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Journal Articles

Evaluation of averted doses to members of the public by tap water restrictions after the Fukushima Daiichi Nuclear Power Plant Accident

Kinase, Sakae; Kimura, Masanori; Hato, Shinji*

Progress in Nuclear Science and Technology (Internet), 4, p.5 - 8, 2014/04

Journal Articles

Characterization of quasi-monoenergetic neutron source using 137, 200, 246 and 389 MeV $$^{7}$$Li(p,n) reactions

Iwamoto, Yosuke; Hagiwara, Masayuki*; Iwase, Hiroshi*; Yashima, Hiroshi*; Satoh, Daiki; Matsumoto, Tetsuro*; Masuda, Akihiko*; Pioch, C.*; Mares, V.*; Shima, Tatsushi*; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.657 - 660, 2014/04

The authors measured the neutron energy spectra of the proton incident reaction on the lithium target with 137, 200, 246 and 389 MeV protons at several angles (0$$^{circ}$$, 2.5$$^{circ}$$, 5$$^{circ}$$, 10$$^{circ}$$, 15$$^{circ}$$, 20$$^{circ}$$, 25$$^{circ}$$ and 30$$^{circ}$$), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. For the neutron energy spectrum at 0$$^{circ}$$, the ratio of the peak neutron intensity to the total one varied between 0.4 and 0.5 depending on the incident energy. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron detectors, the authors showed the subtractions of H*(10) obtained at larger angles from the 0$$^{circ}$$ data in the continuum part. It was found that subtracting the dose equivalent at about 22$$^{circ}$$ from the 0$$^{circ}$$ data reduces the continuum component most efficiency.

Journal Articles

Measurement of neutron energy spectra behind shields for quasi-monoenergetic neutrons generated by 246-MeV and 389-MeV protons using a Bonner sphere spectrometer

Matsumoto, Tetsuro*; Masuda, Akihiko*; Nishiyama, Jun*; Harano, Hideki*; Iwase, Hiroshi*; Iwamoto, Yosuke; Hagiwara, Masayuki*; Satoh, Daiki; Yashima, Hiroshi*; Nakane, Yoshihiro; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.332 - 336, 2014/04

Recently, many high-energy accelerators are used for various fields. Shielding data for high-energy neutrons are therefore very important from the point of view of radiation protection in high energy accelerator facilities. However, the shielding experimental data for high energy neutrons above 100 MeV are very poor both in quality and in quantity. In this study, neutron penetration spectral fluence and ambient dose through iron and concrete shields were measured with a Bonner sphere spectrometer (BSS). Quasi-monoenergetic neutrons were produced by the $$^{7}$$Li(p,xn) reaction by bombarding a 1-cm thick Li target with 246-MeV and 389-MeV protons in the Research Center for Nuclear Physics (RCNP) of the Osaka University. Shielding materials are iron blocks with a thickness from 10 cm to 100 cm and concrete blocks with a thickness from 25 cm to 300 cm.

Journal Articles

Shielding benchmark experiment using hundreds of MeV quasi-monoenergetic neutron source by a large organic scintillator

Hagiwara, Masayuki*; Iwase, Hiroshi*; Iwamoto, Yosuke; Satoh, Daiki; Matsumoto, Tetsuro*; Masuda, Akihiko*; Yashima, Hiroshi*; Nakane, Yoshihiro; Nakashima, Hiroshi; Sakamoto, Yukio; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.327 - 331, 2014/04

We have developed several hundreds of MeV p-$$^{7}$$Li quasi-monoenergetic neutron fields in the Research Center for Nuclear Physics (RCNP), Osaka University, Japan. In this study, we extended the measurements to higher energy with a p-$$^{7}$$Li quasi-monoenergetic neutron source, which was produced from a 1.0-cm-thick lithium target bombarded with 246 and 389 MeV protons, using a larger NE213 scintillator of 25.4-cm in diameter and 25.4-cm in thickness. The large NE213 have good energy resolution for high energy neutrons, because it can stop recoil protons up to 180 MeV. The measured data are compared with the Monte-Carlo codes (PHITS with JENDL-HE data library) in the energy spectra, time spectra and the attenuation length of the peak neutrons. This comparison shows good agreement between experiments and calculations. The attenuation length estimated from the well-fitted curves with single exponential form will be useful for the practical shielding design of high energy accelerator facilities.

