Risk assessment of sodium hydroxide,physical map of united states,economic collapse survival map,high altitude emphysema - Test Out

In this study, hazard evaluation methodologies were developed for the decay heat removal of a typical sodium-cooled fast reactor in Japan against snow, tornado, wind, volcanic eruption, and forest fire. JavaScript is currently disabled, this site works much better if you enable JavaScript in your browser.
Science, Technology and Medicine open access publisher.Publish, read and share novel research. Table showing the type of warning information to appear on pesticide label by hazard class. Pesticides which are classified as extremely hazardous generally need to be used with a great deal more caution and protective equipment than those that are classified as unlikely to present a hazard. The WHO hazard classification system is being replaced in many countries by the GHS classification system – the Globally Harmonised System for Classification and Labelling of Chemicals. The toxicological hazard assessment and the dose response evaluation looked at data from animal studies. The total amount of exposure from all these situations is then put into an exposure model which calculates the dose estimated to be received and the estimated dose is compared to the threshold dose. Dietary risk assessments: As pesticides are applied to food crops, minute remains of the pesticides may still be present in the harvested food at the time that the consumer eats it.
In an average knapsack spray the percentage of droplets that can reach the alveoli is 0.2%. It is clear that some, such as carbaryl, are very easily absorbed, whereas others, such as paraquat, have a very low absorption level. Some substances are absorbed much more readily via the digestive tract than via the skin and vice versa.
The toxic effects can be transitory if the body is able to overcome the effects (eg, through repairing cell damage), or the effects may be more permanent such as liver or lung damage or even death. Risk characterisation is the pulling together of all the above information (toxicological data, hazard profile, exposure modelling etc ) to draw conclusions on the probability of toxic effects under conditions of use and hence decide whether the pesticide can be used safely or not. Different regulators use different approaches but all include a safety margin or safety factor in their risk characterisation process.
Here the calculated safety margin for the particular pesticide and use is compared to the acceptable or allowable safety margin. The European Union Commission uses a slightly different formula that essentially gives the same result. Where AOEL = Acceptable Operator Exposure Level and operator refers to anyone who is using or working with the pesticide.
Risk Management: After the risks are characterised the government regulators will nearly always set conditions of use relating to the pesticide in question, in order to manage those risks adequately. Regulators place the responsibility of implementing these conditions on both the company manufacturing and supplying the pesticide and also on the person purchasing, using and storing the pesticide. The above information is really a simplified explanation of the steps that are carried out to ensure the safety of pesticides in use. For further detailed information on using pesticides safely, look at the other training modules in this series or seek advice from your local dealer, extension officer or industry representative. Determine the enthalpy change of the decomposition of sodium hydrogen carbonate by thermochemical measurement and the application of Hess' Law. You must have JavaScript enabled in your browser to utilize the functionality of this website.
A biurette is the most accurate way of measuring this volume and, in order to keep the experiment 'fair' all variables need to remain constant. This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.
Care should be taken not to inadvertently pierce the bottom of the polystyrene cup (calorimeter) with the thermometer.
My greatest sources of error were the heat loss from the apparatus, the heat lost to the surroundings, and measuring cylinder that I used to measure out my solutions. The heat evolved ion the experiment in noted by the formula Heat given out by the reaction=heat absorbed by water 4.
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The Tolerable Upper Intake Level (UL) refers to the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. Food and Agriculture Organization of the United Nations (FAO), and International Atomic Energy Agency Expert Consultation in Trace Elements in Human Nutrition and Health (WHO, 1996). ULs are useful because of the increased interest in and availability of fortified foods, the increased use of dietary supplements, and the growing recognition of the health consequences of excesses, as well as inadequacies, of nutrient intakes.
Like all chemical agents, nutrients can produce adverse health effects if their intake from a combination of food, water, nutrient supplements, and pharmacological agents is excessive. The possibility that the methodology used to derive Tolerable Upper Intake Levels (ULs) might be reduced to a mathematical model that could be generically applied to all nutrients was considered. Given the current state of knowledge, any attempt to capture in a mathematical model all of the information and scientific judgments that must be made to reach conclusions about ULs would not be consistent with contemporary risk assessment practices. Risk assessment is a scientific undertaking having as its objective a characterization of the nature and likelihood of harm resulting from human exposure to agents in the environment. Performing a risk assessment results in a characterization of the relationships between exposure to an agent and the likelihood that adverse health effects will occur in members of exposed populations.
Risk assessment requires that information be organized in rather specific ways but does not require any specific scientific evaluation methods. Risk assessment is subject to two types of scientific uncertainties: those related to data and those associated with inferences that are required when directly applicable data are not available (NRC, 1994). The organization of risk assessment is based on a model proposed by the National Research Council (NRC, 1983, 1994) that is widely used in public health and regulatory decision making. The risk assessment contains no discussion of recommendations for reducing risk; these are the focus of risk management. A principal feature of the risk assessment process for noncarcinogens is the long-standing acceptance that no risk of adverse effects is expected unless a threshold dose (or intake) is exceeded.
When possible, the UL is based on a no-observed-adverse-effect level (NOAEL), which is the highest intake (or experimental oral dose) of a nutrient at which no adverse effects have been observed in the individuals studied. This section provides guidance for applying the risk assessment framework (the model) to the derivation of Tolerable Upper Intake Levels (ULs) for nutrients.
Although the risk assessment model outlined above can be applied to nutrients to derive ULs, it must be recognized that nutrients possess some properties that distinguish them from the types of agents for which the risk assessment model was originally developed (NRC, 1983).
There is no evidence to suggest that nutrients consumed at the recommended intake (the Recommended Dietary Allowance or Adequate Intake) present a risk of adverse effects to the general population.2 It is clear, however, that the addition of nutrients to a diet through the ingestion of large amounts of highly fortified food or nonfood sources such as supplements or both may (at some level) pose a risk of adverse health effects. If adverse effects have been associated with total intake, ULs are based on total intake of a nutrient from food, water, and supplements. Nutrient requirements and food intake are related to the metabolizing body mass, which is also at least an indirect measure of the space in which the nutrients are distributed. The risk assessment model outlined in this chapter is consistent with classical risk assessment approaches in that it must consider variability in the sensitivity of individuals to adverse effects of nutrients or food components.
Physiological changes and common conditions associated with growth and maturation that occur during an individual’s lifespan may influence sensitivity to nutrient toxicity.
