Aso, Tomokazu; Monde, Masanori*; Sato, Hiroshi; Hino, Ryutaro; Tatsumoto, Hideki; Kato, Takashi
Nippon Genshiryoku Gakkai Wabun Rombunshi, 5(3), p.179 - 189, 2006/09
no abstracts in English
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.
Harada, Masahide; Watanabe, Noboru; Teshigawara, Makoto; Kai, Tetsuya; Maekawa, Fujio; Kato, Takashi; Ikeda, Yujiro
LA-UR-06-3904, Vol.2, p.700 - 709, 2006/06
Pulse characteristics data for every neutron beam line are indispensable in designing devices for neutron scattering experiments of JSNS. A detailed model was built and pulse characteristics of each beam line were estimated using the PHITS code and the MCNP-4C code. These results have been disclosed on the J-PARC homepage since September 2004. Due to changes of moderator shapes in a progress of manufacture design, we observed from the calculation that pulse structures of decoupled moderators were deteriorated, especially, those of pulse tail. We found that this deterioration was caused by leakage neutron from gaps between decouplers and absorbing liners of the reflector. For a final stage of the manufacture design, we carefully tried to find other factors which deteriorated the pulse characteristics. Furthermore, pulse structures of poisoned and unpoisoned decoupled moderators were evaluated with the consideration of heterogeneous burn-up and leakage neutron spectra including high-energy region up to GeV were estimated for each neutron beam hole.
Hasegawa, Shoichi; Kato, Takashi; Aso, Tomokazu; Ushijima, Isamu*; Tatsumoto, Hideki; Otsu, Kiichi*; Ikeda, Yujiro
LA-UR-06-3904, Vol.2, p.402 - 407, 2006/06
In JSNS, the hydrogen of super critical state is adopted as moderators. Therefore the cryogenic hydrogen system is prepared, which consists of hydrogen circulating unit and transfer lines to moderators. The hydrogen system will immediately discharge hydrogen when an off-normal event occurs. In case of emergency, helium gas will be inputted to an insulation vacuum of the transfer line in order to enhance the heat transfer and the hydrogen discharge time should be shortened. Then, it is impotant to estimate the behaviour of pressure and velocity of discharging hydrogen in the emergency. During hydrogen discharge, the pressure rise in the discharge piping should be kept below the design pressure of 0.1 MPa. The result of analysis shows that the pressure of helium gas injection is suitable less than 0.04Mpa, and that the maximum hydrogen discharge flow is evaluated to be 0.047 kg/s after around 150 seconds. After five minutes with this condition, the hydrogen of around 90% in the moderator piping is discharged. Safety hydrogen release in the case of emergency can be established.
Aso, Tomokazu; Monde, Masanori*; Sato, Hiroshi; Tatsumoto, Hideki; Kato, Takashi; Ikeda, Yujiro
LA-UR-06-3904, Vol.2, p.385 - 394, 2006/06
no abstracts in English
Meigo, Shinichiro; Noda, Fumiaki*; Ishikura, Shuichi*; Futakawa, Masatoshi; Sakamoto, Shinichi; Ikeda, Yujiro
Nuclear Instruments and Methods in Physics Research A, 562(2), p.569 - 572, 2006/06
no abstracts in English
Harada, Masahide; Watanabe, Noboru; Konno, Chikara; Meigo, Shinichiro; Ikeda, Yujiro; Niita, Koji*
Journal of Nuclear Materials, 343(1-3), p.197 - 204, 2005/06
For a construction of maintenance and storage scenarios for JSNS, lives of structure material need to be estimated. DPA (Displacement per Atom) was a major index of radiation damage. So we evaluated DPA value of each component. Function of the DPA calculation was equipped to the PHITS code, which was particle and heavy ion transport code. For DPA calculation, displacement cross section was necessary. Displacement cross sections of neutron below 150 MeV were processed by the NJOY code from LA150 library and those of neutron above 150MeV and proton in the all energy region were obtained from energies of fragments calculated in the PHITS. By using the PHITS, we calculated DPA values and DPA mapping. We obtained that the peak DPA values at end of 5000MWh operation were 4.1 for target vessel, 2.8 for reflector and moderator vessels, and 0.4 for proton beam windows, respectively. We estimated the target life at 1 year and the moderator life at 6 year.
