SEVERE ACCIDENT RESEARCH AT ITU, KARLSRUHE: A REVIEW OF PAST EXPERIENCE AND ITS APPLICATION TO FUTURE CHALLENGES

摘要

With the current situation in Japan it is worthwhile to examine previous research into severe accidents and the current state of European severe accident research to assess what are the priorities for research for Japan, Europe and the rest of the world for existing and even future nuclear reactors. The European Commission's SARNET 2 (Severe Accident NET work of Excellence) programme and its SARP (Severe Accident Research Priorities) assessments have been made and have outlined the future needs as seen from the EU point of view. There is considerable research already carried out that will be very valuable in analysing and guiding the investigation and remediation activities at Fukushima Dai-ichi. This includes investigations into previous major accidents and international severe fuel damage projects. There are facilities using analogue materials to analyse large-scale behaviour of materials as well as smaller-scale testing of irradiated fuel and nuclear materials for detailed property measurements that are important for mechanistic studies. The final (and very important) aspect is application of this information to formulate codes to model the identified mechanisms and also to have their predictions validated by the data. This paper will take examples from ITU's contribution to projects such as the TMI-2 accident investigation and the Phebus PF bundle and fission product deposit investigations as well as some of the smaller scale testing and modelling that ITU has performed over the last 20 years. This will show what has been learnt about fuel and structural material degradation and formation of molten materials, fission product release, and subsequent behaviour.