Simulation of the background for detection system in the indoor environments of concrete buildings

Tsutsumi, Masahiro; Oishi, Tetsuya; Kinouchi, Nobuyuki; Sakamoto, Ryuichi; Yoshida, Makoto

Journal of Nuclear Science and Technology, 38(12), p.1109 - 1114, 2001/12

https://doi.org/10.3327/jnst.38.1109

In order to predict the indoor background spectra to gamma detection systems, the gamma radiation field in a concrete building is studied by the Monte Carlo simulations. The parameters of wall thickness, room shape and dimensions were considered in the modeling. The indoor source geometry was simulated by a spherical layer model with the intention of easy and effective calculations. The model was applied to an unshielded germanium detector and the detection system with a more complex shielding configuration. As the results, we found that the indoor radiation field in concrete buildings can be predicted well with the source geometry of a spherical concrete layer of 25cm thickness and with the source of the natural major three components of the U series, Th series and K that are homogeneously distributed. The simulation model is useful for designing and optimizing gamma detection systems or shielding assemblies.

Development of a spherical NE213 spectrometer with 14 mm diameter

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JAERI-M 84-124, 43 Pages, 1984/07

JAERI-M-84-124.pdf:1.58MB

A 14 mm diameter spherical NE213 spectrometer has been developed for applying to fusion neutronics experiments. It is used to measure the fast neutron spectra in assemblies of various materials irradiated with 14 MeV neutrons. The characteristics of neutron gamma-ray discrimination was investigated, and it was found that the wall-escape of recoil protons produced in the detector should be treated carefully in the case of a small size detector such as this one. Response matrix for spectrum unfolding has been calculated by a Monte Carlo code. Calculated response for 14 MeV neutrons agreed well with measured one. The present spectrometer was applied to in-system neutrons spectrum measurements in a lithium-oxide assembly bombarded by D-T neutrons. The spectra obtained by unfolding were compared with the results calculated by the neutron transport code DOT3.5, and with reaction rates measured by fission counters and activation detectors. Consequently it has been demonstrated that the spectrometer is very useful for fusion neutronics experiments.