Characteristics and verification of a car-borne survey system for dose rates in air; KURAMA-II

Tsuda, Shuichi; Yoshida, Tadayoshi; Tsutsumi, Masahiro; Saito, Kimiaki

Journal of Environmental Radioactivity, 139, p.260 - 265, 2015/01

https://doi.org/10.1016/j.jenvrad.2014.02.028

The car-borne survey system, KURAMA-II, developed by the Kyoto University Research Reactor Institute has been used for air dose rate mapping after the Fukushima Daiichi Nuclear Power Plant accident. The KURAMA-II consists of a CsI(Tl) scintillation detector, a GPS device, and a control device for data processing. The dose rates monitored by the KURAMA-II are based on the G(E) function (spectrum-dose conversion operator), which can precisely calculate dose rate from the measured pulse-height distribution even if the energy spectrum changes significantly. The characteristics of the KURAMA-II have been investigated with particular consideration to the reliability of the calculated G(E) function, dose rate dependence, statistical fluctuation, angular dependence, and energy dependence. The results indicate that 100 units of KURAMA-II systems have acceptable quality for mass monitoring dose rates in the environment.

Performance evaluation of the European Committee Standardization Method EN1785 for the detection of irradiated processed food

Tsutsumi, Tomoaki*; Adachi, Rika*; Takatsuki, Satoshi*; Nei, Daisuke*; Kameya, Hiromi*; Todoriki, Setsuko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Matsuda, Rieko*; Teshima, Reiko*

Shokuhin Shosha, 49(1), p.9 - 15, 2014/12

https://doi.org/10.5986/jrafi.49.9

no abstracts in English

Development of portable long counter with two different moderator materials

Tanimura, Yoshihiko; Tsutsumi, Masahiro; Yoshizawa, Michio

Radiation Protection Dosimetry, 161(1-4), p.144 - 148, 2014/10

https://doi.org/10.1093/rpd/nct345

A Long Counter (LC) is the most appropriate detector to measure neutron fluence due to flat response over a wide neutron energy range. Therefore, it is usually employed as a neutron fluence monitor. The weight of the LC used at FRS is 50 kg. It is too heavy to transfer it from one room to another room. Then we developed a new portable long counter whose weight is 15 kg. The portable LC consists of a He or BF counter and a cylindrical moderator. It was designed to have an almost flat response from a few eV to a few MeV. While typical LCs have air gaps in the front surface, which allow lower-energy neutrons to penetrate deeper into the moderator, the portable LC has little space to make such air gaps due to the small size. Then we employed a polystyrene (PS) moderator instead of a polyethylene (PE) one as a front part of the moderator. As the hydrogen density of PS is nearly half that of PE, lower-energy neutrons can penetrate the PS moderator deeper than the PE moderator.

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

https://doi.org/10.15669/pnst.4.392

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 H(p,n)He reaction. For the calibration, neutron fluence should be precisely evaluated. A silicon semiconductor detector with a polyethylene converter (hereinafter CH-SSD) was developed to determine the neutron fluence. The detection efficiency of a common CH-SSD is not large enough to determine the neutron fluence. Then we developed a CH-SSD with high efficiency by using a large silicon semiconductor detector with 3,000 mm sensitive area. This makes it possible to determine the neutron fluence with satisfactory accuracy. The detection efficiency of the CH-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 cms in the 1.2 and 2.5 MeV neutron fields, especially.

Emergency monitoring of environmental radiation and atmospheric radionuclides at Nuclear Science Research Institute, JAEA following the accident of Fukushima Daiichi Nuclear Power Plant

Okura, Takehisa; Oishi, Tetsuya; Taki, Mitsumasa; Shibanuma, Yukio; Kikuchi, Masamitsu; Akino, Hitoshi; Kikuta, Yasuaki; Kawasaki, Masatsugu; Saegusa, Jun; Tsutsumi, Masahiro; et al.

JAEA-Data/Code 2012-010, 37 Pages, 2012/05

JAEA-Data-Code-2012-010.pdf:2.28MB

Due to the accident at Fukushima Daiichi Nuclear Power Plant caused by the 2011 off the Pacific coast of Tohoku Earthquake occurred at 11th March 2011, the emergency environmental radiation monitoring was conducted at Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA). This report provides the monitoring results of ambient -ray dose rate and atmospheric radioactivity concentration until the beginning of June 2011. Some anthropogenic radionuclides such as Cs-134, Cs-137, I-131, I-132, Te-132, Xe-133 and others were detected from air samples. The atmospheric radioactivity concentrations varied with some peaks corresponded with that of ambient -ray dose rate after 15th March 2011. Composition of each peak showed various characteristic. Internal exposure caused by inhalation was estimated from the observed atmospheric radioactivity.

