Contribution of Energetically Reactive Surface Features to the Dissolution of CeO2 and ThO2 Analogues for Spent Nuclear Fuel Microstructures

In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analogues that approximate as closely as possible the microstructure characteristics of fuel-grade UO2 but are not sensitive to changes in oxidation state of the cation. The morphology of grain boundaries (natural features) and surface facets (specimen preparation-induced features) was investigated during dissolution. The effects of surface polishing on dissolution rate were also investigated. We show that preferential dissolution occurs at grain boundaries, resulting in grain boundary decohesion and enhanced dissolution rates. A strong crystallographic control was exerted, with high misorientation angle grain boundaries retreating more rapidly than those with low misorientation angles, which may be due to the accommodation of defects in the grain boundary structure. The data from these simplified analogue systems support the hypothesis that grain boundaries play a role in the so-called “instant release fraction” of spent fuel, and should be carefully considered, in conjunction with other chemical effects, in safety performance assessements for the geological disposal of spent fuel. Surface facets formed during the sample annealing process also exhibited a strong crystallographic control and were found to dissolve rapidly on initial contact with dissolution medium. Defects and strain induced during sample polishing caused an overestimation of the dissolution rate, by up to 3 orders of magnitude

The Effects of a Vegetarian Diet on Iron Status in Female Students

Iron deficiency anemia is the most common nutritional deficiency disease worldwide (Mahan & Escott-Stump, 2004). Iron deficiency anemia is of major concern especially in women of child bearing age and those who follow a vegetarian diet. The objective of this study was to compare the nutrient and hematological values related to iron status in female university students following a vegetarian versus following a nonvegetarian diet. This study took a cross sectional analysis of 39 female students at California Polytechnic State University (Cal Poly State University) in San Luis Obispo, CA. Of the participants 19 were following a vegetarian diet and 20 were following a nonvegetarian diet. To participate, individuals had to be female, current Cal Poly students, and between the ages of 18 and 22 years old. Those taking vitamin or mineral supplements, medications (including oral contraceptives), smokers, and pregnant women were excluded. Characteristic, demographic, and anthropometric data were collected through interview, nutrient intake was accessed by averaging three day food records, and hematological parameters were measured. Statistical analysis used nonparametric techniques including the Mann-Whitney Wilcoxon statistical test for demographics and baseline characteristics, the Spearman Rank Correlation analysis and Fisher’s Exact statistical test for associations between vegetarians and nonvegetarians. Results found no significant difference in iron intake between vegetarians and nonvegetarians, however nonvegetarians had higher mean intakes of iron at 16.82 (SD 6.36) mg/day compared to vegetarians at 14.84 (SD 7.10) mg/day (p=0.482). A similar percentage of vegetarians at 66.7% (n=8) compared to nonvegetarians at 65% (n=13) were under the Recommended Daily Allowance (18 mg per day for females 19 to 30 years of age) for mean iron consumption. There were slightly more nonvegetarians at 10% (n=2) compared to vegetarians at 8.3% (n=1) under the Estimated Average Requirement (8.1 mg/day for females 19 to 30 years of age) for mean iron intake. No significant difference was found for serum iron, serum ferritin, transferrin saturation, and total iron binding capacity between vegetarians and nonvegetarians. Finding revealed serum ferritin, the most common iron status indicator, was lower for vegetarians at 23.16 (SD15.54) ng/mL compared to nonvegetarians at 27.75 (SD 18.01) ng/mL (p=0.47). When looking at the stages of iron balance, there was greater percentage of vegetarians with hematological results (serum iron \u3c40 µg/dL, total iron binging capacity of \u3e410 µg/dL, transferrin saturation \u3c15%, and serum ferritin \u3c10 ng/mL) indicating iron deficiency anemia or stage IV negative iron balance compared to nonvegetarians. There was no significant correlation between iron intake and serum ferritin, however results showed a positive association (r=0.28, p=0.09). In conclusion, vegetarian participants are believed to be at higher risk of developing negative iron balance compared to nonvegetarians due to lower iron consumption and lower serum ferritin concentrations. Female university students following a vegetarian diet should be educated on iron deficiency anemia and prevention of iron depletion

The North American Clear-wing Moths of the Family Aegeriidae

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