bluuebunny/crossref_metadata_2025 huggingface dataset:
Optically Stimulated Luminescence in MgS:Ce,Sm
Authors: Mathur V.K. , Gasiot J. , Abbundi R.J. , Brown M.D.
Published: February 2017

MgS:Ce,Sm has been investigated for optically stimulated luminescence (OSL) characteristics with a view to application in radiation dosimetry. Two dominant glow peaks, around 346 and 449K are observed in this material. The latter peak is suitable for dosimetry. This peak can be optically stimulated under 1317 nm irradiation from a InGaAsP diode laser subsequent to UV or ? ray dose. Optically stimulated luminescence follows the law IOSL=Iot-x, where x is approximately unity. Gamma ray dose relative to total light output of OSL exhibits a linear relationship between 1 and 10 Gy (100-1000 rad). Various observations suggest that the traps empty through the tunnelling of the carriers to Ce3+ recombination centres under optical stimulation.
The Localised Transition Model of Anomalous Fading
Authors: Templer R.H.
Published: February 2017

The currently accepted model for the anomalous fading of TL depends upon the quantum mechanical tunnelling of charge from deep traps to nearby recombination centres. Here a model is described which allows charge recombination to occur by transitions through an excited state common to a trap and luminescence centre pair. The theory is tested with respect to time and temperature for the anomalous fading in zircon and pumice. The results indicate that above room temperature localised transitions occur and at lower temperatures tunnelling predominates.
A Critical Analysis of Neutron RBE, Risk, and Q
Authors: Straume T.
Published: February 2017

The present neutron quality factor (Q) debate appears not to have focussed sufficiently on the implications of combining results obtained under vastly differing exposure conditions. The neutron RBEs that provide the basis for the recent ICRP and NCRP recommendations to increase neutron Q (from 10 to 20) were derived from experimental data obtained using low dose rate photons (fractionated or chronic-exposures) as the comparison radiation. In contrast, the dose limitation system within which the new quality factor would be used is based primarily on linear, non-threshold fits to high dose rate, mostly high dose, human epidemiological data. Combining such disparate data can be expected to over-estimate the neutron risk, perhaps even grossly. Rather than equalising risks for neutrons and gamma rays, the result could be the setting of unnecessarily restrictive neutron dose limits. It is proposed here that attempts be made to base both Q and estimates of human low LET risk coefficients on data obtained under similar irradiation conditions and using consistent dose response models. For example, if Q is to be based on RBEs obtained at low dose rates (RBEM), then the low LET risk coefficients for human stochastic effects should also be based on low dose rates. This, of course, would reduce low LET risk values, which are presently based on linear fits to high dose rate data. (Dose rate reduction factors of 5 to 10 are commonly observed experimentally). Or, because the effect of dose rate on human stochastic responses is largely unknown, it could be argued that application of the (perhaps conservative) linear, non-threshold model to the human epidemiological data should be continued for radiation protection purposes. In this case, Q should be based on RBEs that also are obtained from linear fits to low LET radiation data. Under these conditions, a Q somewhere between 5 and 10 would be consistent with experimental results.
A Neutron Survey Instrument Which Gives Information on the Low Energy Neutron Spectrum and Can be Used for Albedo Dosemeter Calibration
Authors: Harvey J.R. , Hart C.D.
Published: February 2017

An instrument has been developed for surveying neutron environments. It contains two thermal neutron detecting elements which consist of touch proof surface barrier detectors in contact with thin layers of 6LiF. One detector is located at the centre of a 76 mm (3") diameter Polythene sphere. The readings of the two detectors give information on the thermal and intermediate components of the ambient dose equivalent, and can be combined to mirror the response of various albedo dosemeters. The instrument can also be used to scale pulses from a wide energy range neutron survey instrument, and hence be used to assess the proportion of the neutron dose equivalent detected by albedo dosimetry systems.
Calculation of Dose Equivalent Index, Effective Dose Equivalent and Ambient Dose Equivalent for the Giant-Resonance Neutron Spectra Produced at an Electron Accelerator
Authors: Pelliccioni M. , Zanini A.
Published: February 2017

