Investigations and consideration on conditions of contamination and measures of decontamination for motor vehicles at a nuclear emergency

Togawa, Orihiko; Hokama, Tomonori; Hiraoka, Hirokazu

JAEA-Review 2023-013, 48 Pages, 2023/08

JAEA-Review-2023-013.pdf:2.11MB

When radionuclides are released into the atmospheric environment at a nuclear emergency, protective measures such as evacuation and temporal relocation are carried out using motor vehicles such as private cars and buses to reduce radiation exposure to residents. To confirm conditions of contamination for the evacuated or relocated residents, contamination inspection is conducted, in which it is important not to spoil its rapidity. In the present inspection, wipers and tires are designated to first measuring parts, and they are basically inspected by persons using GM survey meters. Utilization of portable radiation portal monitors is also being considered for rapid and efficient inspection of motor vehicles. In order to contribute to rapid and efficient operation of contamination inspection, this report investigated conditions of contamination and measures of decontaminations for motor vehicles at a nuclear emergency. Although available documents and information were quite few, results of the investigations described in the related documents were extracted and rearranged according to the objectives of this report. Furthermore, these results were considered from a viewpoint of rapid and efficient operation of contamination inspection.

Research on atmospheric radioactivity concentration in the specified reconstruction and revitalization base (FY2018-FY2021)

Abe, Tomohisa; Funaki, Hironori; Yoshimura, Kazuya; Shiribiki, Natsu*; Sanada, Yukihisa

JAEA-Data/Code 2023-001, 38 Pages, 2023/05

JAEA-Data-Code-2023-001.pdf:3.04MB
JAEA-Data-Code-2023-001-appendix(CD-ROM).zip:32.02MB

In this study, commissioned by the Cabinet Office, we conducted a survey on radioactive materials in atmospheric dust in three municipalities (Futaba Town, Okuma Town, and Tomioka Town) in Fukushima Prefecture to contribute to the assessment of internal exposure in the Specified Reconstruction and Revitalization Base (SRRB). Air dust samplers were installed in the targeted municipalities to investigate the atmospheric Cs concentrations and to evaluate internal exposure doses based on measured value. This report summarizes the results of measurements between 2018 and 2021. A database of information on internal exposure dose assessment results based on atmospheric radioactivity concentrations and actual measurements, and meteorological observation data was compiled.

Boundary condition free homogenization and evaluation of its performance in fast reactor core analysis

Maruyama, Shuhei

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 10 Pages, 2022/05

This paper proposes a new homogenization method, "Boundary Condition Free Homogenization (BCFH)". The traditional homogenization method separates the core calculation and the cell (assembly) calculation by assuming a specific boundary condition or a peripheral region in the cell calculation. Nevertheless, there are ambiguities and approximation in these assumptions, and they can also cause a decline in accuracy. BCFH aims to avoid these problems and improve the accuracy in the cell calculation such as homogenization. We imposed the conditions that the physical quantities in the cell related to the reaction rate preservation is preserved for any incoming partial current, during the homogenization. That is, the response matrices of cell average (or total) flux and outgoing partial current, to be the same form between heterogeneous and homogeneous system. As a result, homogenized parameters, such as cross-sections, superhomgenization factors, and discontinuity factors, are no longer dependent on a specific boundary condition. The new homogenized parameters obtained in this way are extended from the conventional vector form to the matrix form in BCFH. To investigate the performance of BCFH, numerical tests are done for the simplified models which originates in 750MW-class sodium-cooled fast reactor with MOX fuel core in Japan. It is found that BCFH is particularly effective in evaluating control rod reactivity worth and reaction rate distribution, compared to the traditional method. We conclude that the BCFH can be a promising homogenization concept for core neutronic analysis.

Consistent robin boundary enforcement of particle method for heat transfer problem with arbitrary geometry

Wang, Z.; Duan, G.*; Matsunaga, Takuya*; Sugiyama, Tomoyuki

International Journal of Heat and Mass Transfer, 157, p.119919_1 - 119919_20, 2020/08

https://doi.org/10.1016/j.ijheatmasstransfer.2020.119919

Study of chemical etching conditions for alpha-particle detection and visualization using solid state nuclear track detectors

Yamada, Ryohei; Odagiri, Taiki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Environment and Medicine, 8(1), p.21 - 25, 2019/02

http://crss.hirosaki-u.ac.jp/rem_archive/radiation-environment-and-medicine-vol-8-no-1

We evaluate radon/thoron and its progeny concentration using passive-type monitors using CR-39 plates. After exposure, it is necessary to do chemical etching for CR-39 plates. In the present study, we considered shortening of chemical etching time for CR-39 and enlargement of the track diameter (i.e. etch pit diameter) aiming for introduction of automatic counting system in the future. Optimum conditions were determined by changing solution concentration, solution temperature and etching time. As a result, the optimized conditions (concentration, temperature and etching time) were determined to be 8 M NaOH solution, 75 degrees Celsius and 10 hours. This result of etching time showed that the chemical etching was completed in less than half of conventional etching time. Furthermore, it was suggested that shorter etching time would be possible if we do not consider the enlargement of conventional track diameter.

