Reactor with metallic fuel and lead-208 coolant

Abstract

Abstract This time, several projects dedicated to fast reactors (FRs) with lead and lead-bismuth coolants, BREST-OD-300, SVBR-100, RBETS-M, BRUTs are proposed in Russia. They will have several valuable consuming properties: chemical inertness, low neutron absorption, low activation and others. Usage of lead coolant leads also to the possibility of achieving a hard-enough neutron spectrum that allows increasing the incineration probability of 241Am, 237Np and other low fissile actinides. High power FRs have large-sized cores that limits the value of neutron energy by the value of 0.5 MeV, which is insufficient for incineration of above mentioned actinides. Small and medium power reactors have smaller cores and, respectively, have harder neutron spectra. Usage of lead and low moderating innovative fuel allow further increasing neutron energy to the value inquired for low fissile actinides incineration.In the paper a possibility of obtaining a neutron spectrum with the average value of neutron energy higher than 0.5 MeV is considered. It is performed in the frame of the project of BRUTs series reactors, i.e. small power LFRs proposed in the Obninsk Institute for Nuclear Power Engineering. A scope for achieving a hard neutron spectrum in the reactor BRUTs-25 core of small sizes, D×H = 0.5×0.4 m2, is shown. Findings are that in the core fueled with Pu-Am-Np-Zr alloy and cooled with enriched lead, 208Pb, the average value of neutron energy, , is high-enough, about 0.95 MeV, as well as the share of fast neutron, En>0.8 MeV, in the neutron spectrum is very high, about 40%. In such of conditions, 241Am and 237Np incineration probabilities in the core center are higher than 50% and values of their one-group fission cross-sections are higher than 0.7 barn. This circumstance allows burning 15-16wt% of low fissile isotopes for one campaign of BRUTs-25. The presence of 241Am in the fuel, in a quantity of 28.7 kg, allows transmuting about 8.6 kg of its mass for one reactor campaign that lasts about 3 years (1000 effective days). It means that to transmute the quantity of 241Am produced by the VVER-1000 for one year, equal to 25.8 kg, it will be needed about 3 BRUTs-25 type low power reactors operating for 1000 effective days.