Numerical Study on Tritium Behavior by Using Isotope Exchange Reactions in Thermochemical Water-Splitting Iodine–Sulfur Process

Abstract

One potential problem in the hydrogen production system coupled with the high-temperature gascooled reactor (HTGR) is transmission of tritium from the primary coolant to the product hydrogen by permeation through the heat transfer tubes. Tritium accumulation in the process chemicals in the components of a hydrogen plant, a thermochemical water-splitting iodine-sulfur (IS) process, will also be a critical issue in seeking to license the hydrogen plant as a non-nuclear plant in the future. A numerical analysis model for tritium behavior in the IS process was developed by considering the isotope exchange reactions between tritium and the hydrogen-containing process chemicals, i.e., H 2 O, H 2 SO 4 and HI. The tritium activity concentration in the IS process coupled with the high-temperature engineering test reactor (HTTR), the HTTR-IS system, was preliminarily evaluated in regard to the effects of some indeterminate parameters, i.e., equilibrium constants of the isotope exchange reactions, permeability of tritium through heat transfer tubes, tritium and hydrogen concentrations in the secondary helium coolant, and the leak rate from the secondary coolant loop. The results describing how the tritium activity concentration changes with variations in these parameters and which component has the maximum tritium activity concentration in the IS process are described in this paper.

A Small-Sized HTGR System Design for Multiple Heat Applications for Developing Countries

“…The RELAP5 code [23] was used to calculate short-term transient behavior for the rupture of concentric hot gas duct in the primary cooling system and transient behavior for the SG tube rupture. The graphite oxidation behavior of core internal structure was calculated using the THYTAN code [24], which was originally developed for the calculation of mass balance of tritium and hydrogen in the HTGR hydrogen production system using the flow network. The THYTAN code has been modified to calculate the mass balance of the graphite oxidation reaction and the gas concentration in the primary circuit and containment structure.…”

Hydrogen production using high temperature reactors: an overview

“…Six reports were published by JAERI/JAEA in 2007. The first was an evaluation study on tritium activity concentration, Ohashi H. et al (2007). This was done to check the permeability of tritium through heat transfer tubes and to check deuterium and tritium concentrations in the secondary helium coolant.…”

Tritium Barrier Materials and Separation Systems for the NGNP

“…In the nuclear reactor core, tritium is released to the coolant as T 2 , but will quickly undergo isotope exchange reactions with molecular hydrogen, present as a contaminant in the helium stream, to form tritiated hydrogen [27], as shown in Equation 13.…”