Reactive distillation process using a solid-solid reaction for the separation of strontium from spent nuclear fuel

The separation of high-heat-generating isotopes of Sr from spent nuclear fuel is a significant research area in nuclear waste management. To separate Sr from spent nuclear fuel, the chlorination method using MgCl 2 is known to be very effective. Then, the separated Sr must be oxidized for the solidification process, for example by oxidation using K 2 CO 3 , but this faces challenges owing to the high reactivity of MgCl 2 . Thermodynamic calculations and experiments demonstrated that MgCl 2 has a higher reactivity with K 2 CO 3 than SrCl 2 , forming MgO instead of SrO. This study therefore investigated a novel two-step reactive distillation process employing solid-solid reactions with K 2 CO 3 for the first time. The first step is to completely distill MgCl 2 from the mixture of MgCl 2 and SrCl 2 . Then, the second step involves the addition of 1.7 molar equivalents of K 2 CO 3 to the residue after the distillation of MgCl 2 , in order to obtain SrO through reactive distillation using a solid-solid reaction with SrCl 2 . This study confirms that this method is effective as the next step in the Sr separation utilizing MgCl 2 , and by applying the reactive distillation process to oxidize Sr for the first time, it has contributed to completing the Sr separation process using molten salts.