In 2012, ultrasonic in-service inspections revealed an extensive number of flaw indications in the base metal of the Reactor Pressure Vessels (RPV) of Tihange 2 und Doel 3. As consequence, the Belgian regulatory authority FANC required the licensee re-demonstrate the safety of both reactors. This re-evaluation has been accepted in 2016 and FANC gave permission to resume operation for up to 40 years. There are differing views among experts, whether or not the RPV of Tihange 2 is safe for accident conditions.
The present work therefore postulates a RPV failure, which is a beyond design basis accident. The analysis, based on engineering judgment, showed that containment failure and severe core degradation as consequence of RPV failure are likely, or at least, cannot be excluded at the current state of knowledge. In a second step, potential radiological consequences for Aachen following a large release at the Tihange 2 NPP were evaluated using results of the FlexRISK project. Two types of results from this project – a single, unfavorable weather situation to present a bounding case and the weather-related probability of deposition – are discussed in this paper.
It can be shown that the expected lifetime dose from such an accident at the assumed unfavorable weather conditions for a citizen of Aachen is 20 times higher than the value specified in the German radiation protection ordinance. The calculated dose for a seven-day exposition following the accident, with release at the chosen date, would require an evacuation of the Aachen-area according to the German intervention limits. This impact on Aachen could be compared to that of towns within the 20km exclusion zone of Fukushima. Evaluating a set of representative weather conditions it could be shown that the weather-related probability of deposition is unfavorable for Aachen and the western part of Germany.