The radioisotopes that are used most frequently for radiation absorption and scatter­ing type measurements are listed in Table 11.2.

11.3.2 Level Indication of Materials in Tanks

For detecting the level of materials in industrial equipment, nuclear level indicators and level measuring instruments can be used (Figure 11.20). Level indicators are suitable for detecting and transmitting given level limits (min, max), while level measuring instruments are used for continuous detection, recording, and transmit­ting the material level.

The level of materials in industrial equipment can be continuously determined either by absorption measurement of the radiation or by installing a level indicator on the servo-motor driven mechanism following the material level. Figure 11.21 shows the principle of absorption type measurement. Measurement based on radia­tion absorption utilizes the change in the relative absorption caused by the material level. Similar equipment can utilize reflection of the radiation. Radiation sources

Table 11.2 Radioisotopes Used for Radiation Absorption and Scattering Type Measurement

Radioisotope Half-Life Type of Radiation Application Field

Buzzer

Output connecting to filling unit

Figure 11.20 The principle of level indication with the radioisotope technique.

used for such measurements (depending on the wall thickness of the equipment) are 37 MBq to 3.7 GBq Co-60, and Cs-137 sealed sources. Applied detectors are the Geiger—Muller counter and the scintillation detector.

Examples of industrial level indication and level measuring solutions include:

• Maintaining the level of the mixture between limit values in a blast furnace.

• Automation of a miner’s tram filling.

• Piece counting on tile production lines.