The results of calculations for the attenuation of the giant-resonance neutron spectra produced at an electron accelerator in various shielding materials are presented. As the spectra are similar to those of some radioactive sources, a comparison is made with Cf and Am-Be sources. Considering all the changes that have occurred in recent years regarding the quantities to be used in radiation protection, the results are expressed in terms of dose equivalent index, effective dose equivalent and ambient dose equivalent.
An Investigation of CR-39 Nuclear Track Detector Material as a Fast Neutron Microdosemeter
Authors: Stafford P.M. , Horton J.L. , Hogstrom K.R. , Johnson D.A.
Published: February 2017

This work describes the evaluation of CR-39 for use as a fast neutron microdosemeter, and provides some insight as to the feasibility of such use. The material was calibrated by irradiation with protons and alpha particles accelerated by a tandem electrostatic accelerator. Proton energies of 10, 6, and 3 MeV and alpha particle energies of 15, 10, and 7 MeV were used, at angles of incidence from 0 to 85 deg. The critical angle, normal incidence diameter, and track etching rates versus linear energy transfer (LET) were obtained from these measurements. A method for extracting a LET spectrum from CR-39 irradiated in-phantom with the fast neutron beam was developed and these results are compared with LET spectra measured by a 1.27 cm diameter Rossi chamber.
Response of Polyethylene Embedded TLDs to Neutrons from Some Polyenergetic Sources
Authors: Spurný F. , Luong D.T. , Votocková I. , Charvát J. , Gelev M. , Mishev I.
Published: February 2017

The responses of recently developed polyethylene embedded thermoluminescent detectors, TLDs, to neutrons from the polyenergetic sources 252Cf, PuBe and 9Be(d,n) with EN = 7.2 MeV were studied. The TL materials CaSO4:Dy, CaSO4:Mn and Al2O3 were used. The influence of an external proton radiator (polyethylene cover) on the relative response was also studied. It was found that relative responses increased substantially with both internal and external proton radiators. The enhancement depends not only on the neutron energy but also on the type of TLD. The results obtained are analysed and discussed.
Thermal Neutron Dosimetry with Cadmium Telluride Detectors
Authors: Fasasi M. , Jung M. , Siffert P. , Teissier C.
Published: February 2017

Cadmium telluride, a semiconductor compound with high Z is presently used at room temperature as a gamma ray detector. We have used this material to detect thermal neutrons by making use of the very high cross section of 113Cd to absorb thermal neutrons and emit gamma rays. Two CdTe detectors were exposed to a known thermal neutron beam at the CRN reactor, in order to analyse the performance of this device and a Monte Carlo code was developed to determine the expected response spectrum. For the two devices considered here under a series of experimental conditions, satisfactory agreement was observed between calculations and experimental data. Some of the 113Cd(n,?) radiative capture lines were identified by calibrating the detector with 57Co source. Since the atomic density of CdTe is much higher than in gas detectors, the efficiency under a small volume is very high, even if the total volume is presently limited to 10 x 10 x 2 mm3. In using CdTe as a thermal neutron dosemeter, it is best to use for calibration the line at 560 keV emitted and detected in the same device.
Analysis of Ground Fissures Using Content Ratios of Nuclides by Car-Borne Survey
Authors: Kimura S.
Published: February 2017

A new system was tested for car-borne and manual surveys of natural radiation to detect open fissures concealed in the ground. Positive deviation of the primary gamma ray dose ratio of 214Bi and 208Tl from its moving average was adopted as the main index. Localities where the positive deviation exceeded a threshold value gave a good indication of the existence of covered open fissures. The lowest of the deviations in a traverse was proportional to the amount of 222Rn ascending through fissures. This measurement system proved to be effective in prospecting for ground-water, hot springs, uranium, oil and natural gas resources and in earthquake prediction studies.
210Po in Marine Organisms: A Wide Range of Natural Radiation Dose Domains
Authors: Carvalho F.P.
Published: February 2017

