Anhydrous H/sub 2/SO/sub 4/ shows very little chemical reaction under pile radiation. The presence of dissolved U, however, induces extensive decomposition to SO/sub 2/ and oxygen. The effect is purely chenical and independent of the existence of fission in the solutions, as it is shown by solutions of depleted'' U containing practically no U/sup 235/. The existence of the U-catalyzed decomposition discourages the idea of using concentrated acid as a medium for a honogeneous nuclear reactor. (auth)