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Title: A non-destructive digital imaging approach to locate and discriminate neutron and gamma sources
Author: Gamage, Kelum Asanga Akurugoda
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2011
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In this research, a non-destructive digital imaging approach to locate and discriminate neutron and gamma sources using a single fast organic liquid scintillator detector is demonstrated. The detector is integrated into a ultra-fast digital processing unit, a heavy-tungsten collimator and an adjustable equatorial platform to enable scanning of mixed radiation field environments. Three exemplar environments have being investigated with this system corresponding to a caesium-137 source (a gamma source), an americium-beryllium source (a neutron source) and both sources together separated in space. The sources were attached to a vertical wall and the imaging system was placed near to the wall. The system collected data from a grid of measurement points which covered the source on the wall. The collected events were discriminated between neutron and gamma-ray using pulse gradient analysis. Images have been produced for each measurement in terms of the angular distribution of events for total counts, gamma rays and neutrons. All the experimental measurements were carried at the low scatter facility at the National Physical Laboratory (NPL), London, UK. A selection of pulse shape discrimination techniques for the mixed-field imaging system have been studied. The digitiser was exposed to a range of the radiation fields available at NPL and different pulse shape discrimination algorithms were compared in terms of the separation of the events (figure of merit ). Also, the quality of the mixed radiation imaging was studied for two different tungsten collimator geometries. The principle of using tungsten collimators to scan for both neutrons and gamma rays was demonstrated using Monte Carlo simulations. The capability of imaging mixed radiation field, which comprise both neutrons and gamma rays, has many potential applications in nuclear industry, international border safety and security. The mixed-field imaging system is currently being considered to be commercialised through Hybrid Instruments Ltd. , Lancaster. A novel analytical approach for self-shielding of gamma radiation in decommissioning scenarios is also introduced and have being compared with MCNPX 2.6.0 simulations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available