Disposal system, model

Model Disposal System. The specific disposal systems modeled use lined pits as described by others (1-3). The lining is usually rubber or concrete, and is used to prevent pesticide solution from leaching to the surrounding area. Because of the impervious liner, the only transport route for parent pesticide is volatilization, providing the liner remains intact. The simplicity of these systems allowed the use of a crystallizing dish as a model disposal pit. The dish (50 x 100 mm inside depth, 0.044 m inside diameter, 0.095 m capacity, 310 ml) was filled to the brim with water or soil containing the desired amount of pesticide. 

Assists in planning disposal systems for community waste. The model accepts appropriate inputs describing the community s situation and constraints, performs cost analyses for various scenarios to account for uncertainties in the input, and provides the system with heuristic indicators which describe the results. Interprets the results and provides advice on planning scenarios to be used as guidelines for making a study of appropriate alternative scenarios. 

Sanders PF, Seiber JN. 1983. A chamber for measuring volatilization of pesticides from model soil and water disposal systems. Chemosphere 12 999-1012. 

In this paper, the volatilization of five organophosphorus pesticides from model soil pits and evaporation ponds is measured and predicted. A simple environmental chamber is used to obtain volatilization measurements. The use of the two-film model for predicting volatilization rates of organics from water is illustrated, and agreement between experimental and predicted rate constants is evaluated. Comparative volatilization studies are described using model water, soil-water, and soil disposal systems, and the results are compared to predictions of EXAMS, a popular computer code for predicting the fate of organics in aquatic systems. Finally, the experimental effect of Triton X-100, an emulsifier, on pesticide volatilization from water is presented. 

Environmental Chamber. The model disposal system was placed in an environmental chamber (Figure 1). Details of the chamber and its use are discussed elsewhere (18). The chamber was designed so... 

A simple environmental chamber is quite useful for obtaining volatilization data for model soil and water disposal systems. It was found that volatilization of low solubility pesticides occurred to a greater extent from water than from soil, and could be a major route of loss of some pesticides from evaporation ponds. Henry s law constants in the range studied gave good estimations of relative volatilization rates from water. Absolute volatilization rates from water could be predicted from measured water loss rates or from simple wind speed measurements. The EXAMS computer code was able to estimate volatilization from water, water-soil, and wet soil systems. Because of its ability to calculate volatilization from wind speed measurements, it has the potential of being applied to full-scale evaporation ponds and soil pits. 

Care should be taken when using the HEM to size downstream disposal equipment. It may result in the flow rate being underestimated and the disposal system being undersized. It may be better to use a slip flow model in such cases. An alternative approach would be the application of an appropriate safety factor to a flow rate calculated using the HEM (see 7.2 (b)). 

Recent results obtained during analysis of the VX hydrolysate produced at the Chemical Agent Munitions Disposal System for the planned SCWO EST indicate that the hexane extraction method can repeatably achieve a detection limit of less than 20 ppb (NIVA Consultants et al., 1999). However, this method not only requires approximately six hours to complete under optimum conditions, it also appears to be sensitive to both the technician performing the analysis and the laboratory (e.g., instrumentation model) where the analysis is carried out. These limitations suggest that further specification and validation will be necessary to achieve reliable results for routine use. 

The need to make available a comprehensive, internationally recognised and quality-assured chemical thermodynamic database that meets the modeling requirements for the safety assessment of radioactive waste disposal systems prompted the Radioactive Waste Management Committee (RWMC) of the OECD Nuclear Energy Agency (NEA) to launch in 1984 the Thermochemical Database Project (NEA-TDB) and to foster its continuation as a semi-autonomous project known as NEA-TDB Phase 11 in 1998. 

The framework for total life cycle management is based on the ideas of the Viable System Model and the St. Galler concept of integrated management (Herrmann and Bergmann 2009 Herrmann 2010). The product life cycle phases are shown at the center of the framework — from product idea to disposal. Sustainable... 

The origin of optical activity in molecules often reduces to the question of how the molecule acquires the electronic properties expected of a chiral object when it is formed from an achiral object. Most often an achiral molecule becomes chiral by chemical substitution. In coordination compounds, chirality commonly arises by the assembly of achiral units. So it is natural to develop ideas on the origins of chiral spectroscopic properties from the interactions of chirally disposed, but intrinsically achiral, units. Where this approach, an example of the independent systems model, can be used, it has obvious economic benefits. Exceptions will occur with strongly interacting subunits, e.g., twisted metal-metal-bonded systems, and in these cases the system must be treated as a whole—as an intrinsically chiral chromophore. ... 

The ebb and flow of situational factors such as global economics, international trade laws, technological and engineering advancements, cultural evolution, competitive enviromnents, and infrastructure (including the availability of waste disposal options) are also important factors of the system model. These situational factors are constantly in flux and can impact at both the micro and the macro levels of the system. 

To demonstrate and gain confidence in the long term behaviour of the disposal system, predictive models are developed and applied in performance assessments, covering not only the behaviour of individual components of the system but also the overall multi-barrier system. Many elements of performance assessments can be modelled today. Extensive international programmes and cooperation in this field are underway to improve performance assessment methods (e.g. scenario development, sensitivity/uncertainty analysis...) and with a view to "validate" performance assessment models. In this latter context, Natural Analogue studies and results from in-situ experiments have a great potential for model development and testing purposes. 

Compliance of the overall disposal system with the radiological safety objectives shall be demonstrated by means of safety assessments based on models that are validated as far as possible. 

Every model relevant to safety assessment has to be validated. Validation should give reasonable assurance that the model is applicable to the specific disposal system. It will largely depend on the barrier concept and the specific geological situation for which models have to be validated. As a tentative list of models that are prime candidates for validation, the following processes and models can be mentioned ... 

Made, B., Jamet, P. Salignac, A-L. 1994. Modeling of hydro-geochemical processes in waste disposal systems with a coupled chemical reactions-trans-port code. Mineralogical Magazine Goldschmidt Conference, Edinburgh, 58A, 551-552. 

The system boundary of the LCA study comprises the earlier life cycle stages of the chemicals used, the supply of energy and inert gas, the reahsation of the model reaction, work-up and transports to the disposal of wastes (Figure 7.1). All calculations refer to a production of 10 kg m-anisaldehyde as functional unit. All processes within this system s boundaries were included into the balance. Also, the dependence of the additional... 

---