Contact Author:
Dr. Liviu Popa-Simil
PO. Box 717

Los Alamos, NM 87544

The advantages of the poisons free fuels


The weakness of the actual nuclear fuels is due in part to fission product inappropriate treatment, which seems to oppose the nature’s principle of energy spread and distribution in any available freedom degree. The fission process energy release is based on splitting of a heavy nucleus into two medium nuclei and releasing the difference of bound energy. The fission products energy is about 80% of the total energy release during the fission, and enables them travel several tens of microns inside the fuel lattice. The actual trend in fuels is to increase the incarceration of the fission products by adding supplementary confinement layers and under this aspect the nuclear reactor is similar to a high security prison. The cost of this practice is materialized in low burnup and low reliability of the fuel pellets driving to early immobilization of burnable nuclear fuel in the waste fuel pools, and to a significant nuclear waste quantity. The new approach considers that the fission product removal from the nuclear reactor core would be beneficial to the neutron balance and fuel economy. This removal have to be made considering the fission products stored energy in their excited states with variable decay time such as the most of this energy to be released inside the heavily shielded hot zone of the nuclear reactor. Observing the fission products behavior during the stopping inside the fuel lattice, some fuel structure optimization criteria have been extracted. The resulted optimal structure is heterogeneous having the dimensions in the micrometric domain resembling the Cermet structures but it has the advantages of the molten salt reactor with the safety values of the solid pellets or TRISO fuel. By optimizing the fissile material dimensions versus the fission products effective range the fission products induced damage is eliminated almost completely. The hetero-micro-structured fuel contains liquid metal that has an important contribution to thermal conduction enhancement and fission product agglomeration outside the fuel. This type of new fuel may be encapsulated in pellets as the sintered powder fuel or it may be installed in open tubes where the liquid metal to be used as drain fluid. Similar to the bio-systems this type of nuclear reactor treats continuously the fission products removing them from the hot zone where they have a poisoning effect due to their higher neutron absorption cross-section. This fact has positive consequences in reduction of the initial mass of the nuclear reactor up to 50%, increasing the operation temperature and thermo-mechanical energy conversion efficiency, reducing the remnant radioactivity of the fuel to an equivalent of several weeks of operation and higher burnup suitable with OTTO cycle. The disadvantage compared to actual nuclear reactor consists in higher fuel manufacturing complexity and the presence of the fission products drain out and online purification system, which adds a degree of complexity to the process. Finally, the price of the unit of produced energy and major accident radioactive contamination hazards are smaller.