Marine biota is able to concentrate 210Po to high levels, as 103-105 relative to sea water concentration. 210Po concentrations in mixed zooplankton reaches 34-51 Bq.kg-1 (fresh wt), special groups such as copepods reaching even higher concentrations ~90 Bq.kg-1, whereas gelatinous zooplankton display ~1 Bq.kg-1. Epipelagic teleosts feeding on plankton displayed the highest concentrations found in fish muscle, 2-21 Bq.kg-1. Contrasting with this, demersal teleosts and elasmobranchs display lower 210Po concentrations, in the ranges 0.5-7 Bq.kg-1 and 0.2-1.7 Bq.kg-1, respectively. Much higher concentrations can, however, be measured in fish liver, gonad, bone and piloric caecca, and small mesopelagic fish can reach ~800 Bq.kg-1 on a whole-body basis. Due to these 210Po activity concentrations, dose equivalent rates delivered to biological tissues in marine organisms can vary widely, from 0.4 mSv.y-1 in gelatinous plankton up to 5.6 x 103 mSv.y-1 in the gut wall of sardines. It is concluded that in organisms living in the same ocean layer a wide range of internal radiation doses exist and it is essentially sustained by 210Po food-chain transfer.
Radon and Geology in the United States
Authors: Peake R.T.
Published: February 2017

Regional geology and indoor radon concentrations appear to be related in the US. Using data from probability based samples, indoor radon frequency distributions have been developed in areas with similar regional geology. These frequency distributions can be used to define relative radon potential in the US. The geologic factors which determine regional radon potential are: (1) Lithologic: Rock types with known or potentially high uranium concentrations have a high probability of generating elevated indoor radon levels. Lithologies with US DOE National Uranium Resource Evaluation (NURE) equivalent uranium concentrations greater than 3 ppm may constitute high radon potential areas. (2) Soils: Soil permeability greatly influences radon potential. For Example, evidence suggests that high permeabilities (>0.01 cm.s-1) can cause elevated indoor radon levels even if radium concentrations are low.
Measurement and Calibration Experience with Short-Lived Radon Daughters
Authors: Ullmann W. , Röhnsch W.
Published: February 2017

In view of the health effects of short-lived radon daughters, various methods and instruments for determining their concentrations in air have been developed in the National Board for Atomic Safety and Radiation Protection (SAAS) of the GDR for reasons of radiation protection. A survey is given of the respective measurement requirements and of the quantities measured. Devices for short-term as well as time-integrated measurements of the potential alpha energy concentration, using different kinds of detectors, are described in detail, including the determination of the equilibrium factor and of the free fraction of short-lived daughters. Information is given regarding international comparison of measuring devices, of calibration methods applied at the SAAS and of elaboration of a primary standard for the unit of the potential alpha energy concentration. The use of the methods and instruments in the radiation protection practice of the SAAS is outlined.
Laboratory and Field Tests of a Hassock Fan-Ion Generator Radon Decay Product Removal Unit
Authors: Moeller D.W. , Rudnick S.N. , Maher E.F.
Published: February 2017

Laboratory tests in a radon chamber of a hassock fan-ion generator unit, developed for reducing airborne radon decay product concentrations inside buildings, produced reduction in potential alpha energy concentrations (PAECs) ranging from 83% to 86%. Similar reductions were observed in rooms in a home with relatively high radon concentrations. Reduction in a home with relatively low radon concentrations ranged from 76% to 79%. The time required for the removal unit to reach the point of maximum reduction was 6 to 8 h. A major share of the reduction occurred within the first 3 to 4 h. The speed of the fan, which was variable, had little effect on the ultimate removal efficiency. Reductions in the dose equivalent to the lungs, estimated on the basis of laboratory studies utilising several lung dosimetric models, were only slightly less than the observed reductions in PAECs.
Measurement of Single Event Energy Deposition Spectra at 5 nm to 250 nm Simulated Site Sizes
Authors: Kliauga P.
Published: February 2017

By utilising a simple cylindrical geometry and miniaturising dimensions of all components (anode, field tubes and cavity) so that absolute gas pressures are maintained at > 0.5 kPa (4 Torr) at the smallest simulated size (5 nm) it is demonstrated that the low pressure proportional counter can be made to operate in a proportional mode with adequate gain and resolution to measure single event spectra.
The Dependence of Thermoluminescence Sensitivity Upon the Temperature of Irradiation in Meteorites and in Terrestrial Apatites
Authors: Durrani S.A. , Al-Khalifa I.J.M.
Published: February 2017

