Abstract
The aqueous reprocessing is the current widespread method used in the nuclear fuel cycle and is evaluated as the main concept for the fast reactor (FR) MOX fuel reprocessing in FaCT (Fast Reactor Cycle Technology Development) Project, designated as one of the national critical technologies of Japan. On the other hand, the pyroprocess as a non-aqueous reprocessing, is oriented as a complementary concept for the FR metal fuel cycle.
In this paper, the author has introduced the pyroprocess development, highlighting the spent electrolyte treatment from the viewpoint of economical and environmental load reduction.
The pyroprocess possesses some inherent problems that have yet to be solved. The purification and recycling of the spent electrolyte as a regenerated medium by removing its fission products (FP) must be further investigated to reduce the volume of high-level radioactive waste (HLW) . Some FP elements dissolved in the medium are apt to remain in the spent electrolyte after recovering actinoid elements. To remove such FP, the zeolite sorption is applied as it is considered the most suitable method, but its concept should be modified in order to reduce the generating waste volume.
There are some alternative methods which use phosphates, among them three are presented here, i.e., the phosphates precipitation method developed by RIAR, Russia, the GRSS method using SAP by KAERI, Korea, and the phosphate conversion method by JAEA. In the phosphate conversion method, the iron phosphate glass (IPG) , which shows unique properties, is employed for FP separation and FP immobilization. From preliminary experiments, it found that the IPG could separate insoluble FP in the spent electrolyte when used as a filtration medium. In addition to that, when used as a sorbent, it could remove the soluble FP. The IPG is regarded as a potential effective material to treat FP.
It is necessary to further develop the spent electrolyte treatment method successively as this could contribute to the realization of the pyroprocess.
