DEVELOPMENT OF A MODEL BASED ASSESSMENT PROCESS FOR QUALIFICATION OF EMBEDDED DIGITAL DEVICES IN NPP APPLICATIONS: RESEARCH APPROACH AND CURRENT STATUS

摘要

The instrumentation and control (I&C) equipment used in currently operating U.S. nuclear power plants (NPPs) is primarily based on mature analog technologies that are progressing towards obsolescence. The continued reliance on this legacy analog technology, which is also being propagated into new NPP designs, imposes performance penalties and maintenance burdens in comparison with modern digital I&C instrumentation. In many instances, currently available I&C equipment contain embedded digital devices (EDDs) such as microprocessors and programmable logic devices. Experience in other industries, such as avionics, has shown that digital I&C equipment containing EDDs can provide significant benefits over analog-based equipment in terms of performance, reliability, and maintainability. In recent years, due to the high demand for digital technologies in the industrial l&C marketplace, it is becoming increasingly difficult for NPPs to acquire instrumentation that is not equipped with an EDD. However, the nuclear power industry has been slow to adopt digital technology, especially in safety-related systems, in large part as a result of regulatory concerns about common-cause failure (CCF) vulnerabilities of equipment with EDDs. Consequently, there is a clear need to develop cost effective qualification methods to contribute to the assessment of CCF vulnerability posed by EDDs in modern instrumentation that could be used in NPPs. This paper describes the research regarding qualification methods for equipment with EDDs that is sponsored by the Nuclear Energy Enabling Technologies (NEET) Advanced Sensors and Instrumentation (AS1) program of the U.S. Department of Energy (DOE). The purpose of the current research is to develop an effective approach employing science-based methods to resolve concerns about CCF vulnerability that serve to inhibit deployment of advanced instrumentation (e.g., sensors, actuators, microcontrollers) with EDDs in nuclear power applications.