Murataite Ceramics Doped with Lanthanides and Uranium
- PDF / 234,862 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 105 Downloads / 205 Views
0893-JJ05-10.1
MURATAITE CERAMICS DOPED WITH LANTHANIDES AND URANIUM S.V. Stefanovsky1, S.V. Yudintsev2, B.S. Nikonov2, O.I. Stefanovsky1 1
2
SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121 Russia Institute of Geology of Ore Deposits RAS, Staromonetnii lane 35, Moscow 119017 Russia
ABSTRACT Phase composition of the murataite-based ceramics containing 10 wt.% of mixed oxides simulating rare earth/actinide (REE/An) and actinide (An) fractions of high level waste (HLW) was studied. The ceramics were prepared by melting of oxide mixtures in Pt ampoules in air at ~1500 0C. Ceramics with REE/An and An fractions surrogates are composed of predominant murataite-type phases and minor extra phases: perovskite and crichtonite. Three murataiterelated phases with five- (5C), eight- (8C), and three-fold (3C) elementary fluorite unit cell are present in these ceramics. These phases form core, intermediate zone, and rim of the murataite grains, respectively. They are predominant host phases for the rare earth elements and uranium whose concentrations are reduced in a row: M-5C>M-8C>M-3C. Appreciate fraction of Ce, Nd, and Pu may enter the perovskite phase. In the An-Gd ceramic perovskite and murataite were found to be predominant and secondary in abundance phases respectively. INTRODUCTION According to a high level waste (HLW) partitioning concept a long-lived rare earth/ actinide (REE-An) fraction must be separated from a shorter-lived Cs/Sr fraction [1]. The REE/An fraction requires storage for 105-106 years and only crystalline matrices may guarantee safe disposal for so long period. Reprocessing of 1 metric tonne of spent fuel yields about 15 kg of the REE/An fraction or 1-2 kg of TRU elements (Np, Am, Cm) + residual unrecovered U+Pu [2]. Most of the REE isotopes are stable therefore separation of individual actinide (An) fraction is economically expedient because provides for high volume reduction. Several crystalline phases – pyrochlore, zirconolite, cubic zirconia, zircon, britholite, and murataite were proposed as actinide hosts [3]. Among them murataite (more exactly phases of the murataite-pyrochlore polysomatic series) has some advantages because this phase is capable to incorporate both REE/actinides and iron group elements, and even sodium [3,4] thus accommodating in its structure simultaneously REEs, actinides, corrosion products, and process contaminants normally occurred in the REE/An or An fractions. In our previous works [5-7] we investigated incorporation of individual REEs and actinides in the murataite structure. In the present work we study phase composition and elements partitioning in the ceramics containing surrogates of the REE/An and An fractions of HLW. EXPERIMENTAL Compositions of the ceramics with waste surrogates are given in Table I. In the sample with the REE/An fraction surrogate (Sample REE/An) CeO2 was used as a PuO2 surrogate and Gd2O3 – as a Am2O3 and Cm2O3 surrogate. In the with the An fraction surrogate (Sample An) CeO2 was introduced instead of PuO2 and NpO2 and Nd2O3 substituted for
Data Loading...
