RADIOACTIVE LEVEL MEASUREMENT BY TYPE

LEVEL MEASUREMENT BY RADIOACTIVE EQUIPMENT

There are processes in which it is no longer possible to perform level measurements with the aforementioned elements when they are at high temperatures, high pressures, in corrosive, toxic, or highly explosive environments, etc. In short, we cannot insert a level measurement instrument.

The last extreme alternative is nuclear measurement equipment. This equipment uses an ionizing radiation source, usually Cesium-137 or Cobalt-60, although Cesium-137 is the most common. This radioactive element has a half-life of approximately 15 years. The unit of measurement for the radiation source is Ci, or Curie.

The operation of this equipment is defined by an ionizing radiation source and a detector. In the 100% case, the source has a gate that blocks the radiation beam from exiting, for the protection of personnel. This gate must be opened by qualified personnel authorized by the regulatory body in the corresponding country. The detector can be an inert gas chamber that is excited by the radiation and generates a millivoltage, or a fiber optic tube that concentrates the radiation pulses, which are then amplified and counted by specialized electronics that interpret this as a value.

Most of the time, nuclear equipment is used as Level Contacts or Switches, meaning that the presence of the material to be detected only sees a Point, it can be a High Level or a Low Level, ON-OFF, 0-1, etc.

In the case of needing to detect a level variation, analog values, or continuous measurement, the configuration remains the same, but the detector and its position change, since I must allow the radiation beam projection to have a larger projection area or control surface, and the detector is also larger so that it can cover the entire area I need to measure.

The different ways a source with a detector can be arranged are shown here.

This represents the chamber in which there is an inert gas that, when bombarded by radioactive particles, generates a millivoltage that is proportional to the amount of radiation that arrives. This means that the sensor where it will be installed must be calibrated, but without the presence of the medium to be measured, which will be a 100% of radiation; the missing radiation will be absorbed by the medium to be measured.

This equipment corresponds to a scintillation-type detector, where the radiation creates light traces that are read by the amplification electronics and interpreted as the amount of radiation.