Measurements are reported on the TL sensitivity (i.e. TL glow output per unit ? ray test dose) of meteoritic specimens as well as terrestrial fluor- and chlor-apatites, as a function of irradiation temperature (Tirr). The irradiation temperatures ranged from liquid nitrogen to room temperature (77 - 293 K). A kilocurie 60Co ? ray source was used to deliver test doses of 400 Gy (40 krad) and 40 Gy (4 krad) to the various samples. A strong dependence of the TL sensitivity upon the temperature of irradiation was noted in the case of Kirin meteorite: its TL sensitivity (for the 493 K readout peak) decreased by a factor of ~2 when Tirr rose from liquid nitrogen (77 K) to dry ice in acetone (197 K) temperature, in the case of both 400 Gy and 40 Gy ? ray doses. In the case of the Antarctic meteorite specimen (ALHA 77182,13), there was a smaller effect, viz. a fall of ~14% in the TL output corresponding to dry ice and higher irradiating temperatures as compared to the 77 K irradiation. For chlorapatite, the TL sensitivity decreased monotonically with increasing temperature for both the 563 K and the 448 K glow peaks. For the fluorapatite, the effect of reduced response was observed only between -17 oC (256 K) and room temperature (293 K). Both the theoretical and the practical implications of these observations are discussed.
Compositional Principle in Fast Neutron Thermoluminescence Dosimetry
Authors: Shaver I.Kh. , Krongauz V.G.
Published: February 2017

The principle consists in monitoring the selective phosphor response. The phosphor is one of the elements of the composite detector, the other being a fast neutron scintillator. The selectivity of the phosphor lies in the great difference between accumulation efficiencies of its various traps when passing from high energy photon irradiation to that of light photons, corresponding to the long wavelength band of activator absorption. The luminescence characteristics of SrS:Sm,Tb and CaCO3:Sm,Eu phosphors are presented. The glow curves are shown to have two main peaks: glow peak 1 at 130 oC and glow peak 2 with maximum in the 220-390 oC range. The peak 1 to peak 2 intensity ratio can reach 1000:1 for gamma irradiation and 1:100 for visible light irradiation. The accumulation and luminescence mechanism of selective phosphors is considered. The potential for fast neutron selective dosimetry in mixed fields is also discussed.
Diamond Detectors in Relative Dosimetry of Photon, Electron and Proton Radiation Fields
Authors: Khrunov V.S. , Martynov S.S. , Vatnitsky S.M. , Ermakov I.A. , Chervjakov A.M. , Karlin D.L. , Fominych V.I. , V. Tarbeyev Yu.
Published: February 2017

Characteristics of the diamond detector for use in the radiation therapy for the relative dosimetry of photon, electron, proton beams are given in the paper. The advantages of the detector as compared with ionising chambers and Si-diodes are presented.
Measurements of Radiation Levels by TLD in the Mineral Processing Plant in Bangladesh
Authors: Mollah A.S. , Rahman M.M. , Molla M.A.R. , Das S.C. , Akan Y.
Published: February 2017

As part of the continuing radiometric survey of the environment of Bangladesh, a programme was undertaken to measure the gamma ray field in the beach sand mineral processing pilot plant at Cox's Bazar in order to provide appropriate guidelines for radiation protection and safety of the works and the members of the public in the vicinity. The radiation levels were measured at various locations in and around the area of the plant using LiF (TLD-700) dosemeters. The observed dose rates varied from 0.20 to 8.12 µSv.h-1, however, the dose rates in most of the working areas were less than 3.0 µSv.h-1 resulting in an annual exposure of 7.48 mSv or less.
Feasibility of a High Dosemeter with Metallic Colloid Formation in an Ionic Crystal
Authors: Owaki S. , Nobugai K. , Okada T. , Inabe K.
Published: February 2017