Journal Articles

New approach for describing nuclear reactions based on intra-nuclear cascade coupled with DWBA

Hashimoto, Shintaro; Iwamoto, Yosuke; Sato, Tatsuhiko; Niita, Koji*; Boudard, A.*; Cugnon, J.*; David, J.-C.*; Leray, S.*; Mancusi, D.*

Progress in Nuclear Science and Technology (Internet), 4, p.418 - 421, 2014/04

There is a growing interest in the use of accelerator-based neutron sources for scientific and medical applications. For neutron source design, computer codes that can evaluate neutron yields are indispensable; PHITS (Particle and Heavy Ion Transport code System) is one of suitable candidates. In this study, we proposed a new nuclear reaction model based on INCL coupled with the DWBA calculation for an accurate calculation of neutron yields. The DWBA calculation describes discrete peaks in neutron spectra. Although these peaks are not the major part of neutron sources, the estimation of their contributions is necessary, since neutrons from the peaks have high energies close to those of the incident particle. We will present the calculation method of our approach and results for proton and deuteron induced reactions on Li, Be, and C targets at incident energies from 10 to 100 MeV.

Journal Articles

In-situ radioactivity measurement for the site release after decommissioning of nuclear power plants

Tanaka, Tadao; Shimada, Taro; Sukegawa, Takenori

Progress in Nuclear Science and Technology (Internet), 4, p.832 - 835, 2014/04

According to a basic policy of Japan, nuclear power plant sites are allowed to be released from nuclear safety regulations after the plants are decommissioned. It is necessary to confirm that there is no significant radioactivity remaining on the sites, for the site release beforehand. Cobalt 60 is one of the typical radionuclide for nuclear power plants. In the evaluation concept, all of cobalt 60, which is in reality distributed across the area of interest, are assumed to be the single point source located at the furthest position on the surface of the area from a Ge detector. In such a configuration, minimum detectable time was supplied by Monte Carlo calculations, and the minimum detectable time was approximately equal to the actual measurement time of the point source by the Ge detector. These results mean that the proposed evaluation method was reasonable for the conservative evaluation of cobalt 60 remaining in the nuclear power plant sites.

Journal Articles

Measurement of neutron yields from a water phantom bombarded by 290 MeV/u carbon ions

Shigyo, Nobuhiro*; Uozumi, Yusuke*; Uehara, Haruhiko*; Nishizawa, Tomoya*; Hirabayashi, Keiichi*; Satoh, Daiki; Sanami, Toshiya*; Koba, Yusuke*; Takada, Masashi*; Matsufuji, Naruhiro*

Progress in Nuclear Science and Technology (Internet), 4, p.709 - 712, 2014/04

Heavy ion cancer therapy has been increased by reason of its clinical advantages. During the treatment, the secondary particles such as neutron and $$gamma$$-ray are produced by nuclear reactions of a heavy ion incidence on a nucleus in a patient body. Estimation of the secondary neutrons yields data is essential for assessment of radiation safety on both of workers and public in treatment facilities. Neutron energy spectra from a water phantom simulating the patient body were obtained at GSI only for forward directions. We measured the neutron yields from carbon ion incident on a water phantom in wide angular range from 15$$^{circ}$$ to 90$$^{circ}$$ with the therapeutic ion energy.

