Decontaminating and/or cleansing organic solid substrate with e.g. inorganic contaminants comprises contacting substrate with water-free extraction medium having e.g. carbon dioxide and/or giving mechanical treatment for substrate

Decontaminating and/or cleansing an organic solid substrate with solid, radioactive, inorganic contaminants, comprises contacting the substrate with a water-free extraction medium and/or giving mechanical treatment for the substrate. The extraction has: dense carbon dioxide under pressure, a non-halogenated surfactant compound like block copolymers of poly(ethylene oxide) and poly(propylene oxide); and a polydi(1-6C alkyl)siloxanes e.g. polydimethyl siloxane; and a complexing agent e.g. tributylphosphate, crown ethers, tributylphosphine oxide, triphenylphosphine oxide or tri-n-octylphosphine. Process of decontaminating and/or cleansing an organic solid substrate with solid, radioactive, inorganic contaminants, comprises contacting the substrate with an extraction medium free of water and/or giving mechanical treatment for the substrate. The extraction medium has: dense carbon dioxide under pressure; a non-halogenated surfactant compound like block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PPO) e.g. (EO) x-(PO) y diblock copolymers, (EO) x-(PO) y-(EO) x tri-block or (PO) x-(EO) y(EO) x; and a polydi(1-6C alkyl)siloxanes e.g. polydimethyl siloxane; and a complexing agent e.g. tributylphosphate, crown ethers, tributylphosphine oxide, triphenylphosphine oxide or tri-n-octylphosphine. EO : ethylene oxide; PO : propylene oxide; and x, y : 2-80. Procédé de décontamination, de nettoyage, d'un substrat solide contaminé par des contaminants inorganiques solides en particules, dans lequel on met en contact ledit substrat solide avec un milieu d'extraction, exempt d'eau, comprenant un fluide dense sous pression et au moins un composé tensioactif non halogéné constitué uniquement d'atomes choisis parmi O, N, C et H, et on soumet simultanément le substrat solide et/ou le milieu d'extraction à une action mécanique.