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Journal Articles

Characterization of radionuclides formed by high-energy neutron irradiation

Yokoyama, Sumi; Sato, Kaoru; Noguchi, Hiroshi; Tanaka, Susumu; Iida, Takao*; Furuichi, Shinya*; Kanda, Yukio*; Oki, Yuichi*; Kaneto, Taihei*

Radiation Protection Dosimetry, 116(1-4), p.401 - 405, 2005/12

 Times Cited Count:1 Percentile:11.17(Environmental Sciences)

The physicochemical property of radionuclides suspended in the air is an important parameter to evaluate internal doses due to the inhalation of the airborne radionuclides and to develop the air monitoring system in high-energy proton accelerator facilities. This study focuses on the property of radioactive airborne chlorine ($$^{38}$$Cl and $$^{39}$$Cl) and sulfur ($$^{38}$$S) formed from Ar gas by irradiation with high-energy neutrons. As a result of the irradiation to a mixture of Ar gas and dry air, $$^{38}$$Cl and $$^{39}$$Cl existed as non-acidic gas and $$^{38}$$S was present as acidic gas. Further, it was found that in the high-energy neutron irradiation to aerosol containing-Ar gas, the higher the amount of radioactive aerosols becomes, the lower that of radioactive acidic gas becomes.

Journal Articles

Shielding analysis at the upper section of the accelerator-driven system

Sasa, Toshinobu; Yang, J. A.*; Oigawa, Hiroyuki

Radiation Protection Dosimetry, 116(1-4), p.256 - 258, 2005/12

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The proton beam duct of the accelerator-driven system (ADS) acts a streaming path for spallation neutrons and photons and causes the activation of the magnets and other devices above the subcritical core. We have performed a streaming analysis at the upper section of the lead-bismuth target/cooled ADS (800MWth). MCNPX was used to calculate the radiation dose from streamed neutrons and photons through the beam duct. For the secondary photon production calculation, cross sections for several actinides were substituted for plutonium because of the lack of gamma production cross section. From the results of this analysis, the neutron dose from the beam duct is about 20 orders higher than that of the bulk shield. The magnets and shield plug were heavily irradiated by streaming neutrons according to the DCHAIN-SP analysis.

Journal Articles

Development of three kinds of tissue substitutes for a physical phantom in neutron dosimetry

Tsuda, Shuichi; Endo, Akira; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 42(10), p.877 - 887, 2005/10

 Times Cited Count:2 Percentile:18.81(Nuclear Science & Technology)

Three kinds of tissue substitutes were synthesized in order to develop a physical phantom for neutron dosimetry. The optimal elemental compositions and densities were determined using a Monte Carlo simulation method, based on absorbed dose distributions of neutrons of a few MeV in various materials. The characteristics of the synthesized tissue substitutes were verified by absorbed dose measurements using monoenergetic neutron sources and a $$^{252}$$Cf neutron source. It was found that the developed tissue substitutes, NAN-, HAI- and HONE-JAERI, have tissue equivalence to actual tissues within 10 % accuracy for neutrons in most of common fast neutron fields.

Journal Articles

Development of dose monitoring system applicable to various radiations with wide energy ranges

Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 42(9), p.768 - 778, 2005/09

 Times Cited Count:16 Percentile:74.09(Nuclear Science & Technology)

A new inventive radiation monitor, designated to DARWIN (Dose Assessment system applicable to various Radiations with WIde energy raNges), has been developed for monitoring doses at workspaces of high energy accelerator facilities and on ground. Characteristics of DARWIN were studied by both calculation and experiment. The calculated results indicate that DARWIN gives reasonable estimations of doses at most radiation fields. It was found from the experiment that DARWIN has an excellent property of measuring doses from all particles that significantly contribute to the background dose - photon, muon and neutron with wide energy ranges.

