Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yoshida, Kazuo; Hiyama, Mina*; Tamaki, Hitoshi
JAEA-Research 2024-007, 24 Pages, 2024/08
JAEA-Research-2024-007.pdf:2.1MB
An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. It has been observed experimentally that volatility of RuO
is suppressed by HNO
generated by HNO
radiolysis. The analysis of chemical reactions of NO
including HNO and HNO in the waste tank is essential to simulate of these phenomena. To resolve this issue, an analytical approach has been attempted to couple dynamically two computer codes SHAWED and SCHERN. The simulation of boiling behavior in the tank is conducted with SHAWED. SCHERN simulates chemical behaviors of HNO, HNO and NO in the tank. A programmatic coupling algorithm and a trial simulation of the accident are presented in this report.
Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*
JAEA-Research 2023-001, 26 Pages, 2023/05
JAEA-Research-2023-001.pdf:1.61MB
An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. To resolve this issue, an analytical approach has been developed using computer simulation programs to assess the radioactive source term from those facilities. The proposed approach consists analyses with three computer programs. At first, the simulation of boiling behavior in the HLLW tank is conducted with SHAWED code. Next step, the thermal-hydraulic behavior in the facility building is simulated with MELCOR code based on the results at the first step simulation such as flowed out mixed steam flow rate, temperature and volatilized Ru from the tank. The final analysis step is carried out for estimating amount of released radioactive materials with SCHERN computer code which simulates chemical behaviors of nitric acid, nitrogen oxide and Ru based on the condition also simulated MELCOR. Series of sample simulations of the accident at a hypothetical typical facility are presented with the data transfer between those codes in this report.
Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*
JAEA-Research 2021-013, 20 Pages, 2022/01
JAEA-Research-2021-013.pdf:2.35MB
An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. An idea has been proposed to implement a steam condenser as an accident countermeasure. This measure is expected to prevent nitric acid steam diffusing in facility building and to increase gaseous Ru trapping ratio into condensed water. A simulation study has been carried out with a hypothetical typical facility building to analyze the efficiency of steam condenser. In this study, SCHERN computer code simulates chemical behaviors of Ru in nitrogen oxide, nitric acid and water mixed vapor based on the conditions obtained from simulation with thermal-hydraulic computer code MELCOR. The effectiveness of steam condenser has been analyzed quantitively in preventing mixed vapor diffusion and gaseous Ru trapping effect. Some issues to be solved in analytical model has been also clarified in this study.
Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*
JAEA-Research 2021-005, 25 Pages, 2021/08
JAEA-Research-2021-005.pdf:2.91MB
An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. To resolve this issue, an empirical correlation equation of Ru mass transfer coefficient across the vapor-liquid surface, which can be useful for quantitative simulation of Ru mitigating behavior, has been obtained from data analyses of small-scale experiments conducted to clarify gaseous Ru migrating behavior under steam-condensing condition. A simulation study has been also carried out with a hypothetical typical facility building successfully to demonstrate the feasibility of quantitative estimation of amount of Ru migrating in the facility using the obtained correlation equation implemented in SCHERN computer code which simulates chemical behaviors of nitrogen oxide based on the condition also simulated thermal-hydraulic computer code.
Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*
JAEA-Data/Code 2021-008, 35 Pages, 2021/08
JAEA-Data-Code-2021-008.pdf:3.68MB
An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides (NO
) are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that NOx affects to the migration behavior of Ru at the anticipated atmosphere condition in cells and/or compartments of the facility building. Chemical reactions of NO with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. The analysis program, SCHERN has been under developed to simulate chemical behavior including Ru coupled with the thermo-hydraulic condition in the flow paths in the facility building. This technical guide for SCHERN-V2 presents the overview of covered accident, analytical models including newly developed models, differential equations for numerical solution, and user instructions.
Yoshida, Kazuo; Tamaki, Hitoshi; Yoshida, Naoki; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.69 - 80, 2019/06
An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that nitrogen oxide affects strongly to the transport behavior of Ru. Chemical reactions of nitrogen oxide with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. An analysis method has been developed with coupling two types of computer codes to simulate not only thermo-hydraulic behavior but also chemical reactions in the flow paths of carrier gases. A simulation study has been also carried out with a typical facility building.
