05000219/LER-2007-002

LER-2007-002, AmerGen Energy Company www.exeloncorp.com An Exelon Company
Oyster Creek
US Route 9 South, P.O. Box 388
Forked River, NJ 08731-0388
10 CFR 50.73
September 18, 2007
RA-2007-025
U. S. Nuclear Regulatory Commission
Attn: Document Control Desk
Washington, DC 20555 - 0001
Oyster Creek Nuclear Generating Station
Facility Operating License No. DPR-16
NRC Docket No. 50-219
Subject:ALicensee Event Report 2007-002-00, Intermediate Range Monitor (IRM)
16 Inoperable During Startup
Enclosed is Licensee Event Report 2007-002-00, Intermediate Range Monitor (IRM) 16
Inoperable During Startup. This event did not affect the health and safety of the public or
plant personnel. This event did not result in a safety system functional failure. There are
no new regulatory commitments made in this LER submittal.
If any further information or assistance is needed, please contact Stevie Du Pont,
Regulatory Assurance at 609-971-4033.
Sincerely,
wv
ausch
ice President, Oyster Creek Nuclear Generating Station
Enclosure:ANRC Form 366, LER 2007-002-00
cc:AAdministrator, USNRC Region I
USNRC Project Manager, Oyster Creek
USNRC Senior Resident Inspector, Oyster Creek
File No. 07035
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007
(6-2004) Estimated burden per response to comply with this mandatory collection request:
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and fed back to industry. Send comments regarding burden estimate to the
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Commission, Washington, DC 20555-0001, or by Internet e-mail toLICENSEE EVENT REPORT (LER) infocollects@nrc.gov, and to the Desk Officer, Office of Information and
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1. FACILITY NAME 2. DOCKET NUMBER 3. PAGE
Oyster. Creek, Unit 1 • 05000 219 •1 OF 4
4. TITLE
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Intermedte Range Monitor 16 Inoperable During:Startupia

Docket Number07 20 :' 2007 2007 - 002 - 00 •• 09 18.• •2007...
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2192007002R00 - NRC Website

Unit Conditions Prior to the Event.

The unit was in the Start-up mode and reactor power was at 0 percent. IRM 17 was inoperable and in bypass. There were no other structures, systems, or components out of service that contributed to this event.

Description of the Event

On July 20, 2007, a plant startup from forced outage 1F12 commenced with IRM 17 in the bypassed mode. At 14:40, during the startup, operators noted that IRM 16 was not responding to increasing reactor power. Both IRM 16 and IRM 17 are part of RPS Trip System 2.

IRM 16 was declared inoperable with the mode selection switch maintained in the Startup mode. IRM 16 troubleshooting did not identify any issues with cables, connectors, instrumentation power supplies, or IRM circuitry. The pre-amp was replaced and Post Maintenance Testing (PMT) was completed by verifying proper response at the drawer to a known voltage input.

After the successful PMT, IRM 16 was declared operable and the startup recommenced. After reaching IRM Range 1 power level, IRM 16 again did not respond to increasing reactor power. Power ascension was again stopped and all control rods were inserted to the full in position.

On July 21, 2007, a drywell entry was made to continue troubleshooting of IRM 16. Assistance from a nuclear instrumentation expert and a panel of experienced engineers was obtained. The troubleshooting team determined that IRM 16 detector had failed. The detector was replaced and IRM 16 declared operable at 19:50 on July 21 after successful PMT.

Reactor startup commenced at 23:48 on July 21, 2007, and all 8 IRMs responded as expected.

Analysis of the Event

There were no actual safety consequences associated with this event. The potential safety consequences of this event were minimal with a fully operable IRM trip channel available.

The initial troubleshooting on July 20, 2007, evaluated the nuclear instrumentation by performing Current-Voltage (IV) and Time Domain Response (TDR) testing with no issues identified with cables or connectors internal to or external of the Drywell. Based on these test results, it was incorrectly determined that the problem was not related to the detector or signal path. The high voltage power supply was verified to be approximately 150 V as expected. The pre-amp was replaced and PMT was conducted by applying a signal from a signal generator and verifying proper response at the drawer.

This step was one of the initial troubleshooting actions since IRM 16 did not spike or exhibit noise in the channel indicating a possible instrumentation problem . This activity was performed to simulate detector output as the reactor power was below the IRM range. In addition, a front panel test was performed as part of PMT with satisfactory results. IRM 16 was declared operable by Operations following recommendations from Maintenance and Engineering.

The plant startup was continued and subsequently stopped when IRM 16 did not respond to increasing neutron flux. All control rods were inserted and troubleshooting resumed.

Drywell entry was initiated to continue IRM 16 troubleshooting and effect repairs to both IRM 16 and IRM 17. During initial drywell entry, a complete stroke of IRM 16 was completed with acceptable results. Based on the recommendation of an outside expert in nuclear instrumentation diagnostics, the detector was replaced. After replacement of IRM 16, IV and TDR results were as expected and detector declared operable.

Cause of the Event

The cause for IRM 16 inoperability was a failure of the detector.

Corrective Action Completed.

Replaced IRM 16 detector and repaired IRM 17 instrumentation.

Corrective Action Planned.

Evaluate action plan to bring the Nuclear Instrumentation System back to Maintenance Rule (a)(2) status.

Evaluate the adequacy of IV and TDR testing at Oyster Creek to be able to identify this type of failure.

Provide training to engineers and instrument and control maintenance supervisors and managers to enhance testing and evaluation skills.

Previous Similar Occurrences There have been numerous previous detector failures in the industry including past failures at Oyster Creek Nuclear Generating Station.

Component Data.

Component: IRM Nuclear Instrument Cause: Detector Failure System: Neutron Monitoring Component: IRM Detector Manufacturer: GE Model number: 129B3192