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Journal Articles

Analysis of organ doses from Computed Tomography (CT) examination by the radiation transport calculation to develop the dosimetry system, WAZA-ARI

Takahashi, Fumiaki; Endo, Akira; Sato, Kaoru; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ono, Koji*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

Progress in Nuclear Science and Technology (Internet), 1, p.517 - 520, 2011/02

Several dose assessment system were developed to avoid unnecessary exposure for a patient in a Computed Tomography (CT) examination. Most of these systems contain datasets of organ doses, which had been calculated with mathematical phantoms. The numerical analyses for radiation dosimetry and CT machines have progressed in recent years. Thus, a project is being carried out to develop a new dosimetry system, named WAZA-ARI. The basic data of organ doses are calculated with a male voxel phantom (JM phantom), which defines configurations of the human body more precisely than the mathematical model. The radiation transports in CT examination can be simulated with the Particle and Heavy Ion Transport code System, PHITS. A source model can be set up for emissions of photons from the X-ray tube with a subroutine, including the helical scanning. Thus, the WAZA-ARI system can assess radiation dose based upon the organ doses, which are calculated with the appropriate source and human models.

Journal Articles

Experimental method for neutron elastic scattering cross-section measurement in intermediate energy region at RCNP

Satoh, Daiki; Iwamoto, Yosuke; Hagiwara, Masayuki*; Iwase, Hiroshi*; Yashima, Hiroshi*; Sanami, Toshiya*; Sato, Tatsuhiko; Endo, Akira; Sakamoto, Yukio; Nakane, Yoshihiro; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.20 - 23, 2011/02

An experimental method and data processing procedure have been developed for the measurement of neutron elastic scattering cross sections in intermediate energy region above 100 MeV. The data were obtained at Research Center for Nuclear Physics (RCNP) in Osaka University by utilizing a $$^{7}$$Li(p,n) quasi-monoenergetic neutron source and Time-of-Flight (TOF) technique.

Journal Articles

Fluence-to-dose conversion coefficients for aircrew dosimetry based on the new ICRP recommendations

Sato, Tatsuhiko; Endo, Akira; Zankl, M.*; Petoussi-Henss, N.*; Yasuda, Hiroshi*; Niita, Koji*

Progress in Nuclear Science and Technology (Internet), 1, p.134 - 137, 2011/02

We calculated the dose conversion coefficients for the 2 irradiation geometries; one is for the semi-isotropic irradiation from the upper hemisphere, and the other is for exactly representing the geometrical condition of aircrew exposure, whose angular distribution was estimated from the atmospheric propagation simulation of cosmic-rays performed by PHITS.

Journal Articles

Development of the quasi-monoenergetic neutron calibration fields of several tens of MeV at TIARA

Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro; Uchita, Yoshiaki; Yoshizawa, Michio

Progress in Nuclear Science and Technology (Internet), 1, p.166 - 169, 2011/02

For the reliable dose evaluation in high intensity proton accelerator facilities such as J-PARC, high energy neutron calibration fields above 20 MeV to evaluate energy response of both the monitors and the dosimeters used there, are required. Therefore, development of three neutron calibration fields of 45, 60 and 75 MeV has been in progress at TIARA of JAEA-Takasaki. Evaluation of the neutron fluence and establishment of the monitoring technique are important for the development of the calibration fields. Here, results of the fluence evaluation in the absolute measurement by using proton recoil counter telescope with high detection efficiency, a transmission type neutron fluence monitor newly developed to monitor neutron beam directly and its performance will be reported.

Journal Articles

Study of neutron and photon production cross sections for second cancer risk assessment in heavy-ion therapy

Uozumi, Yusuke*; Iwamoto, Hiroki*; Koba, Yusuke*; Matsufuji, Naruhiro*; Sanami, Toshiya*; Satoh, Daiki; Shigyo, Nobuhiro*; Takada, Masashi*; Ueyama, Masahiko*; Yoshioka, Masakatsu*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.114 - 117, 2011/02

It is important to assess and suppress the potential for second cancer induction by secondary neutrons produced in primary heavy-ion fragmentation in patient body. Since it is very difficult to measure high-energy neutron doses in mixed radiation fields, a Monte-Carlo simulation approach has attracted much attention as an alternative for neutron dose estimation. It is notoriously hard to reproduce the spectral cross sections of neutrons from high-energy heavy-ion collisions. We, therefore, have planned experiments to measure energy-angle double-differential cross sections of nuclear reactions.

