الفهرس 
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Abstract
In a country with nuclear activities, a system of controlling nuclear material is considered as an essential requirement. The main goal of such system is to make sure that nuclear material and activities in state are utilized as planed and not diverted for non-peaceful uses or misused. Part of controlling system is a measurement system that must has the capability to verify all types and categories of nuclear materials exist in the nuclear fuel cycle in state. Nuclear material verification is an activity carried out to confirm that the amount of nuclear material actually present at a given time within a certain place is in agreement with the operator declarations.
In this regard, the verified nuclear material is well known and all the role of verification is to check the correctness of the provided data. To verify the nuclear material, it has to be measured using a suitable device. Nuclear materials are usually measured using gamma-ray spectrometer in order to quantify certain isotopes. The measuring spectrometer has to be calibrated prior to perform measurements on NM under verification. The calibration process necessitates the use of NM standards. Due to the wide Varity of NM present in a nuclear fuel cycle, such standards are not always available. Semi-absolute measurements could be used to solve such a problem. If enough and suitable data are available about the measuring system, it could be mathematically calibrated using Monte Carlo calculation technique. In this work, a HPG e detector is characterized. The results of characterization are combined with the manufacturer data and other data from literature to construct a more refined detector model. The refined model is used to calibrate the measuring system using MC calculations, and estimate the 235U mass content in some NM samples. Measurements of count rate due to the 185.7 keV gamma rays (emitted after decay of 235U nuclei) is combined with the calculated full energy peak efficiency of the detector using MC calculations to estimate the 235U mass. Results show that the estimated 235U mass is in agreement with the declared values within the estimated errors.
A precision of 0.48% is obtained with an accuracy of 1.06%. The used semi-absolute method is compared with relative measurements to investigate the advantages and limitation of each.