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 to determine the potential impact of partitioning and transmutation (P and T) technologies on spent nuclear fuel management in Finland. The focus has been on the transuranic inventories and decay heat production in the 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 fuel cycle scenarios in the present study. The simulations were again performed with COSI6 and one of the objectives was to investigate its applicability to proliferation resistance analysis. The calculated scenarios comprised a reference scenario and fuel cycle scenarios aiming at plutonium and minor actinide incineration through P and T. The reference scenario comprised the currently operating four light-water reactors (LWR) with the combined capacity of ∼2800 MWe and the ones under construction or in preparation, with additional ∼4400 MWe. The last of these units will be closed around 2090 and no new LWRs will be built thereafter. In the basic P and T scenario, some of the retired capacity is replaced with sodium-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 features of the nuclear material streams and inventories at each time step. The main factors of interest with this focus are fissile materials, heat producers and even plutonium isotopes due to their role as major spontaneous neutron source. These figures do not directly provide comparable information about the related proliferation risk, so several methods have been developed to convert them into single comparable risk values. One of them is the Charlton's method that is based on the multi-attribute utility analysis. It was utilised in the present study as far as applicable with COSI6. (authors)