Separative work requirements

In any uranium separation process the work of enrichment increases rapidly with 235U content in the product. Because the price of natural uranium varies widely with time and location (and fluctuating government subsidies) it is useful to distinguish between the price of the feed and the value added by the separative process. For example, the purchaser himself might provide the feed and then pay only for the separative work required to make the desired product. Separative work is defined in Equation 8.7. 

In the future, it is probable that the supplier of emichment services will permit a customer to specify the assay ( U content) of the tails to which feed is to be stripped so as to minimize the combined cost to the customer of natural UF feed and separative work. F re 12.20 shows qualitatively the effect of tails composition on the contributions to product cost arising from costs for feed and for separative work in stripping and enriching sections. The amount of separative work required in the enriching section is independent of tails composition. But the cost of separative work required in the stripping sections varies from zero when = zp (no stripping) to infinity when xw = 0. Conversely, the cost of feed varies from infinity when Xftf = zp to a minimum at rcn =0, as may be seen from Eq. (12.152). There is therefore an optimum tails assay Xo between Xu = 0 and Xfy = zp, at which the sum of the cost of separative work and the cost of natural uranium feed is a minimum. 

The work required to enrich uranium in increases rapidly with the content of the product. Because of varying domestic prices on natural uranium, as well as varying content of in uranium obtained from used reactor fuel elements, so-called toll enrichment has been introduced. In this case, the purchaser himself provides the uranium feed into the separation plant and pays for the separative work required to make his desired product out of the uranium feed provided. Separative work is defined as... 

AgM is negative for the entire concentration range, as seen in Eq. (1-147). The minimum separation work required to separate 1 mol of the k component mixture is... 

Using these equations the separative work required to produce uranium enriched to the levels shown in Table 11.1 are listed in Table 11.2. 

The GT-MHR reactor design can accommodate alternative fuel cycles if supported by external infrastructure. A fuel cycle utilizing recycled water reactor plutonium can be accommodated, and will be effectively demonstrated by the GT-MHR plutonium consumption project in the Russian Federation. Thorium can be used as an alternative to natural uranium in the fertile particles. If reprocessing is supported in the future, fissile particles can incorporate recycled U from thorium fertile particles to reduce the separative work required to produce fissile particles. 

Separators working at unsteady conditions produce products which do not meet the required sales specification. 

The second term in brackets in equation 36 is the separative work produced per unit time, called the separative capacity of the cascade. It is a function only of the rates and concentrations of the separation task being performed, and its value can be calculated quite easily from a value balance about the cascade. The separative capacity, sometimes called the separative power, is a defined mathematical quantity. Its usefulness arises from the fact that it is directly proportional to the total flow in the cascade and, therefore, directly proportional to the amount of equipment required for the cascade, the power requirement of the cascade, and the cost of the cascade. The separative capacity can be calculated using either molar flows and mol fractions or mass flows and weight fractions. The common unit for measuring separative work is the separative work unit (SWU) which is obtained when the flows are measured in kilograms of uranium and the concentrations in weight fractions. 

AU separation operations require energy input in the form of heat or work. In the conventional distillation operation, as typified in Fig. 13-1, energy required to separate the species is added in the form of heat to the rebouer at the bottom of the column, where the temperature is highest. Also, heat is removed from a condenser at the top of the column, where the temperature is lowest. This frequently results... 

The chapter on Radioactive chemicals (Chapter 11) has been updated. Considerations of safety in design (Chapter 12) are presented separately from systems of work requirements, i.e. Operating procedures (Chapter 13). Tlie considerations for Marketing and transportation of hazardous chemicals are now addressed in two separate chapters (Chapters 14 and 15). Chemicals and the Environment are now also covered in two chapters (Chapters 16 and 17) to reflect the requirement that the impact of chemicals on the environment should be properly assessed, monitored and controlled. Although a substantial contribution to atmospheric pollution is made by emissions from road vehicles and other means of transport, and this is now strictly legislated for, this topic is outside the scope of this text. Chapter 18 provides useful conversion factors to help with the myriad of units used internationally. 

In Fig. 8a the dissociation energy is the work required to break up one molecule and leave the ions at rest in a vacuum. In Fig. 8b the dissociation energy D is the work required to break up one molecule and to separate the ions isothermally in a solvent at temperature T. Although... 

The thermodynamic aspect of osmotic pressure is to be sought in the expenditure of work required to separate solvent from solute. The separation may be carried out in other ways than by osmotic processes thus, if we have a solution of ether in benzene, we can separate the ether through a membrane permeable to it, or we may separate it by fractional distillation, or by freezing out benzene, or lastly by extracting the mixture with water. These different processes will involve the expenditure of work in different ways, but, provided the initial and final states are the same in each case, and all the processes are carried out isothermally and reversibly, the quantities of work are equal. This gives a number of relations between the different properties, such as vapour pressure and freezing-point, to which we now turn our attention. 

Records of Tests. Either of two methods may be used for recording routine test results. In the first, measurements and calculations are recorded in the individual worker s notebook and then transferred to the main record book. In the second method, a separate work book is kept for each routinely performed test. Whoever does the testing enters the results in the book and initials it. The pages should be lined with columns to suit each test s requirements. 

A relation between rupture phenomena and (specific) surface energy 7 was postulated by Dupre 4 almost simultaneously with the hypothesis of Quincke. Let a cylindrical rod be broken in tension. After rupture, two new gas — solid interfaces of vr2 each are present, r being the radius of the rupture surface. Consequently, the work of rupture ought to contain a term 2 nr2 7 . Dupre did not indicate how to separate this term from the main component of the work of rupture, which is the work required to extend the rod to its maximum elongation (or strain). The modern development of Dupre s ideas is reviewed in Section III.3. below. 

It has been proposed to define a reduced temperature Tr for a solution of a single electrolyte as the ratio of kgT to the work required to separate a contact +- ion pair, and the reduced density pr as the fraction of the space occupied by the ions. (M+ ) The principal feature on the Tr,pr corresponding states diagram is a coexistence curve for two phases, with an upper critical point as for the liquid-vapor equilibrium of a simple fluid, but with a markedly lower reduced temperature at the critical point than for a simple fluid (with the corresponding definition of the reduced temperature, i.e. the ratio of kjjT to the work required to separate a van der Waals pair.) In the case of a plasma, an ionic fluid without a solvent, the coexistence curve is for the liquid-vapor equilibrium, while for solutions it corresponds to two solution phases of different concentrations in equilibrium. Some non-aqueous solutions are known which do unmix to form two liquid phases of slightly different concentrations. While no examples in aqueous solution are known, the corresponding... 

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