Nuclear fuel mass calculation

The projections are based on a recent forecast (Case B) by the Energy Research and Development Administration (ERDA) of nuclear power growth in the United States (2) and on fuel mass-flow data developed for light water reactors fueled with uranium (LWR-U) or mixed uranium and plutonium oxide (LWR-Pu), a high temperature gas-cooled reactor (HTGR), and two liquid-metal-cooled fast breeder reactors (LMFBRs). Nuclear characteristics of the fuels and wastes were calculated using the computer code ORIGEN (3). 

FOLLOW-UP PROBLEM 23.6 Uranium-235 is the essential component of the fuel in nuclear power plants. Calculate the binding energy per nucleon for Is this nuclide more or less stable than "C (mass of atom = 235.043924 amu) ... 

Conservation of Matter. This is the familiar statement that "mailer is neither destroyed nor created." There must be a weight balance between the sum of the weights entering a process and the sum leaving. In other words. A pounds of fuel combined with B pounds of air will always result in A + B pounds of products. (It should be noted that when a pound of a typical coal is burned, releasing 13.500 Btu, the quantity of mass converted to energy amounts to only 3.5 x 10 1(1 pound, a loss too small to be measured or considered in conventional combustion calculations. Obviously, this conversion is of significance to nuclear reactions.)... 

Calculation of Lattice Porametert of H,0 Moderated UO, Fueled Critical Asson-blies, W. B. Amaid, Jr. (WAPD). A stem, consisting largely of hand calculations, is described which pr cts to edthin 1% in reactivity the critical masses of fourteen sepa rate UO, B,0 critical assemblies. Kght of these were the A1 clad 1.3% enriched cores done by the Bettis TRX group. One was an experiment on steel clad 4% enriched UO, performed imder the Nuclear Ship Savannah program. The other five were performed by WAPIV>three on steel clad 2.7% UO, Yankee criticals, two on steel clad 4,4% BR criticals. Table 1 contains a brief description of these experimental results. 

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. 

The projections made by the U.S. Department of Energy (1982) of installed nuclear capacity and the associated masses of spent fuel discharged are reproduced in Table 3.2. The activity of present in the discharged fuel is also given in the table. The latter was calculated... 

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