Development of Radiological Performance Indicators for Nuclear Power Plants

INTRODUCTION The objective of radiation safety assessment of an operating nuclear power plant (NPP) is to assure that the licensee’s radiation protection program (RPP) has achieved the goal of radiation protection. For this, currently Korean regulatory safety inspection program is aimed at ensuring compliance with licensing requirements and regulations. The legislation requires that inspections be conducted to check the operability and reliability of the systems and the procedures of NPPs. However, with the growing number of NPPs in operation and limited regulatory resources such as manpower, it is necessary to make the regulatory inspection program to be more effective and more focused on safety related aspects. The efforts in new reactor oversight program have recently been made worldwide. In U.S.A, the nuclear regulatory commission (NRC), jointly with the Nuclear Energy Institute (NEI), has developed regulatory approaches employing risk-informed and performance-based regulatory oversight program (1). For radiation protection purpose, they have developed preliminary indicators for worker exposure and public exposure. It is reported that the radiological performance indicators covered those for normal operating conditions as well as anticipated abnormal conditions. The radiation safety of the public includes exposure from radioactive effluents, direct radiation exposure, the inadvertent release of radioactive material from the site and exposure from transportation of radioactive materials. In Canada, the Atomic Energy Control Board (AECB) has developed draft indicators with regard to health, safety, security, and environment (2). They intend to use performance data that can be demonstrated under the control of the AECB. The indicators cover safety-related performance areas of the plant, including operations, maintenance, worker safety, public safety and compliance. Of the indicators, radiation safety-related indicators are non-compliance with number of radiation protection procedures, radiation occurrence index, station whole body dose, frequency of exceeding operating emission levels. In Korea, the Korea Institute of Nuclear Safety (KINS) has been using the performance indicators to conduct the trend analysis (3,4). However, the indicators contain only two indicators directly related with radiological performance, i.e., the station collective dose and the amount of production and release of radioactive effluents. Recently the international radiation protection community has also published reports on the use of radiological performance indicators (5,6,7,8). The purpose of this work was to develop a regulatory approach to assess the licensee's performance in radiation protection at NPPs. In order to assess the radiation safety performance of an operating NPP, it is required to establish radiological performance indicators (RPIs) and the performance criteria related with each indicator. The trend analysis results of RPIs would enable the regulatory body to determine whether the occupational and public dose limits are exceeded and the operational restrictions are breached. The results would also enable the regulators to determine quantitatively whether the licensee’s radiation protection program has achieved the goal of ALARA (as low as reasonably achievable). Such an assessment using RPIs would provide a channel for communicating safety status between the regulator and the licensee as well as a tool for public understanding and acceptance. In this paper, we will discuss some premises and procedures in developing a set of draft RPIs as well as the results. The approaches in formulation and selection of the RPIs are in line with the international radiation protection goals and principles such as the recommendations of the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA).