Oxide fuels are one of the most popular selections for fast reactor fuel systems, metallic fuels being the other.78 The basis of this popularity can be largely attributed to the great successes achieved in fabrica­tion and operation of LWR oxide fuels.42 Nowadays, LWR operators are seeking ever higher burn-ups of their fuel to attain an economical advantage for LWRs compared to other power plants burning coal
and natural gas. However, the current fuel design has reached its limit at an estimated burn-up of ^80 GWd tU_ . 9 In addition, LWRs produce outlet cool­ant water at a maximum temperature of 320 °C; this limits the efficiency of converting heat to elec­tricity to ^33% and precludes its use as process heat for H2 production.29 The above disadvantages in LWRs based on UO2 fuel may possibly be over­come by the very high temperature reactor (VHTR). The VHTR is fueled by tiny fuel particles embedded in graphite and are cooled by helium (see Chapter 3.06, TRISO Fuel Production). Certain R&D pro­jects still remain to introduce the VHTR commer­cially, in place of LWRs.

For next generation fuel systems that need to burn MAs and process the fuel in a manner that never yields pure plutonium, modifications will be required to minimize waste generation, maximize safety, and maintain operation economics.42 At present, oxide fuels have a higher potential for use in next genera­tion reactor systems than other fuels because a wealth of data has been accumulated for oxide fuels such as fuel fabrication, irradiation behavior, and reproces­sing. As time is still needed to switch from LWRs to FBRs, other fuel systems still have a chance to be the next generation fuel systems through development of innovative technologies.