Calibration, performance and type testing of personal dosemeters used in ionising-radiation applications in Greece

Active Personal Dosemeters (APDs) are widely used in real-time personal dosimetry. Their performance, operational characteristics and limitations, as well as their calibration should be routinely checked to assure satisfactory operation and safe use. This study summarises the results of such type tests and calibrations performed in almost 4750 dosemeters at Ionising Radiation Calibration Laboratory (HIRCL) of Greek Atomic Energy Commission (GAEC). About 13.8% of the pencil type and 4.3% of the electronic dosemeters were found to be out of limits of acceptable performance. For the pencil type dosemeters, the mean calibration factor (CF+/-SD) for high- and low-dose categories was found to be 1.014+/-0.102 (range 0.793-1.458) and 0.995+/-0.059 (range 0.794-1.311), respectively. Of these >85% of them had reproducibility better than 90%, while <1% showed remarkable non-linearity and approximately 10% of them failed to retain the dose reading within the limits after 24 h. For the electronic dosemeters, the mean CF was 1.034+/-0.046 (range 0.967-1.238). The majority of them showed good reproducibility and linearity results while, after irradiation, the dose readings were not shifted through time. The energy response varies with the dosemeter type, reaching in one dosemeter type down to 50%. Both electronic and pencil did not showed electronic equilibrium problems.     

X reference radiation qualities produced with tube voltages above 300 kV for the calibration and testing of dosemeters

In the international standard ISO 4037-1, only X reference radiation qualities produced with tube voltages of up to 300 kV and with mean photon energies of lower than 250 keV are defined. Higher energy reference photon fields are given with a mean energy only from 662 keV (S-Cs) upwards. To close this energy gap, four new X radiation qualities, produced with tube voltages of 350 kV and 400 kV, were realised. The filtration of two of these qualities-called N-350 and N-400-was chosen in such a way that they agree with the specifications of the narrow-spectrum series (N-series) defined in ISO 4037-1. The other qualities which have been created-called H-350 and H-400-can be assigned to the high air-kerma rate series (H-series). The fluence spectra of these qualities were measured by using X-ray spectrometry. The values of 23 characteristic parameters were determined and compared with the ISO specifications for X-ray reference fields.     

Calibration of personal dosemeters in mixed neutron-photon fields: some problems and their solution

In neutron reference radiation fields, the conventional true value of the personal dose equivalent, H(p)(10), is derived from the spectral neutron fluence and recommended conversion coefficients. This procedure requires the phantom on which the personal dosemeter is mounted to be irradiated with a broad and parallel beam. In many practical situations, the change of the neutron fluence and/or the energy distribution over the surface of the phantom may not be neglected. For a selection of typical irradiation conditions in neutron reference radiation fields, the influence of this effect has been analysed using numerical methods. A further problem, which is of relevance for the calibration of dosemeters measuring both the neutron and the photon component of mixed fields, is the 'double counting' of the dose equivalent due to neutron-induced photons. The relevance of this conceptual problem for calibrations in mixed-field dosimetry was analysed.     

Upgrading of the Gray Laboratory soft X ray microprobe and V79 survival measurements following irradiation of one or all cells with a CK X ray beam of different size

The X ray microprobe developed at the Gray Laboratory was originally designed to produce carbon K X rays (278 eV) by electron bombardment and focus them to a few hundred nanometers spot by using a circular diffraction grating with increasing line density (zone plate). The very fine focus achieved (< 0.25 micron radius spot) and the highly localised energy deposition of CK X rays (photoelectron range < 7 nm), represent unique tools to investigate modern radiobiological phenomena. Recent improvements have been directed to increase the dose rate (up to approximately 6 Gy.s-1 entrance dose averaged over a typical V79 cell) and to evaluate the possibility of using higher energy photons (AlK of 1.48 keV). The efficiency of the microprobe system has been tested by assessing the clonogenic potential of V79 cells irradiated with CK X ray beams of different sizes (5 and 0.25 microns radius) and investigating the relevance of the spatial distribution of cells for the bystander effect.     

Entrance surface, organ and effective doses for some of the patients undergoing different types of X ray procedures in Bangladesh

Entrance surface doses (ESDs) were measured for the most common types of X ray procedures, such as chest PA, lumber spine AP, lumber spine lateral, skull AP, skull lateral and pelvis AP in four major hospitals of Dhaka, the capital city of Bangladesh. Organ/tissue doses for 29 organs/tissues and effective doses for the patients were also calculated using the entrance surface dose as the input quantity. Organ/tissue doses and effective doses were calculated by using XDOSE software based on the Monte Carlo computation method. It was observed that the fluctuation of the entrance surface dose was too large. The ratio of maximum and minimum ESD values ranged from 4.8 to 35.9. Consequently, variation of organ doses was large even in the same type of X ray examination and in the same facility. Mean effective doses for the above mentioned X ray procedures were also determined and compared with the effective doses of some other countries. In most cases effective doses measured for the different types of X ray procedures were found to be lower than the effective doses of some other countries.     

