Symposium on Advanced Sensors and Modeling Techniques for Nuclear Reactor Safety

Radiation Detection and Measurement

Nuclear radiation detectors are required in all the major fields of nuclear science and technology. Radiations which we detect are (a) alpha, (b) beta, (c) gamma and (d) neutron. Radiation cannot be detected by human senses. A variety of handheld and laboratory instruments is available for detecting and measuring radiation. The most common handheld or portable instruments are: Gas ionization detectors (Ionization chambers, Proportional counters, Geiger-Mueller counters with Geiger-Mueller (GM) Tube or Probe), Scintillation detectors (Micro R Meter with Sodium Iodide Detector), Neutron REM Meter with Proportional Counter, Semiconductor detectors Chemical detectors, Film based imaging detectors used for detection of neutrons (Cr-39) and Radon Detectors (LR-115). In view of these handheld radiation detectors, it is mentioned that detection of nuclear radiation falls into two principal categories, single element detectors and imaging detectors. The limitations of these detectors can be discussed in terms of sensitivity, energy resolution, speed, and ability to discriminate against background radiations. This gives some indication of the directions along which future developments of detectors must proceed. Imaging detectors include both area imaging, such as radio-autography, scintillation counter scanning and track imaging. The ionization chamber is the simplest of all gas-filled radiation detectors and is widely used for the detection and measurement of certain types of ionizing radiation; X-rays, gamma rays, and beta particles. The interaction processes of each type of radiation explain their penetrability through matter, their difficulty or ease of detection, and their danger to biological organisms. The interactions of these radiations with matter are unique and the purpose of the demonstration is to show how the physics determines the detection techniques in each of the four types (alpha, beta, gamma and neutron). The net result of the radiation interaction in a wide variety of detectors is the production of electric charge (either directly or indirectly) within the detector. The working principle of detectors used to detect all these four types of radiation will be explored in detail. Uncertainty in the measurement of activity of a radioactive sample emitting alpha, beta, gamma or neutron via its detection using the suitable detector will be presented. Importance of image analysis for film based neutron and radon detection will be explored.