Metallic colloid formation in an ionic crystal by radiation was investigated for possible application as a high-level dosemeter. Density of the colloids was measured as optical absorption intensity by photo-acoustic spectroscopy. Several kinds of ionic single crystals were irradiated by intense 20 MeV electron pulses from a linear accelerator. In NaCl crystals, the absorption intensity due to the colloid density has a smooth correlation with the number of irradiating electron pulses, ranging from 2 x 103 to 2 x 105. The colloid formation was confirmed using an electron microscope.
Thermal and Fast Neutron Detection in a Polyenergetic Field of Neutrons
Authors: Savvides E. , Zamani M. , Charalambous St.
Published: February 2017

Thermal treatment of irradiated CN-85 results in increasing energy resolution of alpha particles and fading of proton recoils: thus the reconstruction of neutron spectra in a polyenergetic field becomes more precise. The method is applied to the detection of thermal as well as fast neutrons by means of the 6Li(n,a)3H reaction.
Present State and Future of TLD Laser Heating
Authors: Braunlich (INVITED) P.
Published: February 2017

Recent advances are reviewed in laser/electro-optics and dosemeter manufacturing technology which have led to the design and construction of a desk-top laser TLD reader for personnel and environmental dosimetry, a two-dimensional dose distribution mapping system and an advanced remote fibre-optic TLD probe. These instruments are the first laser-heated TLD products offered commercially.
Dosimetric Characteristics of LiF:Mg,Cu,P Phosphors - A Track Structure Interpretation
Authors: Waligorski M.P.R. , Olko P. , Bilski P. , Budzanowski M. , Niewiadomski T.
Published: February 2017

New sintered LiF:Mg,Cu,P detectors with different concentrations of Cu and P are being investigated in this laboratory. These detectors are about 10-30 times more sensitive than LiF:Mg,Ti to gamma ray (60Co, 137Cs) doses and, unlike LiF:Mg,Ti, show no supralinearity up to saturation above 200 Gy of gamma rays, thus being amenable to a 1-hit interpretation, in terms of Katz's track structure theory. Values of model parameters, Eo=200 Gy and ao=20 nm, were estimated after fitting the 1-hit expression to a number of measured X ray and gamma ray dose responses and fitting to the reported measurements of relative efficiency of LiF:Mg,Cu,P after proton and alpha particle irradiations. The gamma ray dose response of LiF:Mg,Ti (e.g. peak 5 in TLD-700) can be described by a mixture of 1-hit and 2-hit expressions, but for model interpretations of exposures to low energy ions, only the 1-hit 'trap' (estimated values: Eo=600 Gy, a=20nm) need be considered. Thus, a quantitative model basis is provided for interpreting the response of LiF:Mg,Cu,P to heavy charged particles and neutrons against the responses of 'classic' LiF:Mg,Ti to the same radiations.
Thermoluminescence, Thermally Stimulated Exoelectron Emission and Emission Spectra of (CaF2:Natural + NaCI) Pellets
Authors: Okuno E. , Owaki S. , Yamamoto T. , Chubaci J.F.D. , Inabe K. , Fukuda Y.
Published: February 2017

Brazilian fluorite-based dosimetric pellets were X irradiated at -170 oC to record simultaneously TL and TSEE glow curves at a heating rate of 1 oC per 6 s. A close relationship between TL and TSEE was observed for all the peaks from -170 to 400 oC. The effect of high dose and high exposure rate on dosimetric pellets was studied by irradiating them with a 21 MeV electron beam from a linear accelerator. TL due to NaCl used as agglutinant arises for exposures equivalent to 2.58 kC.kg-1 in the form of a sharp glow peak at 225 oC, when CaF2 glow peaks are saturated or decreasing due to radiation damage. Emission spectra of dosimetric pellets were obtained for three TL peaks in the range RT to 350 oC. They are different from peak to peak, indicating that some trapping centres are spatially associated with recombination centres.
Diffuse Reflectance and Transmission Measurements on LiF:Mg,Cu,P Powders and Single Crystals
Authors: McKeever J. , Macintyre D. , Taylor S.R. , McKeever S.W.S. , Horowitz A. , Horowitz Y.S.
Published: February 2017

