The physical modeling of uranium isotopes (235U, 238U) separation process by centrifugation is a key aspect for predicting the nuclear fuel enrichment plant performances under surveillance by the Nuclear Safeguards Authorities.
At Joint Research Centre in Ispra ( Italy) the NP (Non Proliferation) analyses of GCEP (Gas Centrifuge Enrichment Plants) make regular use of advanced numerical modeling techniques supported and/or validated with data acquired during field inspections. By adopting this approach, normal and off normal conditions can be tested at an early stage improving the odds of a timely detection of eventual misuses or diversions of Nuclear Materials. This work illustrates some aspects of the CFD modeling of a typical cascades plant for uranium hexafluoride (UF6) enrichment adopting the hypersonic gas centrifuges technology. The 1D CFD simulation with the advanced software tool Flowmaster allows a reliable estimation of the cascade separation performances under different operating conditions once the separation external parameters are set (feed flow rate and feed, product and tails assays). The separation factor of the single centrifuge as a function of the inlet flow rate is the basic knowledge which allows to determine the performances of an entire cascade assuming that all the set of centrifuges connected in series and in parallel (the cascade) are identical.
The Flowmaster model of the cascade consists in a set of interconnected centrifuges grouped in stages; moreover the cascade itself is divided in two sections (stripping and enriching) and is equipped with a inlet feed stage and two output stages (final product and final tails stages). The outputs of the calculation are the concentrations (assays) and the flow rates of the enriched (product) and depleted (tails) gas mixture. This numerical model of GCEP represents a valuable additional tool, in order to verify the compliance of the U enrichment plant operator declarations with the “on site” inspectors’ measurements.