Kikuchi, Masahiro; Ukai, Mitsuko*; Kobayashi, Yasuhiko
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 89, 2015/03
Idesaki, Akira; Morishita, Norio; Ito, Hisayoshi; Kamiya, Tomihiro; Nakamoto, Tatsushi*; Kimura, Nobuhiro*; Makida, Yasuhiro*; Ogitsu, Toru*; Ohata, Hirokatsu*; Yamamoto, Akira*
AIP Conference Proceedings 824, p.330 - 334, 2006/03
Polyimide films and glass fiber reinforced plastics (GFRPs) are used as insulating or structural materials for superconducting magnets in a neutrino beam line of the Japan Proton Accelerator Research Complex (J-PARC). It is indispensable to evaluate radiation resistance of these materials, because they are required to keep their electrical and mechanical properties in a high radiation field of 30 kGy/year at low temperature of 4 K. In this work, the gas evolution resulting from chemical reactions induced in the polyimide films and GFRPs by 
ray irradiation at 77 K was investigated. It was found that the main component of the evolved gas is hydrogen. The amount of hydrogen evolved from the superconducting magnet system used in the neutrino beam line was estimated to be 0.37 mol/year (0.01 L/year as the volume of liquid hydrogen). It indicates that the hydrogen evolved from the organic materials does not influence on the operation of the helium purifying system.
Shiwaku, Hideaki; Mitsui, Takaya; Tozawa, Kazukiyo*; Kiriyama, Koji*; Harami, Taikan; Mochizuki, Tetsuro*
AIP Conference Proceedings 705, p.659 - 662, 2004/00
We developed a multi-crystal switching system on a cryogenically cooled monochromator of JAERI materials science beamline, BL11XU. In order to study our science, it is necessary for ensuring at least the energy range of 6 - 70keV to employ Si(111) and Si(311) crystals. The principle of the crystal switching is that, two pair of crystals is arranged side by side, and they are translated in horizontal direction for exchanging. Indium sheets were inserted between both sides of crystals in order to improve thermal contact. Some adjustment stages of the monochromator were removed to avoid the crystal vibration and a sheet heater was installed on an X-axis stage to prevent over-cooling of X-axis stages. The monochromator is under commissioning at present. In comparison with a previous indirect water cooling diamond (111) crystal monochromator, this monochromator provides high flux intensity from 4 times to 7 times. It takes only 5 minutes to exchange and adjust crystals geometry. This mechanism will be easily applied to other crystals, for example asymmetrical-cut crystals.
Kiriyama, Koji*; Shiwaku, Hideaki; Tozawa, Kazukiyo*
JAERI-Tech 2003-061, 21 Pages, 2003/07
JAERI-Tech-2003-061.pdf:3.25MB
Cryogenically cooled monochromator equipped with circulated-liquid-nitrogen cooling system has been developed on JAERI beam-line, BL11XU, at SPring-8. This cooling system has improved the performance of X-ray reflection. The system has difficulty for the operation because of a lack of the manual. So, it is required to establish a systematic guide of the system. Here we report a manual with fruitful know-how to operate the cryogenic cooling system on BL11XU safely and easily. The new manual is wholly tabulated and shows comments, instructions, and valve conditions in all one-step. The operator, by using this manual, can manipulate the system with no misoperation.
Aso, Tomokazu; Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Takahashi, Toshio*; Hino, Ryutaro
JAERI-Tech 2002-096, 76 Pages, 2002/12
The JAERI and the High Energy Accelerator Research Organization have been developing a Mega-Watt scale spallation target system. In the system, neutrons generated in a target are sorted out their energy to the proper values in liquid-hydrogen moderators. Then, the liquid-hydrogen is forced to circulate in order to suppress hydrogen temperature increase. In the operation of moderators, it is very important to establish a safety protection system against emergency shutdown of the accelerator or accidents of the cold moderator system. In order to obtain a technical data for design and safety review of the liquid-hydrogen system, we have fabricated an experimental apparatus simulated the cold moderator system using liquid nitrogen (max. 1.5MPa, mini. 77K) instead of liquid hydrogen. The experiments on a controllability of the system were carried out to investigate dynamic characteristics of the system. This report presents the experimental results and technical issues for the construction of a practical liquid-hydrogen moderator system of the Mega-Watt scale target system.
Takenaka, Nobuyuki*; Asano, Hitoshi*; Fujii, Terushige*; Ushiro, Toshihiko*; Iwatani, Junji*; Murata, Yutaka*; Mochiki, Koichi*; Taguchi, Akira*; Matsubayashi, Masahito; Tsuruno, Akira
Nuclear Instruments and Methods in Physics Research A, 377(1), p.174 - 176, 1996/07
Times Cited Count：1 Percentile：23.44(Instruments & Instrumentation)no abstracts in English
crystals irradiated with neutrons at liquid nitrogen temperatureOzawa, K.; Kamikawa, T.*
Journal of the Physical Society of Japan, 24(1), p.115 - 119, 1968/00
Times Cited Count：10no abstracts in English
and N centers in NaF crystals irradiated with protons at liquid nitrogen temperatureOzawa, K.;
Phys.Lett., 27A(7), p.443 - 444, 1968/00
no abstracts in English
