Keywords: NE213, scintillator, pulse shape discrimination.

NE213 scintillation detectors are excellent tools for use in a mixed gamma and neutron field due to its established pulse shape discrimination ability. With proper pulse shape discrimination, gamma or neutron responses may be obtained in a mixed radiation field. The neutron response needs to be deconvolved from the detector response function to obtain an energy spectrum. To perform unfolding of neutron spectra, mono-energetic responses are needed and the responses may be obtained via experiment or simulation of the NE213 detector. In this work, response functions were tested with the unfolding of a Cf-252 spectrum. Particularly, experiments were performed at the Los Alamos National Laboratory where Cf-252 spectra were obtained. During the experiment, different pre-amplifier set-ups were tested. Namely, the pulse shape discrimination ability of the system using 50 ohm, 500 ohm, and 1000 ohm termination resistors were compared. However, linear system responses were not observed with the different settings. Thus, the Amoeba Simplex fitting routine was used to augment the charge integration pulse shape discrimination technique to separate the neutron and the gamma signals. Furthermore, a new figure of merit scheme was explored to quantify the pulse shape discrimination ability of the said non-linear system. Alongside the Cf-252 spectra experimental measurements, the program Scinful was used to generate mono-energetic neutron responses needed for unfolding. Consequently, both the Cf-252 neutron spectra and the Scinful responses were used with the program FERD-PC for unfolding. Among the different termination resistors compared with the new figure of merit scheme, the 50 ohm resistor setting was observed to be superior. The resultant unfolded spectrum using the 50 ohm termination resistor shows excellent agreement between 2-10 MeV. However, even with the Amoeba Simplex method, results below 2 MeV are not accurate due to the poor pulse shape discrimination limit of the sys.

This book introduces the physics and chemistry of plastic scintillators (fluorescent polymers) that are able to emit light when exposed to ionizing radiation, discussing their chemical modification in the early 1950s and 1960s, as well as the renewed upsurge in interest in the 21st century. The book presents contributions from various researchers on broad aspects of plastic scintillators, from physics, chemistry, materials science and applications, covering topics such as the chemical nature of the polymer and/or the fluorophores, modification of the photophysical properties (decay time, emission wavelength) and loading of additives to make the material more sensitive to, e.g., fast neutrons, thermal neutrons or gamma rays. It also describes the benefits of recent technological advances for plastic scintillators, such as nanomaterials and quantum dots, which allow features that were previously not achievable with regular organic molecules or organometallics.

The updated and much expanded 3e of the Handbook of Radioactivity Analysis is an authoritative reference providing the principles, practical techniques, and procedures for the accurate measurement of radioactivity from the very low levels encountered in the environment to higher levels measured in radioisotope research, clinical laboratories, biological sciences, radionuclide standardization, nuclear medicine, nuclear power, and fuel cycle facilities and in the implementation of nuclear forensic analysis and nuclear safeguards. The book describes the basic principles of radiation detection and measurement and the preparation of samples from a wide variety of matrices, assists the investigator or technician in the selection and use of appropriate radiation detectors, and presents state-of-the-art methods of analysis. Fundamentals of radiation properties, radionuclide decay, the calculations involved, and methods of detection provide the basis for a thorough understanding of the analytical procedures. The Handbook of Radioactivity Analysis, 3e, is suitable as a teaching text for university and professional training courses. The only comprehensive reference that describes the principles of detection and practical applications of every type of radioactivity detector currently used. The new 3e is broader in scope, with revised and expanded chapters, new authors, and seven new chapters on Alpha Spectrometry, Radionuclide Standardization, Radioactive Aerosol Measurements, Environmental Radioactivity Monitoring, Marine Radioactivity Analysis, Nuclear Forensic Analysis and Analytical Techniques in Nuclear Safeguards Discusses in detail the principles, theory and practice applied to all types of radiation detection and measurement, making it useful for both teaching and research

Failed fuel refers to the breach in the fuel-clad of an irradiated fuel assembly in a nuclear reactor. Neutron detection or gamma detection is commonly used in Failed Fuel Detection and Locating (FFDL) system to monitor the activity of the coolant. Though these methods offer specific advantages under different conditions of the coolant, providing both types of detectors in FFDL system is impractical. This limitation is the motivation for the detector system developed in the present work. In the present work, effort has been made for realising a detector system for simultaneous measurement of neutron and gamma activity of the coolant, thus offering a two-parameter basis for failed fuel detection. NE213 liquid scintillator was chosen for this work as it has good detection capability for both neutrons and gammas. Additionally, the neutrons and gammas interacting with NE213 detector can be separated based on pulse shape discrimination. The work reported in this thesis includes fabrication details and different steps followed in assembling the NE213 detector. Details of experimental set-up developed for pulse height analysis and pulse shape analysis are covered. Results of experiments carried out to study the response of the NE213 detector to gamma and neutron sources using pulse height analyser are presented. The absolute gamma efficiency and relative gamma efficiency of NE213 detector are calculated. Neutron- amma separation capability of NE213 detector based pulse shape analysis system is reported. Application of the developed detector system to analyse the coolant activity in FFDL system in a reactor is described. Response of the detector is compared with the existing FFDL system at different power levels of the reactor. Since failed fuel is a rare event, it was simulated using neutron and gamma sources. Pulse shape analysis spectra obtained under simulated failed fuel condition are presented.

The Theory and Practice of Scintillation Counting is a comprehensive account of the theory and practice of scintillation counting. This text covers the study of the scintillation process, which is concerned with the interactions of radiation and matter; the design of the scintillation counter; and the wide range of applications of scintillation counters in pure and applied science. The book is easy to read despite the complex nature of the subject it attempts to discuss. It is organized such that the first five chapters illustrate the fundamental concepts of scintillation counting. Chapters 6 to 10 detail the properties and applications of organic scintillators, while the next four chapters discuss inorganic scintillators. The last two chapters provide a review of some outstanding problems and a postscript. Nuclear physicists, radiation technologists, and postgraduate students of nuclear physics will find the book a good reference material.