Dysprosium ratio

Two thin 1-mg samples of dysprosium are irradiated and counted in a similar manner, except for the use of a Cd cover foil on one sample. A Cd ratio of 7 is measured, with the bare foil saturation activity of 1 x 104 dpm. Calculate the thermal neutron flux at the irradiation position in the reactor. 

Dy-Cu-Sb. A ternary compound of dysprosium with copper and antimony of the 3 3 4 stoichiometric ratio was identified and studied by means of X-ray analysis by Skolozdra et al. (1993). Dy3Cu3Sb4 compound was found to have the Y3Au3Sb4 type structure with a lattice parameter of a = 0.9503 (X-ray powder diffraction). For experimental details, see the Y-Cu-Sb system. 

Test samples were fabricated by Si and Ge monohydrides pyrolysis in the gas mixture at the total pressure of 35-40 Pa with monogerman to monosilane volume ratio of 0.001-0.002. Temperature of the process was not higher than 680°C. P-doped silicon wafers (100) were used as substrates. Before the pyrolysis process we have oxidized the surface of some silicon wafers in dry oxygen in order to form thin silicon dioxide layer. In addition dysprosium and yttrium oxides were also formed on the wafer surface for other samples by the process of their deposition and following oxidation. 

Dysprosium ions Dy3+ can also be populated by direct absorption in the near U.V. part and blue part of the spectrum, or by energy transfer from U02+. The radiative transitions probabilities and branching ratios of Dy for tellurite and phosphate glasses have been calculated and measured51 and the corresponding values are given in Table 3. 

Figure 10. Plot of the natural logarithm of the ratio of the ion signal (S) to the zero delay ion signal (S0) vs. ionizing pulse delay time for the 21783 cm 1, J =7, odd level of dysprosium. Ionizing wavelength, 2 = 3820 A.

Table VII. Branching ratios, lifetimes, absolute and relative f-values found for dysprosium and the ratio obtained to conve "t- the relative f-values in Ref. (58) to absolute f-values.

Fig. 8.76. Poisson s ratio (j ) and theta (0) of dysprosium computed from the single crystal constants shown in fig. 8.74.

The thermal utilization of the lattice was determined using the known volume fractions of the constituents of a unit cell and the corresponding macroscopic cross sections along with the thermal-neutron distrlbutitms in these constituents. The distributions were obtained from activations of sets of bare and cadmium-covered dysprosium foils placed in the various parts of the central cell at a distance of 18 in. above the bottom of the assembly where the cadmium ratio no longer varied with height. The value of f obtained was 0.9445 0.0009. 

The standard cadmium ratio technique wais used for the measurement of p , the ratio of epi- to subcadmium captures in Th. The 27.4-day half-life Pa produced in ThO, wafers was y counted. The differential technique was used to determine lny> dysprosium thermal disadvantage factor. Dysprosium aluminum foils 1.19-mm diam x 0.127-mm thick were distributed throughout a unit cell. 

Measurements were made of (dysprosium disadvantage factor), poz (ratio of epi- to subcadmium capture ratio in Th), and 6 (ratio of fission in Th to fission in U). The techniques used in measuring C and p were reported elsewhere and will not be reported here. Of more interest is a new technique of measuring the fSst fission ratio. 

REEs are classified as lithophiles and are partitioned into the earth s crust and mantle. The name rare earths originated over a century ago when the elements were first identified in minerals that, at the time, were rare. The elements are actually distributed widely over the earth and relatively accessible on the earth s surface. For a comprehensive description of REE geology, geochemistry, and natural abundances, see Geology, Geochemistry, and Natural Abundances of the Rare Earth Elements. In 2010, the United States Geological Survey (USGS) estimated that there were REE reserves of 110 million metric tons (mt). The static depletion index, the ratio of reserves to present-day production, for REEs is approximately 870 years. Thus, the primary immediate consideration is whether REE production can match demand, and particularly whether it will be possible to increase the use of dysprosium and neodymium in wind turbines and the batteries of electric vehicles. 

Dysprosium-aluminum wire has been chosen to measure the thermal-neutron spatial distribution. Dysprosium has a high cross section for thermal-neutron activation and a convenient half-life of 140 min. Thermal-neutron flux distributions will be made through the glory hole on both sides of core center and along the fine control rod when it is fully inserted. An absolute thermal-flux measurement will be made at the core center with a standard gold foil. This foil will be counted on an end-window GM counter whose efficiency for the standard gold foil has been determined from a previous standard pile irradiation. The results from the two activation detectors will yield the average thermal flux in the reactor core as described in Section II. A cadmium-ratio measurement of AGN-201 fuel can also be made in order to determine the fraction of the total fission rate due to epithermal neutrons. 

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