On-Line Monitoring for Calibration Extension: An Overview and Introduction to NUREG/CR-6895, "Technical Review of On-Line Monitoring Techniques for Performance Assessment"

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Publication Information

Date Published: May 2009

Prepared by:
J.W. Hines
Department of Nuclear Engineering
University of Tennessee
Knoxville, TN 37966-2210

Paul Rebstock, NRC Project Manager

Prepared for:
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Objectives and Document Organization

The three volume NUREG/CR-6895 series was developed to provide background, technical guidance and explore implementation issues related to the use of On-Line Monitoring (OLM) for the extension of safety critical sensor calibration intervals.

Volume 1, entitled "State of the Art", provides a general overview of sensor calibration monitoring technologies and their uncertainty analysis, a review of the supporting information necessary for assessing these techniques, and a cross reference between the literature and the requirements listed in the NRC Safety Evaluation Report: "Application of On-Line Performance Monitoring to Extend Calibration Intervals of Instrument Channel Calibrations Required by the Technical Specifications" which was published in 2000 [NRC Project no. 669, 2000].

Volume 2, entitled "Theoretical Issues", provides an evaluation of the application of the most commonly employed OLM methods. In empirical, model-based OLM, current measurements are applied to an algorithm that uses historical plant data to predict the plant’s current operating parameter values. The deviation between the algorithm’s predicted parameter values and the measured plant parameters is used to detect any instrument faults, including instrument drift. Many algorithms can be used to accomplish OLM; however, only auto-associative neural networks (AANN), auto-associative kernel regression (AAKR), and auto-associative multivariate state estimation technique (AAMSET) are presented in that report. Those techniques were chosen because they were either considered by Electric Power Research Institute's (EPRI) OLM working group that started in the 1990s, applied in EPRI’s OLM Implementation Project which began in 2001, or are available as commercial products.

Volume 3 entitled "Limiting Case Studies", explore assumptions inherent in the model and other special limiting cases. The case studies reported in Volume 3 apply the modeling and uncertainty analysis techniques described in Volume 2 to a wide variety of plant data sets to consider the effects of these modeling assumptions and limitations.

The purpose of this document is to provide a summary and overview for NRC staff using the NUREG/CR-6895 series as an aid to verify conformance with the previously cited regulatory basis and standards in the acceptance of an OLM system for safety-critical sensor calibration extension. Part A provides general OLM background information. Section 1 provides a very brief introduction to OLM. Section 2 outlines the regulatory basis that applies to OLM. Section 3 describes the guidance manuscripts already available for OLM. Part B presents information related to the NRC review and approval of an OLM system. Section 1 offers a brief introduction. Section 2 presents OLM topics and issues which are critical for the implementation of an OLM system. Section 3 describes some OLM activities which should be addressed for regulatory acceptance. Finally, Section 4 examines some acceptance criteria which an OLM system should meet in order to be considered for regulatory approval.

This document is an overview of NUREG/CR-6895. The actual guidance is contained within the three volumes of NUREG/CR-6895. No regulatory decisions or evaluations should be made on the basis of this document alone.

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