Journal Articles

Shielding design of ITER pressure suppression system

Yamauchi, Michinori*; Sato, Satoshi; Nishitani, Takeo; Kawasaki, Hiromitsu*

Proceedings of 21st IEEE/NPSS Symposium on Fusion Engineering (SOFE 2005) (CD-ROM), 4 Pages, 2005/09

no abstracts in English

Journal Articles

Examination for neutron dose assessment method from induced sodium-24 in human body in criticality accidents

Takahashi, Fumiaki; Endo, Akira; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 42(4), p.378 - 383, 2005/04

 Times Cited Count:2 Percentile:18.81(Nuclear Science & Technology)

Experiments were made to verify a dose assessment method from activated sodium in body in criticality accidents. A phantom containing sodium chloride solution was irradiated in the Transient Experiment Critical Facility to simulate activation of sodium. Monte Carlo calculations were performed to obtain quantitative relation between the activity of induced Na-24 and neutron dose in the phantom. In the previous work, conversion coefficients from specific activity of induced Na-24 to neutron dose had been analyzed with the MCNP-4B code concerning neutron spectra at some hypothesized configurations. One of the prepared coefficients was applied to evaluate neutron dose from the measured activity. The estimated dose agreed with the dose analyzed by the Monte Carlo calculation in the present study within an acceptable uncertainty, which is indicated by the IAEA. In addition, the dose calculated with the prepared coefficient was close to the result measured with dosimeters. These results suggest that the prepared coefficients can be applied to dose assessments from induced Na-24 in body.

JAEA Reports

Review of JAERI activities on the IFMIF liquid lithium target in FY2004

Nakamura, Hiroo; Ida, Mizuho*; Matsuhiro, Kenjiro; Fischer, U.*; Hayashi, Takumi; Mori, Seiji*; Nakamura, Hirofumi; Nishitani, Takeo; Shimizu, Katsusuke*; Simakov, S.*; et al.

JAERI-Review 2005-005, 40 Pages, 2005/03

JAERI-Review-2005-005.pdf:3.52MB

The International Fusion Materials Irradiation Facility (IFMIF) is being jointly planned to provide an accelerator-based Deuterium-Lithium (Li) neutron source to produce intense high energy neutrons (2 MW/m$$^{2}$$) up to 200 dpa and a sufficient irradiation volume (500 cm$$^{3}$$) for testing the candidate materials and components up to about a full lifetime of their anticipated use in ITER and DEMO. To realize such a condition, 40 MeV deuteron beam with a current of 250 mA is injected into high speed liquid Li flow with a speed of 20 m/s. In target system, radioactive species such as 7Be, tritium and activated corrosion products are generated. In addition, back wall operates under severe conditions of neutron irradiation damage (about 50 dpa/y). In this paper, the thermal and thermal stress analyses, the accessibility evaluation of the IFMIF Li loop, and the tritium inventory and permeation of the IFMIF Li loop are summarized as JAERI activities on the IFMIF target system performed in FY2004.

JAEA Reports

Estimation methods of blood boron concentration and error evaluation during boron neutron capture therapy for malignant brain tumor

Shibata, Yasushi*; Yamamoto, Kazuyoshi; Matsumura, Akira*; Yamamoto, Tetsuya*; Hori, Naohiko; Kishi, Toshiaki; Kumada, Hiroaki; Akutsu, Hiroyoshi*; Yasuda, Susumu*; Nakai, Kei*; et al.

JAERI-Research 2005-009, 41 Pages, 2005/03

JAERI-Research-2005-009.pdf:1.99MB

The measurement of neutron flux and boron concentration in the blood during medical irradiation is indispensable in order to evaluate the radiation in boron neutron capture therapy. It is, however, difficult to measure the blood boron concentration during neutron irradiation because access to the patient is limited. Therefore we prospectively investigated the predictability of blood boron concentrations using the data obtained at the first craniotomy after infusion of a low dosage of BSH. When the test could not be carried out, the blood boron concentration during irradiation was also predicted by using the 2-compartment model. If the final boron concentration after the end of the infusion is within 95% confidence interval of the prediction, direct prediction from biexponential fit will reduce the error of blood boron concentrations during irradiation to around 6%. If the final boron concentration at 6 or 9 hours after the end of infusion is out of 95% confidence interval of the prediction, proportional adjustment will reduce error and expected error after adjustment to around 12%.

