ML11364A046

Oconee, Unit 2 - Special Report Per Technical Specification 5.6.6, Problem Investigation Process Nos.: 0-11-13855, 0-11-14092

ML11364A046
Person / Time
Site:	Oconee
Issue date:	12/23/2011
From:	Gillespie T P Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
0-11-13855, 0-11-14092
Download: ML11364A046 (4)

Text

Duke T. PRESTON GILLESPIE, JR.Vice President hEnergy Oconee Nuclear Station Duke Energy ON0I VP / 7800 Rochester Hwy.Seneca, SC 29672 864-873-4478 864-873-4208 fax T. Gillespie@duke-energy.

com December 23, 2011 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

Duke Energy Carolinas, LLC Oconee Nuclear Station, Unit 2 Docket No. 50-270 Special Report per Technical Specification

5.6.6 Problem

Investigation Process Nos.: 0-11-13855, 0-11-14092 Pursuant to Oconee Nuclear Station (ONS) Technical Specification 3.3.8, Condition B and Technical Specification 5.6.6, enclosed is a special report regarding the inoperability of the ONS, Unit 2, Post Accident Monitoring System Containment Water Wide Range Level Transmitter 2PAMLT0090.

This transmitter performs a post-accident monitoring function per the Duke Energy Carolinas, LLC response to Regulatory Guide 1.97.The apparent cause of the failure was the failure of a switch internal to the transmitter.

This transmitter is located in containment and is inaccessible during normal operations.

Repairs will be made during the next reasonable opportunity, and no later than the next ONS, Unit 2 refueling outage.This event is considered to be of no significance with respect to the health and safety of the public.There are no regulatory commitments contained in this report. Any questions regarding the content of this report should be directed to Corey Gray, Oconee Regulatory Compliance at 864-873-6325.

Sincerely, T. Preston Gillespie, Jr.Vice President Oconee Nuclear Site Enclosure E MPJL www. duke-energy.

com Document Control Desk December 23, 2011 Page 2 cc: Mr. Victor McCree Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. John Stang Project Manager U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, DC 20555 Mr. Andrew Sabisch NRC Senior Resident Inspector Oconee Nuclear Station INPO (Word File via E-mail)

ENCLOSURE OCONEE NUCLEAR STATION, UNIT 2 SPECIAL REPORT 2011-01 Description of Condition:

On November 14, 2011, during startup from the 2EOC25 Refueling Outage, the Post Accident Monitoring (PAM) System Containment Water Wide Range Level Transmitter 2PAMLT0090 could not be calibrated and was determined to be inoperable.

Troubleshooting determined that an internal switch was open and was not functioning.

Following discovery of the transmitter inoperability, the available replacement level transmitter was determined to not be qualified to perform its function for the specified mission time.Subsequent evaluation determined that the replacement transmitter could be installed but would be operable but degraded/nonconforming (OBDN). However, the plant was in a configuration (Mode 2) that would not permit replacement by the time the determination was made. The opposite channel wide range level transmitter was declared OBDN since it is the same type of transmitter.

Both narrow range level transmitter channels are operable.Background The primary purpose of PAM instrumentation is to display unit variables that provide information required by the control room operators during accident situations.

This information provides the necessary support for the operator to take the manual actions for which no automatic control is provided and that are required for safety systems to accomplish their safety functions for Design Basis Events.The OPERABILITY of the PAM instrumentation ensures that there is sufficient information available on selected unit parameters to monitor and to assess unit status and behavior following an accident.The availability of PAM instrumentation is important so that responses to corrective actions can be observed, and so that the need for and magnitude of further actions can be determined.

These essential instruments are identified by the ONS specific Regulatory Guide 1.97 analysis, Updated Final Safety Analysis Report (UFSAR), Section 7.5, and the NRC's Safety Evaluation Report for the ONS Regulatory Guide 1.97 analysis which address the recommendations of Regulatory Guide 1.97, as required by Supplement 1 to NUREG-0737.

PAM variables are the key variables deemed risk significant because they are needed to:* Determine whether systems important to safety are performing their intended functions;" Provide information to the operators that will enable them to determine the potential for causing a gross breach of the barriers to radioactivity release; and" Provide information regarding the release of radioactive materials to allow for early indication of the need to initiate action necessary to protect the public and to estimate the magnitude of any impending threat.1 Containment Water Level Wide Range instrumentation is a Type B, Category 1 variable provided for verification and long term surveillance of Reactor Coolant System (RCS)integrity.

The Containment Water Level Wide Range instrumentation consists of two channels (2PAMLT0090 and 2PAMLT0091) with readout on two indicators and one recorder.

The indicated range is 0 to 15 feet. Additionally, the sump has two narrow range transmitters with an indication range of 0 to 3 feet.Cause of Inoperability The cause of the inoperable transmitter was equipment failure. The cause of the failure to return the transmitter to service within 30 days is inability to safely access the transmitter location while the plant is in operation.

Preplanned Alternate Method of Monitoring The opposite train PAM System Containment Water Wide Level Transmitter 2PAMLT0091 was determined to be operable but degraded/nonconforming and both trains of the Containment Sump Water Narrow Level Transmitter were determined to be operable.Plans and Schedule for Restoring Operability The failed 2PAMLT0090 will be replaced during the next reasonable opportunity, and no later than the next scheduled Unit 2 refueling outage.2