HEAT SOURCE CONTAINING RADIOACTIVE NUCLEAR WASTE

A heat source includes packages or cans of radioactive heat-producing nuclear waste material contained in vertically disposed heating tubes immediately surrounded and cooled by a "spare" coolant at its boiling temperature which in turn is surrounded by a "primary" coolant from which useful heat is extracted. Immediately above the primary coolant chamber is an emergency coolant chamber which cools vapors of the boiling liquid when an increase in heat caused by interruption of primary cooling causes an increase in the temperature of the boiling liquid so that vapors therefrom rise into a zone cooled by the emergency coolant. Heat pipes having a portion in thermal contact with the top of heating tubes and a portion exposed to the atmosphere are provided as also are fused which permit the radioactive material to drop into a canal beneath the normal heat source zone should all other means for removing heat fail.