Consideration of change over time in nuclear accident consequence assessment to support optimization of long-term remediation strategy

•A framework to consider long-term evolution of nuclear accident consequences is proposed.•Monetization is a good way to capture various consequences to people & environment.•Decontamination dominates the overall accident consequence in the initial stage.•Radiation effects dominate the overall accident consequence in the late stage. Recent studies on nuclear accident consequence assessments that can cover consequences to both people and the environment, cannot capture the change of consequences over time, and vice versa. This study aims to design a framework of nuclear accident consequence assessment that can cover major consequences to people and the environment, and capture the long-term evolution of those consequences. Major long-term accident consequences are quantified using the cost per severe accident. Annual changes of key parameters are monitored to capture the change of each consequence over time. A case study with a hypothetical long-term loss of all AC power in a virtual BWR near Bangkok is conducted. Monitoring of the change of consequences over time leads to a different picture of overall accident consequences. Though decontamination takes up a large share of the cost per severe accident, its effects significantly decrease in several years. Radiation effects then dominate the overall accident consequences from the second decade onward. Parameter survey reveals the effectiveness of limiting and delaying decontamination in reducing the overall accident consequences in initial stage (first two years) and later stage (up to a decade), respectively. This time-dependent nuclear accident consequence assessment framework will be useful for long-term nuclear accident aftermath management planning.