Journal Articles

Measurement of neutron cross sections for yttrium and terbium at 287 MeV

Sekimoto, Shun*; Utsunomiya, Takashi*; Yashima, Hiroshi*; Ninomiya, Kazuhiko*; Omoto, Takashi*; Nakagaki, Reiko*; Shima, Tatsushi*; Takahashi, Naruto*; Shinohara, Atsushi*; Kinoshita, Norikazu*; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.89 - 93, 2011/02

In this work, we tried to determine reaction cross sections for Y and Tb induced by neutrons at 300 MeV, which have never been reported. The irradiations were carried out using neutrons produced through $$^{7}$$Li(p, n) reaction at N0 beam line in the Research Center for Nuclear Physics (RCNP), Osaka University. To estimate quasi-monoenergetic neutron induced cross sections, the target stacks of Y and Tb were irradiated on the two angles of 0 degree and 30 degree for the axis of the primary proton beam. Neutron cross sections were estimated by subtracting the activities produced in the samples placed on 30 degree from those of 0 degree to correct the contribution of the low energy tail in the neutron spectrum.

Journal Articles

Shielding Design of a Neutron Beam Line "NOBORU" at JSNS/J-PARC

Harada, Masahide; Oikawa, Kenichi; Kasugai, Yoshimi; Maekawa, Fujio

Progress in Nuclear Science and Technology (Internet), 1, p.94 - 97, 2011/02

NOBORU is one of 23 neutron beam ports in JSNS/J-PARC to measure neutron source characteristics and to be applicable to various test experiments. Shielding for NOBORU must be tough due to the large neutron beam size and the high beam power at 1MW. In this study, we determined the shielding structure of NOBORU by neutronics calculations. In the shielding calculation, we considered neutron beam loss conditions caused by various beam line components. As a result, shielding structures that satisfied all the necessary radiation dose limits adopted in the J-PARC were determined. We measured dose rates in the experimental room of NOBORU during operation. The measured values were in good agreement with the calculated ones within a factor of 2. In addition, we also evaluated the effectiveness of a neutron beam shutter and radioactivity of the T$$_{0}$$ chopper.

Journal Articles

Conservative evaluation of remaining radioactivity on decommissioned nuclear power plant sites

Tanaka, Tadao; Shimada, Taro; Ito, Takeshi*; Hirano, Takahiro*; Sukegawa, Takenori

Progress in Nuclear Science and Technology (Internet), 1, p.408 - 411, 2011/02

Nuclear power plant sites are allowed to be released from nuclear safety regulations after the plants are decommissioned in Japan. The regulatory compliance will require confirming that there is no significant radioactivity remaining on the sites for the site release. In the present study, we propose an evaluation method of Cs-137 remaining on sites of decommissioned nuclear power plants. The method is time-efficient and gives a conservative result. In the evaluation method concept, all of the Cs-137, which is in reality distributed across the area of interest, is assumed to be the single point source located at the furthest position on the surface of the area from a detector. For such a configuration, the counting time that the Cs-137 point source is detectable is predicted using Monte Carlo calculations. If radiation from the Cs-137 point source is not detected for longer than the predicted counting time, it can be proven that the radioactivity remaining on the surface of the area is lower than the radioactivity corresponding to the assumed Cs-137 point source. A Cs-137 radiation source was placed at a fixed distance from the Ge detector, and the peak counting rate of Cs-137 were measured. The detectable time predicted by Monte Carlo calculations was approximately equal to the actual measurement time by the Ge detector, which means that the proposed evaluation method was reasonable for the conservative evaluation of remaining radioactivity.

