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

Development of a National Marine Oil Transportation System Model

This paper presents the development of a model of the marine oil transportation in the United States. NMOTSM, the National Marine Oil Transportation System Model, is a high-level strategic decision-making tool that will be used to systematically identify causes of oil spills and prioritize oil pollution R and D needs for prevention and response. Three distinct phases in the analysis are identified, namely the formulation of the oil transport model, the risk and safety performance assessment and the evaluation of potential prevention, and response measures and approaches

Field validation of cable monitoring and rating system (CMARS) laboratory model. Semi-annual report, 1 May 1979-31 December 1979

One year of research on validating the performance of the Cable Monitoring and Rating System (CMARS) is reported. The performance testing was conducted on underground 230-kV and 345-kV pipe type cable circuits owned by the New Jersey Public Service Electric and Gas Co. Laser temperature monitoring systems and a data acquisition system were installed. Software installation and development is discussed. The CMARS testing program is described. (LCL

Bayesian risk analysis of municipal solid waste workers' occupational health and safety problems

A study of the risk of occupational injuries and diseases to municipal solid waste workers is reported in this paper. Using Florida Workers' Compensation data from 1993 to 1997, principal injuries among municipal solid waste workers were identified. The size of Worker's Compensation claims was found to have the lognormal distribution. The annual numbers of injuries and annual costs of Workers' Compensation claims were assessed by a predictive Bayesian adaptation of the basic compound Poisson model. The risk assessment indicated that Workers' Compensation costs for municipal solid waste workers in Florida average $10.2 million per year, constant 1998 dollars, and have a 5$38.4 million in any year. Fifty-two percent of this cost is attributed for injuries to drivers/helpers; Forty-four percent of the cost is attributed to strains/sprains. The total economic and non-economic costs for occupational injuries and diseases will be much higher than Workers' Compensation costs