Neutronic Preliminary Study of Fixed Bed Nuclear Reactor

A preliminary study on the neutronics of Fixed Bed Nuclear Reactor (FBNR) has been performed by using the SRAC code. Uranium dioxide is used as fuel in pebble form (i.e. Micro Fuel Elements), in which coated particles are embedded. The analysis was performed on a clean core without control rods nor burnable poisons. The objective of the study is to obtain a preliminary reactor design having more than ten years of operational periods and negative reactivity coefficients. The analysis was performed by varying enrichment of the fuel and height of the active core. The results showed that an enrichment of 17.8% and an active core height of 235 cm is required to obtain the intended objectives. Such condition gives a fuel temperature reactivity coefficient of -2.575 pcm/K (BOL) to -2.14 pcm/K (EOL), a coolant temperature reactivity coefficient of -0.438 pcm/K (BOL) to -4.469 pcm/K (EOL) and a void reactivity coefficient of -147. 78 pcm/% void (EOL) to -186.45 pcm/% void (EOL). (author)