Nuclear Fission, Byproducts, and Affect on Burnup

2396 Words10 Pages
Abstract The process of nuclear fission causes the formation of fission products. The source and quantity of byproducts of fission are explained to provide a foundation for a discussion of the effects of fission products. The swelling effect of both solid and gaseous byproducts of fission is explained and the negative effect that swelling has on fuel performance as well as its limiting affect on burnup is described. Finally, potential solutions to deal with the effects of fission products and subsequently allow for increased burnup are discussed. Introduction The quantity of fission products in a nuclear reactor is dependent on the amount of fission occurring, which is directly related to fuel burnup. Therefore it follows that increased fuel burnup causes a rise in the quantity of fission products. Fission product behavior negatively impacts fuel performance in a number of different ways. The negative impacts on fuel performance that fission byproducts have include fuel swelling, pressure and stress on the cladding, as well as decreased thermal performance of the fuel; all of which limit the amount of burnup a reactor can undergo. The neutralization, reduction, or removal of fission products and subsequently their associated negative effects will allow for higher burnup in nuclear reactors. Source and Quantity of Fission Products The total quantity of fission products present in the fuel can be determined by a direct mass balance relating the rate of production by fission (requires that the fission product yield be known) to the rate of loss by radioactive decay. In order to determine the overall fission product yield the contribution from beta decaying precursors to the independent yield of the isotopes must be accounted for. The independent fission yield (iy) is the
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