protection Systems (APS) channels receiving simultaneous IRM Hi-Hi signals on IRM channels 12, 13, 14, 17, and 18.

Testing conducted by Analysis and Measurement Services (AMS) identified low shield to ground insulation resistances on multiple channels of the IRM system. This condition allowed significant noise coupling to occur which resulted in the erratic behavior of the IRM channels that led to the full reactor SCRAM. The noise which was received by the IRM channels has been determined to be caused by a shorted SRM 22 detector. The short circuit provided a path to ground for the high voltage potential used to bias the SRM detector.

The root cause of the SCRAM was the susceptibility of the Intermediate Range Monitor (IRM) channels to electrical noise due to low shield to ground insulation resistance. Contributing to this event was an internal fault of Source Range Monitor (SRM) detector 22 which caused a significant amount of noise to propagate onto the IRM channels resulting in spiking. SRM-22 was replaced during a subsequent maintenance outage on November 20, 2013.

There were no safety consequences as a result of this event. All control rods fully inserted and plant response was as expected, This event is being reported pursuant to: 10CFR50.73(a)(2)(N)(A) due to an autmatic actuation of the Reactor Protection System (RPS).

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Plant Conditions Prior To Event

Event Date: October 3, 2013 Event Time: 0643 EDT

Description of Event

An automatic reactor SCRAM occurred on October 3, 2013 at 0643 EDT during the plant startup from 1M30. The SCRAM was caused by both Reactor Protection Systems (RPS) charnels receiving simultaneous IRM HI-Hi signals on IRM channels 12, 13, 14, 17, and 18. The IRMs all became Waft at the same time, cycling between Hi-Hi and downscale. Source Range Monitors (SRMs) 23 and 24 also became erratic at this time. These erratic output signals occurred coincidentally with Source Ra Monitor (SRM) 22 withdrawal to maintain counts In their acceptable range.

Testing conducted by Analysis and Measurement Services (AMS) identified low shield to ground insulation resistances on multiple channels of the IRM system. This condition allowed significant noise coupling to occur which resulted in the erratic behavior of the 1RM channels that led to the full reactor SCRAM. The noise which was received by the IRM channels has been determined to be caused by a shorted SRM 22 detector, The short circuit provided a path to ground for the high voltage potential used to bias the SRM detector.

Analysis of Event

A full SCRAM was received due to actuation of RPS sub-channel relays 1K1, 1K2, and 2K2. It was determined from PPC trend data that IRMs 12-14, 17, and 18 caused the SCRAM. At the time of the event, IRMs 11 and 16 were bypassed. Further troubleshooting identified that the SCRAM occurred while withdrawing SRM detectors out of the core. It was identified that SRM 22 motion caused spiking of all IRM channels.

There were no safety consequences as a r ft of this event. All control rods tufty gn and plant response was as expected. This event is being r pursuant to: 10CFR50.73(a)(2)(iv)(A) automatic actuation of the Reactor Protection System (RPS).

Cause of Event

Troubleshooting has identified the motion of SRM-22, in and out of the core, as the sou noise causing spiking on the IRMs. When the high voltage to the SRM-22 detector was disconnected, there was no IRM spiking when the SRM detector was moved.

The root cause of the SCRAM w the susceptibility of the intermediate Range Monitor (IRM) channels to electrical noise due to low shield to ground insulation resistance. Contributing to this event is an internal fault of Source Range Monitor (SRM) detector 22 which caused a sign amount 01 noise to propagate onto the IRM channels resulting in spiking.

Corrective Actions

2 OF NRC FORM WA (10-2010)

S. UR NUMMI

s. PDX SRM-22 high voltage cable was disconnected per the simple troubleshooting process. When the high voltage to the SRM-22 detector was disconnected, there was no IRM spiking when the SRM detector was moved. SRM-22 was not initially repaired, but electrically isolated. SRM-22(General Electric Part number 112C31440037) was subsequently replaced during a Maintenance outage on November 20, 2013.

Actions were created to troubleshoot and repair low insulation resistances on IRM channels and implement a mitigation strategy to address EMI issues with the Nuclear Instrumentation System.

Previous Occurrences

There have been no similar Licensee Event Reports associated with this component failure submitted at OCNGS in the last two years.

Component Data Components IEEE 805 System ID IEEE 803A Function Neutron Monitors 10 RI