Journal Articles

Development of neutron-monitor detector using liquid organic scintillator coupled with $$^{6}$$Li+ZnS(Ag) sheet

Sato, Tatsuhiko; Endo, Akira; Yamaguchi, Yasuhiro; Takahashi, Fumiaki

Radiation Protection Dosimetry, 110(1-4), p.255 - 261, 2004/09

 Times Cited Count:8 Percentile:50.96(Environmental Sciences)

For monitoring of neutron doses in high-energy accelerator facilities, we have developed a neutron-monitor detector applicable to energies from the thermal energy to 100 MeV. The detector is composed of a cylindrical (12.7 cm in diameter and 12.7 cm in length) liquid organic scintillator BC501A covered with $$^{6}$$Li+ZnS(Ag) sheets. Characteristics of this phoswitch-type detector were studied experimentally in moderated neutron fields of $$^{241}$$Am-Be and $$^{252}$$Cf sources, and in quasi-monoenergetic neutron fields of 40 and 70 MeV. It was found from the experiments that the detector is enough sensitive to both thermal and fast neutrons, and has an excellent property of pulse-shape discrimination between them. We concluded, therefore, that the detector can be used for monitoring of neutron doses over a wide energy range from the thermal to 100 MeV.

Journal Articles

Conceptual design of spectrum changeable neutron calibration fields in JAERI/FRS

Saegusa, Jun; Tanimura, Yoshihiko; Yoshizawa, Michio; Yoshida, Makoto

Radiation Protection Dosimetry, 110(1-4), p.91 - 95, 2004/09

 Times Cited Count:3 Percentile:24.74(Environmental Sciences)

For the accurate estimation of neutron dose equivalents, it is important to calibrate dosemeters in the field whose energy spectrum is similar to that in the workplace. For the purpose, studies are made toward the built of the spectrum changeable neutron calibration fields with the Van-de-Graff accelerator in the FRS in JAERI. The fields are produced by bombarding proton or deuteron beam from the accelerator to suitable targets surrounded by quasi-cylindrical moderators and absorbers of various materials. In the fields, neutron spectra with wide range energy index should be provided with sufficient fluence rate for the calibration of dosemeters. The objectives and conceptual design of the fields are discussed here, followed by the test simulation results of neutron spectra produced by various arrangements of a target and moderators.

Journal Articles

Neutron spectra and angular distributions of concrete-moderated neutron calibration fields at JAERI

Yoshizawa, Michio; Tanimura, Yoshihiko; Saegusa, Jun; Nemoto, Hisashi*; Yoshida, Makoto

Radiation Protection Dosimetry, 110(1-4), p.81 - 84, 2004/09

 Times Cited Count:3 Percentile:24.74(Environmental Sciences)

The facility of Radiation Standards (FRS) of JAERI has equipped with the concrete-moderated neutron calibration fields as simulated workplace neutron fields. The fields use an Am-Be (37GBq) neutron source placed in the narrow space surrounded by concrete wall and bricks to produce scattered neutrons. The neutron spectra of the fields were measured with Bonner multi-sphere spectrometer system (BMS), spherical recoil-proton proportional counters (RPCs), and a liquid scintillation counter (NE-213). The results were compared with each other, and the neutron spectra and the ambient dose equivalent rate, ${it H}$$$^{*}$$(10), were agreed well within the uncertainty. The angular distributions of neutron fluence were calculated by the MCNP-4B2 Monte Carlo code to obtain the reference personal dose equivalent rate, ${it H}$$$_{p}$$(10). The calculated results show that the scattered neutrons have a wide variety of incident angles. The reference ${it H}$$$_{p}$$(10) values considered the angular distribution were found to be 10-18% smaller than those without consideration.

