[en] The main task of this study is to calculate the radiological hazards due to gamma rays emitted from naturally occurring radionuclides (²²⁶Ra, ²³²Th, ²³⁵U and ⁴⁰K) in soil samples from some areas in Egypt. The mean activity concentration of ²³²Th, ²²⁶Ra, ²³⁵U and ⁴⁰K are 26.7, 31.1, 11 and 320.1 Bq/kg, respectively. The parameters which are used to assess the radiological hazard from exposure to these soil samples are estimated. The average absorbed dose rate of the radionuclides of interest for all measured samples is 43.5 nGy/h, while the average annual effective dose in air outdoors and indoors due to gamma radioactivity are calculated to be 53.6 and 213.9 µSv/h, respectively. The data obtained by this study will offer a base for ecologists, geophysicists and soil scientists to explain and solve easier some radio-ecological problems related to the areas under investigation. The results are intended to be further used in order to develop a data base for building a radio-ecological atlas for Egypt, in the near future. (author).

[en] This Regulation refers to the requirements of the Regulation CNEN-NN.3.01. 'Basic Act of Radiological Protection', as expressed in the section 5.9, and its application to the effective dose calculation for individual occupationally exposed. from the internal and external individual monitoring data

[en] A method for the quantitative four-dimensional (4D) evaluation of discrete dose data based on gradient-dependent local acceptance thresholds is presented. The method takes into account the local dose gradients of a reference distribution for critical appraisal of misalignment and collimation errors. These contribute to the maximum tolerable dose error at each evaluation point to which the local dose differences between comparison and reference data are compared. As shown, the presented concept is analogous to the γ-concept of Low et al (1998a Med. Phys. 25 656-61) if extended to (3+1) dimensions. The pointwise dose comparisons of the reformulated concept are easier to perform and speed up the evaluation process considerably, especially for fine-grid evaluations of 3D dose distributions. The occurrences of false negative indications due to the discrete nature of the data are reduced with the method. The presented method was applied to film-measured, clinical data and compared with γ-evaluations. 4D and 3D evaluations were performed. Comparisons prove that 4D evaluations have to be given priority, especially if complex treatment situations are verified, e.g., non-coplanar beam configurations

No abstract available

[en] In an incident, the operational control staff needs a rapid general view of the radiological situation in the vicinity of the emission source which is suitable for decision support. Because the measuring team cannot provide sufficient measurements immediately, model calculations based on the available information about the course of the accident are additionally required. Such calculations do not only serve to create an overview of the current situation but can also provide prognoses for several hours. For this purpose, a software system for environmental impact forecasting was developed at Research Centre Juelich, which calculates time-integrated doses as well as ambient gamma dose rates and activity values. The latter can be directly compared with values measured during the incident and consequently can be used to assess the model assumptions. (orig.)

[en] Published in summary form only

[en] The optimum location of dosemeters used in centralized personnel monitoring systems for assessing external radiation exposure in handling radioactive materials has been determined. Using thermoluminescent detectors, dose distributions have been measured at the body surface of 31 persons working in various areas of industry and research. Comparison of the regression coefficients has shown that out of 11 measurement points the chest is the most adequate location for monitoring the exposure of the whole body. However, in certain cases hand exposure must be measured additionally. The results permit to establish a dose distribution model divided into the fore-part including head and lower extremities and the back of the body. (author)

[en] Short note

[en] Purpose: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR) for local tissue dose rates between those 'averaged over the whole pulse' and the instantaneous high dose rates close to the dwell positions. Increased effect is more likely for tissues with short half-times of repair of the order of a few minutes, similar to pulse durations. Methods and Materials: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to exponential repair. The situation with two components of T₍₁₍₂₎₎ is addressed. A constant overall time of 140 h and a constant total dose of 70 Gy were assumed throughout, the continuous low dose rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, covering the gap in an earlier publication. Four schedules were examined: doses per pulse of 0.5, 1, 1.5, and 2 Gy given at repetition frequencies of 1, 2, 3, and 4 h, respectively, each with a range of assumed half-times of repair of 4 min to 1.5 h. Results are presented for late-responding tissues, the differences from CLDR being two or three times greater than for early-responding tissues and most tumors. Results: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (2 Gy) if the half-time of repair in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in tissue, and--when T₍₁₍₂₎₎ is short--the instantaneous dose rate. Maximum ratios of PDR/CLDR occur when the dose rate is such that pulse duration is approximately equal to T₍₁₍₂₎₎. As dose rate in the pulse is increased, a plateau of effect is reached, for most T₍₁₍₂₎₎s, above 10 to 20 Gy/h, which is therefore radiobiologically equivalent to the highest HDR. A stepping source of 1 curie carries a sphere of 'HDR' of radius 20 mm with it in its track through tissue. High ratios of PDR/LDR effect can be avoided by keeping dose per pulse below 1 Gy. Conclusions: Therefore, about 75% of the total dose is delivered at HDR in a PDR implant of moderate volume, reducing to 40% as the source decays from 1 to 0.3 curies. Even so, restricting the dose per pulse to 0.5 or 0.6 Gy should avoid ratios of increased effect larger than about 10%. It appears likely that PDR delivered by stepping source might behave more like HDR than LDR, especially for tissues with a substantial component of repair of very short T₍₁₍₂₎₎

[en] Short communication