Simulation of the radiation transport and radiation field in decommissioned nuclear facilities

Following Germany's decision to phase out nuclear power by 2022, the question of the concrete implementation of the decommissioning of many nuclear reactors and the final disposal of nuclear waste has become particularly urgent. In order to solve this complex task effectively, the development and use of automated procedures for dismantling is necessary. In particular, the type and composition of the radioactive waste and the resulting radiation field must be clear in order to be able to take suitable local radiation protection measures. In this thesis a method is presented that uses two numerical methods for the neutron and photon transport calculation and couples them by a program routine developed whithin the framework of this work. MCNP6 is used to determine neutron fluence in the entire reactor block of a research reactor (FRJ-2) and a pressurized water reactor. The simulation program ORIGEN2 is used to calculate the source term and activity distribution. To achieve high simulation efficiency, advanced reduction techniques are used with the ADVANTG software package. A spatially resolved activity distribution within the biological shield is determined and the resulting dose rate is determined. In addition to the complete radiological characterization, conditions for recycling can be evaluated component by component and in dependence of the decay time. The dose rate field can also be adjusted to different decommissioning phases. With the development of the program routine presented here the preparation, evaluation and use of the resulting data will be considerably improved and accelerated by the automated methodology.