The Study of CECE Process for Low-Tritiated Liquid Waste Prior to Experimental Phase

In order to ensure the efficient management of radioactive waste in the form of tritiated light water and tritiated heavy water with low tritium and/or deuterium concentration, Institute for Cryogenics and Isotopic Technologies (ICSI) Rm.Valcea is developing an experimental demonstration facility based on the combined electrolysis catalytic exchange (CECE) separation process. The facility is completing the experimental pilot plant for tritium and deuterium separation—the installation support for heavy water detritiation from the CANDU reactors in Romania.

The concentration of deuterium from low-concentrated waste extends the recovery area from below 1% D₂O/(D₂O + H₂O), corresponding to the minimum threshold of the Cernavoda Upgrading Facility, thus contributing to the reduction of heavy water losses. At the same time the tritium recovery process will be increased.

The experimental installation has an innovative solution that reconfigures a proton exchange membrane (PEM) electrolyzer for tritium qualification thereby improving equipment specific to hydrogen isotope separation processes.

This paper presents the experimental installation conceptual scheme, including the measurement and control elements. A modeling software for simulation of the nonsteady-state regime of the CECE separation process, specific to the deuterium/tritium isotopes concentration process in the liquid phase, is also presented. The mathematical model integrates the characteristic equations of separation by liquid phase catalytic exchange (LPCE), the mathematical representation of isotope separation by electrolysis, and the water distillation from the oxygen purification process in a nonstationary regime.

An analysis is presented for the concentration of various low-concentrated tritium waste. We also investigate the influence of the electrolyzer liquid holdup and the isotopic separation column holdup on concentrated water production.