Even within relatively homogeneous life stage groups, there is a range of sensitivities to toxic effects. In the context of toxicity, the bioavailability of an ingested nutrient can be defined as its accessibility to normal metabolic and physiological processes. Some nutrients may be less readily absorbed when they are part of a meal than when consumed separately. A diverse array of adverse health effects can occur as a result of the interaction of nutrients. In addition to nutrient interactions, other considerations have the potential to influence nutrient bioavailability, such as the nutritional status of an individual and the form of intake. Based on a thorough review of the scientific literature, the hazard identification step outlines the adverse health effects that have been demonstrated to be caused by the nutrient. Key issues that are addressed in the data evaluation of human and animal studies are described below (see Box 3-1).
The hazard identification step involves the examination of human, animal, and in vitro published evidence addressing the likelihood of a nutrient eliciting an adverse effect in humans.
Consideration of the following issues can be useful in assessing the relevance of experimental data. Route of Exposure.3 Data derived from studies involving oral exposure (rather than parenteral, inhalation, or dermal exposure) are most useful for the evaluation of nutrients. When available, data regarding the rates of nutrient absorption, distribution, metabolism, and excretion may be important in the derivation of Tolerable Upper Intake Levels (ULs).
In some cases, there may be limited or even no significant data relating to nutrient toxicity. Knowledge of molecular and cellular events underlying the production of toxicity can assist with addressing the problems of extrapolation between species and from high to low doses.
The ULs are based on protecting the most sensitive members of the general population from adverse effects of high nutrient intake. The data evaluation process results in the selection of the most appropriate or critical data sets for deriving the UL. Human data, when adequate to evaluate adverse effects, are preferable to animal data, although the latter may provide useful supportive information. In the absence of appropriate human data, information from an animal species with biological responses most like those of humans is most valuable.
If it is not possible to identify such a species or to select such data, data from the most sensitive animal species, strain, and gender combination are given the greatest emphasis.
The route of exposure that most resembles the route of expected human intake is preferable.
The critical data set documents the route of exposure and the magnitude and duration of the intake.
A nutrient can produce more than one toxic effect (or endpoint), even within the same species or in studies using the same or different exposure durations. Because adverse effects are almost certain to occur for any nutrient at some level of intake, it should be assumed that such effects may occur for nutrients for which a scientifically documentable UL cannot now be derived. The absence of sufficient data to establish a UL points to the need for studies suitable for developing them. In addition, probabilistic risk assessment and margin assessment methodologies against snow were developed as well. Applicants must provide an extensive data package of studies complying with international guidelines (eg OECD Guidelines ). The GHS system uses different toxicity levels and effects than the WHO system, and also uses different pictograms and warning statements.
The approach most commonly used for pesticides is to find the dose below which no toxicologically significant effect occurs i.e.
The human exposure assessment stage examines how this data relates to humans, in particular in relation to real exposure situations.
How often a person is likely to use the product and for what length of time they will spray each day is also factored in.
This is where the pesticide is actually applied by a person in a test situation and then samples of urine or in some cases blood are taken and tested for traces of the pesticide. In addition to how often and for how long exposure occurs (frequency and duration), the route of exposure is important. This rarely occurs through occupational use of pesticides when very small amounts of spray mist may enter the nose and mouth and be swallowed. Substances can have different rates or levels of absorption depending on their chemical and physical properties. This means that if the same amount of skin exposure occurs to each, a high amount of the carbaryl will enter the body but only a minute amount of the paraquat will. This is mainly related to the thickness of the skin; the thinner the skin the more easily the chemical is absorbed and the higher the absorption rate.
And obviously gases (substances in the air) are much more likely to be absorbed through the lungs. If absorbed into the blood stream, there is the potential for the substance to be moved around the body from the site of absorption to other organs or parts of the body.
Excretion is elimination from the body – via urine, faeces, through the skin (sweat) or the lungs. The degree and type of effect depends on the factors described on the page basic principles of toxicology. Since government regulatory systems have become more stringent in recent years, very toxic pesticides no longer pass the requirements and cannot be registered and sold in some countries. For example, in most cases it is mandatory that impermeable gloves are worn whilst mixing pesticides sprays to reduce the risk of dermal exposure.
AS-Level Chemistry CH3c Assessed Coursework - Experiment 2 Aim:- to determine the enthalpy change of the decomposition of sodium hydrogen carbonate by thermochemical measurement and the application of Hess' Law.
All Rights Reserved.Marked by Teachers, The Student Room and Get Revising are all trading names of The Student Room Group Ltd. It is beyond the scope of this report to address the possible therapeutic benefits of higher nutrient intakes that may offset the risk of adverse effects. In the case of nutrients, it is exceedingly important to consider the possibility that the intake of one nutrient may alter, in detrimental ways, the health benefits conferred by another nutrient. ULs are based on total intake of a nutrient from food, water, and supplements if adverse effects have been associated with total intake. This does not mean that there is no potential for adverse effects resulting from high intake. Some lower level of nutrient intake will ordinarily pose no likelihood (or risk) of adverse health effects in normal individuals even if the level is above that associated with any benefit.
Although members of the general population should not routinely exceed the UL, intake above the UL may be appropriate for investigation within well-controlled clinical trials. Such a model might have several potential advantages, including ease of application and assurance of consistent treatment of all nutrients. Instead, the model for the derivation of ULs consists of a set of scientific factors that always should be considered explicitly. In the present context, the agents of interest are nutrients, and the environmental media are food, water, and nonfood sources such as nutrient supplements and pharmacological preparations. Scientific uncertainties are an inherent part of the risk assessment process and are discussed below.
Rather, risk assessors must evaluate scientific information using what they judge to be appropriate methods and must make explicit the basis for their judgments, the uncertainties in risk estimates, and, when appropriate, alternative scientifically plausible interpretations of the available data (NRC, 1994; OTA, 1993). Data uncertainties arise during the evaluation of information obtained from the epidemiological and toxicological studies of nutrient intake levels that are the basis for risk assessments. Hazard identification involves the collection, organization, and evaluation of all information pertaining to the adverse effects of a given nutrient. Dose-response assessment determines the relationship between nutrient intake (dose) and adverse effect (in terms of incidence and severity). Intake assessment evaluates the distribution of usual total daily nutrient intakes for members of the general population. Risk characterization summarizes the conclusions from Steps 1 and 2 with Step 3 to determine the risk.
The adverse effects that may be caused by a nutrient almost certainly occur only when the threshold dose is exceeded (NRC, 1994; WHO, 1996). For any given adverse effect, if the distribution of thresholds in the population could be quantitatively identified, it would be possible to establish ULs by defining some point in the lower tail of the distribution of thresholds that would protect some specified fraction of the population.
