Europe and China unite to investigate severe accident scenarios in nuclear power plants
ALISA (Access to Large Infrastructures for Severe Accidents) benefits both parties: China has one of the most rapidly growing nuclear programmes in the world and ALISA was a one-of-a-kind opportunity to access Europe’s expertise and well-established experimental network. European researchers, on the other hand, were provided access to Chinese facilities and use them to launch new research avenues. The stakes are high. Experimental research on severe accidents is of high importance not only to proof established knowledge, but also to elucidate new phenomena. It provides data for code development and enriches guidelines for severe accident management. The problem is, such research requires international cooperation, as the nature of severe accident phenomena usually relates to high temperature and large amounts of prototypical corium, and its complex chemical and physical interactions with the environment. “Severe accident research often relates to complex problems involving significant human and financial resources, to the point where investigation under a national programme is just not feasible,” explains Dr-Ing Xiaoyang Gaus-Liu, technical coordinator of ALISA and Head of the Severe Accident Research Group (SAR) at Karlsruhe Institute of Technology (KIT), Germany. “Thanks to ALISA, we could access a wide network of existing experimental rigs necessary to conduct severe incident research, gather research topic proposals from researchers within the network and select the best ones for experiments.” Cooperation from East to West ALISA was actually made up of two financially independent projects, one in Europe and one in China, which both provided a similar scale of experimental programmes for mutual access. The selected large-scale experiments focused on remaining R&D issues related to severe accident management in light-water reactors. Most high-priority research issues, from early core degradation to late in-vessel phase melt retention in the lower head, continuation to ex-vessel fuel-coolant interaction, and hydrogen behaviour in containment, were investigated. A total of 12 experiments were conducted under the project, with each bringing its own valuable findings. “These experiments provide scaling data for in-vessel corium behaviour and H2 combustion character in containment, indicate the multiple criteria for ex-vessel cooling of corium in-vessel, and highlight important thermal-physical properties of corium in different scenarios. On fuel-coolant interaction, we notably discovered a two-stage pressurisation during the release of corium in water,” says Dr-Ing Gaus-Liu. In Fukushima’s shadow If there is one thing Fukushima has taught us, it’s that no matter how costly it is, severe accident research is well worth the trouble. The nuclear disaster also reminded Europe of the potential powder keg it was sitting on: a long list of ageing nuclear power plants posing serious security concerns. Thanks to ALISA, research on potential accidents has been considerably advanced and severe accident management has taken a leap forward. Further cooperation with Chinese institutes is already being considered, either under a follow-up EU project or through a bilateral cooperation agreement.
Keywords
ALISA, China, Europe, severe accident, nuclear, core quenching, core melt cooling, hydrogen, experimental rig, KIT
