Abstract: A process for reducing a radioactive material of an object containing a radioactive material to a safe level in a living environment includes releasing pressure including carrying out a heating process on an aqueous liquid that includes water, water-soluble liquid, or a mixture of water and water-soluble liquid, and the object in a state where temperature is less than or equal to a critical temperature of the aqueous liquid and pressure is greater than or equal to a saturated vapor pressure of the aqueous liquid when the object is immersed in the aqueous liquid to such a degree that the object is covered or to a greater degree and then abruptly releasing the pressure, and separating, after the releasing pressure, the mixture of the object and the aqueous liquid into liquid and solid.

Abstract: Provided are a process and device for reducing radioactive material of an object containing the radioactive material to a safe level in a living environment. Included are a step of performing at least a step of carrying out a heating process on the object, into which radioactive material is absorbed and/or adsorbed from an environment or which absorbs and/or adsorbs radioactive material from an environment, in a state where temperature is less than or equal to the critical temperature of water and pressure is greater than or equal to the saturated vapor pressure of water, or a step of abruptly releasing the pressure; and a step of separating, after the above step, into liquid and solid.