TRITIUM DETECTION METHODS

The quantity or activity of tritium is determined by measuring the energy released as it decays. At very high levels, it is possible to use calorimetric methods, measuring the heat generated as the tritium decays. More usually, however, measurement methods involve the detection of the beta particles (electrons) that are created during decay.

 

1. SCINTILLATION COUNTING

If tritium is in liquid form, its activity can easily be measured by a scintillation counting technique. A fluorescing additive, mixed with the liquid to be evaluated, will emit a scintillation when intercepting each beta particle that is released. The scintillations are then counted using a photomultiplier tube amplifier system.

 

2. GAS PROPORTIONAL COUNTERS

If tritium is in gaseous form, rather than liquid, and the application is to detect individual decay events, then proportional counters are used.

Basically, a proportional counter is a device that uses a process known as gas multiplication to linearly amplify the charge generated by a nuclear event. When used for the detection of tritium, the purpose of the proportional counter is to amplify the very weak beta energy to a level where it can be further processed, pulse by pulse, by conventional electronic means. OTC Proportional counters selectively measure tritium in concentrations below 10-3 mCi/m3.

 

3. LINEAR IONIZATION CHAMBERS

If tritium is contained in a volume under an electric field, the electric charges that are generated by a radioactive decay can be collected in the form of an averaged electric current. Although tritium is a very weak radioisotope, it is feasible to use ionization chambers for measurements as low as a few hundred Bequerels per cubic meter (10-7 to 10-9 Ci/m3). The sensitivity of measurement attainable by the use of ionization chambers depends on several factors, including the size of the chambers and the quality of the electrometer ionization current amplifier.

 

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