Reducing the user burden when running MELCOR for accident analysis for a tokamak.

• Do version control of hand-written input decks. • Wrapper script to check output and monitor logs. • Substitution allows automated parameter sweeps. • Using batch system features gives better throughput. MELCOR is a software tool for accident analysis with a long history in the fission sector. A model has been developed for use in MELCOR, using proposed layouts of EU DEMO and assumptions based on current design choices, to facilitate safety design and development for fusion power plants. There seems however to be a misconception that MELCOR is difficult to run and that the tasks must be executed sequentially. Accident analysis also requires reruns of multiple slightly different scripts. We have streamlined the running of MELCOR tasks to allow simultaneous execution on a computing cluster. The input decks are version controlled within UKAEA's internal GitLab repository, and shell scripts wrap the separate MELCOR invocations, embed specific job parameters, and keep separate the inputs and outputs of multiple separate instances. We illustrate the streamlined running using two examples: a matrix representing potential responses to an incident by different valves, and a parameter sweep across a range of response times for a single valve. The new technique is shown to be a much faster method of carrying out sensitivity studies and allowing further investigations into specific areas of concern in more detail. [ABSTRACT FROM AUTHOR]