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Journal Articles

Feasibility study of tritium recoil barrier for neutron reflectors

Ishitsuka, Etsuo; Sakamoto, Naoki*

Physical Sciences and Technology, 6(2), p.60 - 63, 2019/12

https://doi.org/10.26577/phst-2019-2-p8

Tritium release into the primary coolant of the research and test reactors during operation had been studied, and it is found that the recoil release from chain reaction of $^{9}$ Be is dominant. To reduce tritium concentration of the primary coolant, feasibility study of the tritium recoil barrier for the beryllium neutron reflectors was carried out, and the tritium recoils of various materials were calculated by PHITS. From these calculation results, it is clear that the thickness of tritium recoil barrier depends on the material and 2040 m is required for three orders reduction.

Journal Articles

Calculation of tritium release from driver fuels into primary coolant of research reactors

Ho, H. Q.; Ishitsuka, Etsuo

Physical Sciences and Technology, 5(2), p.53 - 56, 2019/00

https://doi.org/10.26577/phst-2018-2-158

Increasing of tritium concentration in the primary coolant of the research and test reactors during operation had been reported. To check the source for tritium release into the primary coolant during operation of the JMTR and the JRR-3M, the tritium release from the driver fuels was calculated by MCNP6 and PHITS. It is clear that the calculated values of tritium release from fuels are as about 10 $^{7}$ and 10 $^{6}$ Bq for the JMTR and JRR-3M, respectively, and that calculated values are about 4 order of magnitude smaller than that of the measured values. These results show that the tritium release from fuels is negligible for both the reactors.

JAEA Reports

Calculations of Tritium Recoil Release from Li and U Impurities in Neutron Reflectors (Joint research)

Ishitsuka, Etsuo; Kenzhina, I.*; Okumura, Keisuke; Ho, H. Q.; Takemoto, Noriyuki; Chikhray, Y.*

JAEA-Technology 2018-010, 33 Pages, 2018/11

JAEA-Technology-2018-010.pdf:2.58MB

As a part of study on the mechanism of tritium release to the primary coolant in research and testing reactors, tritium recoil release rate from Li and U impurities in the neutron reflector made by beryllium, aluminum and graphite were calculated by PHITS code. On the other hand, the tritium production from Li and U impurities in beryllium neutron reflectors for JMTR and JRR-3M were calculated by MCNP6 and ORIGEN2 code. By using both results, the amount of recoiled tritium from beryllium neutron reflectors were estimated. It is clear that the amount of recoiled tritium from Li and U impurities in beryllium neutron reflectors are negligible, and 2 and 5 orders smaller than that from beryllium itself, respectively.

Journal Articles

Evaluation of tritium release curve in primary coolant of research reactors

Ishitsuka, Etsuo; Kenzhina, I. E.*

Physical Sciences and Technology, 4(1), p.27 - 33, 2018/06

https://doi.org/10.26577/phst-2017-1-120

Increase of tritium concentration in the primary coolant for the research and testing reactors during reactor operation had been reported. To clarify the tritium sources, a curve of the tritium release rate into the primary coolant for the JMTR and the JRR-3M are evaluated. It is also observed that the amount of released tritium is lower in the case of new beryllium components installation, and increases with the reactor operating cycle. These results show the beryllium components in core strongly affect to the tritium release into the primary coolant. As a result, the tritium release rate is related with produced $^{6}$ Li by (n,) reaction from $^{9}$ Be, and evaluation results of tritium release curve are shown as the dominant source of tritium release into the primary coolant for the JMTR and the JRR-3M are beryllium components. Scattering of the tritium release rate with irradiation time were observed, and this phenomena in the JMTR occurred in earlier time than that of the JRR-3M.