Journal Articles

Neutronic analysis of fusion tokamak devices by PHITS

Sukegawa, Atsuhiko; Takiyoshi, Koji*; Amano, Toshio*; Kawasaki, Hiromitsu*; Okuno, Koichi*

Progress in Nuclear Science and Technology (Internet), 1, p.36 - 39, 2011/02

A complete 3D radiation shielding analysis by PHITS has been performed for the JT-60U and JT-60 superconducting tokamak device (JT-60SA) in the present study. The PHITS has been developed for high energy particles physics in Japan. The neutron and photon transport analysis less than 20 MeV with the general cross section library is the same algorism of MCNP-4C code. The monoenergetic neutron (E$$_{rm n}$$ = 2.45 MeV) of the DD fusion devices are used for the neutron source in the analysis. The neutron source distribution are available a toroidally symmetric source for the analysis. The toroidal source has a poloidal distribution, so that a source routine in the PHITS has been replaced a newly developed source routine. The visual nuclear responses such as the neutron flux distribution, the photon flux distribution, the nuclear heating of the coils and the dose rate around the devices has been calculated by the PHITS for the fusion tokamak devices. Initial results by the PHITS have been demonstrated.

Journal Articles

New criticality accident alarm system detectors at the JAEA Tokai Reprocessing Plant

Tsujimura, Norio; Yoshida, Tadayoshi

Progress in Nuclear Science and Technology (Internet), 1, p.202 - 205, 2011/02

In the Tokai Reprocessing Plant (TRP) of the NCL, criticality accident alarm systems (CAAS) were installed in 1984 and have still been in service. Due to the advanced ages of the system, a new CAAS detector was developed for replacement. A new detector was composed of a plastic scintillator coupled with a photomultiplier tube, placed into a cadmium-lined polyethylene moderator, and has a feature to respond to both neutrons and $$gamma$$-rays via capture $$gamma$$-rays from Cd(n,$$gamma$$) reactions. The prototype detectors were built and the operation tests under critical bursts at a pulsed reactor were conducted. The test results demonstrated satisfactory performance. The new systems of commercial version are now under field tests at the TRP and will launch its operation in October 2009.

Journal Articles

Integral experiment on beryllium with DD neutrons for nuclear data benchmarking

Kondo, Keitaro; Ochiai, Kentaro; Tatebe, Yosuke; Yagi, Takahiro; Onishi, Seiki; Takakura, Kosuke; Sato, Satoshi; Konno, Chikara

Progress in Nuclear Science and Technology (Internet), 1, p.61 - 64, 2011/02

At the Fusion Neutronics Source (FNS) facility of JAEA we have conducted various integral experiments with DT neutrons for fusion reactor materials and have made a significant progress in the verification of their nuclear data. Recently we started a new series of integral experiments with DD neutrons at FNS in order to verify nuclear data relating to DD neutrons effectively. An integral experiment on beryllium with the DD neutron source will be presented in this conference. A beryllium pseudo-cylinder assembly of 45 cm in thickness and 63 cm in the diameter was built at the distance of 20 cm from the DD neutron source, and reaction rates of the $$^{115}$$In(n,n')$$^{rm 115m}$$In, $$^{197}$$Au(n,$$gamma$$)$$^{198}$$Au and $$^{6}$$Li(n,$$alpha$$)T reactions and a $$^{235}$$U fission rate were measured. The measured values were compared with calculations with the MCNP5 code and the latest nuclear data libraries; JENDL-3.3, ENDF/B-VII.0 and JEFF-3.1. A slight disagreement between the measurement and the calculation was found in the reaction rate of In, which is sensitive to neutrons above 0.3 MeV. We identified that the disagreement originated from the angular differential cross section data of the elastic scattering around 3 MeV and from the (n,2n) reaction cross section data near its threshold energy. The calculated reaction rates of Au, Li and $$^{235}$$U, which are sensitive to low energy neutrons, showed a large overestimation, which also appeared at the beryllium integral experiment with DT neutrons previously carried out at FNS. This problem has not been solved yet.

Journal Articles

Neutron flux measurements in ITER-TBM simulating assemblies by means of multi-foil activation method

Ochiai, Kentaro; Tatebe, Yosuke; Kondo, Keitaro; Onishi, Seiki; Sato, Satoshi; Takakura, Kosuke; Konno, Chikara

Progress in Nuclear Science and Technology (Internet), 1, p.142 - 145, 2011/02

Nuclear performances of the ITER Test Blanket Module (TBM) can be calculated with a neutron transport code and nuclear data library. Neutron flux spectra in the TBM should be measured in order to validate the calculated nuclear performances of the TBM. The multi-foil activation method (MFAM) is considered to be one of the most prospective candidates for the neutron flux spectrum measurement. We have examined to measure neutron flux spectra in TBM simulating assemblies with a DT neutron source by using MFAM. We deduced neutron flux spectra in the simulated assemblies with a Monte Carlo code MCNP4C, some nuclear data and unfolding code NEUPAC. The results indicated that the adjusted neutron flux was reasonable for fast neutrons and that measured reaction rate data of more (n,$$gamma$$) reactions were necessary for more adequate adjustment for slow neutrons.