Hamon, 15(1), p.10 - 13, 2005/01
Most parts of the 1 MW pulsed spallation neutron source JSNS are regarded as radiation shield in complicated 3-D geometry. We have developed a shielding calculation method with a particle simulation code that is based on the Monte Carlo method. The method enabled us shielding designs for the 3-D shielding structure of JSNS with high accuracy. Basic structure of JSNS was optimized by the design calculations.
Tamura, Itaru; Aizawa, Kazuya; Harada, Masahide; Shibata, Kaoru; Maekawa, Fujio; Soyama, Kazuhiko; Arai, Masatoshi
Proceedings of ICANS-XVI, Volume 1, p.529 - 539, 2003/07
Moderator components of the McStas code have been created for the design of the spectrometers of JSNS. Three cryogenic moderators are adopted in JSNS, One is a coupled H moderator for high intensity experiments and other two are decoupled H with poisoned or unpoisoned for high resolution moderators. Monte Carlo simulations have turned out to be useful for design of neutron scattering instruments with high complexity. The software package McStas is selected for its own flexibility. Since the characteristics of neutron beams generated from moderators make influence on the performance of pulse neutron spectrometers, it is important to perform the simulation with neutron source component written precisely. Both Energy dependence of neutron spectrum and time structure of neutrons were calculated using NMTC/JAERI97 and MCNP4a codes.The simulation parameters, which describe the pulse shape as a function of time, are optimized. The creation of neutron source components viewed to coupled H moderator and viewed to decoupled H moderator of JSNS are reported.
Proceedings of ICANS-XVI, Volume 1, p.13 - 24, 2003/07
no abstracts in English
Harada, Masahide; Teshigawara, Makoto; Watanabe, Noboru; Kai, Tetsuya; Ikeda, Yujiro
Proceedings of ICANS-XVI, Volume 2, p.697 - 706, 2003/07
For two decoupled moderators in JSNS, optimization studies were performed by model calculations using NMTC/JAM and MCNP-4C codes. The model was based on a realistic Target-Moderator-Reflector Assembly. We assumed a para-hydrogen ratio of 100%. The shape of poisoned and unpoisoned moderators is a canteen type with dimensions of 13126.2 cm. A decoupling energy of about 1 eV was adopted to meet the user's requests. As a decoupler material we selected silver-indium-cadmium alloy. It was found that for the decoupled moderators, especially the poisoned moderator, pulse broadening due to a finite beam-extraction angle () was very serious. Therefore, for the poisoned and the unpoisoned moderators were limited to be 7.5 and 17.5, respectively. Cadmium (Cd) was selected as a poison material due to higher cut-off energy than gadolinium and higher peak intensity with narrower pulse width. The poison plate will be placed at 25 mm from the viewed surface which meets the user's requirements.
Harada, Masahide; Saito, Shigeru; Teshigawara, Makoto; Kawai, Masayoshi*; Kikuchi, Kenji; Watanabe, Noboru; Ikeda, Yujiro
Proceedings of ICANS-XVI, Volume 2, p.677 - 687, 2003/07
As a decoupler material for intense neutron sources, we proposed a new composite material based on the (n,) reaction, silver-indium-cadmium alloy (AIC), which had lettle helium gas production rate and higher decoupling energy (1eV). We compared an AIC decoupler with Cd and BC decouplers from various viewpoints and finally selected AIC as decoupler and liner materials. In the current design, we adopted AIC of 2.5mm thick with a composition of Ag-35wt%Cd and 0.5mm thick with Ag-15wt%In. A decoupler and a liner can be bonded to structural material (Al-alloy) by HIP for water cooling through Al-alloy. To find the optimal HIP condition, small pieces of Ag-Cd and Ag-In (202mm) were enclosed in Al-alloy capsules (22mm, 3mm thick bottom plate and 1mm thick cap) of several Al-alloys. The optimal condition was found to be 500C with a holding time of 60 minutes under a fixed pressure of 100MPa. Large pieces (Ag-Cd: 2002002.5mm, Ag-In: 2002000.5mm, A5083 and A6061: 21021021mm) were also tested aiming at more realistic size conditions.
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.
Center for Neutron Science; Advanced Science Research Center
JAERI-Review 2002-002, 40 Pages, 2002/03
no abstracts in English