JAEA Reports

Calculation by PHITS code for recoil tritium release rate from beryllium under neutron irradiation (Joint research)

Ishitsuka, Etsuo; Kenzhina, I. E.*; Okumura, Keisuke; Takemoto, Noriyuki; Chikhray, Y.*

JAEA-Technology 2016-022, 35 Pages, 2016/10

JAEA-Technology-2016-022.pdf:3.73MB

As a part of study on the mechanism of tritium release to the primary coolant in research and testing reactors, the calculation methods by PHITS code is studied to evaluate the recoil tritium release rate from beryllium core components. Calculations using neutron and triton sources were compared, and it is clear that the tritium release rates in both cases show similar values. However, the calculation speed for the triton source cases is two orders faster than that for the neutron source case. It is also clear that the calculation up to history number per unit volume of 210 $^{4}$ (cm $^{-3}$ ) is necessary to determine the recoil tritium release rate of two effective digits precision. Furthermore, the relationship between the beryllium shape and recoil tritium release rate using the triton sources was studied. Recoil tritium release rate showed linear relation to the surface area per volume of beryllium, and the recoil tritium release rate showed about half of the conventional equation value.

Journal Articles

Progress of target system operation at the pulsed spallation neutron source in J-PARC

Takada, Hiroshi; Naoe, Takashi; Kai, Tetsuya; Kogawa, Hiroyuki; Haga, Katsuhiro

Proceedings of 12th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '15), p.297 - 304, 2016/00

In J-PARC, we have continuously been making efforts to operate a mercury target of a pulsed spallation neutron source with rated power of 1-MW. One of technical progresses is to mitigate cavitation damages at the target vessel front induced by the 3-GeV proton beam injection at 25 Hz. We have improved the performance of a gas micro-bubbles injection into the mercury target, resulting that no significant cavitation damages was observed on the inner surface of target vessel after operation for 2050 MWh with the 300-kW proton beam. Another progress is to suppress the release of gaseous radioactive isotopes, especially tritium, during the target vessel replacement. We have introduced a procedure to evacuate the target system by an off-gas processing apparatus when it is opened during the replacement operation, achieving to suppress the tritium release through the stack. For example, the amount of released tritium was 12.5 GBq, only 5.4% of the estimated amount, after the 2050 MWh operation. After these progresses, the operating beam power for the pulsed spallation neutron source was ramped up to 500-kW in April, 2015.

Journal Articles

Development of dose assessment code for accidental tritium releases; ACUTRI

Yokoyama, Sumi; Noguchi, Hiroshi; Kurosawa, Naohiro*

Hoken Butsuri, 40(4), p.376 - 384, 2005/12

https://doi.org/10.5453/jhps.40.376

A computer code named ACUTRI has been developed to assess tritium doses due to inhalation to the general public. ACUTRI can calculate the radiological impact of tritium gas (HT) and tritiated water (HTO) released accidentally to the atmosphere. The models in this code consist of a tritium transfer model including the oxidation of HT to HTO and the reemission of HTO from soil to the atmosphere and a dose calculation model. The atmospheric dispersion of the primary HT and HTO plumes and secondary HTO plume, which is reemitted from soil to the atmosphere, is calculated by using the Gaussian plume model. In this calculation, it is possible to analyze statistically on meteorology in the same way as a conventional dose assessment method according to the meteorological guideline of the Nuclear Safety Commission of Japan. Tritium concentrations in air and their resultant doses were calculated using the ACUTRI code under some conditions. In order to validate the model, calculations were compared with experimental results.

JAEA Reports

Proceedings of the 11th International Workshop on Ceramic Breeder Blanket Interactions; December 15 - 17, 2003, Tokyo, Japan

