Bi-210 has been separated on nickel plate by electrolysis, and then bismuth sulfide has been prepared. This has been used for the radioactive indicator of proteins.

8.5.1.2 Po-210

Po-210 has been used for the preparation of alpha radiation sources.

From the members of the decay series of Th-232 (see Figure 4.6), Ra-228, Th-228, Rn-220, and Pb-212 isotopes have been used as radioactive indicators. Since these are the isotopes of the same elements as the members of the decay series of U-238, the applications are also similar. An emanation source can be pro­duced from Th-228, from which Rn-220, and its daughter nuclide, Pb-212 can be separated electrostatically (see Figure 8.6) and applied as radioactive indicators. The electrostatic separation is based on the recoil of the daughter nucleus when emitting the alpha particle (as discussed in Section 4.4.1). As a result of the recoil, the daughter nuclide is ionized; the positive ions can be collected electrostatically on the negative electrode.

In Table 8.3, the quantities of radioactive isotopes in secular equilibrium in 1 g uranium-238, uranium-235, and thorium-232 isotopes are shown. These are the upper limits of the quantities of isotopes that can be obtained from 1 g of uranium and thorium isotopes. According to the natural isotopic ratio of uranium, 1 ton of uranium contains 993 kg of 238U and 3 kg of 235U. In addition, the uranium and thorium concentration of the rocks is also very small (<0.1%). These data illustrate that the separation of the natural radioactive isotopes is very difficult.

— Electrode holder

— Electric insulation

■ Wall of the tank (positively charged)

Pt electrode (negatively charged)

Th-228 precipitated onto iron(III) oxide

Figure 8.6 Electrostatic separation of daughter elements of Th-228.