Uranium mass fraction, calculating

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. 

Determination of the D/H ratio of water is performed on H2-gas. There are two different preparation techniques (1) equilibration of milliliter-sized samples with gaseous hydrogen gas, followed by mass-spectrometric measurement and back calculation of the D/H of the equilibrated H2 (Horita 1988). Due to the very large fractionation factor (0.2625 at 25°C) the measured H2 is very much depleted in D, which complicates the mass-spectrometric measurement. (2) water is converted to hydrogen by passage over hot metals (uranium Bigeleisen et al. 1952 Friedman 1953 ... 

She remembered it in 1938, on the day before Christmas. She also had the packing fractions in her head, says Frisch—she had memorized Francis Aston s numbers for the mass defects of nuclei. If the large uranium nucleus split into two smaller nuclei, the smaller nuclei would weigh less in total than their common parent How much less That was a calculation she could easily work about one-fifth the mass of a proton less. Process one-fifth of the mass of a proton through E = mc. One fifth of a proton mass, Frisch exclaims, was just equivalent to 200 MeV. So here was the source for that energy it all fitted ... 

The calculations included two systems a configuration of a solution of uranyl nitrate or a mixture of UO2 and water in spherical symmetry and in slabs of 0.5 in. thickness. For example, the critical mass of a system that consists of a water-reflected sphere of UO2 + H2O at 5% and 20% U-235 enrichment with a 30 cm diameter depends on the U/H ratio. The minimum mass drops from 1.8 to 1.0 kg as the enrichment increases from 5% to 20% and the volume fraction of uranium decreases from 0.1 to 0.03. However, if the concentration of uranium is shifted (increased or decreased) from the optimal volume fraction ratio, then the mass needed for criticality will increase. 

In principle, two fundamentally different methods can be applied to solve this task. The first one is determination of the residual concentrations of the fissile nuclides after irradiation and calculation of the burnup from the difference between final and initial values. For this purpose, the uranium and plutonium fraction has to be separated from the fission and activation products and from each other (e. g. by extraction chromatography) subsequently, the concentrations of the individual isotopes, in particular of the fissile isotopes, are analyzed by mass spectrometry. Well-established analytical techniques for performing such analyses are available, so that only small error margins are to be expected in the determination of the concentrations of the isotopes under consideration. However, there are two problems that can potentially cause systematic errors. The first one is the well-known question of the accuracy of results which have been obtained as a difference between two numbers, which limits the accuracy at lower burnup values in particular. The second problem is that the fissile nuclides are not only consumed by nuclear fission but by neutron capture as well in order to avoid systematic errors here, the capture-to-fission ratio valid for the particular irradiation conditions has to be taken into account in the calculation of depletion during irradiation. If one recalls the complicated buildup and decay mechanisms of actinide nuclides during reactor irradiation (see Fig. 3.5.), it is obvious that such correction requires complex calculations. On the other hand, the direct determination of the residual concentration of fissile nuclides is not influenced by errors due to inaccuracies in the fission yields of fission products to be measured nor by migration-induced inho-mogenities in the fuel. 

Inductively Coupled Plasma Mass Spectrometry (ICP-MS). After conducting uranium separation, 1 ml of the uranium fraction stripped from the column was dried in a clean beaker, then 1 ml of cHNOs was added and dried again to remove any residual HCl. The residue was then dissolved in 10 ml 2 % HNO3. From ICP-MS analysis, the 235yy238y determined and used with the known activities to calculate... 

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