Pyroprocessing is a promising technology for managing spent nuclear fuel. The nuclear material accounting of feed material is a challenging issue in safeguarding pyroprocessing facilities. The input material in pyroprocessing is in a solid-state, unlike the solution state in an input accountability tank used in conventional wet-type reprocessing. To reduce the uncertainty of the input material accounting, a double-stage homogenization process is proposed in considering the process throughput, remote controllability, and remote maintenance of an engineering-scale pyroprocessing facility. This study tests two types of mixing equipment in the proposed double-stage homogenization process using surrogate materials. The expected heterogeneity and accounting uncertainty of Pu are calculated based on the surrogate test results. The heterogeneity of Pu was 0.584% obtained from Pressurized Water Reactor (PWR) spent fuel of 59 WGd/tU when the relative standard deviation of the mass ratio, tested from the surrogate powder, is 1%. The uncertainty of the Pu accounting can be lower than 1% when the uncertainty of the spent fuel mass charged into the first mixers is 2%, and the uncertainty of the first sampling mass is 5%.

1. Introduction
2. Research Method
    2.1 Performance Evaluation of Nauta andTumbler Mixers
    2.2 Powder Heterogeneity
    2.3 Distributions of Pu Concentration inSpent Fuel Powder
    2.4 Pu Heterogeneity
3. Discussion
    3.1 Pu Accounting Uncertainty in theDouble-Stage Homogenization Process
4. Conclusion
Acknowledgements
REFERENCES

• Chaehun Lee(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Dajeon 34057, Republic of Korea) Corresponding author
• Bong Young Kim(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Dajeon 34057, Republic of Korea)
• Byung-Hee Won(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Dajeon 34057, Republic of Korea)
• Hee Seo(Jeonbuk National University, 567, Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 54896, Republic of Korea)
• Se-Hwan Park(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Dajeon 34057, Republic of Korea)