UFs are used to make inferences about the threshold dose of substances for members of a large and diverse human population using data on adverse effects obtained in epidemiological or experimental studies. This is identified for a specific circumstance in the hazard identification and dose-response assessment steps of the risk. The derivation of a UL from a NOAEL (or LOAEL) involves a series of choices about what factors should be used to deal with uncertainties. It is derived by application of the hazard identification and dose-response evaluation steps (steps 1 and 2) of the risk assessment model.
Nonetheless, they may share with other chemicals the production of adverse effects at excessive exposures. The UL is the highest level of daily nutrient intake that is likely to pose no risks of adverse health effects for almost all individuals in the general population. For cases in which adverse effects have been associated with intake only from supplements and food fortificants, the UL is based on intake from those sources only, rather than on total intake. Data from such findings are generally not useful for setting ULs for the general North American population.
However, excessive intake of a single nutrient from supplements or fortificants may compromise this homeostatic mechanism. A discussion of how variability is dealt with in the context of nutritional risk assessment follows. The model described below accounts for normally expected variability in sensitivity but excludes subpopulations with extreme and distinct vulnerabilities. Bioavailability influences a nutrient’s beneficial effects at physiological levels of intake and also may affect the nature and severity of toxicity due to excessive intakes. Supplemental forms of some nutrients may require special consideration if they have higher bioavailability and therefore may present a greater risk of producing adverse effects than equivalent amounts from the natural form found in food. The potential risks of adverse nutrient-nutrient interactions increase when there is an imbalance in the intake of two or more nutrients. Human data provide the most relevant kind of information for hazard identification and, when they are of sufficient quality and extent, are given the greatest weight. All these advantages of animal data, however, may not always overcome the fact that species differences in response to chemical substances can sometimes be profound, and any extrapolation of animal data to predict human response needs to take into account this possibility. As explained in Chapter 2, the criteria of Hill (1971) are considered in judging the causal significance of an exposure-effect association indicated by epidemiological studies. Some animal data may be of limited utility in judging the toxicity of nutrients because of highly variable interspecies differences in nutrient requirements.


Data derived from studies involving parenteral, inhalation, or dermal routes of exposure may be considered relevant if the adverse effects are systemic and data are available to permit interroute extrapolation. They may also assist with identifying life-stage differences in response to nutrient toxicity. It is conceivable that, in such cases, pharmacokinetic and metabolic data may provide valuable insights into the magnitude of the UL. It may also aid in understanding whether the mechanisms associated with toxicity are those associated with deficiency. Human or animal data are reviewed for suggestions that the substances have the potential to produce additional adverse health effects.
The risk assessment process recognizes that there may be individuals within any life stage group who are more biologically sensitive than others, and thus their extreme sensitivities do not fall within the range of sensitivities expected for the general population. It includes selection of the critical data set, identification of a critical endpoint with its no-observed-adverse-effect level (NOAEL) or lowest-observed-adverse-effect level (LOAEL), and assessment of uncertainty. Pharmacokinetic, metabolic, and mechanistic data may be available to assist with the identification of relevant animal species. Data on bioavailability are considered and adjustments in expressions of dose-response are made to determine whether any apparent differences in response can be explained. The lack of reports of adverse effects following excess intake of a nutrient does not mean that adverse effects do not occur.
Until a UL is set or an alternative approach to identifying protective limits is developed, intakes greater than the Recommended Dietary Allowance or Adequate Intake should be viewed with caution.
Snow hazard curves were developed based on the Gumbel and Weibull distributions using historical records of the annual maximum values of snow depth and daily snowfall depth. The NOAEL is set just below the point where the dose response curve crosses the vertical toxic line.
So for pesticides, we need to look at the people who are using them – the spray operators - by means of exposure modelling and personal monitoring and also conduct dietary risk assessments for consumers.
Conversely, the thicker the skin, the less chemical is absorbed and the lower the absorption rate. A simple example is when a lot of garlic is eaten, it is absorbed via the digestive tract into the blood where a portion of it is circulated to the lungs and expired back out in the breath (which is normally quite noticeable!). Again using food as an example, the food we eat is not in the form that the body can actually use – it must be broken down into simpler components that can be moved into the various tissues and cells to provide the nutrients we need to sustain life.
Steady the cup with the thermometer in it with a laboratory clamp if necessary, so that it will not tip over. If you break any glass make sure you clean it up straight away as it could be a danger to you and others. The term tolerable is chosen because it connotes a level of intake that can, with high probability, be tolerated biologically by individuals; it does not imply acceptability of that level in any other sense. Any such alteration (referred to as an adverse nutrient-nutrient interaction) is considered an adverse health effect. However, if adverse effects have been associated with intake from supplements or food fortificants only, the UL is based on a nutrient intake from those sources only, not on total intake.
It is not possible to identify a single risk-free intake level for a nutrient that can be applied with certainty to all members of a population.
It was concluded, however, that the current state of scientific understanding of toxic phenomena in general, and nutrient toxicity in particular, is insufficient to support the development of such a model. Deciding whether the magnitude of exposure is acceptable or tolerable in specific circumstances is not a component of risk assessment; this activity falls within the domain of risk management. Examples of inferences include the use of data from experimental animals to estimate responses in humans and the selection of uncertainty factors to estimate inter- and intraspecies variabilities in response to toxic substances. It concludes with a summary of the evidence concerning the capacity of the nutrient to cause one or more types of toxicity in humans. This step concludes with an estimate of the Tolerable Upper Intake Level (UL)—it identifies the highest level of daily nutrient intake that is likely to pose no risks of adverse health effects for almost all individuals in the general population.
In cases where the UL pertains only to supplement use and does not pertain to usual food intakes of the nutrient, the assessment is directed at supplement intakes only. The risk is generally expressed as the fraction of the exposed population, if any, having nutrient intakes (Step 3) in excess of the estimated UL (Steps 1 and 2).
The critical issues concern the methods used to identify the approximate threshold of toxicity for a large and diverse human population. The method for identifying thresholds for a general population described here is designed to ensure that almost all members of the population will be protected, but it is not based on an analysis of the theoretical (but practically unattainable) distribution of thresholds.
These factors are applied consistently when data of specific types and quality are available. If there are no adequate data demonstrating a NOAEL, then a lowest-observed-adverse-effect level (LOAEL) may be used. To determine whether populations are at risk requires an intake or exposure assessment (step 3, evaluation of intakes of the nutrient by the population) and a determination of the fractions of these populations, if any, whose intakes exceed the UL.
