Method of cleaning nuclear facility structures

Purpose: To effectively clean the corners of equipments having complicate structures difficult to be cleaned because of stagnation of cleaning liquid chemicals. Method: Structures to be cleaned are installed within a tightly closed cleaning vessel that can be pressurized or depressurized, or they are constituted by themselves as a tightly closed cleaning vessel. A cleaning solution in which gases are dissolved under pressure is supplied to the cleaning vessel and pressurization and depressurization are repeated within a vessel. That is, gaseous CO2, NH3, etc. having high solubility to cleaning liquid chemicals are at first dissolved under pressure. The solutions are supplied to the corners of equipments difficult to be cleaned by way of a pump pressure or the like. Then, when the entire pressure is reduced, evolution of the gases dissolved in the cleaning liquid chemicals is taken place by which the solutions are stirred vigorously. This phenomenon occurs in the same way also in the cleaning liquid chemicals at the corners of equipments of complicate structures thereby enabling effective cleaning. (Takahashi, M.)