Journal Articles

Study for shielding efficiency of evacuation facilities in nuclear emergency

Oguri, Tomomi*; Takahara, Shogo; Kimura, Masanori; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 4, p.767 - 770, 2014/04

Sheltering is one of the protective actions in a nuclear emergency. To introduce the actions with effect, preparedness is needed from a point of efficiency of reduction of radiation exposure and also capacity and location. In this study, we surveyed building materials and construction of real facilities listed in prefectural regional emergency prevention plans and then evaluated the shielding efficiency of these facilities for external exposure. As the results, we obtained knowledge of distribution of shielding factor for actual evacuation facilities by cloudshine and groundshine. Moreover, based on the sensitivity analyses, basic data was obtained that easily evaluate the shielding efficiency of facilities with different structures and materials from basic building models.

Journal Articles

Development of internal dosimetry evaluation code for chronic exposure after intake of radionuclides

Kimura, Masanori; Kinase, Sakae; Hato, Shinji*

Progress in Nuclear Science and Technology (Internet), 4, p.60 - 63, 2014/04

Journal Articles

Evaluation of retention and excretion function to members of the public for chronic intake of radionuclides

Hato, Shinji*; Kinase, Sakae; Kimura, Masanori

Progress in Nuclear Science and Technology (Internet), 4, p.36 - 38, 2014/04

Journal Articles

Response measurement of various neutron dose equivalent monitors in 134-387 MeV neutron fields

Nakane, Yoshihiro; Hagiwara, Masayuki*; Iwamoto, Yosuke; Iwase, Hiroshi*; Satoh, Daiki; Sato, Tatsuhiko; Yashima, Hiroshi*; Matsumoto, Tetsuro*; Masuda, Akihiko*; Nunomiya, Tomoya*; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.704 - 708, 2014/04

no abstracts in English

Journal Articles

Development of boron sheet and DT neutron irradiation experiments of multi-layered concrete structure with boron sheet

Sato, Satoshi; Maegawa, Toshio*; Yoshimatsu, Kenji*; Sato, Koichi*; Nonaka, Akira*; Takakura, Kosuke; Ochiai, Kentaro; Konno, Chikara

Progress in Nuclear Science and Technology (Internet), 4, p.623 - 626, 2014/04

In the previous study, we developed a multi-layered concrete structure to reduce induced activity in concrete applied for neutron generation facilities such as a fusion reactor. This structure is composed of low activation concrete as the first layer, boron doped low activation concrete as the second layer and ordinary concrete as the third layer from the side of the neutron source. In this study, as an alternative of the boron doped low activation concrete we have developed the boron doped resin sheet with boron carbonate and resin to reduce the construction cost. The weight ratio of the boron carbonate to the resin is 0.75. The developed boron sheet has good flexibility and sufficient strength for repeated bending. DT neutron irradiation experiments for four multi-layered concrete structures with the boron sheet have been performed at the FNS (Fusion Neutronics Source) facility in JAEA in order to study shielding performance of the structures with the boron sheet. Structure-1 of about 30 cm in width, 30 cm in height and 50 cm in thickness is composed of low activation concrete of 20 cm in thickness as the first layer and ordinary concrete of 30 cm in thickness as the second layer. The boron sheet is inserted between the first and second layers. In Structure-2 one more boron sheet is inserted at the 10 cm depth from the surface of Structure-1. Structure-3 added one more boron sheet at 30 cm depth from the surface of Strucure-2. For comparison, Structure-4 has no boron sheet. The reaction rates were measured every 5 cm in depth with activation foils of gold and niobium. By inserting the boron sheet, the reaction rate of the gold generated by low energy neutrons decreases by a factor of about four. It is demonstrated that the multi-layered concrete structure with the boron sheet effectively reduces low energy neutrons.

