Research study to advance irradiation field characterization method of Joyo MK-III core, 2; Evaluation of neutron irradiation condition by mean of neutron dosimetry

Maeda, Shigetaka   ; Ito, Chikara   ; Aoyama, Takafumi ; Saikawa, Takuya*; Masui, Tomohiko*

In 2003, Joyo MK-III core was upgraded to increase the irradiation testing capability. This paper describes the details of distributions of neutron flux and reaction rate in the MK-III core that was measured by characterization tests during the first two operating cycles. The calculation accuracy of the core management codes HESTIA, TORT and MCNP, was also evaluated by the measured data. The calculated fission rates of U by HESTIA agreed well with the measured one within approximately 4% in the fuel region. MCNP could simulate within 6% in the central non-fuel irradiation test subassembly and the radial reflector region, while large discrepancies were obtained in TORT results. Hence, the precise geometry model was effective in evaluating the neutron spectrum and the flux at such locations.