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| Study on detection limit of direct measurement system for internal exposure using anticoincidence method |
| PANG Hongchao, WANG Ying, YUAN Guojun, WU Mengmeng, GUO Luzhen, LUO Zhiping |
| China Institute of Atomic Energy, Department of Radiation safety, Beijing 102413 China |
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Abstract Objective At present, there is a problem that the lower detection limit of lung counter is higher in the direct measurement of internal exposure of transuranic nuclides. In this paper, the anti-coincidence method is used to reduce the system's background and further reduce the detection limit of the system.Methods A new cosmic ray detector based on anti-coincidence method were established in the lung counter system to study the influence of hard components such as muon in cosmic rays on the background of the lung counter system. The cosmic ray detecting system was organized by a large area of plastic scintillator (140 cm (length)×110 cm(width)×5 cm(height)) and anti-coincidence circuit.Results For the energy between 6 keV and 2 MeV, the background count rate of this system decrease from 2.5 cps to 2.2 cps by using the anti-coincidence technique. And the detection limits of 241Am (59.5 keV) and 239Pu (13.6 keV) after 1 800 seconds counting could reach 1.4 Bq and 1700 Bq, respectively.Conclusion In the process of direct measurement of transuranium nuclides with lung counter, the use of anti-coincidence method to reduce the hard component of cosmic rays can better reduce the background of some systems and play a role in reducing the lower limit of radionuclide detection.
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Received: 12 June 2018
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