Journal Articles

Research activities on JASMIN; Japanese and American Study of Muon Interaction and Neutron detection

Nakashima, Hiroshi; Mokhov, N.*; 28 of others*

Progress in Nuclear Science and Technology (Internet), 4, p.191 - 196, 2014/04

In JASMIN, a series of experiments has been performed with the intense 120-GeV proton beams at Fermilab. The secondary particles created in such interactions were measured around the targets as well as in their penetration through steel, concrete and rock. Nuclear data such as activation and mass distributions of residual nuclei have been measured by activation methods. Double differential neutron production yield has also been measured by a time of flight techniques. Comparison of results calculated by PHITS and MARS reveals in general a good agreement. Further analyses are in progress.

Journal Articles

Measurement of radioactive fragment production excitation functions of lead by 400 MeV/u carbon ions

Ogawa, Tatsuhiko; Morev, M.*; Iimoto, Takeshi*; Kosako, Toshiso*

Progress in Nuclear Science and Technology (Internet), 4, p.574 - 577, 2014/04

Depth distributions of radioactive fragments in a thick lead target exposed to 400 MeV/u carbon ions were measured to obtain isotopic production cross-sections of $$^{Nat}$$Pb(C,x) X reactions as excitation functions. The procedure of this experiment was validated by comparing the obtained data with the available thin target experimental data. Energy and mass dependences of the obtained cross-sections give insight into the reaction mechanism and will be useful for radiation transport code benchmarking.

Journal Articles

Estimation of dry deposition velocities of radionuclides released by the accident at the Fukushima Dai-ichi Nuclear Power Plant

Takeyasu, Masanori; Sumiya, Shuichi

Progress in Nuclear Science and Technology (Internet), 4, p.64 - 67, 2014/04

On the basis of I-131 measured after Fukushima primary nuclear power plant in nuclear fuel cycle engineering laboratory and atmosphere radioactive material concentration of cesium isotope and atmospheric deposition quantity data, the deposition velocity of atmosphere radioactive material to the surface was estimated. As the result, the deposition velocity was the 10$$^{-3}$$m/s order. It was the order equal to I-131 deposition velocity estimated after Chernobyl accident estimated from until now environmental radiation monitoring result around Tokai Nuclear Fuel Reprocessing Plant from the monitoring result in I-129 deposition velocity and this laboratory. It was guessed that it included the gaseous component for I-131 and cesium isotope discharged by Fukushima accident in atomic powered generation and that the deposition velocity varied by the ratio of the component.

Journal Articles

Practice for reducing contamination of controlled area under the influence of Fukushima nuclear accident

Yoshitomi, Hiroshi; Tatebe, Yosuke; Kawai, Keiichi; Kowatari, Munehiko

Progress in Nuclear Science and Technology (Internet), 4, p.81 - 84, 2014/04

The Facility of Radiation Standards of the Japan Atomic Energy Agency provides various radiation fields for calibration and testing. It is located about 120 km away from Fukushima Dai-ichi Nuclear Power Plant, and radioactive materials discharged by the Fukushima nuclear accident contaminated around the FRS, even inside the building including radiation controlled areas. One month after the accident, the maximum contamination level in the controlled areas was 3.8 Bq/cm$$^2$$. $$^{134}$$Cs, $$^{137}$$Cs, $$^{131}$$I, $$^{132}$$Te and $$^{132}$$I were detected by $$gamma$$ spectrometry using an HPGe detector. However, contamination in controlled areas under widely contaminated environment have not been discussed in detail. As for FRS, practices for reducing contamination in the controlled areas were necessary to avoid the influence of the contamination to the calibration works. These practices described that the following two approaches were effective: (1) decontamination of the controlled areas by wiping out with wet cloth or steam cleaners, and (2) to prevent the dust with radioactive materials from letting in the controlled areas. As a result, surface contaminates inside the controlled areas were reduced to be dozens of times lower as compared with outside.

