Assessment of proliferation risk related to various fuel cycle scenarios in Finland

Some advanced fuel cycle scenarios have been previously calculated with the COSI6 code in order todetermine the potential impact of partitioning and transmutation (P&T) technologies on spent nuclear fuelmanagement in Finland. The focus has been on the transuranic inventories and decay heat production inthe final repository, the latter of which was assumed to be the restricting factor for the repository capacity.As an extension to these calculations the proliferation resistance considerations were added to the fuelcycle scenarios in the present study. The simulations were again performed with COSI6 and one of theobjectives was to investigate its applicability to proliferation resistance analysis.The calculated scenarios comprised a reference scenario and fuel cycle scenarios aiming at plutoniumand minor actinide incineration through P&T. The reference scenario comprised the currently operating fourlight-water reactors (LWR) with the combined capacity of ~2 800 MWe and the ones under construction or inpreparation, with additional ~4 400 MWe. The last of these units will be closed around 2090 and no newLWRs will be built thereafter. In the basic P&T scenario, some of the retired capacity is replaced withsodium-cooled fast reactors (SFR) and a gradual nuclear phase-out is assumed in 120 years.Proliferation resistance is a broad subject comprising several factors such as government policy,facility security and nuclear material properties. The present study concentrates on the technical featuresof the nuclear material streams and inventories at each time step. The main factors of interest with thisfocus are fissile materials, heat producers and even plutonium isotopes due to their role as majorspontaneous neutron source. These figures do not directly provide comparable information about therelated proliferation risk, so several methods have been developed to convert them into single comparablerisk values. One of them is the Charlton’s method that is based on the multi-attribute utility analysis. It wasutilised in the present study as far as applicable with COSI6.