Unsealed Radionuclides Used for Labeling in Industrial Tracer Studies

Considering the characteristics of nuclear data, the time needed for the investiga­tions (several days) should match the half-life of the radionuclides. For measure­ments outside the equipment wall, gamma-emitting radionuclides with relatively high energy (>300 keV) are suitable. Radionuclides emitting a high number of gamma quantums per decay are advantageous; because of their higher count rate, lower activity is necessary for the investigations (see the role of the a factor in Eq. (11.3)). Certainly an important consideration when selecting the radionuclide is simplicity of its preparation, which should take place in the research reactor through the (n, Y) nuclear reaction, favorably with a high activity yield (as discussed in Section 8.5.2).

In addition to nuclear data, physical and chemical features will determine which radionuclides can be selected for a given tracer study. Radionuclides most fre­quently used for industrial tracer studies are summarized in Table 11.1.

In the preparatory phase of the tracer study, at the preparation of the radionu­clide, and during the investigation, rules governing the handling of radioisotopes must be complied with. The fate of the radioactive isotopes used for industrial tracer studies is important to define in advance and solve in an authorized manner.

The simplest way is to store the material labeled with relatively short-lived radionuclides in a well-separated place until its radioactivity decays below the

Table 11.1

Radionuclides Used for Industrial Tracer Studies

Radioisotope

Half-Life

Gamma Photon Energy (keV)

Application Field

Na-24

15 h

1370

For labeling solid grains

K-42

12 h

1520

For labeling solid grains

Sc-46

84 days

890

For labeling solid grains, e. g., in silicate industry

Cr-51

28 days

323

For labeling metals and alloys

Mn-56

2.6 h

1360

For labeling metals and alloys

Fe-59

45 days

1100

For labeling ferrous metals

Cu-64

13 h

510

For labeling metals and alloys

Zn-65

245 days

1110

For labeling metals and alloys

Br-82

36 h

780

For labeling stream waters

I-131

8 days

360

For halogenation

Rb-86

19 days

1080

For labeling solid grains

Ag-110m

253 days

660

For labeling metals and alloys

La-140

40 h

1600

For labeling solid grains, e. g., in silicate industry

Au-198

2.7 days

412

For labeling solid grains as colloid

Hg-203

47 days

279

For mercury electrolysis as metal

Kr-85

10 years

510

For labeling gases

exempted activity level. Storing time can be considerably reduced if the labeled material is diluted during the technological processes or is artificially diluted after the study. In such cases, the exempted radioactive concentration will be the precon­dition of the release. For instance, the dilution rate of a radioactive-labeled compo­nent that is introduced into a huge storing container with a great volume of nonradioactive material can even grant an exemption from separated storage.

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