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Report No.

Thin slit streaming experiment for ITER by using D-T neutron source

Ochiai, Kentaro; Sato, Satoshi; Wada, Masayuki*; Kubota, Naoyoshi; Kondo, Keitaro; Yamauchi, Michinori; Abe, Yuichi; Nishitani, Takeo; Konno, Chikara

Neutron streaming experiments have been conducted by using the FNS D-T neutron source at Japan Atomic Energy Agency under the ITER/ITA Task 73-10 in order to evaluate effects of the slit on nuclear properties and validate prediction accuracies on numerical simulations. The experimental assembly with a slit of 2 cm in width and 55 cm in depth was prepared with two iron blocks of 30 cm in height, 100 cm in width and 55cm in thickness as first campaign. The slit was located in the 12-cm upper part from the D-T neutron source point. In order to evaluate distributions of the neutron fluxes along the slit as a function of the depth from the assembly surface, fission reaction rates were measured by U-238 and U-235 micro-fission chambers. The experimental accuracies of these fission reaction rates are within 5%. Monte-Carlo calculation code, MCNP-4c, was used to calculate the U-238 and U-235 reaction rates and neutron energy spectra due to each measured position. From our first experiment, the following facts were found: (1) At d = 20 and 40 cm, reaction rates on U-238, which represent fast neutron flux, decreased by about three orders of magnitude along slits with 50 cm in depth. Monte Carlo calculation results agree well with measured values within 6 %. (2) Reaction rates on U-235, which represent thermal neutron flux, decrease by about one order of magnitude along slits with 50 cm in depth. Values of C/E of U-238 and U-235 reaction rates were 1.10-1.22 and 1.10-1.23 respectively and the calculated values overestimated slightly.



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Category:Nuclear Science & Technology



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