Because the consumption of balanced diets is consistent with the development and survival of humankind over many millennia, there is less need for the large uncertainty factors that have been used for the risk assessment of nonessential chemicals. The effects of nutrients from fortified foods or supplements may differ from those of naturally occurring constituents of foods because of the chemical form of the nutrient, the timing of the intake and amount consumed in a single bolus dose, the matrix supplied by the food, and the relation of the nutrient to the other constituents of the diet.
Such elevations alone may pose risks of adverse effects; imbalances among the vitamins may also be possible. During pregnancy, the increase in total body water and glomerular filtration results in lower blood levels of water-soluble vitamins dose for dose and therefore results in reduced susceptibility to potential adverse effects. Such subpopulations consist of individuals needing medical supervision; they are better served through the use of public health screening, product labeling, or other individualized health care strategies.
The concentration and chemical form of the nutrient, the nutrition and health of the individual, and excretory losses all affect bioavailability. Excessive intake of one nutrient may interfere with absorption, excretion, transport, storage, function, or metabolism of a second nutrient. ULs must therefore be based on nutrients as part of the total diet, including the contribution from water.
However, the number of controlled human toxicity studies conducted in a clinical setting is very limited because of ethical reasons. Such data are used in part because human data on nonessential chemicals are generally very limited. Although toxicologists generally regard any demonstrable structural or functional alteration as representing an adverse effect, some alterations may be considered to be of little or self-limiting biological importance.
Nevertheless, relevant animal data are considered in the hazard identification and dose-response assessment steps where applicable, and, in general, they are used for hazard identification unless there are data demonstrating they are not relevant to human beings or if it is clear that the available human data are sufficient.
Thus, if there are significant pharmacokinetic and metabolic data over the range of intakes that meet nutrient requirements, and if it is shown that this pattern of pharmacokinetic and metabolic data does not change in the range of intakes greater than those required for nutrition, it may be possible to infer the absence of toxic risk in this range. In most cases, however, because knowledge of the biochemical sequence of events resulting from toxicity and deficiency is still incomplete, it is not yet possible to state with certainty whether these sequences share a common pathway.
Where this is not possible, the differences in route of exposure are noted as a source of uncertainty.
As the intake of any nutrient increases, a point (see Figure 3-2) is reached at which intake begins to pose a risk. Wind hazard curves were also evaluated using the maximum wind speed and instantaneous speed. 25 Feb 2012 (online)4.Yamano H, Nishino H, Kurisaka K, Sakai T, Yamamoto T, Ishizuka Y, Geshi N, Furukawa R, Nanayama F, Takata T (2014) Development of margin assessment methodology of decay heat removal function against external hazards – project overview and preliminary risk assessment against snow. To find the NOAEL for a particular product, the NOAEL is found for each of the short-term and chronic studies conducted as part of the toxicological hazard assessment.
This evaluation takes into account different diets, for example Europeans consume a large amount of wheat bread where as Asians consume a large amount of rice. The same process happens for many other substances that are commonly ingested such as drugs, pharmaceuticals and pollutants in the air. The safety factor is like an allowance for the uncertainty of applying results of laboratory studies with animals to real-life situations with humans. If the hydrochloric acid comes into contact with skin, notify supervisor and wash affected area with water. The setting of a UL does not indicate that nutrient intakes greater than the Recommended Dietary Allowance (RDA) or Adequate Intake (AI) are recommended as being beneficial to an individual.1 The UL is not meant to apply to individuals who are treated with the nutrient under medical supervision or to individuals with predisposing conditions that modify their sensitivity to the nutrient. When evidence for such adverse interactions is available, it is considered in establishing a nutrient’s UL. However, it is possible to develop intake levels that are unlikely to pose risks of adverse health effects for most members of the general healthy population, including sensitive individuals. Scientific information about various adverse effects and their relationships to intake levels varies greatly among nutrients and depends on the nature, comprehensiveness, and quality of available data. Risk management decisions depend on the results of risk assessments but may also involve the public health significance of the risk, the technical feasibility of achieving various degrees of risk control, and the economic and social costs of this control. Because most nutrients are not considered to be carcinogenic in humans, approaches used for carcinogenic risk assessment are not discussed here. By using the model to derive the threshold, however, there is considerable confidence that the threshold, which becomes the UL for nutrients or food components, lies very near the low end of the theoretical distribution and is the end representing the most sensitive members of the population.
The problems of both data and inference uncertainties arise in all steps of the risk assessment. In the intake assessment and risk characterization steps (steps 3 and 4), the distribution of usual intakes for the population is used as a basis for determining whether and to what extent the population is at risk (Figure 3-1). In addition, if data on the adverse effects of nutrients are available primarily from studies in human populations, there will be less uncertainty than is associated with the types of data available on nonessential chemicals. These reasons and those discussed previously support the need to include the form and pattern of consumption in the assessment of risk from high nutrient or food component intake.
However, in the unborn fetus this may be offset by active placental transfer, accumulation of certain nutrients in the amniotic fluid, and rapid development of the brain. Such populations may not be at negligible risk when their intakes reach the UL developed for the healthy population. Bioavailability data for specific nutrients must be considered and incorporated by the risk assessment process.
Such studies are generally most useful for identifying very mild (and ordinarily reversible) adverse effects. Moreover, there is a long-standing history of the use of animal studies to identify the toxic properties of chemical substances, and there is no inherent reason why animal data should not be relevant to the evaluation of nutrient toxicity. As noted earlier, adverse nutrient-nutrient interactions are considered in the definition of an adverse effect.
In contrast, an alteration of pharmacokinetics or metabolism may suggest the potential for adverse effects.
As indicated earlier, the extent to which a distinct subpopulation will be included in the derivation of a UL for the general population is an area of judgment to be addressed on a case-by-case basis. Because the selection of uncertainty factors (UFs) depends in part on the seriousness of the adverse effect, it is possible that lower ULs may result from the use of the most serious (rather than most sensitive) endpoint. The tornado hazard was evaluated by an excess probability for the wind speed based on the Weibull distribution multiplied by an annual probability of the tornado strike at a target plant. In: Proceedings of the 12th probabilistic safety assessment and management conference (PSAM 12), Honolulu, Hawaii, USA, 22–27 June 2014, No.
