Modelling and simulation of activation product transport in helium cooling loops

This study presents models to describe the mobilisation, mass transport and deposition mechanisms of active and non-active species in the cooling loop of helium-cooled fusion power plants. A simple nuclear sputtering model has been developed in order to determine the active source term entering the coolant and the flux of sputtered particles ejected from the pipe surfaces. A time independent mass transfer model has been formulated to determine the transport and deposition of nuclides around the primary cooling circuit and the computer code HETRAN has been written to solve the mass transport of stable and active species at discrete locations around the cooling loop. The model describes the mass balance of each species accounting for the particle production and loss mechanisms in the coolant, the surface and the bulk solid. These models have been validated against experimental data and existing computer codes, where possible and found to be in good agreement with published work. Example calculations are performed, to determine the coolant, bulk solid and pipe surface atomic and activity concentrations for the primary circuit of the helium cooled SEAFP Plant Model 1.