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Journal Articles

Combustion properties of glove-box panel resins under fire accidents

Tashiro, Shinsuke; Uchiyama, Gunzo; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Watanabe, Koji*; Abe, Hitoshi; Yamane, Yuichi

Nuclear Technology, 10 Pages, 2024/00

https://doi.org/10.1080/00295450.2024.2329832

Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)

Contributing to the confinement safety evaluation of glove-box (GB) connected with high efficiency particle air (HEPA) filters for radioactive materials under fire accidents, combustion tests of a flammable polymer, Polymethyl methacrylate (PMMA), and a flame retardant polymer, Polycarbonate (PC), as typical GB panel resins have been conducted with an engineering-scale combustion apparatus. The combustion properties such as the mass loss rate (MLR) and the heat release rate (HRR) of PMMA and PC were investigated in the combustion tests. In the tests with the same shapes, it was found the followings; MLRs and HRRs of PMMA were larger than those of PC under the same supply flow rate into the combustion cell (Fv); MLRs and HRRs of PMMA and PC were constant under different Fv. Moreover, in the tests of PMMA with different cross section areas (S), MLRs and HRRs were found to be proportional to S. Using these results, the relationships of MLR and HRR to S of PMMA and PC were deduced.

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.

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.

JAEA Reports

Investigation of release behavior of volatile ruthenium species from thermal decomposition of ruthenium nitrosylnitrate

Abe, Hitoshi; Masaki, Tomoo; Amano, Yuki; Uchiyama, Gunzo

JAEA-Research 2014-022, 12 Pages, 2014/11

JAEA-Research-2014-022.pdf:1.03MB

To contribute safety evaluation of boiling and drying accident of high active liquid waste (HALW) in fuel reprocessing plant, release behavior of Ru, which was considered as an important nuclide for evaluating public dose from the volatile viewpoint, has been investigated. It has been reported that release of Ru becomes conspicuously after HALW is dried up. In this work, to grasp the release behavior of Ru, release ratio of Ru with thermal decomposition of Ru nitrate, which would be in the dried HALW, was measured and release rate constant of Ru from the nitrate was estimated. It was found that the calculation result of release rate of Ru from the nitrate with rise of temperature by using the constant could well simulate the result acquired from the beaker-scale experiment.

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.

Journal Articles

Influence of pressure on cesium release from irradiated fuel at temperatures up to 2,773K

Kudo, Tamotsu; Hidaka, Akihide; Nakamura, Takehiko; Uetsuka, Hiroshi

Journal of Nuclear Science and Technology, 38(10), p.910 - 911, 2001/10

https://doi.org/10.3327/jnst.38.910

Times Cited Count：10 Percentile：58.40(Nuclear Science & Technology)

This article describes the effects of system pressure on the cesium release obtained in the first two tests of radionuclides release from irradiated fuel, VEGA-1 and VEGA-2, which were conducted at the same maximum temperature of 2773K and different system pressures. The fractional releases of Cs in VEGA-2 test at 1.0MPa were smaller than those in VEGA-1 test at atmospheric pressure. In order to quantify the difference of the release rate in the two tests due to the pressure, the release rate coefficients of Cs were evaluated. The Cs release rate coefficient in VEGA-2 was smaller by a factor of about 2.8 than that in VEGA-1 at temperature above about 1900K.

JAEA Reports