| 摘要 |
<p>PURPOSE:To collect almost the whole quantity of nitric acid and to enable reuse of decontaminated magnesium nitrate as an evaporation auxiliary by extracting radio active material by adding a solvent to a residual liquid of distillation containing the radioactive material and magnesium nitrate after a nitric-acid water solution containing the radioactive material is distilled in the existence of the magnesium nitrate. CONSTITUTION:A nitric-acid water solution 2 containing a radioactive material and magnesium nitrate 11 are introduced into an evaporator 1 from supply routes and distillation is executed. A distillation temperature is about 120 to 160 deg.C under a normal pressure, for instance. Almost the whole quantity of nitric acid vapor produced at the time of distillation is collected from the top part of the evaporator through a mist-removing tray 4. The vapor is cooled down and liquefied in a condenser 5 and then it is reused as a decontaminated nitricacid water solution 8 in a reprocessing plant. When the-quantity of the magnesium nitrate 11 is 40wt.% or above, the concentration of the nitric acid in a vapor phase is higher than that of the nitric acid in a liquid phase, and when it is in the range of 45 to 55wt.%, the concentration of the nitric acid in the vapor phase is twice or more that in the liquid phase. Thus, sharp reduction of the volume of nitric acid water solutions 8 and 17 is attained.</p> |