C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo, Queretaro, Mexico[2] Centro Nuclear “Dr. The toxicological properties are investigated by conducting a set of internationally approved animal (normally rat and another animal) studies. Using wine as an example, many people can drink one glass of wine with no observable effects but two glasses might start to give observable effects such as mood change, light-headedness, flushed face and quickening pulse rate. The United States Environmental Protection Agency (USEPA) uses different approaches depending on the hazard profile of the pesticide. For some nutrients, these intake levels may pose a risk to subpopulations with extreme or distinct vulnerabilities. The hallmark of risk assessment is the requirement to be explicit in all of the evaluations and judgments that must be made to document conclusions.
Because there is no single scientifically definable distinction between safe and unsafe exposures, risk management necessarily incorporates components of sound, practical decision making that are not addressed by the risk assessment process (NRC, 1983, 1994). Scientific uncertainties associated with both the UL and the intake estimates are described so that risk managers understand the degree of scientific confidence they can place in the risk assessment. For some nutrients, there may be subpopulations that are not included in the general distribution because of extreme or distinct vulnerabilities to toxicity. These adopted or recognized UFs have sometimes been coupled with other factors to compensate for deficiencies in the available data and other uncertainties regarding data. A discussion of options available for dealing with these uncertainties is presented below and in greater detail in Appendix K.
Examples of life stage groups that may differ in terms of nutritional needs and toxicological sensitivity include infants and children, the elderly, and women during pregnancy and lactation.
Nutrient-nutrient interactions may be considered either as a critical endpoint on which to base a UL or as supportive evidence for a UL based on another endpoint. Observational studies that focus on well-defined populations with clear exposures to a range of nutrient intake levels are useful for establishing a relationship between exposure and effect. There has been no case encountered thus far in which sufficient pharmacokinetic and metabolic data are available for establishing ULs in this fashion, but it is possible such situations may arise in the future. Thus, it is often necessary to evaluate several endpoints independently to determine which one leads to the lowest UL. For some nutrients and for various reasons, there are inadequate data to identify this point or even to estimate its location. The volcanic eruption hazard was evaluated using geological data and tephra diffusion simulation which indicated tephra layer thickness and tephra diameter. 445.Nishino H, Kurisaka K, Yamano H (2014) Development of margin assessment methodology of decay heat removal function against external hazards (2) Tornado PRA methodology.
Thus, in this example one glass of wine would be the No Observed Adverse Effect Level, because above this level effects start to occur. This is the amount of the pesticide that we can confidently predict that a person can consume over the course of their lifetime without any adverse effects. These droplets would then normally be sneezed or spat out however some very small amounts may be ingested (see below).
This mostly applies to fat-soluble substances, because fat is the body’s storage material, and fat-soluble substances can get trapped in the body fat. Observational data in the form of case reports or anecdotal evidence are used for developing hypotheses that can lead to knowledge of causal associations. They can, for example, be readily controlled so that causal relationships can be recognized. The forest fire hazard was evaluated based on numerical simulation which contributed to creating a response surface of frontal fire intensity and Monte Carlo simulation for excess probability calculation. IntroductionThere are many uses of radioactive materials which improve or facilitate human activities or quality of life of people. Only droplets less than 7 µm VMD can travel into the trachea or bronchi, and only extremely small droplets, less than 2 µm VMD, can reach the alveoli and hence get into the blood stream via respiration. Such distinct groups, whose conditions warrant medical supervision, may not be protected by the UL. Sometimes a series of case reports, if it shows a clear and distinct pattern of effects, may be reasonably convincing on the question of causality. It is possible to identify the full range of toxic effects produced by a chemical over a wide range of exposures and to establish dose-response relationships. In: Proceedings of the international congress on advances in nuclear power plants (ICAPP2015), Nice, France, 3–6 May 2015, No. These uses are given in different fields of technology, ranging from power generation to supply entire cities or areas, to medical and industrial uses, even the smoke detectors in buildings. The LD50 is the amount of substance that causes one half of the animals in a toxicological test to die, i.e. The typical spray contains a range of droplet sizes depending on the equipment used (eg, type of nozzle and pressure). Event sequence assessment methodology was also developed based on plant dynamics analysis coupled with continuous Markov chain Monte Carlo method in order to apply to the event sequence against snow. 150317.Connor CB, Hill BE, Winfrey B, Franklin NM, Lafemina PC (2001) Estimation of volcanic hazards from tephra fallout. All these applications generate radioactive waste that may represent risks to the environment or to human beings, but it is necessary to have special attention to the management of radioactive waste.In this chapter there are information about the generalities of radioactive wastes, such as its definition, origin, classification and stages of radioactive waste management. For knapsack spraying most droplets are between 200 to 250 µm VMD although the range may be from 10 to 1000 µm VMD.
Your eyes are a highly sensitive region of your body and care should be taken to protect them.
Furthermore, this study developed the snow margin assessment methodology that the margin was regarded as the snowfall duration to the decay heat removal failure which was defined as when the snow removal speed was smaller than the snowfall speed. In addition, there are information about the current state of research and technologies which have been proposed for the treatment of radioactive waste, with their advantages and disadvantages, in special case of the electrochemical techniques to treat radioactive waste with theoretical considerations and cases of study.
This is one of the most commonly used measures (endpoints) of relative toxicity.All substances theoretically have an LD50, and thousands of common substances (including food ingredients) and chemicals have been tested. Apparatus Two plastic cups Two large beakers Two thermometers - graduated in 0.5c divisions Biurette NB. Japan Geoscience Union Meeting 2014, 28 Apr–2 May 2014, SVC52-019.Nanayama F, Furukawa R, Ishizuka Y, Yamamoto T, Geshi N, Oishi M (2013) Characterization of fine volcanic ash from explosive eruption from Sakurajima Volcano, South Japan. At the end of this chapter, there is information about the risk assessment and development of future strategies.2.
The lower the LD50 the more toxic the substance is taken to be, because it means a relatively smaller dose gives the same toxic effect (in this case death) if exposure occurs.
Considering that sprays are already dilute forms of pesticide, this is an insignificant amount.
Transaction of American Geophysical Union 2013 Fall Meeting, San Francisco, CA, USA, 9–13 Dec 201310.Okano Y, Yamano H (2014) Development of margin assessment methodology of decay heat removal function against external hazards (3) Forest fire hazard assessment methodology. Origin of radioactive wasteRadioactive waste are created from all activities that radioactive materials are used, either as part of the process or the use of such materials as a constituent of equipment or instruments that allow the realization of a practice. Classification of radioactive wastesClassification of radioactive waste is in order of any stage from its origin just to their collection, segregation, treatment, conditioning, storage, transportation and final disposal.


