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Abstract
The present thesis is concerned with neutron flux and spectrum measurements performed for the Cairo Fourier Difractometer Facility (CFDF); installed in front of one of the ET-RR-1 reactor horzontal channels. The CFDF applies two neutron guides to transfer the neutron flux from the reactor beam hole to the Fourier chopper and the sample position. The neutron flux and spectrum measurements were carried out at the exits of both the curved and straight neutron guides, in order to estimate the neutron flux value at the sample position. For such purpose 3He and BF3 neutron detectors were used along with the activation method; using different foils. Besides, the neutron detectors were calibrated using both 252Cf and Pu-Be neutron sources. The neutron flux was found to be 6.66x106 n/cm2.s and 1.15x106 n/cm2.s at the exits of the curved and straight neutron guides respectively. Moreover, the neutron flux was estimated from the neutron spectrum measured at the sample position using a Fermi disc type chopper; and good agreement was found between both calculated and measured values. The present thesis contains four chapters: Chapter one presents a general introduction including: - Neutrons and their basic properties Literature review on neutron flux and spectrum measurements as well as 3He , BF3 detectors. - Aim of the work. Chapter two presents theoretical considerations and method of data analysis and includes: - Theoretical considerations in case of neutron diffraction measurements and neutron flux estimation; mainly -The activation method for neutron flux and spectrum measurements. -The calibrated detectors for neutron flux and spectrum measurements. Chapter three deals with the experimental facilities and measurements. It presents: - The Cairo Fourier Diffractometer Facilty (CFDF). - Calibration of 3He and BF3 detectors using gold foils activation and Californium source. - Calibration of NaI (Tl) Detector. - Calculation of thermal and epithermal neutron flux distributions in irradiation channel. - The pulse height spectra of 3He and BF3 detectors. - The neutron flux measurements at CFDF. -Measurements using activation method and 3He and BF3 Detectors. - Neutron Spectrum Measurements. Chapter four presents the results and their discussion; with concentration on: - Calibration of gas Detectors Using gold foils and Californium source. - Calculation of thermal and epithermal neutron flux distributions in irradiation channel using MCNP code. - Calibration of gas detectors using activation method with neuron sources. - Neutron flux measurements at different places in the way of the CFDF neutron beam; using different detectors along with the activation method. - The neutron spectrum and neutron flux evaluation at the sample position. The obtained neutron flux values were compared and it has been verified that the 3He detectors are superior, for neutron beam monitoring at the CFDF, to the BF3 detectors. The main results of the present thesis have been presented in a paper entitled: “Neutron Flux Measurements at the CFDF using Different Detectors” By: R.M.A. Maayouf, I.I. Bashter, W.M. El-Maamly and M.I. Khalil. The paper was accepted for puplication in: Arab J.Nucl.sci. and Applications (In print).