Study on method to achieve high transmutation of LLFP using fast reactor

Area of Science:

• Nuclear Engineering
• Materials Science

Background:

• Long-lived fission products (LLFPs) pose significant challenges in nuclear waste management.
• Efficient transmutation is crucial for reducing the long-term radiotoxicity of nuclear waste.

Purpose of the Study:

• To develop and validate a method for achieving high transmutation rates of specific LLFPs (79Se, 99Tc, 107Pd, 129I) in fast reactors.
• To design innovative LLFP target assemblies that mitigate thermal effects on adjacent fuel.

Main Methods:

• Inventing new LLFP target assemblies incorporating YD2 and YH2 moderators or thermal neutron filters.
• Loading these assemblies into the blanket region of a sodium-cooled, MOX-fueled fast reactor.
• Conducting material property and fabrication experiments for LLFP targets and moderators.

Main Results:

• Achieved a high transmutation rate of approximately 8% per year for the four targeted LLFPs.
• Demonstrated the suppression of thermal spikes in adjacent fuel assemblies through the new target designs.
• Confirmed the feasibility of the LLFP transmutation target through experimental validation.

Conclusions:

• The developed LLFP target assemblies are effective for high-rate transmutation in fast reactors.
• The proposed method offers a viable solution for managing long-lived fission products.
• Experimental validation supports the practical application of these transmutation strategies.