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Published: 1996

Total Pages: 7

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A fuel development campaign that results in an aluminum plate-type fuel of unlimited LEU burnup capability with an uranium loading of 9 grams per cm3 of meat should be considered an unqualified success. The current worldwide approved and accepted highest loading is 4.8 g cm−3 with U3Si2 as fuel. High-density uranium compounds offer no real density advantage over U3Si2 and have less desirable fabrication and performance characteristics as well. Of the higher-density compounds, U3Si has approximately a 30% higher uranium density but the density of the U6X compounds would yield the factor 1.5 needed to achieve 9 g cm−3 uranium loading. Unfortunately, irradiation tests proved these peritectic compounds have poor swelling behavior. It is for this reason that the authors are turning to uranium alloys. The reason pure uranium was not seriously considered as a dispersion fuel is mainly due to its high rate of growth and swelling at low temperatures. This problem was solved at least for relatively low burnup application in non-dispersion fuel elements with small additions of Si, Fe, and Al. This so called adjusted uranium has nearly the same density as pure [alpha]-uranium and it seems prudent to reconsider this alloy as a dispersant. Further modifications of uranium metal to achieve higher burnup swelling stability involve stabilization of the cubic [gamma] phase at low temperatures where normally [alpha] phase exists. Several low neutron capture cross section elements such as Zr, Nb, Ti and Mo accomplish this in various degrees. The challenge is to produce a suitable form of fuel powder and develop a plate fabrication procedure, as well as obtain high burnup capability through irradiation testing.