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Journal Articles

Numerical simulation on dispersion of hydrogen leaked in particle layers of glass beads and soil

Terada, Atsuhiko; Nagaishi, Ryuji

Nuclear Technology, 210(10), p.1871 - 1887, 2024/10

https://doi.org/10.1080/00295450.2024.2302747

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

In order to understand dispersion of H $_{2}$ leaked in packed beds of non-porous/porous particles in a partially open space practically, the dispersion of H $_{2}$ in the particle layers of glass beads and soil was analytically studied using a CFD code to be compared with the experiments and to elucidate the effects of particle layer. H $_{2}$ flowed out from a single leak point in the particle layer of non-porous glass beads was affected by buoyancy around the leak point, and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, H $_{2}$ spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H $_{2}$ concentration became about 1/3 or less of the concentration near the surface of particle layer. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H $_{2}$ in the particle layer proceeded in the same manner as in the case of glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H $_{2}$ diffused in the air layer until the H $_{2}$ concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of H $_{2}$ concentration distribution. Based on the above, we further simulated H $_{2}$ behavior in the vessel containing the H $_{2}$ leaked particle layer. By inserting multiple vent pipes without considering H $_{2}$ generation distribution and particle properties in the particle layer, H $_{2}$ accumulated from one pipe was discharged by buoyancy without depending on the H $_{2}$ generation distribution and particle properties in the particle layer, and air flowed in from the other pipe.

Journal Articles

Improvement of Worldwide Version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), 1; New combination of models, atmospheric dynamic model MM5 and particle random walk model GEARN-new

Terada, Hiroaki; Furuno, Akiko; Chino, Masamichi

Journal of Nuclear Science and Technology, 41(5), p.632 - 640, 2004/05

https://doi.org/10.3327/jnst.41.632

Times Cited Count：23 Percentile：79.19(Nuclear Science & Technology)

The new version of WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information) is developed by introducing the combination of models, the atmospheric dynamic model MM5 and the Lagrangian particle dispersion model GEARN-new to improve the prediction capability. One of the improvements by the new system is that Environmental contaminations in multi domains are predicted simultaneously, and the other is that more precise physical processes are considered by using predicted meteorological conditions with high resolution in time and space. The performance of the system is evaluated for the test calculations of hypothetical nuclear accident in the East Asia region and the Chernobyl accident. The results of test calculation in East Asia seem to be reasonable and the calculated surface air concentrations of $^{137}$ Cs from Chernobyl show good agreement with measurements.

Journal Articles

The High temperature gas cooled reactor fuel

Sawa, Kazuhiro; Ueta, Shohei; Iyoku, Tatsuo

Proceedings of International Conference on Global Environment and Advanced Nuclear Power Plants (GENES4/ANP 2003) (CD-ROM), 10 Pages, 2003/09

This paper provides present status of research and development for the coated fuel particle (CFPs) including the advanced ZrC-CFP. Current HTGR employs so-called TRISO-CFPs with SiC layer. In safety design of the HTGR fuels, it is important to retain fission products within CFPs so that their release to primary coolant does not exceed an acceptable level. The behavior of TRISO-CFPs has been investigated through experiments and reactor operation. These data show excellent performance of the TRISO-CFPs when they are correctly fabricated. On the other hand, the crystalline material comprising the SiC layer has a tendency to decompose at high temperature. The transition temperatures of beta-SiC (as-deposited) to alpha-SiC vary from 1600 to 2200 $^{circ}$ C. ZrC is one of the transition metal carbides which are characterized by the high melting point and the thermodynamic stability etc. The CFPs with CVD-ZrC coatings have been investigated including the fabrication processes and characterization techniques developments.