Journal Articles

Collimator system design for a DT neutron beam at the first target room of JAEA/FNS

Onishi, Seiki; Sato, Satoshi; Ochiai, Kentaro; Takakura, Kosuke; Kondo, Keitaro; Konno, Chikara

Progress in Nuclear Science and Technology (Internet), 1, p.73 - 76, 2011/02

There are two target rooms at the Fusion Neutronics Source (FNS) facility in Japan Atomic Energy Agency (JAEA). Recently it becomes increasingly difficult to meet needs for experiments with a DT neutron beam such as instrument development for ITER, because of shortage of the large target. Therefore we plan to construct a neutron beam inside TR1 by using the small tritium target of TR1, which is easier to obtain. We designed the collimator system based on the cylindrical assembly used in the previous ITER shielding experiments at JAEA/FNS. Neutron spectra at the exit of the collimator and at the offset position by 20 cm from the collimator axis were calculated with the two dimensional Sn code DORT and FENDL/MG-2.1 multi-group library in order to investigate the effect of the collimator system.

Journal Articles

Monte Carlo simulations of photon specific absorbed fractions in a mouse voxel phantom

Mohammadi, A.; Kinase, Sakae

Progress in Nuclear Science and Technology (Internet), 1, p.126 - 129, 2011/02

Journal Articles

Neutron spectra measurements at JAEA MOX fuel facility

Tsujimura, Norio; Yoshida, Tadayoshi; Sagawa, Naoki; Shoji, Shigeru

Progress in Nuclear Science and Technology (Internet), 1, p.154 - 157, 2011/02

Journal Articles

Insufficient self-shielding correction in VITAMIN-B6

Konno, Chikara; Ochiai, Kentaro; Onishi, Seiki

Progress in Nuclear Science and Technology (Internet), 1, p.32 - 35, 2011/02

We carried out a simple benchmark calculation test with the multigroup cross-section library VITAMIN-B6 generated from ENDF/B-VI. The model of this test consisted of an iron sphere of 1 m in radius with an isotropic 20 MeV neutron source in the center. Neutron spectra in the sphere were calculated with the Sn code ANISN and VITAMIN-B6 or FENDL/MG-1.1. A calculation with MCNP and FENDL/MC-1.1 was carried out as a reference. The neutron spectra with ANISN and FENDL/MG-1.1 agreed with those with MCNP, while those with ANISN and VITAMIN-B6 were by at most 50% larger than those with MCNP. We examined VITAMIN-B6 in detail in order to investigate causes for the discrepancy. As the result, it was founded out that reasons of the discrepancy were the followings; (1) The smallest background cross section of $$^{56}$$Fe in VITAMIN-B6 is 1. (2) The weighting function used in generating VITAMIN-B6 is not adequate. VITAMIN-B6 should be revised for adequate self-shielding correction.

Journal Articles

Measurement of environmental $$gamma$$-ray dose rate around the Nuclear Fuel Cycle Engineering Laboratories, JAEA

Mizutani, Tomoko; Onuma, Toshimitsu; Sugai, Masamitsu*; Watanabe, Hajime*; Morisawa, Masato; Takeyasu, Masanori; Sumiya, Shuichi

Progress in Nuclear Science and Technology (Internet), 1, p.380 - 383, 2011/02

The Nuclear Fuel Cycle Engineering Laboratories (NCL), JAEA operates the Tokai Reprocessing Plant (TRP), plutonium fuel fabrication facilities and the supplemental facilities. In the terrestrial environment, environmental $$gamma$$-ray dose rate was measured continuously using an energy-thermo-compensation-type NaI(Tl) scintillation counter. The data of environmental dose rate measured in 5 monitoring stations and 8 monitoring posts were collected and analyzed to monitor on real-time. This paper summarizes the monitoring data of environmental dose rate around the NCL during the past 10 year (fiscal 1998-2007). The monthly average of the environmental dose rate for all monitoring stations and posts were in the range of 31-48 nGy h$$^{-1}$$, except the value influenced by the criticality accident at the JCO in 1999. The long-term variation in the environmental dose rate was not found. The cases of the short-term increases occurred by the operations of the facilities in the NCL were concluded by the discharges of $$^{85}$$Kr from the TRP, transportation of MOX fuels or radioactive solid wastes, X-ray generator to calibrate the radiation monitoring instruments. The other cases to affect the change of the environmental dose rate were the scavenging of the airborne natural radionuclides, a patient cured by the radiation therapy and the shield effect by cars.

