Session: 02-14: Structural Evaluation, Performance Assessment, Multiphysics Coupling - IV

Paper Number: 134482

134482 - A Review of the Chemical Forms and Transport Behavior of Tritium in Nuclear Energy Systems 

Abstract: 

Tritium is an important nuclide in the environmental impact assessment and source term analysis of commercial nuclear power plants, and the maximum energy of β^-rays released by tritium is 18.6 keV. Tritium in nature is mainly produced by cosmic rays interacting with atoms such as nitrogen and oxygen in the atmosphere and undergoing a series of nuclear reactions. With the continuous development of human science and technology and the usage of nuclear energy, human activities, including nuclear weapons testing and the operation of nuclear reactors, can also produce a certain amount of tritium. At present, there are experimental designs based on reactor conditions to study the chemical speciation of tritium. In this paper, the main chemical speciation and transport behavior of tritium in various reactors are reviewed, which can provide a basis for studying the physical and chemical behavior of tritium in nuclear energy systems.

In light water reactors, tritium is produced by a nuclear reaction of a coolant and a neutron-absorbing material for reaction control. Normally, more tritium is produced in pressurized water reactors (PWRs) than in boiling water reactors. Most of the tritium in PWRs was released into the environment in liquid effluents, while most of the tritium in boiling water reactors was released into the environment in gaseous effluents. The PWRs release about six times more tritium into the environment than those in boiling water reactors. In molten salt reactors, irradiated tritium is present in the melt as an oxidized form of T⁺ ions or TF, or as a dissolved form of T₂ or HT. The chemical form of tritium also affects its transport path in the reactor. When tritium is present in both TF and T₂ forms, only T₂ can penetrate into the metal. In fusion reactors, a significant portion of tritium produced by proliferation is released in the form of HTO, and some in the form of HT. In 2015, 10 MW high temperature gas-cooled reactor (HTR-10) was measured and found that tritium in the primary circuit was mainly in the form of HTO, while in HTTR and AVR, tritium was mainly in the form of HT.

In this paper, we summarize the production mechanism and main chemical forms of tritium in PWRs, molten salt reactors, fusion reactors and high-temperature gas-cooled reactors, and clarify the chemical forms of tritium with the change of environmental conditions (temperature, pressure, irradiation, etc.) in nuclear energy systems. In addition, the transport behavior of tritium in nuclear energy systems with different chemical forms was discussed, which can provide an important basis for the study of tritium storage, control, monitoring and prevention of its leakage and disposal.

Presenting Author: Ling Liu Tsinghua university

Presenting Author Biography: Mr. Ling Liu is a senior reactor operator of 10MW high temperature gas cooled reactor. His major is nuclear science and technology. He has explored in behaviors and features of HTGR for over 20 years.

Authors:

Jingni Guo Tsinghua university
Ziling Zhou Tsinghua university
Yu Wang Tsinghua university
Ling Liu Tsinghua university
Feng Xie Tsinghua university
Liqiang Wei Tsinghua university
Jianzhu Cao Tsinghua university
Peng Li Shanxi university
Vladimir B. Sovkov St. Petersburg State University
Sofiia Onishchenko P. Hertsen Moscow Oncology Research Institute