Liquid divertor

Shimada, Michiya; Miyazawa, Junichi*

Purazuma, Kaku Yugo Gakkai-Shi, 92(2), p.119 - 124, 2016/02

AA2015-0751.pdf:0.61MB

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2016_02/jspf2016_02-119.pdf

Actively convected liquid metal divertor is promising for providing a solution for issues of DEMO reactors including heat removal and disruptions. This chapter gives an overview of the motivation, research history, recent development, future perspective and issues to be resolved.

Condition number estimation of preconditioned matrices

Kushida, Noriyuki

PLOS ONE (Internet), 10(3), p.e0122331_1 - e0122331_16, 2015/03

https://doi.org/10.1371/journal.pone.0122331

The present paper introduces a condition number estimation method for preconditioned matrices. The newly developed method provides reasonable results, while the conventional method which is based on the Lanczos connection gives meaningless results. The Lanczos connection based method provides the condition numbers of coefficient matrices of systems of linear equations with information obtained through the preconditioned conjugate gradient method. Estimating the condition number of preconditioned matrices is sometimes important when describing the effectiveness of new preconditionerers or selecting adequate preconditioners. Operating a preconditioner on a coefficient matrix is the simplest method of estimation. However, this is not possible for large-scale computing, especially if computation is performed on distributed memory parallel computers. This is because, the preconditioned matrices become dense, even if the original matrices are sparse. Although the Lanczos connection method can be used to calculate the condition number of preconditioned matrices, it is not considered to be applicable to large-scale problems because of its weakness with respect to numerical errors. Therefore, we have developed a robust and parallelizable method based on Hager's method. The feasibility studies are curried out for the diagonal scaling preconditioner and the SSOR preconditioner with a diagonal matrix, a tri-daigonal matrix and Pei's matrix. As a result, the Lanczos connection method contains around 10% error in the results even with a simple problem. On the other hand, the new method contains negligible errors. In addition, the newly developed method returns reasonable solutions when the Lanczos connection method fails with Pei's matrix, and matrices generated with the finite element method.

Local structure around cesium in montmorillonite, vermiculite and zeolite under wet condition

Tsuji, Takuya; Matsumura, Daiju; Kobayashi, Toru; Suzuki, Shinichi; Yoshii, Kenji; Nishihata, Yasuo; Yaita, Tsuyoshi

Clay Science, 18(4), p.93 - 97, 2014/12

Study on the etching conditions of polycarbonate detectors for particle analysis of safeguards environmental samples

Iguchi, Kazunari; Esaka, Konomi; Lee, C. G.; Inagawa, Jun; Esaka, Fumitaka; Onodera, Takashi; Fukuyama, Hiroyasu; Suzuki, Daisuke; Sakurai, Satoshi; Watanabe, Kazuo; et al.

Radiation Measurements, 40(2-6), p.363 - 366, 2005/11

https://doi.org/10.1016/j.radmeas.2004.12.018

In particle analysis for safeguards environmental samples, the fission track technique is very important to detect sub-micrometer particles containing uranium. In the technique the authors developed, the particles were recovered onto the polycarbonate membrane filter. The filter was dissolved in solvent and dried to form a thin film of detector, in which the particles were confined. After thermal neutron irradiation and etching, the particles of interest in the detector were easily identified with fission tracks, and were picked up for isotope ratio analysis. It was found, however, that the particles in the vicinity of the detector surface may fall off during the etching process. Therefore, optimization of the etching condition is required. In this work, the effects of etching time and enrichment of uranium in particles were investigated. Preliminary results suggest that etching time should be shorter with the increase in the enrichment.

Accurate basis set by the CIP method for the solutions of the schrdinger equation

Utsumi, Takayuki*; Yabe, Takashi*; Koga, J. K.; Aoki, Takayuki*; Sekine, Masatoshi*

Computer Physics Communications, 157(2), p.121 - 138, 2004/02

https://doi.org/10.1016/S0010-4655(03)00496-X

no abstracts in English