Journal Articles

Dose evaluation in criticality accident conditions using transient critical facilities fueled with a fissile solution

Nakamura, Takemi*; Tonoike, Kotaro; Miyoshi, Yoshinori

Radiation Protection Dosimetry, 110(1-4), p.483 - 486, 2004/09

 Times Cited Count:2 Percentile:17.98(Environmental Sciences)

Dose measurement and evaluation technique in criticality accident conditions with a thermo luminescence dosimeter (TLD) was studied at the Transient Experiment Critical Facility (TRACY) of Japan Atomic Energy Research Institute (JAERI). The tissue absorbed dose can be derived from the ambient dose equivalent given by measurement with a TLD using the conversion factor given by computation. Using this technique, the neutron dose around the SILENE reactor of the Institute for Radioprotection and Nuclear Safety (IRSN) of France was measured in the Accident Dosimetry Intercomparison Exercise (June 10-21, 2002) organized by OECD/NEA and IRSN. In this exercise, the $$gamma$$ dose was also measured with a TLD. In this report, measurements and evaluation results at TRACY and SILENE are presented.

Journal Articles

Experimental study on induced radioactivity in boron-doped low activation concrete for DT fusion reactors

Sato, Satoshi; Morioka, Atsuhiko; Kinno, Masaharu*; Ochiai, Kentaro; Hori, Junichi; Nishitani, Takeo

Journal of Nuclear Science and Technology, 41(Suppl.4), p.66 - 69, 2004/03

no abstracts in English

Journal Articles

Energy dependence of absorbed dose distributions in a soft tissue substitute for neutron dosimetry

Tsuda, Shuichi; Endo, Akira; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 41(Suppl.4), p.132 - 135, 2004/03

A solid material improved in hydrogen and oxygen contents was synthesized for development of a physical phantom for neutron. The elemental composition and density are aimed for those of the soft tissue in ICRU Report 44. The soft tissue equivalence has been verified by an absorbed dose measurement using a 252Cf neutron source. In the present work, absorbed doses were measured for the purpose of examinations of the characteristic of the synthesized soft tissue substitute for neutron of various energies, using mono-energetic 0.565 MeV neutrons from $$^{7}$$Li(p,n) reaction and 5 MeV from D(d,n) reaction, and quasi-mono-energetic ones (40 and 65 MeV) produced via $$^{7}$$Li(p,n) reaction. The measured absorbed doses were compared with those calculated by Monte Carlo simulation codes. The results indicate that the tissue substitute has a characteristic of soft tissue equivalence for neutron in the energy range from several hundred keV up to approximately 100 MeV.

Journal Articles

Synthesis and characterization of a soft-tissue substitute for neutron dosimetry

Tsuda, Shuichi; Endo, Akira; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 40(12), p.1027 - 1031, 2003/12

 Times Cited Count:1 Percentile:11.39(Nuclear Science & Technology)

To develop a physical phantom for neutron dosimetry, a solid soft-tissue substitute was synthesized. The hydrogen and oxygen compositions of the synthesized tissue substitute, NAN-JAERI, are similar to those of the soft tissue in ICRU Report 44. To examine the radiation characteristics of the new soft-tissue substitute, absorbed dose distributions in NAN-JAERI were measured using a $$^{252}$$Cf neutron source. The measured absorbed dose distributions of neutrons and photons agree with those calculated by a Monte Carlo simulation code MCNP. The agreement between the experiment and the simulation verifies this method of evaluating the soft-tissue equivalence of NAN-JAERI for $$^{252}$$Cf neutrons. Similar simulations for some mono-energetic neutron sources showed that the newly developed tissue substitute has soft-tissue equivalent characteristics in the neutron energy range up to 14 MeV, in terms of the absorbed dose distributions in a slab phantom.

