Design of a liquid scintillator-based prototype neutron coincidence counter for Nuclear Safeguards

A liquid scintillator-based neutron coincidence counting system designed to address a number of safeguards applications is under development by the IAEA in collaboration with the Joint Research Centre-ITU and Hybrid Instruments LTD. Liquid scintillators are a promising technology due to their good fast-neutron detection capabilities. The characteristic fast response of scintillators is particularly beneficial for coincidence counting applications, for which a performance level higher than that associated with moderated thermal detectors might be expected. Fast neutron detection requires no thermalization process and therefore, does not incur the resulting neutron detection delays. These features reduce the length of the coincidence gate by three orders of magnitude, reducing practically to negligible values the accidental coincidence rate which dominates the uncertainty in thermal neutron detectors. Recent progress in fast electronic digitizers offers the possibility to perform on-line, real-time pulse shape discrimination (PSD) between gamma and neutron radiation detection, making this technology suitable for nuclear safeguards and security applications. This paper will describe the experiments and Monte Carlo modeling activities engaged to design a prototype liquid scintillator-based neutron coincidence collar for fresh fuel assembly verification. The characterization of the system response requires accurate calibration measurements to determine the operational parameters of the liquid scintillator cell, including gain, pulse shape discrimination and energy thresholds. Extensive Monte Carlo simulations are essential to understand and characterize the system response. The MCNPX-PoliMi Monte Carlo code is used to simulate the radiation transport within the system and to optimize the detector design. A description of the different detector configurations investigated and the characteristic features of the final design will be addressed.

TOMANIN Alice;  PEERANI Paolo;  TAGZIRIA Hamid;  JANSSENS-MAENHOUT Greet;  SCHILLEBEECKX Peter;  PAEPEN Jan;  LAVIETES Antony;  PLENTEDA R.;  MASCARENHAS Nicholas;  CRONHOLM Marie; 

2014-01-16

European Commission - Joint Reserach Centre - Institute for Transuranium Elements

JRC81970

978-92-79-32730-8,   

1831-9424,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC81970,