Simulation of technetium rejection in an advanced PUREX flowsheet

Controlling the routing of technetium to keep it away from the uranium product streams is essential in order to deliver efficient and safe recycling of spent nuclear fuel in future processes such as Advanced PUREX. In this paper, a flowsheet simulation code is developed for the simulation of technetium and zirconium routing in an Advanced PUREX flowsheet. The essence of this code is its consideration of the slow conversion of inextractable forms of zirconium to extractable forms in the modelling of mass transfer rates. The code is applied to model a flowsheet tested experimentally and is validated by experimental results. Sensitivity of the flowsheet to operating parameters, including temperature, organic-to-aqueous (O/A) flow ratio, and scrub nitric acid concentration is investigated; an optimized set of operating conditions is suggested that could result in lower amounts of technetium being routed to the uranium product.