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

https://doi.org/10.15669/pnst.1.166

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.

Evaluation of target photon dose mixed in mono-energetic neutron fields using Li(p,n)Be reaction

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

Radiation Measurements, 45(10), p.1163 - 1166, 2010/12

https://doi.org/10.1016/j.radmeas.2010.06.013

Mono-energetic neutron calibration fields have been developed at the Facility of Radiation Standards of Japan Atomic Energy Agency using a 4MV Pelletron accelerator. The fields of 8, 27, 144, 250, 565 keV and 1.2, 2.5, 5.0, 14.8 MeV neutrons were established using scandium, lithium, deuterium and tritium targets. The nuclear reactions between the accelerated particles and the target materials produce not only the mono-energetic neutrons but also unwanted photons. As the photons can affect the readings of dosemeters, their effects should be evaluated. In this work the photons in the 144, 250 and 565 keV neutron fields from a lithium fluoride target were measured using a cylindrical NaI(Tl) detector with 7.62 cm both in diameter and in length. The ambient dose equivalent H*(10) for the photons was evaluated by applying the "G(E) function" to the measured pulse height spectrum.

Development of highly efficient proton recoil counter telescope for absolute measurement of neutron fluences in quasi-monoenergetic neutron calibration fields of high energy

Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro

Nuclear Instruments and Methods in Physics Research A, 615(2), p.211 - 219, 2010/04

https://doi.org/10.1016/j.nima.2010.01.032

In precise calibration of the monitors and the dosimeters for high energy neutrons, it is desirable to evaluate the neutron fluence at a reference point. In order to evaluate the neutron fluence of the quasi-monoenergetic neutron fields, a proton recoil counter telescope (PRT) with high efficiency has been developed for the absolute measurements at the reference point. Relatively large design of the PRT's components contributed to high detection efficiency at the reference point with a large irradiation area at a long distance from a target. The converter thicknesses were adjusted to keep same carbon density per unit area for easy background subtraction. As a result of the high detection efficiency and the adjustment, statistical precision could be improved. Neutron fluences were evaluated with uncertainties within 6% on the basis of the analysis of measured data and of the detection efficiency calculated by using the MCNPX code.

An Inter-comparison of the neutron calibration fields by DO moderated Cf source at JAEA and KAERI

Kowatari, Munehiko; Fujii, Katsutoshi; Tsutsumi, Masahiro; Kim, B.-H.*; Lee, K.-C.*; Yoshizawa, Michio; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 45(Suppl.5), p.217 - 220, 2008/06

https://doi.org/10.1080/00223131.2008.10875826

no abstracts in English

Investigation of properties of the TIARA neutron beam facility of importance for calibration applications

Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro; Yamaguchi, Yasuhiro; Uchida, Yoshiaki*

Radiation Protection Dosimetry, 126(1-4), p.163 - 167, 2007/08

https://doi.org/10.1093/rpd/ncm035

For neutron energy more than 20 MeV, the international standard of the calibration fields and techniques has not been established. Therefore, by using the quasi-monoenergetic neutron irradiation field of 40-90 MeV at TIARA of JAEA Takasaki, we are developing the calibration field. Here we evaluated the properties of the neutron field, where neutrons were produced in the nuclear reaction of the Li target with 45, 50 and 70 MeV protons. We investigated the neutron beam profile at different distance from the target by using the imaging plates with a polyethylene converter to measure the recoil protons produced in the converter. From the results, properties of the neutron beam profile were found as follows: (1) Irradiation field area was fixed geometrically by the distance from the target and the diameter of the collimator exit; (2) The beam intensity within the irradiation field was in inverse proportion to the square of the distance from the target. Also, we measured the peak energy and energy spectrum of neutron through TOF method by using organic liquid scintillation detector. Then we evaluated the energy spectra of the scattered neutrons at various positions outside the irradiation field through unfolding method. The FORIST unfolding code and the response of SCINFUL-QMD code were used here. From the neutron energy spectra obtained in the different method mentioned above, peak fluence for on-beam position was evaluated comparing with the results in previous evaluation of the neutron field at TIARA.