Borosilicate and lead silicate glass matrix composites containing pyrochlore phases for nuclear waste encapsulation

Processing glass–pyrochlore composites for nuclear waste encapsulation

“…Based on those findings, an approach for actinides waste immobilisation is being developed by our group [17][18][19]: the primary immobilization of radioactive waste is achieved within a pyrochlore phase, which is itself encapsulated into a silicate glass matrix. The use of sintered silicate glass for the matrix has the important advantage of allowing relatively low processing temperatures (<700°C) which are much lower than those required for densification of pyrochlore crystalline ceramics (about 1200°C).…”

“…In our previous studies with lead silicate glass matrix, the use of lanthanum zirconate (La 2 Zr 2 O 7 , pyrochlore structure) has been proposed as host phase for actinides not only due to the radiation resistance exhibited by this compound [13] but also because it has a thermal expansion coefficient very close to that of the lead silicate glass used as matrix. The use of an alternative glass matrix based on a soda borosilicate glass of low sintering temperature has been preliminary explored [18]. The main reason to investigate a borosilicate glass matrix is the intrinsic high chemical durability of this glass, which is higher than that of the lead silicate glass used earlier [17].…”

Studying the shielding properties of lead glass composites using neutrons and gamma rays

“…One way to do this is through vitrification and, namely, lead silica glass composites are a good candidate for such application. These composites should possess desirable properties such as good chemical durability, radiation resistance, good resistance towards devitrification as well as potential shielding from radiation (Santos and Vasconcelos, 1996;Boccaccini et al, 2004). Vitrification has long been developed for high-level waste, however it has been developed for low-level waste as well (Spence et al, 1999).…”

Glassy Wasteforms for Nuclear Waste Immobilization

“…GCMs include the following: (1) glass ceramics in which a glassy waste form is crystallized in a separate heat treatment [7,78] ; (2) GCMs in which, e.g., a refractory waste is encapsulated in glass such as hot-pressed lead silicate glass matrix encapsulating up to 30 vol pct of La 2 Zr 2 O 7 pyrochlore crystals to immobilize minor actinides [9] ; (3) GCM formed by pressureless sintering of spent clinoptiloite from aqueous waste processing [10] ; (4) some difficult wastes such as the French HLW U/Mo-containing materials immobilized in a GCM termed U-Mo glass formed by cold crucible melting that partly crystallize on cooling [11] ; (5) yellow phase containing wastes are immobilized in Russia in a yellow phase GCM containing up to 15 vol pct of sulfates, chlorides, and molybdates [12] ; and (6) GCM that immobilizes ashes from incineration of solid radioactive wastes. [13] Note that alkali-rich wastes at the Hanford site are also immobilized in glassy wasteforms with high crystal contents that characterize them as GCMs.…”