Typical waste in this class includes soil and rubble with low levels of activity concentration. Such waste requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near surface facilities. However, ILW needs no provision, or only limited provision, for heat dissipation during its storage and disposal.
ILW may contain long lived radionuclides, in particular, alpha emitting radionuclides that will not decay to a level of activity concentration acceptable for near surface disposal during the time for which institutional controls can be relied upon.
Management of radioactive wasteThe ultimate goal of waste management lies in its restraint and seclusion of the human environment, for a period of time and under conditions such that any release of radionuclides does not pose unacceptable radiological risk to people or the environment.
Management should ensure that all charges are minimal for future generations.A responsible management of radioactive waste requires the implementation of measures aimed at protecting human health and the environment.
Inspections and measurements have to being performed and the associated records maintained. Safety guideSafety is a top priority in radioactive waste management, because of this, the purpose of this section is to present a brief guideline of recommended procedures for working with radioactive wastes.
The composition of waste should be known with sufficient accuracy that nuclear and conventional safety and environmental protection are not compromised. Toxic or hazardous constituents should be characterized by analytical means or from knowledge of the processes, so that hazards associated with treatment methods of waste can be identified. The reachability of radionuclides, toxic materials and the generation rates for volatile organic compounds or powders and other hazardous gases should be determined. It is important to know the chemical stability of radioactive waste: flammability, corrosively, reactivity, pyrophoricity, rapid oxidation promotion, biodegradability and the chemically incompatible waste forms should be carefully controlled.
The amount of mobilizing agents such as chelating compounds, particularly stable ones, should be kept to a minimum. Waste containing hazardous constituents that are mobile in the environment, or constituents that enhance the mobility of radionuclides should avoid.Several possible process options have to be identified for treating radioactive wastes and before selecting it should include a safety analyses. Treatment of radioactive wasteThe aim of the radioactive waste treatment is to minimize the volume of waste requiring management.
However, liquid containing suspended matter must be treated to remove the particulates before primary treatment or after it.
Chemical precipitationChemical precipitation processes are regularly used for removing radioactivity from low and intermediate level aqueous wastes at fuel reprocessing facilities, research laboratories and power stations.
Precipitation processes are greatly versatile, relatively low investment and operational costs; and may treat from large volumes of liquid effluents containing relatively low concentrations of active species to those containing large amounts of particulates or high concentrations of inactive salts.
However, in some cases, a pretreatment stage, such as oxidization of organic contaminants, decomposition of complexed species, pH adjustment, change of the valency state or adjust the ionic species, should be applied prior to the formation of precipitate in order to improve the process. It is very effective at transferring the radioactive content of a large volume of liquid into a small volume of solid.Ion exchange process involves the replacement of cations or anions between an insoluble solid matrix containing ionizable polar groups and a liquid solution.
When the ionic groups are negatives the exchange will involve cations and when they are positively charged they involve anions. EvaporationEvaporation process is effective for concentrating or removing salts, heavy metals and a variety of hazardous materials from waste effluent, reducing large volumes of liquid wastes with high factor decontaminations. The process is commonly used for the treatment of high, intermediate and low level waste effluents; in particular for the treatment of small volumes of highly active effluents and may be carried out through the use of commercially available evaporation equipment. Treatment of radioactive organic liquidLiquid scintillation, solvents, oils and diverse biological fluids, generated in nuclear research centers, medical centers or industries are considered as radioactive organic liquid wastes. These wastes may present radioactive and chemical or biochemical hazards requiring treatments to remove or destroy chemically or biochemically hazardous components. IncinerationIncineration is used for reduction of solid and liquid radioactive waste volume, downscaling land requirements for disposal. Incineration combusts or oxidizes wastes at high temperatures, generating as end products of the complete incineration: CO2, H2O, SO2, NO, and HCl gases. Acid digestion process uses a mixed of nitric acid in a phosphoric acid carrier solution at temperatures below 200°C and at atmospheric or moderate pressures (< 20 psig).
DistillationDistillation is a radioactive waste volume reduction technique used for pretreating liquid scintillation and miscellaneous solvent waste in conventional equipment. The process is simple, known, and cost effective if the valuable solvent is recycled or reused.
Treatment of solid wasteSolid wastes are produced by all applications and uses of radioactive materials, in normal operations and maintenance activities. DecontaminationDecontamination is defined as the removal of contamination from areas or surfaces of facilities or equipment by washing, heating, chemical or electrochemical action, mechanical cleaning or by other means. The decontamination objectives are mainly: to reduce the volume of equipment and materials requiring storage and disposal in licensed disposal facilities, to remove contamination from components or systems, to reduce dose levels in the installations and to restore sites and facilities to an unconditional-use condition. Decontamination processes may divide into chemical, electrochemical and mechanical processes:Chemical decontamination. In the chemical decontamination are used concentrated or dilute chemical reagents in contact with the contaminated item, to dissolve the contamination layer, covering the base metal and eventually a part of the base metal.Decontamination by melting presents the particular advantage of homogenising a number of radionuclides in the ingots and concentrating other radionuclides in the slag and filter dust resulting from the melting process, thus decontaminating the primary material. The problem with inaccessible surfaces or complex geometries is eliminated and the remaining radioactivity content is homogenised over the total mass of the ingot.Mechanical and manual decontamination included wet or dry abrasive blasting, grinding of surfaces and removal of concrete by spalling or scarifying, washing, swabbing, foaming agents, and latex-peelable coatings. These techniques are most applicable to the decontamination of structural surfaces which may be cleaned by sweeping, wiping, scrubbing or removed by grit blasting, scarifying, drilling and spalling.A wet abrasive-blasting system uses a combination of water, abrasive media and compressed air, and is normally applied in 24 a self-contained, leaktight, stainless steel enclosure. The dry abrasive-blasting technique, commonly called sandblasting or abrasive jetting, uses abrasive materials suspended in a medium that is projected onto the surface being treated, resulting in a uniform removal of surface contamination.
CompactionCompaction is performed in order to reduce the waste volume and concentrates the radionuclides. Metal pipe, valves, conduit, wood, and other like items are compatible in super compactors. Compactors can range from low-force compaction systems (~5 tons or more) through to presses with a compaction force over 1000 tons (super compactors). CuttingCutting and sawing operations are carried out mainly on large items which consist usually of metals or plastics.
