Efforts towards improvement of systems codes for the Broader Approach DEMO design

We report our recent efforts towards improvement of systems codes for the Broader Approach DEMO design, i.e. benchmarking the two systems codes the Japan and EU home teams are developing independently. The main result is that most of calculated outputs from the two codes are in good agreement. The main disagreement in the current benchmarking is the calculated radiation power losses from the plasma. Close examination shows that this is due to differences in the impurity radiation and transport models. Some issues for development/improvement of systems codes relevant to DEMO plasma physics are discussed.