Insights into near-surface distribution characteristics of multi-form tritium with consideration of atmospheric buoyancy and gravitational deposition

Deyi Chen; Baojie Nie; Bing Dong; Derui Yang; Siyuan Wu; Jinpeng He; Weiguo Gu; Dezhong Wang

doi:10.1016/j.chemosphere.2022.137231

Insights into near-surface distribution characteristics of multi-form tritium with consideration of atmospheric buoyancy and gravitational deposition

Chemosphere. 2023 Jan;312(Pt 1):137231. doi: 10.1016/j.chemosphere.2022.137231. Epub 2022 Nov 11.

Authors

Deyi Chen¹, Baojie Nie², Bing Dong¹, Derui Yang¹, Siyuan Wu¹, Jinpeng He¹, Weiguo Gu¹, Dezhong Wang³

Affiliations

¹ School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
² School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address: niebaojie@sjtu.edu.cn.
³ School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address: dzwang@sjtu.edu.cn.

PMID: 36375611
DOI: 10.1016/j.chemosphere.2022.137231

Abstract

Tritium contributes majority to the total airborne radioactive effluents from the nuclear facility because of its considerable production and difficulty in separation. Tritium inventory in the fusion reactor would reach an unprecedented magnitude which brings new safety concern. After being released into the atmosphere, inconsistent atmospheric dispersion behaviors might appear regarding different physicochemical forms such as gaseous state HT, gaseous-aerosol-droplet state HTO. In this study, atmospheric dispersion characteristics of multi-form tritium were investigated based on the computational fluid dynamics method validated by multi-fan type wind tunnel experiments. Species transport model and discrete phase model were used to describe atmospheric dispersion of gaseous and aerosol-droplet state tritium, respectively. Deposition velocity was predicted for gaseous and aerosol-droplet state tritium with different particle sizes. Conditions for describing the changes of particle diameter and its influencing on near-surface tritium distribution due to condensation were provided. The results show that buoyancy effect would strengthen along with the increasing gaseous tritium mass fraction in the airborne effluents. We also indicated that obvious gravitational deposition would appear once gaseous HTO was transformed into droplet state HTO with the particle diameter larger than 20 μm. Both the atmospheric buoyancy and deposition phenomenon would result in a quite different near-surface tritium distribution.

Keywords: Atmospheric dispersion; Buoyancy; Gravitational deposition; Nuclear facility; Tritium.