A nonuniform layer of deuterium‐tritium (DT) ice inside a spherical inertial confinement fusion (ICF) target held in an isothermal cryogenic environment should be driven toward uniformity by the beta‐decay heat of the tritium. Experiments have been performed at KMS fusion to verify this hypothesis. Two major conclusions may be drawn from the initial results: (1) the beta decay of the tritium does deposit energy in the target, as evidenced by melting of DT ice when the target is well insulated from its surroundings, and (2) solid layers of DT ice sublime because of beta‐decay heat. Both conclusions are reinforced by companion studies with nonradioactive hydrogen‐deuterium (HD) ice in similar targets held under similar experimental conditions.