ML13009A329
| ML13009A329 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/07/2013 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Special Report 12-01 | |
| Download: ML13009A329 (4) | |
Text
'L Duke 16Energy January 7, 2013 T. PRESTON GILLESPIE, Jr.
Vice President Oconee Nuclear Station Duke Energy ON01 VP / 7800 Rochester Hwy.
Seneca, SC 29672 864-873-4478 864-873-4208 fax T. Gillespie@duke-energy. com U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station, Unit 3 Docket No. 50-287 Special Report 2012-01 per Technical Specification 5.6.6 Problem Investigation Process No.: 0-12-13808 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 3 Inadequate Core Cooling Monitor (ICCM) Train B Pressurizer Level Indication. This level indication performs a post-accident monitoring function per the Duke Energy Carolinas, LLC response to Regulatory Guide 1.97.
The apparent cause of the inoperability was the failure of the pressurizer resistance thermal detector (RTD) 3RC RD0043B. The RTD provides pressurizer water temperature indication to ICCM Train B, which uses that input to temperature compensate the pressurizer level indication.
This RTD is located in containment and is inaccessible during normal operations, The repairs will be made during the next reasonable opportunity, and no later than the next ONS Unit 3 refueling outage.
This event is considered to be of no significance with respect to the health and safety of the public.
This submittal contains no new regulatory commitments. Any questions regarding this report should be directed to Corey Gray, Oconee Regulatory Affairs Group at 864-873-6325.
Sincerely, T. Preston Gillespie, Jr.
Vice President Oconee Nuclear Site Enclosure www. duke-energy. corn
Document Control Desk January 7, 2013 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 Boska Project Manager U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 C2 Rockville, MD 20882-2738 NRC Senior Resident Inspector Oconee Nuclear Station
ENCLOSURE OCONEE NUCLEAR STATION, UNIT 3 SPECIAL REPORT 2012-01 Description of Condition:
On November 24, 2012, while performing operator rounds, it was noticed that the Pressurizer temperature 3B was reading 7 degrees less than temperature 3A on the Dixon indicators.
Looking at the Operator Aid Computer (OAC) trends, OAC indication had dropped 4 degrees in August and on 11/23/2012 at 20:00 it dropped another 2 degrees. Per procedure guidance the surveillance requires the temperatures to be within 7 degrees. The OAC indication now indicated a 6.5 degree separation with a downward trend. The Senior Reactor Operator (SRO) decision making process was implemented and the decision was made to declare the 3B ICCM Pressurizer Level Train Out of Service (OOS) at 0948 on November 24, 2012.
Background:
The primary purpose of the Post Accident Monitoring (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 the 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, 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.
Pressurizer Level instrumentation is a Type A, Category 1 variable used in combination with other system parameters to determine whether to terminate safety injection (SI), if still in progress, or to re-initiate SI if it has been stopped. Knowledge of pressurizer water level is also used to verify the unit conditions necessary to establish natural circulation in the RCS and to 1
ENCLOSURE OCONEE NUCLEAR STATION, UNIT 3 SPECIAL REPORT 2012-01 verify that the unit is maintained in a safe shutdown condition. The Pressurizer Level instrumentation consists of two channels (Train A channel consisting of two indications and Train B channel consisting of one indication) with two channels indicated and one channel recorded.
Cause of Inoperability:
The cause of the inoperable level indication was equipment failure. The cause of the failure to return the level indication to service within 30 days is inability to safely access the RTD location while the plant is in operation.
Preplanned Alternate Method of Monitoring The Pressurizer Level indication for train A is still operable.
Plans and Schedule for Restoring Operability The failed RTD will be replaced during the next reasonable opportunity, and no later than the next scheduled Unit 3 refueling outage.
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