Publications
Nuclear Fuel Cycle (NFC) Technology and Policy Program
The CAFCA Code for Simulation of Nuclear Fuel Cycles: Description of Methodology, Assumptions, and Initial Results
T. Boscher, A. Romano, P. Hejzlar, M.S. Kazimi, and N.E. Todreas
MIT-NFC-TR-069 (December 2004)
Abstract
A fuel cycle simulation code called CAFCA (Code for Advanced Fuel Cycles Assessment) has been developed to study the worldwide deployment of two closed advanced fuel cycle strategies and to evaluate their impact. Actinide burning in the thermal spectrum CONFU (COmbined Non-Fertile and UO2) fuel assembly for LWRs and in fast spectrum ABR (Actinide Burner Reactor) reactors are compared to the Once-Through LWR reactor system over the next 50 and 100 years under the assumption of a growing nuclear energy power demand. It is assumed that the CONFU system will be available from 2015 while the ABRs are to be built only after 2028. The systems are simulated as a combination of source, storage and sink units, and the model accounts for the heavy metal mass flows among them. The advanced reactors are represented by a matrix where each column is one reactor and a row in the column is a fuel batch in the reactor. The content of the batches can be therefore tracked to determine the cooling required by the spent fuel before processing. The composition of fresh and spent fuel is approximated to that of equilibrium. Variations over the first few recycles of the TRU content are not taken into account. The chosen goal is to maximise the amount of transuranic elements (TRUs) loaded in the advanced reactors and thus to reduce as quickly as possible the stockpiles of spent fuel. The only constraint in the growing power demand is the availability of separation and reprocessing capacity. This capacity controls the mass of TRU recycled, the number of advanced reactors and finally the need for traditional LWRs and uranium ore to fulfil the power demand.
In a second part of the CAFCA code, the cost of electricity is calculated for each strategy over the next 100 years. The electricity cost is composed of capital costs, operation and maintenance (O&M) costs and fuel cycle costs and is evaluated at each time step as the total expenses divided by the power produced. The capital costs include the cost of the new reactors and of the reactors replacing decommissioned ones. A reactor is paid off over 20 years and is licensed for 60 years. The O&M costs are defined as proportional to the power produced. The fuel cycle costs for each process are the sum of the direct expenditure and of a corrective term accounting for the time value of money between the investment and the collection of the money. The unit costs for the fuel cycle process are expressed in dollar per kilogram of heavy metal treated and do not take into account the distinction between capital and O&M costs for the various plants (i.e. separation or fabrication). The financing is done half by debt and half by equity. The payment of taxes is included in the costs. No inflation is added to the results.
This report provides sample results for the mass balances for heavy metal and TRUs. They are checked by comparing them with the results for the Once-Through cycle which are easy to calculate. The number of advanced reactors, the number of processing plants and the uranium ore needs are also estimated. The cost of electricity is given for nominal unit cost values. The last section explores comprehensively the impact of variations of the main constraint on separation and reprocessing plants fabrication rate. The nominal constraint aims to recycle as fast as possible but results in overcapacity and thus poor economic performance. A better trade-off between overcapacity and rapidity of TRU stockpile reduction can be reached by new rate constraints.
