Analysis of risk reduction effect of supposed steam condenser implementation as accident measure for accident of evaporation to dryness by boiling of reprocessed high level liquid waste

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.

Analysis of behavior of Ru with nitrogen oxide chemical behavior in accident of evaporation to dryness by boiling of reprocessed high level liquid waste

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.

Analysis of chemical behavior of nitrogen oxide formed by thermal decomposition of FP nitrates in accident of evaporation to dryness by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo; Tamaki, Hitoshi; Yoshida, Naoki; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.69 - 80, 2019/06

https://doi.org/10.3327/taesj.J18.019

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.

Synchrotron radiation photoemission spectroscopy for chemical bonding of N atoms in oxynitride films formed at SiO/Si(001) by N beam irradiation

Hachiue, Shunsuke; Teraoka, Yuden

Shinku, 48(5), p.343 - 345, 2005/05

https://doi.org/10.3131/jvsj.48.343

Silicon oxynitride layers were formed by irradiation of nitrogen ion beams at silicon substrates with ultrathin oxide layers. The nitrogen beam was mass-selected N ion beam. The translational kinetic energy was about 3 keV. The dose was 6.310 ions/cm. This value is almost equal to the atom density at the Si(001) surface. Chemical bonding states of irradiated nitrogen atoms were analyzed by photoemission spectroscopy with synchrotron radiation. Although the nitrogen dose was a low density, N-1s photoemission spectra could be deconvoluted into four peaks. The chemical bonding state of each peak was assigned with a reference of a oxide layer thickness dependence of the N-1s photoemission peak profile.

Enhancement of removals of SO and NOx by powdery materials in radiation treatment of exhaust gases

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Int.J.Appl.Radiat.Isot., 36(10), p.807 - 812, 1985/00

https://doi.org/10.1016/0020-708X(85)90032-8

no abstracts in English

Radiation chemical reactions in NO and SO removals from flue gas

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Radiation Physics and Chemistry, 24(1), p.145 - 165, 1984/00

no abstracts in English