Concept of On-site Two Point Beta Detection System by Using Scintillating Fiber

An on-site real-time monitoring system to analyse radioactive contamination due to beta emitting nuclides in the decontamination and decommissioning (D and D) of nuclear facilities was proposed. The system was established using scintillating fiber for detection of short-range beta particle at on-site radioactivity measurement, photomultiplier tubes (PMT), amplifier and counting device. 20 scintillating fibers were combined for better experimental characterization, where 90Sr and 14C sources were used for beta detection of the scintillating fiber and PMT was positioned at the end of the scintillating fiber bundle. Variations of count rates were analysed according to the change of the distance between PMT and radioactive source. The change of the count rate by decreasing the distance was verified using the ratio of count rate to the radioactivity at the distance from the PMT which was experimentally fitted. Two PMTs were positioned at both ends of scintillating fiber bundle to set two points beta detection. When the two point sources interacted with scintillating fiber bundle, the recorded result of each PMT was the sum of the signals from short and long distance points. Each radioactivity at both points was analysed in terms of each point of radioactive source and experimentally fitted function where it was calculated by solving the simultaneous linear equations with two unknowns. The relative errors were 1.06 percent and 6.11 percent at each point.(author).