Journal Articles

Neutron fluence monitoring system in mono-energetic neutron fields at FRS/JAEA

Tanimura, Yoshihiko; Fujii, Katsutoshi; Tsutsumi, Masahiro; Yoshizawa, Michio

Progress in Nuclear Science and Technology (Internet), 4, p.388 - 391, 2014/04

Mono-energetic neutron calibration fields have been developed at Facility of Radiation Standards (FRS) using a 4 MV Pelletron accelerator. The neutron energies are available between 8 keV and 19 MeV for determining the energy responses of neutron dosemeters. The neutron energies are well adjusted to the energy points specified in the international standard (ISO 8529-1) and Japanese standard (JIS Z4521). Precise neutron fluence is the most important parameter for the calibration. In order to determine the fluence a Long Counter (hereinafter LC) is installed in the field for monitoring the neutron emission rate from the target. The fluence can be precisely determined using the output counts of the LC, the distance from the target, calibration coefficient of the LC and the air attenuation factor. This presentation describes the neutron monitors, outline of our monitoring system, determination of the air attenuation factor and procedure to determine the neutron fluence.

Journal Articles

Determination of neutron fluence in 1.2 and 2.5 MeV mono-energetic neutron calibration fields at FRS/JAEA

Tanimura, Yoshihiko; Tsutsumi, Masahiro; Yoshizawa, Michio

Progress in Nuclear Science and Technology (Internet), 4, p.392 - 395, 2014/04

1.2 and 2.5 MeV Mono-energetic neutron calibration fields have been developed at Facility of Radiation Standards (FRS) by using a 4MV Pelletron accelerator and employing $$^3$$H(p,n)$$^3$$He reaction. For the calibration, neutron fluence should be precisely evaluated. A silicon semiconductor detector with a polyethylene converter (hereinafter CH$$_2$$-SSD) was developed to determine the neutron fluence. The detection efficiency of a common CH$$_2$$-SSD is not large enough to determine the neutron fluence. Then we developed a CH$$_2$$-SSD with high efficiency by using a large silicon semiconductor detector with 3,000 mm$$^2$$ sensitive area. This makes it possible to determine the neutron fluence with satisfactory accuracy. The detection efficiency of the CH$$_2$$-SSD was calculated with NRESP-ANT code and PHITS code. The maximum neutron fluence at 1 m from the target were evaluated to be about 1,000 and 2,000 cm$$^{-2}$$s$$^{-1}$$ in the 1.2 and 2.5 MeV neutron fields, especially.

Journal Articles

Development of radionuclide distribution database and map system on the Fukushima nuclear accident

Seki, Akiyuki; Takemiya, Hiroshi; Takahashi, Fumiaki; Saito, Kimiaki; Tanaka, Kei*; Takahashi, Yutaka*; Takemura, Kazuhiro*; Tsuzawa, Masaharu*

Progress in Nuclear Science and Technology (Internet), 4, p.47 - 50, 2014/04

The radionuclide distribution database and map system, which provide basic information for evaluations and countermeasures of the Fukushima nuclear accident, are explained. Due to massive earthquake and tsunami, Fukushima Dai-ichi Nuclear Power Plant has been damaged and had spread out radioactive materials around the Fukushima site. It is necessary to collect, analyze, and provide the information of radioactivity correctly and immediately. We developed two providing systems to identify the current distribution of released radionuclides and support decontamination activities.

Journal Articles

Overview of the PHITS code and its application to medical physics

Sato, Tatsuhiko; Niita, Koji*; Matsuda, Norihiro; Hashimoto, Shintaro; Iwamoto, Yosuke; Noda, Shusaku; Iwase, Hiroshi*; Nakashima, Hiroshi; Fukahori, Tokio; Chiba, Satoshi; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.879 - 882, 2014/04

PHITS is a general purpose 3-dimensional Monte-Carlo particle transport simulation code developed under collaboration of Japan Atomic Energy Agency (JAEA), Research Organization for Information Science and Technology (RIST), High Energy Accelerator Research Organization (KEK) and a couple of other institutes in Japan and Sweden. General features of the PHITS code together with details of the established model will be presented at the meeting.

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