Development of Fast Reactor Metal Fuels Containing Minor Actinides

Abstract

Fast reactor metal fuels containing minor actinides (MAs) Np, Am, and Cm and rare earths (REs) Y, Nd, Ce, and Gd are being developed by the Central Research Institute of Electric Power Industry (CRIEPI) in collaboration with the Institute for Transuranium Elements (ITU) in the METAPHIX project. The basic properties of U-Pu-Zr alloys containing MA (and RE) were characterized by performing ex-reactor experiments. On the basis of the results, test fuel pins including U-Pu-Zr-MA(-RE) alloy ingots in parts of the fuel stack were fabricated and irradiated up to a maximum burnup of $10 at% in the Phénix fast reactor (France). Nondestructive postirradiation tests confirmed that no significant damage to the fuel pins occurred. At present, detailed destructive postirradiation examinations are being carried out at ITU.

Anodic dissolution of irradiated metallic fuels in LiCl–KCl melt

“…According to the previous reports [19][20][21], some alkalis and alkaline earths could dissolve in the Na bond and be transported to the upper gas plenum together with the Na bond during the irradiation. This, although a further quantitative analysis is needed, could explain qualitatively that low mass balance values were obtained for alkali and alkaline earth elements.…”

“…15, some cracks and a gap between the fuel residue and the cladding are observed. Since METAPHIX-1 fuel swelled and contacted with the cladding at the end of irradiation, there was no gap observed before the electrorefining run [19][20][21]. Thus the gap was formed during the electrorefining run.…”

“…Before the irradiation, the gap between the fuel rod and the cladding was filled with a Na bond, in the present case a gap volume was 0.278 cm 3 . Due to radial swelling during the irradiation, the Na bond moved to the upper gas plenum or remained in the open pores generated [19][20][21]. In the present case a weight increase of Na in the melt of 0.044 g was determined.…”

“…Furthermore, it was found that the anode residue was made up of three distinct concentric areas: A center area (r/r 0 = 0-0.1, r: distance from the center of the fuel residue, r 0 : radius of the fuel residue), an intermediate area (r/ r 0 = 0.1-0.5) and an outer area (r/r 0 = 0.5-1). Due to the radial temperature gradient in the METAPHIX-1 fuel rod (from about 670°C in the center to about 550°C at the periphery), the fuel components are redistributed, generating three concentric areas with different alloy compositions during irradiation [20,21]. The three distinct concentric areas found in the anode residue were considered to be strongly correlated with the fuel components re-distribution as discussed in the following subsections.…”

“…Therefore, for designing and optimizing the process, it is necessary to collect more experimental data, especially using irradiated fuels, which have not been reported yet. In this study, electrorefining of irradiated metallic fuels (U-19 wt%Pu-10 wt%Zr alloy irradiated at the PHENIX reactor in France, approximate maximum burn-up 2.5 at%, so-called METAPHIX-1 [19][20][21]) was demonstrated with a limited Zr co-dissolution. …”