[en] The national centre for radiation research and technology (NCRRT) is carrying scientific research and technological Activities related to ionizing radiations. About 800 workers are now working in the plant and about 10% of them are working usually in the so-called radiation controlled and supervised areas radiation levels around the irradiation facilities as well as the annual occupational radiation doses during 1985-1989 are reported. The mean annual collective dose is 0.13 man-sievert. The highly exposed group recorded an individual average annual dose of about 3.1 mSv, with the maximum individual annual dose of 7.7 mSv. About 90% of the radiation workers are dosed below 5 mSv/y. The mortality risk is calculated and compared with other industries

[en] The main aim of the present experimental investigation is to study the dosimetric energy response of CaSO₄: Dy thermoluminescence dosimeter to alpha particles. For proper estimation of the dose absorbed by the dosimeter, the alpha particle fluence must be measured. In order to do so, CR-39 plastic track detector is used. Experimental results indicated that CaSO₄: Dy dosimetrie response to alpha particle is not only function to the alpha particle energy but also to the emission rate of the source

[en] There are practical advantages in incorporating a ⁷LiF thermoluminescent dosimeter (TLD) for the measurement of γ-ray dose, into the personnel criticality dosimeter. This paper investigated the corrections necessary for the inherent direct response of the TLD neutrons, and its enhanced indirect response from prompt γ-rays resulting from neutron interactions with the metallic foils contained in the criticality dosimeter. The response of the TLD to fast fission neutrons was measured to be 0.02 γ rad/n rad. The indirect response of the TLD to thermal neutrons was measured to be 4.8 x 10^-10 rad n^-1 cm² for dosimeters exposed in free air, and 7 x 10^-10 rad n^-1 cm² for dosimeters worn on the body respectively. Application of these correction factors to TLD measurements made at International Dosimetry Intercomparisons (sponsored by the I.A.E.A.) gave improved agreement with the values given by other participants. (author)

[en] The photon dose distribution along the beam direction of the 2.5 MeV electrostatic generator of the Nuclear Physics Department, AEE of Egypt has been measured by different type of detectors. The experiments were carried out under different machine operating conditions while the (p,α) reaction on a Co⁵⁹ target takes place. In this case, detectors of high sensitivity and known energy dependence are required to measure only one sort of radiation (photons). The detectors were located at sites where personnel might possibly be exposed to an adverse amount of radiation. The results affored, give useful estimate of the photon dose distribution at the different Van De Graaff areas. (author)

[en] Calcium Sulfates: Dy thermoluminescence dosimeters could be useful for measurements when the dose levels are relatively low. The used material is a home-made Calcium Sulfates: Dy prepared under controlled laboratory conditions with certain activator concentration to optimize its sensitivity and to improve stability of dosimetric traps. The experimental result indicated that the response of the prepared Calcium Sulfates: Dy phosphor to gamma-rays is linear over the range from 0.01 mGy up to 0.57 mGy which is the useful range for environmental application. It was also found that, the energy response is not tissue-equivalent, but this disadvantage could be overcomed by using 0.3 mm lead as a compensation shield. Long term TL storage was investigated and improved by proper choosing of the initial reading temperature. After correction against the recorded fading, the home-made Calcium Sulfates: Dy TL dosimeter could be considered as a suitable technique for application in environmental dosimetry. The results of measurements in 6 locations in Nasr-City, Cairo indicated an average annual background dose of 704+ 40 Gy/y.5 fig.,1 tab

[en] The trapping parameters, namely, the frequency factor and activation energy for natural quartz, feldspar and barite are investigated. The frequency factor is calculated sing the Randell and Wilkins model whereas the initial rise method is viewed suitable to evaluate the trap depth. The inconsistency between the experimentally and theoretically glow curves are attributed to the retrapping effects and randum impurity levels leading to numerous overlapping peaks

[en] The effects of ducts on the dose distribution of γ-rays in an ilmenite-concrete shield have been investigated using a collimated beam of neutrons and γ-rays from a reactor. Measurements were performed in a homogeneous concrete medium and repeated in a medium containing cylindrical air-filled ducts having different lengths and diameters. The γ-ray doses were measured using ⁷LiF in Teflon matrix discs. The results show that the presence of ducts increases the γ-ray doses in the regions surrounding the ducts except for thicknesses less than 20 cm. This increase has a maximum value at positions located approx. 10 cm after the duct ends. The observed increase at peak positions depends on the duct diameters and vertical distances. (author)

[en] Thermal annealing effect and pre-dose effect on the TL properties of Egyptian sand (97.94% SiO₂) of grain size between 71 and 200 micron was investigated. Experimental results indicated that thermal annealing above 600⁰C introduces a new trap level at 140⁰C and the sensitivity of the phosphor to radiation increases as the annealing temperature is increased. The sensitivity of sand is enhanced by previous exposure to a high level of radiation. (U.K.)

[en] It is the aim of the present study to investigate some thermoluminescence properties of pyramid stones. Using a few grammes of pyramid stones from Pyramids I and II, the TL glow peaks were observed at 250 and 310⁰C, respectively. The TL glow peaks of samples annealed at 600⁰C, then exposed to ⁶⁰Co γ-rays were observed at 120, 190 and 310⁰C, respectively. The accumulated dose of natural samples is estimated to be around 310 Gray (31 krad). By assuming an annual dose is 1 mGy, the estimated age of pyramid stones is 0.31 M year. (author)

[en] Radiation response to absorbed gamma doses in the range of 10 to 750 kGy and absorbed neutron doses in the range of 10 mGy to 700 Gy was investigated using the Swedish silicon diode type 5422. The results indicated that its sensitivity to gamma rays is 17.6 mV/kGy in the range up to 60 kGy, which decreases to 10.17 mV/kGy in the range 70 kGy to 700 kGy with an error of +- 7%, while its response to fast fission neutrons is 67 mV/Gy. Factors affecting dosimeter reading, such as high temperature, dosimeter annealing and re-usability were also studied. The system was used for gamma and neutron dosimetry around strong gamma sources and ducted reactor concrete shields. Its applicapility to reactor core dosimetry was also examined. (author)