Phase and defect evolution in uranium-nitrogen-oxygen system under irradiation

Uranium mononitride (UN) with 5 wt.% uranium dioxide (UO2) is used as a model system to study the phase and defect evolution under proton irradiation in nitride-oxide composite. Phase composition, crystallographic orientation relationships (ORs) and dislocation loops were characterized using X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy techniques. Proton-irradiation at elevated temperatures promoted the transformation of UN into uranium sesquinitride (U2N3) and UO2 phases. U2N3 and UO2 formed a fully coherent structure with two ORs: {002}U2N3 parallel to{002}UO2 and [001]U2N3 parallel to[001]UO2; U2N3{101}parallel to UO2{101} and U2N3[101]parallel to UO2[101] due to low lattice misfit (2.3%) and low interfacial energy (127 mJ/m(2)). Observed oxidation of UN and coherent interface are consistent with density-functional theory calculations which suggest lower energy for oxidized configuration and low energy of the interface. The dislocation loops grew while their number density decreased with the temperature and dose. The loop size was over three times larger in two nitride phases than that in UO2, while the number density was one order of magnitude higher in UO2 than in nitride phases. Loop density and diameter were analyzed using a kinetic rate theory that considers stoichiometric loop evolution. This analysis led to the conclusion in all compounds loop growth is governed by mobility of uranium interstitials, and enabled measurement of diffusion coefficients of uranium interstitials and non-metal interstitials and vacancies. This analysis provided a comparative study of early stage of microstructure evolution under irradiation which has implications for use of this mixture as advanced fuel in nuclear energy systems

Phase and defect evolution in uranium-nitrogen-oxygen system under irradiation

Uranium mononitride (UN) with 5 wt.% uranium dioxide (UO2) is used as a model system to study the phase and defect evolution under proton irradiation in nitride-oxide composite. Phase composition, crystallographic orientation relationships (ORs) and dislocation loops were characterized using X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy techniques. Proton-irradiation at elevated temperatures promoted the transformation of UN into uranium sesquinitride (U2N3) and UO2 phases. U2N3 and UO2 formed a fully coherent structure with two ORs: {002}U2N3 parallel to{002}UO2 and [001]U2N3 parallel to[001]UO2; U2N3{101}parallel to UO2{101} and U2N3[101]parallel to UO2[101] due to low lattice misfit (2.3%) and low interfacial energy (127 mJ/m(2)). Observed oxidation of UN and coherent interface are consistent with density-functional theory calculations which suggest lower energy for oxidized configuration and low energy of the interface. The dislocation loops grew while their number density decreased with the temperature and dose. The loop size was over three times larger in two nitride phases than that in UO2, while the number density was one order of magnitude higher in UO2 than in nitride phases. Loop density and diameter were analyzed using a kinetic rate theory that considers stoichiometric loop evolution. This analysis led to the conclusion in all compounds loop growth is governed by mobility of uranium interstitials, and enabled measurement of diffusion coefficients of uranium interstitials and non-metal interstitials and vacancies. This analysis provided a comparative study of early stage of microstructure evolution under irradiation which has implications for use of this mixture as advanced fuel in nuclear energy systems.</p

The prevalence, types and perceived outcomes of crisis episodes in early adulthood and midlife: a structured retrospective-autobiographical study

The objective of the study was to gain data on the prevalence, types and perceived outcomes of crisis episodes in three age decades of adult life: 20–29, 30–39 and 40–49. A further aim was to explore the relationship between crisis occurrence and empathy. A retrospective-autobiographical survey instrument and an empathy questionnaire were administered to 1023 UK-based adults. Prevalence data showed that crisis in the 20–29 decade was reported by 39% of men and 49% of women, while in the 30–39 decade 47% of men and 51% of women reported a crisis, and 46% of men and 59% of women reported a crisis occurring in the 40–49 decade. When prevalence rates were compared by participants’ current age, a recency effect in crisis reporting was apparent. Work-related crises were more common in men, while relationship and family were more common in female crisis. The most common crisis contents across decades and genders were divorce/relationship break-up and debt/financial difficulties. Post-crisis growth was significantly lower in the 40–44 age range in men than in other age ranges for both genders. There was a positive relationship between self-report empathy and number of crisis episodes experienced