Thorium fuel cycle models in DIONISIO

MARTIN EMILIO GONZALEZ; ALEJANDRO SOBA; ALICIA DENIS

Bariloche

Congreso; IYNC2018; 2018

IAEA

The present work reflects an initial approach to the Thcycle problem in the DIONISIO code and is aimed atobtaining expressions to predict the evolution of the morerepresentative species in the fuel, with respect to burnup andpellet radius, by solving the corresponding balance equations.Reactor physics codes perform these calculations, solving theBoltzmann transport equations in a number of energyintervals (groups) and including adequate considerations inthe region of the resonant absorption peaks of the relevantnuclei. They predict with the radial distribution of neutronflux, burnup and concentration of every species, fissile,fissionable or fertile, gaseous or solid, within the rod for theoverall process, all of them as functions of time. Among theknown reactor codes we mention CONDOR , from whichthe cross section values were obtained for this work. Asimplified treatment was proposed in the past , whichconsists in reducing the energy spectrum to a single group.The purpose is to obtain empirical expressions to represent,with the higher possible approximation degree, theabsorption and capture cross sections as functions of theinitial enrichment in 235U, the average burnup and the radialcoordinate. The curves obtained with such a drasticsimplification demand validation before their incorporationin the general fuel behaviour code. This validation isperformed via comparison with the reliable reactor codes.With these curves already incorporated, the fuel code isexpected to give, with a reasonable precision, the timeevolution of the local burnup and hence the size of the rimzone.