Decontamination of nuclear power station prim. cycle to remove metal oxide - by adding chelating agent to prim. coolant to dissolve contaminated oxide

摘要

Decontamination of the prim. cycle of a nuclear power station, to remove contaminated metal oxide (I), is carried out in 1 stage, by adding a chelating agent (II) to the prim. coolant (III) in the prim. cycle at a temp. above 140 deg.C. (I) growing or deposited on the walls of the prim. cycle and the radionuclides present in (I) are brought into soln. by formation of metal complexes and removed. Pref. (II) is nitrilotriacetic acid or EDTA. Pref. (III) is also treated with H2 or HCOOH as reducing agent and/or with N2H4 as reducing agent and an additive producing alkaline conditions. Pref. the soln. is regenerated over a cation exchanger, which binds dissolved metals except Cr and liberates (II), then (II) enriched with a Cr complex is subjected to thermal or thermo-oxidative decomposition in the prim. cycle. The remaining soln. is purified over a mixed bed resin or anion exchanger. USE/ADVANTAGE - For removing soluble oxides (spinels) contg. Cr. It is as simple and economical as possible and also rapid and reliable, requires few chemicals and produces little radioactive waste