Recent Progress on Removal of Sr/Cs from Molten Salt in Dry Reprocessing

doi:10.15541/jim20250101

Abstract

Abstract:

Dry reprocessing technology has advantages of irradiation resistance, proliferation resistance and simplified waste treatment, thereby rendering it a preferred technology for reprocessing of spent fuel of advanced fast reactors. Molten salt electrolytic refining serves as the core technology of dry reprocessing, primarily capitalizing on the difference in redox potential between actinides such as uranium and plutonium and other fissionable elements within a molten salt system. This technology facilitates separation and recovery of actinides. During the electrolytic refining process, lanthanide elements and fission elements, such as Sr and Cs, tend to accumulate within the molten salt, which can change the physicochemical properties of molten salt, thus seriously affecting the efficiency of electrolytic refining. In addition, fission products such as ⁹⁰Sr and ¹³⁷Cs are water-soluble and long-lived nuclides, posing significant environmental hazards if inadequately managed. Therefore, effective purification of fission elements such as Sr and Cs from molten salt is imperative, not only to improve the efficiency of dry reprocessing via molten salt electrolysis, but also as a crucial strategy to reduce the discharge of radioactive waste. This paper summarizes the current research status of Sr and Cs removal methods in molten salts, comparatively analyzes the separation principles and separation effects of different methods, such as electrolysis, crystallization, decompression distillation, precipitation, and ion exchange. Furthermore, it explores prospective direction of development and potential applicability of various material systems.

Key words: dry reprocessing, electrolytic refining, Sr, Cs, molten salt purification, review

CLC Number:

TL24

LIU Zhanyi, LI Mian, OUYANG Xiaoping, CHAI Zhifang, HUANG Qing. Recent Progress on Removal of Sr/Cs from Molten Salt in Dry Reprocessing[J]. Journal of Inorganic Materials, 2026, 41(2): 150-158.

Figures/Tables 11

Fig. 1 Schematic diagram of electrorefining for spent metallic fuel[10]

Fig. 2 Wastes arising from typical light water reactor fuel irradiated to 40000 MW·d/t[11] Elements present shadowed in grey. Numbers represent amount in milligram per kilogram of uranium

Fig. 3 Schematic diagram of experimental setup for the electrolysis method[27]

Fig. 4 Schematic illustration of purification of waste molten salt from pyro-processing of spent nuclear fuels[30]

Fig. 5 Schematic diagram of experimental setup for the cold finger separation[31]

Fig. 6 Schematic diagram of multi-pass zone-refining process[35] 1-Heater; 2-Thermocouple (k type); 3-Melt of the salt; 4-Boat

Fig. 7 Schematic diagram of sequential separation process[36]

Fig. 8 Schematic diagram of experimental equipment for the reactive distillation[43]

Fig. 9 Flow chart of sequential precipitation method[49]

Fig. 10 Schematic diagrams of zeolite structure and zeolite ion exchange device[52,56] (a, b) Schematic structure of zeolite[52]; (c) System for molten salt-zeolite ion exchange tests[56]

Table 1 Available methods for removing Sr and Cs from molten salts and their advantages and disadvantages

Method		Working salt	Nuclide	Advantages	Disadvantages	Ref.
Physical method	Cold finger separation	LiCl	Sr, Cs	No impurities introduced	Difficult to scale application	[31]
	Zone-refining process	LiCl	Sr, Cs	No impurities introduced, high removal rate, easy accessibility	Long processing time	[34]
	Zone-refining process	LiCl-KCl	Sr, Cs		Long processing time	[35-36]
Chemical method	Precipitation	LiCl-KCl	Sr, Cs	Short processing time, low cost	Low removal rate of Cs, introduction of impurities	[11, 49-50]
	Electrolysis	LiCl-KCl	Sr	High efficiency	Low removal rate, high corrosivity to equipment	[27-28]
	Electrolysis	NaCl-KCl	Sr	High efficiency	Low removal rate, high corrosivity to equipment	[29-30]
	Ion exchange	LiCl-KCl/ NaCl-KCl	Sr, Cs	Good selectivity, high removal efficiency	Introduction of new impurities	[57-58, 61]

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