This waste has to be reduced in size to make it fit into packaging containers or to submit it to treatment such as incineration. The cutting is carried out either in the dry state in cells, using remote control when necessary and with conventional tools, or underwater. CrushingCrushing techniques may be used for size reduction of friable solids (glass, concrete, ceramics).
ShreddingShredding reduces void space and is particularly effective when plastics are compacted.
Air, which is trapped between the folds of bulk plastic and in plastic bags and sleeving, takes up storage space.
IncinerationThe size reduction, mixing and blending of the solid wastes is necessary for successful combustion operation.4.
ElectroremediationThe electrochemical treatment, electroremediation, also known as electrokinetic remediation (EKR) process is classified as a physicochemical technology by the electrochemical transformation or destruction of organic and inorganic wastes, which offers many advantages such as the capacity to remove organic and inorganic pollutants by applying direct electric current into the soil. The EKR is easy to operate and involves the installation of electrodes into the organic or inorganic waste and the application of a low voltage gradient or direct current through them (Vazquez et al, 2007). This process is capable of mineralizing the organics into carbon dioxide and water completely, without emission of any toxic materials like dioxins.
During this process, electrode reactions take place on its surface, generating protons (H+) and hydroxyl (-OH) at the anode and the cathode, respectively.
The concentration of these ions near the electrodes creates an acid front that moves from anode to cathode and a basic front that moves from cathode to anode. Some transport phenomena occur in the liquid phase of soil when direct current or voltage gradient is passed through the electrodes, such as ion migration (electromigration), electroosmosis and electrophoresis (Murillo – Rivera et al, 2009; Alcantara et al, 2008), inducing complex and coupled electrochemical and properties of matrix. If the ions have negative charge (anions) they will move toward the anode, and if they have positive charge (cations) they will move toward the cathode, an important characteristic which can determine where the metal, in ionic form, can be recovered (Virkutytea et al, 2002; Figure 4). Non-polar pollutants or organic pollutants can be removed by electroosmosis, attributed to the excess charges on the soil surface. There occurs the net ionic migration that represents the bulk movement along pore fluid through the electrical double layer of charge at the solid–liquid interface (Al-Shahrani and Roberts, 2005).
And finally, electrophoresis is the movement of charged solid particles, including clay particles and bacterial cells with size less than 20 m, in response to the electrostatic potential gradient. However, when the pollutants are persistent, toxic or simply have low solubility and a strong adsorption to soil surfaces and organic matter, the traditional remediation technologies are used, such as washing, and land-farming, amongst others. In these cases, electroremediation, also known as electrokinetic remediation (EKR) process is classified as a physicochemical technology, which offers many advantages such as the capacity to remove organic and inorganic pollutants by applying direct electric current into the soil, even in clays (Virkutytea et al, 2002).
The EKR is easy to operate and involves the installation of electrodes into the soil or waste and the application of a low voltage gradient or direct current through them.
However, a disadvantage was the time required to achieve over 90 % metal removal.In order to improve the EKR process and diminish the removal time, some efforts have been focused on changing some operational parameters.
However, it is important to select a good electrode material, especially when electrochemical technologies are used. Electrodes during the electrokinetic remediation of wastesIn that sense, some materials, as the case of titanium (Vazquez et al, 2004), platinum, gold, silver, stainless steel, among others used in EKR, suffer a kind of passivation, generating an oxide film on their surfaces which cover the active sites. This behavior occurs during the experimental conditions, which increases the electrical resistances in the system. For that reason, it is necessary to pre-treat or pre-activate the material before using, to increase roughness or surface active sites. Also, carbon electrodes have been used in EKR processes because of their low cost and accessibility (Saichek and Reddy, 2003; Hu et al, 2002) and because they are inert. However, these kinds of materials commonly form bonds with the species in solution or form oxide film.
As well, they can adsorb some species on their surface.In order to increase the active sites, eliminate the passivation phenomenon, increase electrode life and improve the oxidant activity, it is necessary to modify electrode surfaces to obtain high overpotentials.
Consequently, some electrode materials have been modified with metallic oxide, forming a thin layer on a base metal (usually titanium), i.e. These kinds of electrodes can be used as anodes in order to promote electrochemical oxidation.
For that reason, the name “Dimensionally Stable Anodes” (DSA) was proposed by Comninellis and Pulgarin (Comninellis and Pulgarin, 1991) who demonstrated the high reactive surface of iridium DSA.
Also, there are reports about the successful implementation of electrokinetic treatment in situ; one example is reported by Monsanto, DuPont and General Electric, who used the LasagnaTM remediation treatment in situ to remove trichloroethylene with 98 % of efficiency (USEPA, 1997).
Most laboratory or pilot electroremediation studies have been carried out in one dimension (1D) array, having only one anode (+) and one cathode (-), separated by the polluted soil. In practice, acid washing and chelator soil washing are the two most prevalent removal methods (Giannis et al, 2007; Rampley and Ogden, 1988). Destruction of radioactive organic wastesThe process developed for the removal of organic contaminants from bulk water using graphite based adsorbents with electrochemical regeneration at the University of Manchester (Brown and Roberts, 2007), was adjusted for the destruction of radioactive organic wastes, specifically oils contaminated with alpha radioactivity produced at Magnox Ltd nuclear decommissioning site in UK (Wickenden, 2001). Oxidation of the organic matter may produce soluble breakdown products or off gases (CO, CO2) and small amounts of H2 and Cl2 at the electrodes.
After electrochemical treatment, the regenerated adsorbent is ready for immediate reuse and the whole cycle is repeated (Brown et al, 2013).The treatment of radioactive oils by adsorption and electrochemical regeneration systems has been achieved at pilot scale 200 L. The latter consisted of three bipolar stacks of six electrochemical cells of each with an electrode area of 2 500 cm2. Graphite plate bipolar electrodes were used and a micro-porous polyethylene membrane (Daramic, Grace GMBH) separated the adsorbent bed from the cathode. The catholyte solution, 0.3 wt % NaCl solution acidified to a pH of less than 2, was stored in a small tank and pumped through the cathode compartments of the six cells.
Regeneration was carried out a current of 1 A (20 mA cm?2) for 25 h L?1 of oil with a regeneration energy of 48 kWh L?1 of oil. And the oil loading on the adsorbent was less than 25 wt % on the adsorbent to avoid excessive cell voltage.The process of adsorption coupled with electrochemical regeneration can remove and destroy around 95 % radioactive oils in the first cycle, and over 99 % of the emulsified oil.
