SUPERFACT: A Model Fuel for Studying the Evolution of the Microstructure of Spent Nuclear Fuel during Storage/Disposal.

Thierry Wiss,Rudy Konings,Emanuele De Bona,Vincenzo Rondinella,Alessandro Benedetti,Oliver Dieste

doi:10.3390/ma14216538

Abstract

The transmutation of minor actinides (in particular, Np and Am), which are among the main contributors to spent fuel α-radiotoxicity, was studied in the SUPERFACT irradiation. Several types of transmutation UO2-based fuels were produced, differing by their minor actinide content (241Am, 237Np, Pu), and irradiated in the Phénix fast reactor. Due to the high content in rather short-lived alpha-decaying actinides, both the archive, but also the irradiated fuels, cumulated an alpha dose during a laboratory time scale, which is comparable to that of standard LWR fuels during centuries/millenaries of storage. Transmission Electron Microscopy was performed to assess the evolution of the microstructure of the SUPERFACT archive and irradiated fuel. This was compared to conventional irradiated spent fuel (i.e., after years of storage) and to other 238Pu-doped UO2 for which the equivalent storage time would span over centuries. It could be shown that the microstructure of these fluorites does not degrade significantly from low to very high alpha-damage doses, and that helium bubbles precipitate.

Highlights

IntroductionIn the case of spent fuel reprocessing and minor actinide separation, americium can be transmuted in fast reactors in so-called Minor Actinide Bearing Blankets (MABB), reducing the global inventory of High Level Waste (HLW)
Aside from plutonium, the radiotoxicity of spent fuel during the first centuries of storage/disposal is largely due to Minor Actinides (MA), americium. [1]
In the case of spent fuel reprocessing and minor actinide separation, americium can be transmuted in fast reactors in so-called Minor Actinide Bearing Blankets (MABB), reducing the global inventory of High Level Waste (HLW)

Summary

Introduction

In the case of spent fuel reprocessing and minor actinide separation, americium can be transmuted in fast reactors in so-called Minor Actinide Bearing Blankets (MABB), reducing the global inventory of High Level Waste (HLW). The project investigated the possibility of transmuting those minor actinides into less dangerous elements and at the same time obtain energy from waste. Two different sets of samples were prepared: one set with a low content of MAs (homogeneous mode), and another with a high content of MA (heterogeneous mode). These samples were irradiated up to a burnup of 6.5 at% in the case of the homogeneous, and 4.5 at% for the heterogeneous

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