LORA Analysis Using Thorium in 220 MWe PHWR Fuel

Thorium is not a fissile material and cannot either start or sustain a chain reaction. Therefore, a reactor using thorium would also need either enriched uranium or plutonium to initiate the chain reaction and sustain it until enough of the thorium has converted to fissile uranium (U233). U233 can be produced on a regular basis by irradiating thoria pins in existing PHWRs. In order to retrieve and reprocess the irradiated fuel, the bundle is designed with few thoria pins and rest SEU pins. Another way is to uniformly mix the plutonium with thorium in all the pins. The reactivity load due to thoria pins is compensated by SEU/plutonium. The objective is to irradiate thorium for production of U233 and compensate the burnup loss by using SEU in separate pins of PHWR fuel bundle. In this paper, the loss of reactivity accident has been discussed for 220 MWe PHWR. The analysis has been carried out using computer code MRIF-FUEL (Jain, Yadav in Point kinetics code MRIF-FUEL, Theoretical Physics Division, BARC, 1989, [1]). The input data are generated using computer code CLUB (Krishnani in CLUB, a multigroup integral transport theory code for lattice calculations of PHWR cells, BARC/1992/E/017 [2]).