Weimin Ma

I am a professor in nuclear power safety at the Department of Physics and the deputy head of the Division of Nuclear Science and Engineering at KTH.

My research and teaching focus on nuclear power safety. Nuclear power has been playing a critical role in low-carbon energy supply. Over a fifth of the electricity in the EU and a third of the electricity in Sweden were generated by nuclear energy in 2022. Safety is an absolute priority for nuclear power. It requires ensuring proper design and operation of nuclear power plants so that nuclear power should not contribute significantly to individual and societal health risks. It also requires preventing accidents and mitigating the consequences if an accident occurs. Nuclear power safety is therefore a multidisciplinary subject, involving multiphase/multi-physics analyses of accidents and sophisticated risk assessment.

Toward reducing the uncertainties in risk assessment of both existing and future nuclear reactors,  my research activities cover (i) basic understanding of physical phenomena which may appear in accidents of nuclear reactors, including boiling two-phase flow and heat transfer, as well as molten fuel coolant interactions; (ii) modeling of accident phenomena important to risk assessment to nuclear reactors; and (iii) performing safety analyses for nuclear power plants, from design basis accident (DBA) analysis for events which may occur in reactor lifetime, to beyond design basis accident (BDBA) analysis for low-probability, high-consequence events. The goal is to ensure that the risks of accidents in nuclear power plants are kept as low as reasonably achievable.

My group has been developing new knowledge (data, models, codes, methodologies, insights) in physical phenomena encountered in core meltdown accidents of nuclear power plants, the ones similar to the Fukushima accident which occurred in 2011. Simulant melt materials are employed in our experimental studies, to reveal the mechanisms and characteristics of melt coolant interaction, steam explosion, debris bed formation and cooling in such accidents. Models and computer codes are developed accordingly for reactor application. The research outcomes significantly improve our confidence in accident management measures intended to terminate/stabilize severe accidents postulated in risk assessment of existing nuclear power plants. In addition, we develop advanced methodologies and models for reactor safety analyses, such as best-estimate plus uncertainty (BEPU) methods, and coupled thermo-mechanical analysis of the reactor pressure vessel under core melt attack. We also conduct research on the safety of future reactors, including lead-cooled fast reactors (LFRs) and small modular reactors (SMRs).