Crystalline structure variation within phlogopite, muscovite and talc under 0–1000 kGy γ ray irradiation: A clear dependence on intrinsic characteristic

Abstract A clear cognition on how structure difference affects crystalline structure variation within phyllosilicate especially for “2:1” layered phyllosilicate under irradiation is essential to explore the procedure for damage formation within matrix of clay used in disposal high radioactive waste (HLRW) practically and also beneficial for evaluating the effect of nuclear accident to environment, which is of great significance. In this work, phlogopite, muscovite and talc were irradiated by Co-60 γ rays in air at a dose rate of 54 Gy/min with doses at 0–1000 kGy. Then, variation in crystalline structure and intrinsic mechanism were explored. Main results show phlogopite occurred expansion while muscovite and talc occurred shrink in z-direction lattice. Simultaneously, H2O amount declined and valence for metal was elevated. For 1000 kGy-irradiated sample, interlayer space d varied 1% and binding energy for metal was elevated near 1.5–2 eV. It seems phlogopite, muscovite and talc show poor radiation-resistance. Main mechanisms involve intrinsic characteristic, framework break and H2O radiolysis. Upon irradiation, framework break and H2O radiolysis occurred synchronously. Framework break mainly resulted in shrink, H2O radiolysis mainly led extra OH introduction leading expansion. In reality, all these three materials showed extra OH introduction while only phlogopite occurred expansion. It seems the variation trend in lattice mainly relies on material's intrinsic characteristic, H2O radiolysis is secondary. To talc or muscovite, for compact stacking or idle space existence, they are difficult to expand, lattice shrink observed even under extra OH introduction. To phlogopite, for moderate structure, its lattice is easy to expand. For 1000 kGy-irradiated sample, the interlayer space d was enlarged by 1%. For H2O radiolysis, its amount declined and HO• radical was formed, elevating valence for metal as Mg/Al. It seems phyllosilicate shows poor radiation-resistance, and the apparent variation trend in lattice induced by γ ray irradiation seems mainly rely on material's intrinsic characteristic, H2O radiolysis is secondary.