Journal Articles

Measurement of radiation skyshine with D-T neutron source

Yoshida, Shigeo*; Nishitani, Takeo; Ochiai, Kentaro; Kaneko, Junichi*; Hori, Junichi; Sato, Satoshi; Yamauchi, Michinori*; Tanaka, Ryohei*; Nakao, Makoto*; Wada, Masayuki*; et al.

Fusion Engineering and Design, 69(1-4), p.637 - 641, 2003/09

 Times Cited Count:7 Percentile:47.54(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Analysis of time evolution of neutron intensity measured with a high-sensitive neutron collar during the JCO criticality accident

Endo, Akira; Yamaguchi, Yasuhiro; Sumita, Kenji*

Journal of Nuclear Science and Technology, 40(8), p.628 - 630, 2003/08

 Times Cited Count:4 Percentile:32.68(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Study of particle size distribution and formation mechanism of radioactive aerosols generated in high-energy neutron fields

Endo, Akira; Sato, Kaoru; Noguchi, Hiroshi; Tanaka, Susumu; Iida, Takao*; Furuichi, Shinya*; Kanda, Yukio*; Oki, Yuichi*

Journal of Radioanalytical and Nuclear Chemistry, 256(2), p.231 - 237, 2003/05

 Times Cited Count:6 Percentile:43.28(Chemistry, Analytical)

Size distributions of $$^{38}$$Cl, $$^{39}$$Cl, $$^{82}$$Br and $$^{84}$$Br aerosols generated by irradiations of argon and krypton gases containing di-octyl phthalate (DOP) aerosols with 45MeV and 65MeV quasi-monoenergetic neutrons were measured to study the formation mechanism of radioactive particles in high energy radiation fields. Effects of the size distribution of the radioactive aerosols on the size of added DOP aerosols, the energy of irradiation neutrons and the kinds of nuclides were studied. The observed size distributions of the radioactive particles were explained by attachment of the radioactive atoms generated by the neutron-induced reactions to the DOP aerosols.

Journal Articles

Analysis of dose distribution for heavily exposed workers in the first criticality accident of Japan

Endo, Akira; Yamaguchi, Yasuhiro

Radiation Research, 159(4), p.535 - 542, 2003/04

 Times Cited Count:13 Percentile:39.42

The first criticality accident in Japan occurred in a uranium processing plant in Tokai-mura in September, 1999. In this accident, two workers on the site were heterogeneously exposed to neutrons and $$gamma$$ rays produced by the nuclear fission. Heterogeneous exposure influenced the clinical course observed in the skin and organs of these workers. By request from medical groups, we attempted to clarify the dose distribution of the two heavily exposed workers with the aid of computer simulation, which is currently the only means by which to address this complicated problem. This paper presents elucidated skin dose distributions, depth dose distributions inside the trunk, and neutron-to-$$gamma$$ dose ratios.

Journal Articles

Dose assessment from activated sodium within a body in criticality accidents

Takahashi, Fumiaki; Endo, Akira; Yamaguchi, Yasuhiro

Radiation Protection Dosimetry, 106(3), p.197 - 206, 2003/00

 Times Cited Count:3 Percentile:26.72(Environmental Sciences)

Some data were derived using recent sophisticated methods to convert rapidly specific activity of induced sodium-24 to average dose over a whole body in criticality accidents. Monte Carlo calculations using the MCNP-4B code were performed to study energy spectra of neutrons and gamma rays for some criticality systems with fissile uranium. Absorbed dose to human body and activation of sodium were also analysed against external radiation by simulations using a phantom. It was found that neutron dose assessment from induced $$^{24}$$Na would be important to give an initial guidance of a treatment. The condition of neutron exposure, however, did not influence the quantitative relation dose by gamma rays induced within a body and activity of $$^{24}$$Na. Analyses were made to clarify the dependence of conversion from $$^{24}$$Na specific activity to dose on the orientation and the size of human body. This study suggested that the size of uranium solution and material around the fuel should be informed to properly estimate dose against external photons from neutron dose.

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