In the expression 1/&agr;=c[1+(&kgr;/&rgr;R)] for the advantage (&agr;) of decreased resonance absorption of uranium in adE/Eneutron spectrum brought about by lumping UO2into spheres, the temperature dependence ofcis measured and &kgr; is measured also. &rgr; is the density of UO2in g/cm3;Rthe radius of the sphere in cm. In the range 20° to 1000°C, &Dgr;c/&Dgr;Taverages 1.8×10−6per degree centigrade and is positive as expected. This temperature dependence decreases by about a factor of three from the lowest to the highest measured temperatures. &kgr; is 5.06 g/cm3leading to a value of &mgr; in the expression [Phys. Today5, 32 (May, 1952)]&sgr;(E)dEEeff=A1+&mgr;SMof 1.69 g/cm2.&Dgr;A&Dgr;T is 4×10−4barns∘C.