METHOD FOR METAL PLATING OF RADIOACTIVE GRAPHITE REMOVED FROM OPERATING OR DECOMMISSIONED NUCLEAR POWER PLANTS Russian patent published in 1998 - IPC

FIELD: nuclear power engineering. SUBSTANCE: method involves graphite plating with thin copper-nickel double layer. Graphite part is placed in bath filled with volatile organic solvent. Upon drying, catalyst (cations of transition metals) is fixed on its surface by means of chemical sorption followed by treatment with potassium boron hydride. Then graphite part is rinsed with cobalt salt and plated with copper using autocatalysis process of chemical copper salt reduction. To this end, graphite part is immersed in bath filled with copper salt, reducing agent, binder, and additives. Then graphite surface is reactivated and plated with second nickel layer using electrolytic autocatalysis process of chemical reduction. To this end, graphite part is immersed in bath filled with nickel salt, reducing agent, binder, and additives. Upon metal plating, graphite part is rinsed out. Acetone is used in most cases as volatile solvent. Aqueous solution usually employed for applying copper layer has the following composition: CuCl₂ or Cu(CH₃COO)₂, 0.02-0.06 M; CoCl₂ or Co(CH₃COO)₂, 0.015 M; HCHO, 0.2 M; polyethylene glycol-400, 1.5 vol.%, and Na₂ЭДТA. Aqueous solution used for applying nickel layer has the following composition: NiCl₂, 0.15-0.38M; CoCl₂, 0.02 M; NH₄Cl, 1.0 M; NH₃, 0.5 M; NaH₂PO₂, 0.6 M, and sodium citrate. Water solution used in most cases for reactivating copper-plated graphite has the following composition: KBH₄, 0.1 M; NaOH, 0.1 M. EFFECT: improved water- tightness of coating, minimized leaching of radionuclides, reduced oiliness of surface. 12 cl, 2 tbl, 4 ex