Dosimetry technique to characterize neutron field of JOYO MK-II

Maeda, Shigetaka   ; Saikawa, Takuya*; Aoyama, Takafumi 

Neutron fluence and related spectral information are key parameters in post-irradiation test analysis so they need to be evaluated accuracy. Nuclear calculations and a number of reactor dosimetry tests have been conducted in the JOYO experimental fast reactor to assure reliable and accurate neutron fluence for fuel and material irradiation tests. This paper describes the multiple activation foil dosimetry technique for neutron fluence evaluation. Neutron fluence was determined with neutron spectrum adjustment using measured reaction rates of a set of activation foils. Dosimetry results from individual fuel and material irradiation tests and a surveillance test characterized the neutron field of the JOYO MK-II core. Neutron flux in the JOYO core region was calculated using diffusion theory in a three-dimensional Hex-Z geometry. Flux in the stainless steel reflector region, which is outside the core, was calculated using the DORT two-dimensional transport calculation code. It is essential to correct the dosimetry results for locations far outside the core region. With corrected values, the calculated to experimental value (C/E) was approximately 1.05 in the core region and 1.11.5 in the reflector region.