Enoeda, Mikio

JAERI-Conf 2004-012, 237 Pages, 2004/07

JAERI-Conf-2004-012.pdf:44.1MB

This report is the Proceedings of "the Eleventh International Workshop on Ceramic Breeder Blanket Interactions" which was held as a workshop on ceramic breeders Under the IEA Implementing Agreement on the Nuclear Technology of Fusion Reactors, and the Japan-US Fusion Collaboration Framework. In the workshop, information exchange was performed for designs of solid breeder blankets and test blankets in EU, Russia and Japan, recent results of irradiation tests, HICU, EXOTIC-8 and the irradiation tests by IVV-2M, modeling study on tritium release behavior of Li $_{2}$ TiO $_{3}$ and other breeders, fabrication technology developments and characterization of the Li $_{2}$ TiO $_{3}$ and Li $_{4}$ SiO $_{4}$ pebbles, research on measurements and modeling of thermo-mechanical behaviors of Li $_{2}$ TiO $_{3}$ and Li $_{4}$ SiO $_{4}$ pebbles, and interfacing issues, such as, fabrication technology for blanket box structure, neutronics experiments of blanket mockups by fusion neutron source and tritium recovery system.

JAEA Reports

Nuclear, thermo-mechanical and tritium release analysis of ITER breeding blanket

Kosaku, Yasuo; Kuroda, Toshimasa*; Enoeda, Mikio; Hatano, Toshihisa; Sato, Satoshi; Sato, Shinichi*; Osaki, Toshio*; Miki, Nobuharu*; Akiba, Masato

JAERI-Tech 2003-058, 69 Pages, 2003/06

JAERI-Tech-2003-058.pdf:5.86MB

The design of the breeding blanket in ITER applies pebble bed breeder in tube (BIT) surrounded by multiplier pebble bed. It is assumed to use the same module support mechanism and coolant manifolds and coolant system as the shielding blankets. This work focuses on the verification of the design of the breeding blanket, from the viewpoints which is especially unique to the pebble bed type breeding blanket, such as, tritium breeding performance, tritium inventory and release behavior and thermo-mechanical performance of the ITER breeding blanket.

Journal Articles

I-A. Models for atmospheric releases: I-A.1. Models used by JAERI, Japan

Amano, Hikaru; Atarashi-Andoh, Mariko; Takahashi, Tomoyuki*

IAEA-BIOMASS-3, p.163 - 164, 2003/03

no abstracts in English

Journal Articles

Formation and retention of organically bound deuterium in rice in deuterium water release experiment

Atarashi-Andoh, Mariko; Amano, Hikaru; Kakiuchi, Hideki; Ichimasa, Michiko*; Ichimasa, Yusuke*

Health Physics, 82(6), p.863 - 868, 2002/06

https://doi.org/10.1097/00004032-200206000-00015

Times Cited Count：6 Percentile：39.48(Environmental Sciences)

As a substitute of tritium, deuterium water (D2O) vapor release experiments were performed to estimate the difference of formation and subsequent retention of organically bound deuterium (OBD) in rice plants between daytime and nighttime exposure. Potted plants were exposed to deuterium water vapor in a greenhouse for 8 hours, under day and night conditions. Deuterium concentrations in free water and organic matter in rice leaves and ears were investigated until the harvest time. Data analysis was carried out using a model in which different generating processes of organic matter were considered. The calculated results agreed with the measured value.

Journal Articles

Conversion rate of HTO to OBT in plants

Atarashi-Andoh, Mariko; Amano, Hikaru; Ichimasa, Michiko*; Ichimasa, Yusuke*

Fusion Science and Technology, 41(3), p.427 - 431, 2002/05

In processes of tritium transfer in the environment, conversion of HTO to OBT in plant by photosynthesis is important for both aspects of monitoring and dose estimation. Because once OBT is formed in plant, it stays in the plant for longer time than HTO, and OBT is more harmful than HTO for human body. Conversion rate of HTO in plant leaf to OBT in plant edible parts in the open air were obtained for some plants (komatsuna, radish and cherry tomato) during the chronic HT release experiment at Chalk River in 1994. At the experiment, HT gas was released to the atmosphere at the cultivated site for 12 days continuously [1]. HTO and OBT concentration in cultivated plants were measured during the experiment. For plant leaves conversion rate of HTO to OBT was about 0.2 (% h $^{-1}$ ) but it varied with their growth stage. A chamber experiment in laboratory was also carried out for comparison.