Analysis of irradiation experiments with activated water radiation source at the JSI TRIGA Research Reactor

Abstract

Abstract Activated cooling water in nuclear facilities can present a significant radiation source around primary cooling system causing radiation damage to electrical components, increasing doses to personnel and in the case of fusion facilities additional heating to superconducting coils. As currently no fusion reactors fusing deuterium and tritium are capable to perform water activation experiments with sufficient accuracy, fission research reactors present an opportunity to study the effects of activated water decay that can be extrapolated to fusion reactors. An irradiation system using activated cooling water as the source of energetic gamma rays is proposed at the Jožef Stefan Institute TRIGA Mark II research reactor. The conceptual designs utilizing radial piercing port for water activation is presented and analysed in the paper. At reactor full power and the maximum flow rate of 1 l/s the 16 N decay rate in the irradiation facility was calculated to be around 1.7 × 10 8 s−1 which will produce ambient dose equivalent rates up to 2 mSv/h. The proposed irradiation facility will allow shielding characterization at high gamma energies. An analysis of shielding experiment with fusion relevant materials, such as tungsten, Eurofer, SS 304L, etc., which can be implemented in the proposed water activation facility was performed. From all analysed material SS 304L and Eurofer are the best candidate materials for shielding around primary cooling water in fusion reactors to reduce additional nuclear heating to superconducting coils and other important tokamak components. From the analysis it can be concluded that around 30 cm of SS 304L or Eurofer is needed to reduce the high energy gamma ray flux by half.