It is often required to estimate the dose rate at a distance from radionuclides that are sources of X rays and gamma rays. Such calculations may be required for planning radiation protection measures in the vicinity of radioactive sources or patients containing radionuclides, calibrations of radiation instruments or for estimating the absorbed dose rate to patients receiving brachytherapy. The factor relating activity and air kerma rate is called air kerma rate constant--gamma(delta). In this paper, the results of recalculation of this quantity for unfiltered point sources of radionuclides in practice used most often are given. The calculations included corrections for internal conversion of X rays and gamma rays and detailed accounting of the generation of the K and L series X rays from internal conversion and electron capture. Particular air kerma rate constants were calculated for each discrete line in the photon spectrum of radionuclide with a yield per decay event >0.01% and the energy >20 keV. Since the energy structure of the photon spectra and accessible discrete numerical values of the mass energy-transfer coefficient for air are not the same, the cubic spline interpolation was used to obtained the coefficient, where the photon spectrum data are available. In the calculation, the latest gamma ray spectral data for all radionuclides and latest data for the mass energy-transfer coefficient for air are used. Air kerma rate constants for the following 35 radionuclides are calculated: 11C, 13N, 15O, 18F, 24Na, 42K, 43K, 51Cr, 52Fe, 59Fe, 57Co, 58Co, 60Co, 67Ga, 68Ga, 75Se, 99Mo, 99mTc, 111In, 113mIn, 123I, 125I, 131I, 127Xe, 133Xe, 137Cs, 152Eu, 154Eu, 170Tm, 182Ta, 192Ir, 197Hg, 198Au, 201Tl and 241Am.
Experimentally determined values of x-ray backscatter factors are presented in this paper. Measurements were made for x-rays generated at voltages between 60 kV and 300 kV and three water phantoms different in shape and size. To study the influence of the irradiation geometry on the backscatter factors, the measurements were performed for different photon beam field diameters at the phantom front face, at a fixed source-to-phantom distance of 1 m. An ionization chamber of volume 1 cm3 was used for dose measurement. Measured results are analysed and discussed in comparison with measured and calculated values given in the cited references.
Environmental radiation monitoring in the vicinity of coal-fired power plants which are used primarily to determine the variability in measured background exposures are presented in this article; this is in order to estimate the contribution due to the plants' operation. Measurements have been done using a multi-element, high sensitive dosemeter system composed of three solid, properly filtered, sintered CaSO4:Dy thermoluminescent detectors, and one low-atomic number, MgB4O7:Dy,Na thermoluminiscencent detector produced at the Vinca Institute. The dosemeters were deployed quarterly 1 m above ground level at locations within 20 km of the power plants. Twenty urban and suburban measured stations were established. Measurements were carried out over one year period, from the beginning of the summer of 1995 to the end of the spring of 1996. The registered annual absorbed dose in air, from all of the 20 stations, vary from 0.91 to 1.46 mGy a(-1). One of the highest values of the annual absorbed dose was measured at the station near to the plant, i.e. at the place the most exposed to the lighter fly ash from the plant stack, as it was expected. The annual absorbed dose registered at the measuring stations that were selected as a control because they were situated practically away from possible influence of the plants were from 0.91 to 0.98 mGy a(-1). The above values of absorbed doses become very important, by concurrence of the circumstances, because they represent the zero background radiation level before the incidence of depleted uranium over former Yougoslav territory in the Kosovo region in the spring of 1999. These measured absorbed dose exposures have to be compared with corresponding absorbed dose rates from the natural sources, such as soil having an exposure of 18-93 nGy h(-1) (average 35 nGy h(-1)) according to the UNSCEAR 2000 Report. This investigation has been primarily done in order to check the impact of coal-fired power plants on the background radiation level in its vicinity. According to the experimental results, influence was confirmed both qualitatively and quantitatively.
A critical look at UNEP Reports concerning depleted uranium on Yugoslav territory is presented in this paper. The subjects of the analysis are summarized as remarks high-lighting the following three points: (a) those concerning the use of terms significant and insignificant doses (risks), (b) those concerning the use of 1 mSv as a border between these two risk types and (c) those concerning the composition of ex pert UNEP Teams investigating the depleted uranium issue. To start with, the assumption that it should be possible to express the risks (con sequences) caused by the in take of depleted uranium ( by ingestion/ inhalation and/ or external exposure) to b and g rays from depleted uranium as insignificant or significant for comparison purposes is, in our view, in collision with the linear non thresh old hypothesis, still valid in the radiation protection field. Secondly, the limit of 1 mSv per year as a reference dose level between insignificant and significant risks (con sequences) is not accept able in the case of military depleted uranium contamination. This is because the reference level of 1 mSv, according to the ICRP Recommendation, can be used in the optimization of radiation protection as an additional annual dose limit for members of the public solely for useful practices. Military usage of depleted uranium can not be classified as being useful for both sides - the culprit and the victim alike. Our third objection concerns the composition of ex pert UNEP teams for Kosovo (Desk Assessment Group, Scientific Reviewer Group, and UNEP Scientific Mission) as not being representative enough, bearing in mind all UN member-countries. This last objection may be rather difficult to understand for any one viewing it from the perspective other than that of the victims
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