RFX radiological analysis and testing for improved tokamak and deuterium operation mode

The RFX-mod device is a nuclear fusion facility based on the magnetic confinement of a plasma in the Reversed Field Pinch configuration, characterized by comparable toroidal and poloidal magnetic fields, with the toroidal field reversing near the edge. RFX-mod is equipped with a state-of-art active feedback control system of magnetic instabilities based don 192 saddle coils independently driven. Recently, such control system has been exploited to operate the device also as a Tokamak. In addition, the use of deuterium as feeding gas has been proposed. Such new operation regimes are likely to produce X radiation and neutrons. The licensing of the facility for the new operative configurations has been obtained at the end of 2012. At the completion of the licensing process a measurement campaing was performed to assess the good function of the radiological security systems. The two operation modes (tokamak and deuterium) were studied from the radiation protection point of view and both experimentally tested in two separated campaings. Special shielding requirements were evaluated for passages and ducts inside the controlled area. In both the experimental sessions, monitoring networks of passive dosimetric systems were placed in the areas designed to be accessible by personnel during the normal operation. Active monitors were used in parallel to control the spots more likely occupied by the staff. The testing process for the tokamak operation was performed with X and gamma ray monitors and dosimeters while for the deuterium operation also neutrons monitors and dosimeters were used. The short pulse of RFX-mod required specific measurement techniques, mainly for the counting integration with the active monitors. The results were completely acceptable for both the operation modes. The design assessment was confirmed with a security gap that is important for the operation to be initiated without any additional recommendation.