钢绞线拉伸试验用大标距引伸计的标定

对发生故障的钢绞线拉伸试验用大标距引伸计进行了修复和标定，并对标定结果进行了处理和分析。分析结果表明：标定后的大标距引伸计的误差与出厂时标定的误差具有可比性，可以运用到钢绞线的拉伸试验中。     

Energy response of different types of RADOS personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) TL detectors

The photon energy response of different RADOS (Mirion Technologies) personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) thermoluminescence (TL) detectors was investigated. Three types of badges were applied. The irradiation with reference photon radiation qualities N (the narrow spectrum series), and S-Cs and S-Co nuclide radiation qualities, specified in ISO 4037 [International Organization for Standardization (ISO). X and gamma reference radiations for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy. ISO 4037. Part 1-4 (1999)], in the energy range of 16-1250 keV, were performed at the Dosimetry Laboratory Seibersdorf. The results demonstrated that a readout of a single MTS-N or MCP-N detector under the Al filter can be used to determine Hp(10) according to requirements of IEC 61066 [International Electrotechnical Commission (IEC). Thermoluminescence dosimetry systems for personal and environmental monitoring. International Standard IEC 61066 (2006)] for TL systems for personal dosimetry. The new RADOS badge with the experimental type of a holder (i.e. Cu/Al filters) is a very good tool for identifying the radiation quality (photon energy).     

Transient elastic waves in a half-space: comparison of the DBIE-method with the method of generalized ray

Summary The two-dimensional problem of wave propagation in an elastic half-space is studied by the DBIEM (Direct Boundary Integral Equation Method) combined with the finite difference procedure applied to the time variable. The present hybrid formulation employs the fundamental solution depending neither on the frequency nor on the time variable. Time records of surface responses of the half-space are computed and compared with those obtained by the numerical evaluation of exact analytical solutions to this problem.     

Positions of cations and molecules in zeolites with the faujasite-type framework VIII. Hydrated Ca-exchanged X

The extra-framework electron density in hydrated Ca-exchanged X, at room temperature, is assigned to 13 Ca and 17 H₂O in S(I'), 6 Ca and 26 H₂O in S(II'), 27 H₂O in S(II1) and mixed Ca and H₂O occupancy in S(IV). Not all extra-framework components were detected thus subjecting the above assignments to considerable uncertainty. A model is proposed which predicts the cation site distribution in sodalite units as a function of total sodalite unit cation content.     

The MiniWiD-COATER: II. Comparison of acid resistance of enteric-coated bisacodyl pellets coated with different polymers

Neutral pellets were loaded with bisacodyl and enteric-coated with hydroxypropyl methylcellulose acetate succinate (HPMCAS), carboxymethyl ethylcellulose (CMEC), cellulose acetate trimellitate (CAT), and poly(ethylacrylate, methacrylic acid) (Eudragit L 30 D) in a miniature fluid-bed pan coater called MiniWiD. Gastric juice resistance was tested by dissolution using USP Apparatus 2 (paddle) in 0.1 N hydrochloric acid under sink conditions over 6 hours. As a measure of enteric coating quality the USP specifications were used meaning that no more than 10 % of the drug should be released within 2 hours.

Organic-solvent based films of HPMCAS, CMEC and CAT at a coating level of 18 to 25 % provided gastroresistance for more than 6 hours. Aqueous suspensions of HPMCAS and CMEC as well as the ammonium salt aqueous solutions of CAT produced films with a short gastroresistance of below 0.6 hours. By doubling the coating level of water-based HPMCSD films the protection was prolonged to 3.4 h.

Enteric coatings were obtained from all aqueous latex dispersions of Eudragit L 30 D at a coating level of 24 %. The alteration of coating temperature between 25 and 45 °C had no significant effect on the release rates, whereas the variation of type and amount of plasticizer led to a different release rate after 2 hours. Best protection was obtained using films plasticized with 20 % of dibutyl phthalate (DBP) allowing a release of only 4 % of the drug in 6 hours although the application temperature was 15 °C below the minimum film-forming temperature (MFT). All coatings dissolved in artificial intestinal fluid within 15 minutes.     

