Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Maekawa, Fujio; Oikawa, Kenichi; Tamura, Masaya; Harada, Masahide; Ikeda, Yujiro; Watanabe, Noboru
LA-UR-06-3904, Vol.1, p.129 - 138, 2006/06
Total 23 neutron beam-lines will be installed for JSNS in the J-PARC project. One of them is assigned for the Materials and Life Science Facility (MLF), and the MLF will construct a neutron beam-line to demonstrate and monitor neutronic performance of JSNS. The neutron beam-line was accordingly named as "Neutron Beam-line for Obserbation and Research Use (NOBORU)". Major parts of the NOBORU, i.e., beam ducts, shield, a beam stop, slits, a cabin for measurement, a pillar crane, a sample table, etc., have been ordered in March 2004, and installation will be completed in 2007. A T0 chopper, a frame-overlap chopper, detector systems, samples, etc. will be ordered later on. The sample position is at 14 m from the decoupled moderator. Approximate sample room dimensions are 3 
2.5 m in area and 3 m in height. A shield structure was determined by shielding calculations in which detailed 3-D structure was considered. The design of NOBORU will be presented in the session.
Oikawa, Kenichi; Maekawa, Fujio; Tamura, Masaya; Harada, Masahide; Kato, Takashi; Ikeda, Yujiro; Niita, Koji*
LA-UR-06-3904, Vol.2, p.139 - 145, 2006/06
A preliminary investigation on a satellite building for a long-beamline instrument of MLF is now in progress. In order to estimate the total cost of the building, we started the shielding analysis of the beamline using MCNPX and PHITS, where the latest beamline design and the neutron spectrum have been adopted.
Tamura, Masaya; Maekawa, Fujio; Harada, Masahide; Haga, Katsuhiro; Konno, Chikara
JAERI-Tech 2005-020, 58 Pages, 2005/03
JAERI-Tech-2005-020.pdf:18.82MB
no abstracts in English
Maekawa, Fujio; Tamura, Masaya
Proceedings of ICANS-XVI, Volume 3, p.1051 - 1058, 2003/07
A three-dimensional (3-D) shielding calculation model for MCNPX was produced for shielding design of 1-MW JSNS. The model included simplified target-moderator-reflector assembly, helium-vessel and neutron beam extraction pipes, shutters, shield blocks, gaps and void spaces between these components, and so on, and could treat streaming effects precisely. The particle splitting and kill method with cell importance parameters was adopted as a variance reduction method. The cell importance parameters for such a large target station of about 15 m in diameter and 12 m in hight in which neutron fluxes attenuated more than 12 orders of magnitude could be determined appropriately by automated iteration calculations. This calculation procedure enabled detailed 3-D shielding design calculations for the whole target station in a short time, i.e., within 2 days, and contributed for progress of shielding designs of JSNS.
Maekawa, Fujio; Tamura, Masaya; Kawai, Masayoshi*; Furusaka, Michihiro*; Watanabe, Noboru
Proceedings of ICANS-XVI, Volume 3, p.1247 - 1255, 2003/07
A method for neutron-beam-line shielding calculation with a Monte Carlo code was newly developed. In the first step, components inside the biological shield such as a target-moderator-reflector-assembly and a neutron-beam-line were modeled, and a neutron current distribution along a duct of the neutron-beam-line was calculated. In the second step, decreases of neutron current along the beam-line were regarded as source terms for the beam-line shield, and required beam-line shield thickness was calculated. The most remarkable feature of this method was accurate treatment of the neutron source term distribution along the beam-line in the second step calculation. The followings were evaluated for JSNS by applying this method: (1) neutron-beam-line shield thickness with an empirical formula for estimating shield thickness conveniently, (2) beam stop sizes, (3) dose rates at a sample position when a shutter was closed, and (4) activation level of a To-chopper blade. These results gave conditions for determining the layout of 23 neutron-beam-lines in the experimental hall.
Tamura, Masaya; Maekawa, Fujio
JAERI-Tech 2003-010, 54 Pages, 2003/03
JAERI-Tech-2003-010.pdf:7.97MB
Evaluation of shielding performance for a spallation neutron source facility in the J-PARC Project is important from a viewpoint of radiation safety and optimization of arrangement of components. This report describes evaluated results for the shielding performance with modeling three-dimensionally whole structural components including gaps between them in detail. A Monte Carlo calculation method with MCNPX2.2.6 code and LA-150 library was adopted. Streaming and void effects, optimization of shield for cost reduction and optimization of arrangement of structures such as shutters were investigated. Horizontal required shield thicknesses were ranged from about 6.5m to 7.5m as a function of neutron beam line angles. A shutter mechanism for a horizontal neutron reflectometer that was directed downward was devised, and it was shown that the shielding performance of the shutter was acceptable. An optimal biological shield configuration was finally determined according to the calculated results.