Ten-year results from unsaturated drip tests with UO2 at 90°C: implications for the corrosion of spent nuclear fuel

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

“…The first oxidized alteration phase from the weathering of synthetic or natural UO 2 (s) is typically a simple oxyhydroxide, either schoepite ((UO 2 ) 8 O 2 (OH) 12 Á12H 2 O) or metaschoepite ((UO 2 ) 4 O(OH) 6 Á5H 2 O) (Finch and Ewing, 1992). Under most natural conditions, however, schoepite is metastable with a strong tendency to undergo structural transformation to more stable secondary phases, such as becquerelite (Ca(UO 2 ) 6 O 4 (OH) 6 Á8H 2 O) or compreignacite (K 2 (UO 2 ) 6 O 4 (OH) 6 Á7H 2 O) after incorporation of Ca and K, respectively (Sandino and Grambow, 1994;Wronkiewicz et al, 1996). A Na analogue of compreignacite (Na 2 (UO 2 ) 6 O 4 (OH) 6 Á7(H 2 O)) was tentatively identified among the alteration phases observed on spent fuel in contact with groundwater for six years , and is an important alteration phase due to the ubiquitous presence of dissolved Na in groundwaters (Gorman-Lewis et al, 2008a).…”

Dissolved Concentration Limits of Radioactive Elements

“…Laboratory studies are the basis for the selection of the controlling phases (Finch et A recent and thorough laboratory study (Wronkiewicz et al 1996 [DIRS 102047]) describes the results of a 10-year study of UO 2 degradation at 90ºC in dripping J-13 type water equilibrated with tuff. The U-bearing alteration phases observed in that study are given in Table 6.7-1.…”

“…Uranophane is also an important secondary silicate but it is clear that the final silicate phase is Na-boltwoodite (Wronkiewicz et al 1996 [DIRS 102047], Section 4.2.1 and Figure 7). As waste packages degrade, the total aqueous U concentration is controlled by the concentration of the complexing ligands (Section 6.4.3) in solution and by the least-soluble uranium phase that is stable for the current fCO 2 and pH conditions.…”

The question of water content in parsonsite: a model case - occurrence at the Červené žíly vein system, Jáchymov (St. Joachimsthal), Czech Republic

“…Study of these phases is important in the context of uranium use as nuclear fuel. Related problems include sites of old mining, ore dressing settling pits, mine dumps or even spent nuclear fuel ("SNF") management (Finch and Ewing 1992;Wronkiewicz et al 1992Wronkiewicz et al , 1996Finn et al 1996;Murakami et al 1997;Finch et al 1999;Fayek et al 2000;Čejka 2002;Shueneman et al 2003;Catalano et al 2004;Pittauerová and Goliáš 2006;Catalano et al 2006;Procházka 2007;Procházka et al 2009). Uranyl phosphates occur commonly as abundant phases in the supergene zones of most uranium deposits (Finch and Murakami 1999).…”