Journal Articles

Tritium concentration and diffusion in seawater discharged from Tokai Reprocessing Plant

Kokubun, Yuji; Fujita, Hiroki; Nakano, Masanao; Sumiya, Shuichi

Progress in Nuclear Science and Technology (Internet), 1, p.384 - 387, 2011/02

The Tokai Reprocessing Plant has reprocessed the total amount of 1,140 tons of spent fuels since 1977 to the end of fiscal year 2008. During the operation, radioactive liquid effluent has been discharged into the sea from the outlet of the pipeline stretching about 3.7 km from shoreline, after the discharge approval and discharged total amounts of 4.5 PBq of $$^{3}$$H to the sea. Therefore, since 1978, JAEA has sampled seawater around the outlet every month. Tritium concentrations in seawater were analyzed and measured using a liquid scintillation counter. All data were used to calculate the dilution factor which means the ratio of the $$^{3}$$H concentration in seawater to that in liquid effluent. The number of $$^{3}$$H concentrations below the detection limit was 9,079 (82.0%) and the number of those from the limit to 40 Bq/L (as quantification limit) was 1,964 (17.7%). The maximum concentration was 1,700 Bq/L at the point just above the outlet in 1979. Moreover, the dilution factors were ranged between 240 and 6,500,000. All the concentrations were confirmed to be those below 60,000 Bq/L of $$^{3}$$H concentration limit included in water decided by the law and that it were not concern of environmental safety.

Journal Articles

Recent developments of the PHITS code

Niita, Koji*; Iwase, Hiroshi*; Sato, Tatsuhiko; Iwamoto, Yosuke; Matsuda, Norihiro; Sakamoto, Yukio; Nakashima, Hiroshi; Mancusi, D.*; Sihver, L.*

Progress in Nuclear Science and Technology (Internet), 1, p.1 - 6, 2011/02

PHITS, the general-purpose Particle and Heavy Ion Transport code System, has been used for various research fields such as radiation science, accelerator and its shielding design, space research, medical application, material research, and so on. Further developments and improvements for general-purpose, multi-particles, wide-energy range, reliable and easy-use Monte-Carlo calculations, are actively performed by the collaboration between RIST, JAEA, KEK, and Chalmers University. PHITS provides also accurate biological-dose and DPA value just by switching the build-in function, and it is an advance to other codes. Recent developments of the PHITS code will be presented, especially integrating EGS5 and high energy physics extension.

Journal Articles

Shielding experiments at high energy accelerators of Fermilab, 1; Dose rate around high intensity muon beam

Sanami, Toshiya*; Iwamoto, Yosuke; Shigyo, Nobuhiro*; Hagiwara, Masayuki*; Lee, H.-S.*; Leveling, A.*; Vaziri, K.*; Boehnlein, D.*; Mokhov, N.*; Sakamoto, Yukio; et al.

Progress in Nuclear Science and Technology (Internet), 1, p.44 - 47, 2011/02

Muons become important particle for radiation safety design of high energy and intense accelerator since muons penetrate a thick shielding wall. In this study, the dose rate distributions around high intensity muon beam were measured at the muon alcoves and the bypass tunnel of Neutrinos at the Main Injector (NuMI) facility in Fermi National Accelerator Laboratory (Fermilab). The dosimeters of Luxel budges (OSL, CR39) and TLD budges (UD813PQ) were placed in the second, third and forth alcoves to measure muons, photons, and, thermal and fast neutrons. Neutrons and photons were measured in the bypass tunnel using a Bonner sphere and an ionization chamber. The spatial distribution of muons is calculated using MARS code. The results of dosimeters show same spatial distribution including attenuation along the beam line in comparison with the calculation results.

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