Tritium extraction and recovery system (TER) for the helium cooled pebble beds with steam in the helium purge gas

Abstract

The Tritium Extraction and Recovery (TER) system is a He-loop with the main purpose to purge the HCPB BBs and consequently remove tritium from the pebble beds, followed by tritium recovery from the purge gas. The tritium recovery from Q2 and Q2O forms from the He purge gas is realized by adsorption of the Q2O form in the Reactive Molecular Sieve Bed (RMSB) followed by Q2 adsorption in the Cryogenic Molecular Sieve Bed (CMSB)/getter beds (Q stands for any H/D/T). During the regeneration of the RMSB and CMSB/getter beds the tritium will be recovered in the Q2 form and finally is processed in the Tritium Plant.The adsorption/desorption process using Reactive Molecular Sieve Beds (RMSB) can be successfully used for removal of the tritiated water from helium purge loop of the TER HCPB. In this case, the tritium recovery from the tritiated water is straight forward by isotopic exchange with a hydrogen/deuterium swamping gas. In addition, the use of the RMSB for the helium purge gas containing steam allows that slightly tritiated water, resulted as tritium recovery by isotopic swamping, to be returned in the helium purge loop. Therefore, there is no need for further processing of tritiated water since the water is used as carrier closed loop of the tritium in the helium purge loop. The water that will be recovered during the full regeneration of the RMSB will contain tritium at levels of at least two order of magnitude lower that in the tritiated water coming out from the BB. By doing so it is not necessary to process the significant amount of water that is contained in the purge gas. Two order of magnitude difference in the tritium concentration in the water, mining the tritium concentration in the water fed in the BB and the tritium concentration in the water coming out from the BB, provides the required gradient in the tritium concentration for the isotopic exchange at the level of pebble beds.The paper aims to present the main advantages of tritium removal from the helium purge loop containing steam based on RMSB technology and a proposal for the configuration of the TER HCPB based on RMSB technology will be presented. The estimation of the tritium inventory based on various purge gas flow rates and steam content in the purge gas will be introduced as well.