Liquid Scintillation In Line With The Method Of Measuring The Complex Decay Of The Nuclide Activity

The study of coincidence method is based on A 4% beta-gamma coincidence liquid scintillation counting system. This work applies the method of double dead-time coincidence for absolute radioactivity measurements, which is based on the possibility of sending detector output pulses to two parallel extending-type dead-time circuits. As there is no coincidence circuit, the method decreases uncertainty of result caused by accidental coincidences and gives activity values with good precision.This liquid scintillation counting system is used for absolute radioactivity measurements. It allows measurements of most beta-gamma decay nuclides as well as pure beta decay ones by the use of a suitable efficiency tracer.The detection equipment includes a beta-ray detector which is performed with a matched double-phototube liquid-scintillation coincidence system, and a gamma-ray detector.(NaI(Tl) cristal detector). Three counting channels are needed. Two are independent and process respectively the beta and gamma pulses. The same beta and gamma pulses are sent to the additional channel. Each counting channel is equipped with an extending-type dead-time circuit and an associate live-time integrator that allows the measurement of live times. It is required that the dead time imposed in the additional channel is chosen longer than or equal to thedead time imposed in both independent channels.A series of measurements on 134Cs , 60Co, 90Sr-90Y samples are undertaken. Each sample is made up to 10 ml with liquid scintillation solution. The experimental result of 134Cs, compared with the data of standard activity of reference solution, the agreement is within 1%. As for 60Co and 90Sr-90Y, compared with the data of standard laboratory of CIAE, the agreement is within 1% and 1.7% respectively.The method presented shows promise as a simple direct method for absolute radioactivity measurements. Compared with the conventional coincidence technology, it avoids problems as accidental coincidences and gives activity values with good precision. There remains a need for additional investigations in both expanding the measurement scope and improving the accuracy to attain better agreement.