Pyroprocessing is a promising technology for recycling spent nuclear fuel due to its compact system design, high tolerance 

to radiation and heat, and inherent resistance to nuclear proliferation. However, thermal treatment of spent fuel during the 

process results in the release of gaseous fssion products, which must be managed to ensure environmental safety and regulatory

compliance. In contrast to aqueous reprocessing, where many fssion products remain in solution, pyroprocessing 

involves direct high-temperature volatilization of radionuclides, resulting in distinct release behaviors that require tailored 

management. This review provides an overview of the of-gas behavior of key fssion products such as Cs-137, I-129, Tc-99, 

Se-79, H-3, C-14, and Kr-85 during the process steps, including voloxidation and sintering. The release characteristics are 

analyzed with respect to their chemical forms, thermal stability, and sensitivity to process conditions. The recent advances 

in capture technologies are also reviewed, focusing on materials and methods applicable to the pyrochemical environment. 

These include both conventional and emerging strategies for selective capture and immobilization of radioactive gases. 

By integrating fndings from thermodynamic and experimental studies, this review highlights critical considerations for 

designing efcient of-gas treatment systems in pyroprocessing, providing guidance for future development of sustainable 

radionuclide management.