A Brief Comparative Study on Stress Tests Specifications of the EU and Korea

After Fukushima accident, stress tests are considered as an important evaluation method for ensuring the safety of NPPs under extreme natural disasters beyond Design Basis Accident (DBA) together with post-Fukushima action items and the development of Accident Management Plans (AMPs). Successful implementation of stress tests will ensure nuclear safety on extreme conditions and improve public acceptance. Stress tests of the two NPPs were also a prerequisite for the extended operations of the two plants. Stress tests have been carried out in accordance with the specifications provided by the Nuclear Safety and Security Commission (NSSC). As a result of the stress tests, 14 and 19 action items were derived for Kori unit 1 and Wolsong unit 1, respectively and implementation action items have been conducted. In 2016, the NSSC decided to apply the stress tests to all operating NPPs in Korea. The stress tests in Korea are based on the evaluation method of the stress tests conducted by the European Union (EU) after the Fukushima accident. KHNP aims to verify and reinforce the safety margins of all operating NPPs in Korea against extreme disasters exceeding DBA through the tests. Stress tests in Korea are based on the EU case. However, NSSC have developed more enhanced specifications. Major improvements are as follows. First, the scope of the evaluation was further diversified. Unlike the EU specifications that only assumed earthquakes and flooding in initiating events, KHNP evaluated various natural disasters such as fire, strong winds and rising water temperature. In the areas of 'loss of safety function' and 'severe accident management', more conservative and strengthened safety are pursued by assuming simultaneous accidents of multiple reactors on the same site by extreme natural disasters. In addition, emergency preparedness area has been newly added to evaluate the resident protection measures. Operational management capability area was also introduced to improve the reliability of verification. Second, Korea pursued the objectivity and reliability of review by including civil experts as well as the regulatory body in the review process.