Investigation of Radiation Effects in the Uranyl Mineral Metaschoepite

Schematic depicting irradiation of metaschoepitepowderalong with subsequent reactions with water vapor and atmospheric constituentsto ultimately form studtite. Crystal structures show the intermediateuranium oxide phase that contributes to the accelerated rate of studtiteformation in irradiation systems compared to high relative humiditysystems alone. The effects of water vapor and Heion irradiation on the alterationof particles of the uranyl hydroxide phase metaschoepite, [(UO2)(8)O-2(OH)(12)](H2O)(10), are determined. Raman spectra collected immediatelypostirradiation revealed the presence of a uranyl oxide phase structurallysimilar to & gamma;-UO3 or U2O7. Short-termstorage postirradiation at elevated relative humidity acceleratedformation of the uranyl peroxide phase studtite, [(UO2)(O-2)(H2O)(2)](H2O)(2). Experiments examining the degradation of metaschoepite and thehydration of UO3 enabled spectral assignments and identificationof reaction pathways. The results provide insights into thermal andradiolytic degradation products in both irradiated uranyl hydroxidephases and uranyl peroxide phases, which follow similar degradationpathways.

Automated summary

Irradiation of metaschoepite powder leads to its reaction with water vapor and atmospheric constituents, resulting in the formation of studtite. Crystal structures show an intermediate uranium oxide phase that accelerates the formation of studtite compared to high relative humidity systems alone. The effects of water vapor and He ion irradiation on metaschoepite particles are studied, revealing the presence of a uranyl oxide phase similar to γ-UO3 or U2O7. Short-term storage at elevated relative humidity accelerates the formation of studtite. The results provide insights into thermal and radiolytic degradation products in both uranyl hydroxide phases and uranyl peroxide phases.