Amorphization of rare earth aluminate garnets under ion irradiation and decay of 244Cm admixture

Abstract

The stability of synthetic REE aluminate garnets irradiated by accelerated Kr 2+ ions and affected by alpha decay of 244 Cm (T 1/2 = 18.1 yr) has been studied. The dose of irradiation sufficient for the complete disordering of the aluminate garnet structure is 0.40-0.55 displacements per atom. This value increases with rising temperature due to the increasing intensity of recovery from radiation damage to the lattice by heating. The critical temperature above which the structure of REE aluminate is not damaged by radiation is 550°C. The amorphization dose for aluminates with garnet structure is two to three times higher than of that previ ously studied ferrites; the critical temperature of both is similar. In resistance to radiation, aluminate garnets do not yield to zirconolite and exceed titanate pyrochlore. Heating to 250°C does not lead to substantial recovery from radiation defects in the garnet structure. The radiation impact on matrices of real actinide (An) wastes is lower than that related to ion irradiation and 244 Cm doping, and this facilitates a higher radiation resistance of garnets containing HLW.

Phase evolution and chemical stability of Nd‐doped Y3Fe5O12 waste forms synthesized in molten salt at a low temperature

“…17 R. C. Ewing studied the sensitivity of garnet structure of 244 Cm-doped samples to radiation damage by means of ion irradiation and decay. 9 The critical amorphization dose observed is about 0.4 displacements/atom (dpa), which is close to that of zircon (ZrSiO 4 ) or britholite [A 4 B 6 (XO 4 ) 6 Y 2 ]. Most importantly, the radiation damage from alpha-decay of actinides to the garnet structure has a negligible effect on its chemical stability in aqueous solutions.…”

Irradiation of synthetic garnet by heavy ions and α-decay of 244Cm

“…Three chemical compositions of the garnets (listed in [29]. Initial Cm used for sample preparation contained not only 244 Cm (75% of total Cm), but also long-lived 245 Cm and 248 Cm (25%) and also 240 Pu (0.36 wt.%).…”

“…G -garnet, Cor -corundum, T -Teflon (germetizaion of sample for XRD investigations), D -diamond (standard). Data from Livshits et al[29].…”

Study of the Hydrolytic Stability of Fine-Grained Ceramics Based on Y2.5Nd0.5Al5O12 Oxide with a Garnet Structure under Hydrothermal Conditions

“…The study of such compounds is very important for the immobilization of actinide elements (which constitute a special group of long-term ecologically hazardous radionuclides) in order to isolate these ones from the biosphere for the long time required for the storage and disposal. For this purpose, the world's leading laboratories are currently studying ceramic materials based on natural minerals [1]: monazite [2,3], garnet [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], kosnarite [18][19][20][21], pyrochlore [10,[22][23][24][25], scheelite [26], etc. The garnet structure is one of the most promising matrices for the MA immobilization.…”

“…The position of the R 3+ cation can be occupied by Al, Fe, Cr, and Ga, the position of the X cation-by Al, Fe, Ga, and Si cations [3,6]. In addition, compounds with a garnet structure have high hydrolytic and radiation stability [3,4,[7][8][9]27].…”