Development of dynamics code and proposal of start-up procedure for accelerator driven system

A dynamics code for Accelerator Driven System (ADS) has been developed to analyze behaviors of a subcritical core coupled with an accelerator. This computer code named DSE (Dynamics calculation code system for Sub-critical system with External neutron source) is able to treat changes of the neutron source distribution produced by the spallation reactions, which have not been treatable by existing dynamics codes. The DSE code consists of the high energy part and the reactor part. For the high energy part, a database for neutron source distributions which were results of transport calculations in the high energy region was developed to treat the changes of beam parameters and target parameters. For the reactor part, the IBIS code which is a dynamics code for fast reactors was adapted for the core dynamics calculation. Some modifications were carried out to treat the dynamics calculation in a subcritical state with an external neutron source. The DSE was used to calculate various events from which new procedures for ADS operation control were investigated. From these calculation results, it was found that the change of the surface location of a heavy liquid metal target (target level) was useful to control the power from 0 to 100% with a gradual variation. A new procedure for the ADS start-up was proposed by using the change of the target level and beam intensity instead of the present one which is simply to start the accelerator only. The DSE and the proposed procedure will contribute to the research and development of the ADS. (author)