The boron-doped diamond (BDD) electrodes contain non-aggressive and non-corrosive chemicals, are ease of disposal of the spent electrolyte and allow simple electrochemical cell configuration. Electro-oxidation tests were performed into an electrochemical cell which comprised a 250 mL beaker fitted with a rubber bung that held a BDD (DIAFILM PE TM) anode and a stainless steel cathode applied 0.1 A, a cell potential of 5 – 15 V and sonication. The electrolyte contained oil, sodium sulphate and sodium hydroxide added at the start of the test to maintain an alkaline pH in order to trap the carbon dioxide as carbonate. The method was effective for unused hydraulic oil, vacuum pump oil and a waste used machine tool oil (Taylor et al, 2009).Mediated Electrochemical Oxidation (MEO) process has been used by destroying the organic components of combustible mixed wastes and for dissolving radioactive materials, such as transuranic oxides (PuO2). The radioactive components of the wastes dissolved in the electrolyte, can be recovered or immobilized for disposal (Chiba et al, 1995).
The resulting Ag(I) is recycled to Ag(II) at the anode of an electrochemical cell to maintain a supply of oxidant and minimize consumption of Ag. A microporous membrane is usually placed between the electrodes to prevent the oxidizer produced at the anode from being reduced at the cathode. Ag(II) is a very effective oxidizing agent for the destruction of nonhalogenates organic compounds.
Unfortunately, halide ions liberated during the destruction of halogenated organics react with Ag(II) to form insoluble precipitates. A washing–electrokinetic decontamination method was developed by Kim and collaborators to decontaminate these radioactive ashes (Kim et al, 2002 y 2003). If the residual radioactivity of the washed ash is higher than the clearance concentration level, the washed ash is treated by electrokinetic equipment for decontamination.
The equipment consisted of 200 L washing equipment, 50 L electrokinetic equipment, and 150 L precipitation equipment.
The electrokinetic equipment consisted of a couple of anode rooms, electrokinetic ash cells, cathode rooms and metal oxide separators. Cesium from radioactive ashes moves to the cathode room through electro-migration and electro-osmosis.
Sodium recovery from alkaline nuclear wasteAn electrochemical salt-splitting process has been developed to recover and recycle NaOH from radioactive wastes containing large amounts of sodium salts. Sodium separation process can save costs by reducing the disposal volume of wastes and by producing NaOH for recycle into waste treatment processes such as sludge leaching, regenerating ion exchange resins, inhibiting corrosion in carbon-steel tanks, or retrieving tank wastes (Fontain et al, 2009). The waste enters into the anolyte electrodes, sodium ions migrate across membrane into the catholyte, under the influence of an applied electrical potential. This approach allows retain anionic species such as nitrate, aluminate or sulfate in the compartment anolyte of the electrochemical cell, and can produce caustic from radioactive wastes with low levels of gamma radioactivity, which could be released for off-site use without further treatment (Hobbs, 1999).Pacific Northwest National Laboratory (PNNL) and Ceramatec Inc. The process selectively removed up to 80 % of sodium hydroxide from LAW and produced up to 50 % concentrated caustic for reuse in removal aluminum during sludge washing as a pretreatment step in the vitrification of radioactive waste; reducing about 39 % the waste volume.
Due to this, electrolytes with a very low toxicity from which the radioactive materials can be easily separated and recycled, are investigated and applied.
Sodium nitrate has been chosen as electrolyte to decontaminate metals contained Pu and Am (Wedman et al, 1996). In this medium, both actinides can be precipitated or entrained in the ferric hydroxide formed as surface metal is removed, resulting a clean surface, free of contamination, and the separation of the radioactive waste from the solution.
Higher current densities result in higher metal removal rates, but adversely affect the surface morphology by causing roughening, pitting, or burning. Optimum situation for the electrolytic decontamination process is the treatment of metal surfaces that have been electropolished before contamination (Wedman et al, 1996).NaOH solutions have been used as electrolytes to decontaminate metal surface contaminated by tritium.
In this approach, the metal to be decontaminated is submerse in the electrolyte, connected to the negative pole, and the anode (polytetrafluoroethylene wax-impregnated graphite), to positive pole; applying a current densities in the range of 10 - 50 mA cm-2. The tritium adsorbed on the cathode surface is replaced by the hydrogen and ejected to the electrolytic solution.
By using cesium as a test pollutant, we could clearly observe the effect of the electrolysis without taking into account complicated interactions between the contaminant and the soil, such as dissolution of soil particles and adsorption phenomena.The water supply to the anode well was effective to enhance the removal rate.
From the observed fast migration of the pore water, as well as from the result of a simple calculation on the electrophoretic flow velocity, it was concluded that the migration of cesium observed was due mainly to the electroosmotic flow. Remediation performance by increasing the electric conductivity of the soil by mixing NaCl was possible.
This result was consistent with the reduction of the electroosmotic flow velocity due to the elevated ionic strength. It was found that the addition of NaCl makes no sense also from the viewpoint of the potential hazard due to toxic gas emission as well as the cost of electricity.
Owing to the interference by major metallic elements in the soil, the detection sensitivity of the present method based on the simple LX-ray measurement was not enough to investigate behavior of the trace level Cs contaminants.
The radioactive concentration was strongest in the soil particle smaller than 0.063 mm, as predicted. A scrubbing time of 4 h was the optimum time to obtain a removal efficiency of more than 75 % for 137Cs and 60Co. The experimental results indicate that the technique is effective in radionuclide contaminants from soils with a relatively small amount of energy. Uranium and strontium were efficiently removed from kaolinite by electrokinetic remediation.
In the case of cesium, the removal rate may be significantly slower than those of uranium and strontium.
Acetic acid was effective as enhancing agent for buffering hydroxide ions produced by the cathode reaction, and prevented the precipitation of uranium ions in the cathode region.Accordingly, the acetic acid increased the removal efficiency and decreased energy consumption. The use of citric acid was not efficient in removing uranium from kaolinite, because the direction of electromigration was opposite to that of electroosmosis. Since most metal–citrate chelates were negatively charged, they were transported toward the anode by electromigration while electroosmosis flowed toward the cathode.
This result indicates that the selection of enhancement agent should be considered with respect to contaminant type and site characteristics. The electrokinetic removal of uranium from the soil weathered from uraniferous black shale was not efficient. This was due to the low proportion of the mobile fraction, since most uranium exists as residual fractions derived from enriched uraniferous parent rocks (Kyeong-Hee et al, 2003).5. Risk assessment and development of future strategiesNuclear site operations and successful site restoration depend on the availability of suitable waste management routes and facilities.




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