Ahmed M. Maghraby

Ionizing Radiation Induced Radicals

When ionizing radiation passes through a material it imparts some of its energy to that material. The imparted energy may be high enough to cause a break in bonds inside the molecules or between molecules or both, in such cases, free radicals are created. The type, lifetime, extent, fate and origin of those free radicals may differ according to several factors; most of them are beyond the subject of this chapter. However, the abundance of ionizing radiation induced radicals in a material is directly proportional (unless saturated) to the amount of ionizing radiation received by that material, hence it could be a method for determination of radiation doses passively by accurate evaluation of the extent of free radicals created. Study of radiation induced radicals is not always related to radiation dose assessment; sometimes it is of great importance to investigate what type of radicals are produced when a specific material is exposed to a specific radiation dose, and for how long those induced radicals can persist. This could be of specific interest specially when dealing with environments of high radiation levels, for example: in space environments. Behavior of radiation induced radicals may lead to further understanding of molecular interactions or molecular dynamics, or may lead to a decision on the preference of a material for a specific design from the material science point of view.

Uncertainty attributed to signal averaging in a single averaged alanine EPR spectrum for low-dose applications.

During the past 50 y alanine has been considered a reference dosimetry system using electron paramagnetic resonance (EPR), especially for the high doses associated with radiation processing. Extension of alanine/EPR system applications to the lower doses associated with radiation therapy and/or radiation protection is limited by the ability to extract the dosimetric signal with minimum associated noise. The signal-averaging technique is one of the common numerical methods used for enhancing the signal-to-noise ratio, through which the accumulated repetitive scans causes the reduction of noise due to its random behaviour and the signal growth due to its persistence. However, the use of signal averaging is usually associated with some uncertainty, which is not usually considered. In this work, there is a clarification of the importance of the evaluation of uncertainty associated to the single averaged alanine spectrum.

Estimation of the residential radon levels and the population annual effective dose in dwellings of Al-kharj, Saudi Arabia

Abstract Indoor radon levels and the annual effective dose are measured in Al-kharj city, Saudi Arabia dwellings using CR-39 detector. The dwellings are classified according their types (schools, homes and working area). The influence of some factors like number of floors and ventilation conditions on indoor radon levels, equilibrium factor and radon effective doses were studied. Can and bare method is used for determine the equilibrium factor between radon and its daughters. Based on the dosemetric approach and epidemiological determinations conversions convention for radon exposures, the annual effective doses are calculated and compared. The average radon concentration varies from 76±38Bqm−3 in work places to 114±41Bqm−3 in homes. About 77% of the studied dwellings give radon concentration in the range from 50 to 150Bqm−3. The overall weighted mean of radon level is equal to 94±41Bqm−3 which about 2.5 times the global average. The equilibrium factor has a wide range from 0.1 to 0.6 with overall weighted average equal to 0.308±0.13. The variety of living style, constructed materials and ventilation rates are responsible for this wide range and subsequently the obtained high uncertainty (42%). Homes showed larger annual effective dose (3.186±0.75mSv) than other dwellings which locate in the range of the recommended action level but about three times the global average. The result shows that the ventilation condition is the major but not the only factor affects the results. Poor ventilated dwellings showed the maximum annual effective dose on the other hand the number of floor has insignificant difference.

Taurine-EVA copolymer-paraffin rods dosimeters for EPR high-dose radiation dosimetry

Abstract Taurine/EPR rods (3 × 10 mm) have been prepared by a simple technique in the laboratory where taurine powder was mixed with a molten mixture of paraffin wax and an ethylene vinyl acetate (EVA) copolymer. The binding mixture EVA/Paraffin does not present interference or noise in the EPR signal before or after irradiation. The rods show good mechanical properties for safe and multi-use handling. An EPR investigation of radiation induced radicals in taurine rods revealed that there are two types of radicals produced after exposure to gamma radiation (60Co). EPR spectra were recorded and analyzed - also the microwave power saturation and modulation amplitude were studied and optimized. Response of taurine to different radiation doses (1.5-100 kGy) was studied and found to follow a linear relationship up to 100 kGy. Radiation induced radicals in taurine persists and showed a noticeable stability over 94 days following irradiation. Uncertainities associated with the evaluation of radiation doses using taurine dosimeters were discussed and tabulated. It was found that taurine possesses good dosimetric properties using EPR spectroscopy in high doses in addition to its simple spectrum.

Radon levels and the expected population mortality in dwellings of Al-Kharj, Saudi Arabia

Abstract Internal exposure from inhalation of radon and its progeny is one of the most significant sources of natural radiation exposure of the population. Radon levels and radon equilibrium factor were measured in the dwellings of Al-Kharj, Saudi Arabia using passive technique. Calibrated CR-39 diffusion type radon detectors were used for radon measurements and the method of can and bare is adapted for the measurement of radon equilibrium factor. Passive measurements enable the accumulation of the result over a long period and cover a wide area. The probability of cancer induction and then the expected mortality was calculated based on different approaches. The results show that the overall weighted mean of annual effective dose for Al-Kharj resident is equal to 1.51±0.8mSv and The average expected mortality for residents in dwellings of Al-Kharj city is ranged from 0.596±0.25 to 0.369±0.15 death per 10,000 persons of ages from 40 to 70 years respectively. Also, the lifetime excess absolute risk (LEAR) of the residents of the Al-Kharj city is equal to (2.06±0.8)×10−4. The effect of dwelling types, ventilation and construction materials on the expected mortality is discussed.