R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.

RIST News, (69), p.2 - 18, 2023/09

https://www.rist.or.jp/rnews/69/69s2.pdf

The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd(Al,Ga)O scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

https://doi.org/10.1080/00223131.2016.1185980

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 44 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the -ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10).

Investigation of radionuclide distribution using aircraft for surrounding environmental survey from Fukushima Dai-ichi Nuclear Power Plant

Torii, Tatsuo; Sanada, Yukihisa; Sugita, Takeshi; Kondo, Atsuya*; Shikaze, Yoshiaki; Takahashi, Masaki; Ishida, Mutsushi; Nishizawa, Yukiyasu; Urabe, Yoshimi

JAEA-Technology 2012-036, 182 Pages, 2012/12

JAEA-Technology-2012-036.pdf:41.89MB

We carried out aerial radiation monitoring (ARM) of all Japan area in order to investigate the influence of the radio cesium which was emitted into the atmosphere by disaster of the Fukushima Dai-ichi Nuclear Power Plant of Tokyo Electric Power Co., Inc.. AMS can measure a ray quickly by flight from 300 m height above the ground. Moreover, ARM has an advantage which can grasp self-possessed quantity distribution of an air dose rate and radioactive cesium in "field", and is visually intelligible. Although there were apparatus and the technique of ARM in our country, sufficient preparations for wide area monitoring were not made. Therefore, it fixed based on the method of the U.S. Department of Energy (DOE) about the method of the conversion to all radiation dose, and the conversion method to radiocesium deposition and the method of mapping. It is possible to discriminate from a background (cosmic-ray, self-contamination and natural nuclides) at the time of western-part-of-Japan measurement by improving of the method in parallel to data acquisition. By this monitoring, it was able to check about the distribution situation of the air dose rate of the Japanese whole region, or the radioactive cesium deposition. Here, the measurement technique and a result are described.

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.

Development of the neutron calibration fields using accelerators at FRS and TIARA of JAEA

Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro; Shimizu, Shigeru; Yoshizawa, Michio; Yamaguchi, Yasuhiro

Journal of Nuclear Science and Technology, 45(Suppl.5), p.209 - 212, 2008/06

https://doi.org/10.1080/00223131.2008.10875824

The neutron calibration fields is necessary to evaluate the energy response of the neutron monitors and dosimeters used in the facility such as J-PARC. The neutron calibration fields using accelerators, for the purpose, have been developed at the Facility of Radiation Standards (FRS) of JAEA-Tokai for neutrons below 20MeV and at Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) of JAEA-Takasaki for those over 20 MeV. At FRS, a 4 MV Van-de-Graaff (Pelletron) accelerator is used. Up until the present, developments of the 8, 144, 250, 565 keV, 5.0 and 14.8 MeV fields have been completed. At TIARA, an AVF cyclotron is used, and three neutron fields of 45, 60 and 75 MeV are planned to be established. For the development, evaluation of the characteristics of the field have been in process.

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.

Development of the 14.8 MeV monoenergetic neutron field using the d-T reaction

Tanimura, Yoshihiko; Shikaze, Yoshiaki; Fujii, Katsutoshi; Saegusa, Jun; Tsutsumi, Masahiro; Harano, Hideki*; Matsumoto, Tetsuro*; Shimoyama, Tetsuya*

no journal, , 

no abstracts in English

Development of dose monitor and dosimeter applicable to high-energy neutron

Endo, Akira; Sato, Tatsuhiko; Satoh, Daiki; Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro; Yamaguchi, Yasuhiro; Kaneko, Hirohisa; Oda, Keiji*; et al.

no journal, , 

no abstracts in English