Response of TLD and RPL personal dosimeters in a national inter-comparison test program

Background: Different kinds and models of personal dosimeters are used in individual monitoring by workers. Performance testing as part of approval procedures is carried out to demonstrate that the essential performance specifications are routinely maintained. There are four service providers in Iran which use different luminescence techniques [i. e. TLD and RPL] with various kinds of dosimeter materials/reader instruments in personal dosimetry services. Materials and Methods: A national performance approval tests program was performed for the dosimeters of the service providers in energy range of soft, 660 keV and 1.25 MeV, at the doses values around the recoding, investigation and annual dose limits, and different angle of incidents [e. g. 0, 20, 40 and 60 degree]. Results: The results of this testing satisfies the overall accuracy criteria with 95% confidence levels specified by the ICRP, except that of RPL technique in low energy which overestimates the dose out of the acceptable accuracy band defined as the ICRP trumpet curves. Conclusion: The inter-comparison has proved that the personal dose equivalent quantity, H[p][10], defined by the ICRU and recommended by the IAEA are becoming widely accepted and implemented in most participated laboratories

Calibration and optimization of a low cost diffusion chamber for passive separated measurements of radon and thoron in soil by Lexan PC SSNTD

Separate radon and thoron measurements in soil are very important in assessment of internal exposure due to inhalation of such radioactive gases. In this study, a low cost, small size, passive diffusion chamber has been developed for simple measurement of Radon-222 and Radon-220[Thoron] gases separately in soil. The diffusion chamber consists of two films and two fiber glass filters. Lexan polycarbonate films were used as Solid State Nuclear Track Detectors [SSNTDs] and optimized film to filter distance was obtained. Calibration factors for the designed diffusion chamber were measured using flow through method which was 16.85[track.cm[-2] [kBq. m-3d] [-1]] and 17.25 [track.cm[-2][kBq.m[-3]d][-1]] for radon for the lower and upper Lexan films, respectively and 1.76 [track.cm[-2] [kBq.m[-3] d][-1]] for thoron. The designed chamber is an economic, applicable and efficient detector for measurement of radon and thoron separately in soil

Natural ventilation considerations for radon prone areas of Ramsar

In Iran, architectures are often unaware of the risk of radon inhalation and how to reduce radon levels. Furthermore, radon considerations are not implemented in construction methods, construction materials and building utilization by regulatory authorities. In this study after reviewing the meteorological changes of Ramsar over the past 50 years [1955-2005], a novel design for constructing dwellings in radon prone areas is introduced. Out of building interventions such as planting wind-tunnel-making trees will be discussed in another paper. Ramsar soil samples with 4 levels of specific activities [extremely hot, severely hot, very hot, and hot] were placed in a model house. Radon level monitoring was performed by using a PRASSI portable radon gas survey meter. For extremely hot soil samples, the radon levels inside the model house when windows were closed for 24 hours were 1615 +/- 516 Bq/m3. When windows which were in the wind direction or opposite the wind direction were opened for 24 h, the radon level decreased to 89 +/- 286 and 139 +/- 314 Bq/m3, respectively. Interestingly, when crossed windows were opened for the same duration, Radon level was 144 +/- 92 Bq/m3. In cold seasons, when windows are usually closed, Chimney effect reduced the radon level to 323 +/- 641. For severely hot, very hot and hot soil samples, natural ventilation-based interventions effectively reduced the radon level. Results obtained in this study clearly show that natural ventilation-based simple cost-effective interventions can significantly reduce the radon concentration in radon prone areas of Ramsar

Alterations of PSA, CA15.3, CA125, Cyfra21-1, CEA, CA19.9, AFP and Tag72 tumor markers in human blood serum due to long term exposure to high levels of natural background radiation in Ramsar, Iran

Ramsar [Mazandran province] is known for its extremely high levels of natural background radiation. Although no excess cancer rate is reported in these areas by epidemiological studies, the study of tumor markers in the inhabitants of these areas may shed some light on the impact of high levels of background radiation on cancer induction. The level of background gamma radiation as well as indoor radon was determined using RDS-110 and CR-39 dosimeters. Thirty five individuals from a high background radiation area [HBRA] and 53 individuals from a normal background radiation area [NBRA] were randomly selected to participate in the study. Commercial ELISA kits [sandwich type ELISA tests] were used to measure the serum levels of PSA, CA15.3, CA125, Cyfra21-1, CEA, CA19.9, AFP and Tag72 tumor markers. Among the eight biomarkers investigated, the means of PSA, CA15.3, CA125, CA19.9 and AFP concentrations between the HBRAs and NBRAs were not significantly different. However, Cyfra21, CEA and Tag72 in HBRA group revealed statistically significant increases compared to those of NBRA group [P<0.05]. Furthermore, a statistically significant correlation between the external gamma dose as well as indoor radon level and the concentration of CEA [P<0.001], Cyfra-21[P<0.001] and TAG 72 [P<0.001 and 0.01 respectively] biomarkers were observed. Chronic exposure to high background radiation induces significant alterations in Cyfra21, CEA and Tag72 levels. We believe that studies with other relevant tumor markers might overcome the limitations of epidemiological studies on cancer incidence in high background radiation areas

Patient effective dose evaluation for chest x-ray examination in three digital radiography centers

The radiation doses resulting from diagnostic X-ray examinations are routinely measured in terms of entrance surface dose [ESD] and effective dose [ED]. In this study, for the purpose of radiation protection, the radiation doses received from Digital chest X-ray examination were evaluated in terms of ESD and ED. The ED was calculated by using the MCNP Monte Carlo code and an adult hermaphrodite mathematical phantom. The effects of both operating high voltage and projection geometry on the effective dose were investigated. The absolute values of the ED were calculated for digital and conventional Posterior-Anterior [PA] and Lateral [LAT] projections of chest radiography. The results show ED for PA projection in digital chest radiography in some major hospitals is higher than National Diagnostic Reference Level [NDRL]. Therefore optimization process should be considered seriously at national level to reduce patient exposure in digital chest radiography in Iran

Experimental and Monte Carlo studies on the response of CR-39 detectors to Am-Be neutron spectrum

The Poly-Allyl Diglycol Carbonate [PADC] detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and 0 recoils, as well as [n, a] reaction. These neutron- induced charged particles contribute towards the response of CR-39 detectors. Material and Electrochemical etching was used to enlarge track diameter which was made by low energy recoil protons. Before electrochemical etching, a chemical etching was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated. The optimized condition of etchant was obtained to be 6N KOH 15kV.cm[1], and 6 hours etching time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV. The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of [241]Am - Be bare source and [241]Am-Be was softened with a spherical polyethylene moderator of radius of 20 cm