The MiniWiD-COATER: II. Comparison of acid resistance of enteric-coated bisacodyl pellets coated with different polymers

Abstract

Neutral pellets were loaded with bisacodyl and enteric-coated with hydroxypropyl methylcellulose acetate succinate (HPMCAS), carboxymethyl ethylcellulose (CMEC), cellulose acetate trimellitate (CAT), and poly(ethylacrylate, methacrylic acid) (Eudragit L 30 D) in a miniature fluid-bed pan coater called MiniWiD. Gastric juice resistance was tested by dissolution using USP Apparatus 2 (paddle) in 0.1 N hydrochloric acid under sink conditions over 6 hours. As a measure of enteric coating quality the USP specifications were used meaning that no more than 10 % of the drug should be released within 2 hours.

Organic-solvent based films of HPMCAS, CMEC and CAT at a coating level of 18 to 25 % provided gastroresistance for more than 6 hours. Aqueous suspensions of HPMCAS and CMEC as well as the ammonium salt aqueous solutions of CAT produced films with a short gastroresistance of below 0.6 hours. By doubling the coating level of water-based HPMCSD films the protection was prolonged to 3.4 h.

Enteric coatings were obtained from all aqueous latex dispersions of Eudragit L 30 D at a coating level of 24 %. The alteration of coating temperature between 25 and 45 °C had no significant effect on the release rates, whereas the variation of type and amount of plasticizer led to a different release rate after 2 hours. Best protection was obtained using films plasticized with 20 % of dibutyl phthalate (DBP) allowing a release of only 4 % of the drug in 6 hours although the application temperature was 15 °C below the minimum film-forming temperature (MFT). All coatings dissolved in artificial intestinal fluid within 15 minutes.     

Thin layer alpha-Al2O3:C beta dosemeters for the assessment of current dose rate in teeth due to 90Sr intake,and comparison with electron paramagnetic resonance dosimetry

The use of thin-layer alpha-Al2O3:C thermoluminescent detectors (TLDs) for the assessment of current beta dose rate in human teeth due to 90Sr intake is investigated. The teeth used in this study were collected from members of the Techa river population who were exposed to radiation as a result of releases of the Mayak plutonium production facilities (Southern Urals-Russia) between 1949 and 1956. The beta dose rates from different parts of the tooth (enamel, crown dentine, and root) were determined by storing the detectors over the samples in a shielded environment. The cumulative dose measured by electron paramagnetic resonance (EPR) in different dental tissues is found to be proportional to current dose rate obtained from alpha-Al2O3:C thermoluminescence dosemeters. The retention of 90Sr in various parts of the teeth is discussed.     

Ozone reaction with carbon nanostructures. 2: The reaction of ozone with milled graphite and different carbon black grades

Synthetic graphite particles 0.2 microns in diameter react with O3 at room temperature with evolution of CO2. Graphite is less reactive with ozone than carbon blacks having different surface area ranging from 120 to 8 m2/g, but graphite reactivity is comparable to that shown by powdered solid C60 and C70 fullerenes. The kinetic rate constant derived from the ozone consumption k appears in relation with the rate of CO2 evolution suggesting a very simple reaction stoichiometry at the early stages. The reaction between ozone and graphite or carbon blacks essentially involves two stages: the gasification of the surface to CO2 and its functionalization with oxygenated chemical groups, mainly as COOH but also other oxygenated chemical moieties. The pseudofirst order kinetics appears adequate to describe the heterogeneous reaction between ozone and the selected carbon materials. The discussion of the results is focused on the role played by fullerene-like carbon nanostructures, present in graphene sheets to explain the observed gasification rates and surface functionalization.     

Examination of ionic liquids and their interaction with molecules, when used as stationary phases in gas chromatography.

Stable room-temperature ionic liquids (RTILs) have been used as novel reaction solvents. They can solubilize complex polar molecules such as cyclodextrins and glycopeptides. Their wetting ability and viscosity allow them to be coated onto fused silica capillaries. Thus, 1-butyl-3-methylimidazolium hexafluorophosphate and the analogous chloride salt can be used as stationary phases for gas chromatography (GC). Using inverse GC, one can examine the nature of these ionic liquids via their interactions with a variety of compounds. The Rohrschneider-McReynolds constants were determined for both ionic liquids and a popular commercial polysiloxane stationary phase. Ionic liquid stationary phases seem to have a dual nature. They appear to act as a low-polarity stationary phase to nonpolar compounds. However, molecules with strong proton donor groups, in particular, are tenaciously retained. The nature of the anion can have a significant effect on both the solubilizing ability and the selectivity of ionic liquid stationary phases. It appears that the unusual properties of ionic liquids could make them beneficial in many areas of separation science.