Measurements of optical absorption on LiF:Mg,Cu,P powders and single crystals are described. The absorption spectra for the powders and the single crystals are very similar. The dominant feature is the F centre while absorption in the region of 300-400 nm is related to the presence of Mg. The thermal stability properties of the radiation-induced bands can be correlated with the production of TL and are similar for both powders and crystals. Absorption features due to Cu and P are not observed. The absorption intensity is seen to vary with the Mg,Cu and P contents in a similar fashion to the TL sensitivity.
LiF:Mg,Ti Versus LiF:Mg,Cu,P: The Competition Heats Up
Authors: Horowitz (INVITED) Y.S.
Published: February 2017

Current knowledge concerning the dosimetric characteristics of LiF:Mg,Cu,P and LiF:Mg,Ti is reviewed, including glow curve structure, response to annealing procedures, trap conversion processes, dose response, tissue-equivalence, residual signal and others. The relative merits of these two materials in various dosimetric applications; occupational exposure, clinical and environmental, as well as in mixed field beta/gamma and neutron/gamma dosimetry are evaluated and compared. LiF:Mg,Cu,P emerges as a very useful material with significant advantages over LiF:Mg,Ti in most dosimetric applications. However, it does share some of the faults of LiF:Mg,Ti mainly, complicated glow curve structure and thermal instability. Commercially available LiF:Mg,Cu,P (GR-200) is interior to LiF:Mg,Ti (TLD-100) in one important aspect - its relatively high residual signal. Future elimination/minimisation of the residual signal via materials research and/or readout/annealing procedures should lead to LiF;Mg,Cu,P totally replacing LiF:Mg,Ti.
Confirmation of the Evolution of TLD-100 Glow Peaks 4 and 5 During Storage at Ambient Temperatures
Authors: Delgado A. , Gómez-Ros J.M. , Muñiz J.L. , Bos A.J.J. , Piters T.M.
Published: February 2017

The results obtained in an IRI-CIEMAT joint study on the evolution of the main TLD-100 glow peaks 4 and 5 during storage at temperatures in the ambient range are presented. In order to investigate the effect of the fitting procedures on the peak evolution results, IRI and CIEMAT carried out an experiment in which a common set of glow curves were analysed by the computer codes for glow curve analysis independently developed by both laboratories. The results of this experiment confirm previous results on peak 4 and 5 evolution. Both peaks are modified during storage depending not only on the storage conditions but also on the readout parameters. The implications of these peak variations on practical environmental dosimetry are also discussed.
Individual Thermoluminescence Dosemeters for Extremities and Eyes
Authors: Goldfinch E.P.
Published: February 2017

An International Standards Organisation working group (ISO/TC85/SC2/WG7) has developed a draft standard specifying dosimetric performance requirements and recommending appropriate tests, for dosemeters to be used for extremity or eye dose measurements. The standard is complementary to the IEC standard Thermoluminescence Dosimetry Systems for Personal and Environmental Monitoring (IEC 1066 1991). The new draft standard is due to be circulated by ISO for international 'Member States' comments late in 1992. This paper summarises the content of the draft and gives some background to the technical requirements.
Personal Neutron Diode Dosemeter
Authors: Barthe J. , Lahaye T. , Moiseev T. , Portal G.
Published: February 2017

The control and management of neutron doses, received by workers in nuclear power plants or research facilities, requires a knowledge of cumulated dose equivalent or dose equivalent rate in real time. Individual dosemeters so far developed for this purpose are scarce and not very satisfactory. Passive dosemeters such as TLD systems based on the albedo effect, nuclear emulsions or solid track detectors, do not give sufficiently accurate measurements. Furthermore, the increase in the quality factor and the more restrictive new ICRP recommendations diminish the maximum admissible threshold making currently used systems obsolete. Other than bubble dosemeter systems, based on thermodynamic effects of a superheated gel, no simple electronic device is available at the present time. The development of diode based dosimetric gamma badges, having a size similar to that of credit cards, has stimulated us to design and develop a personal neutron dosemeter based on a double diode system. The results obtained are very encouraging and practical models should become available in the near future.
Extremity Dosimetry in Nuclear Medicine Services using Thermoluminescent Detectors
Authors: Mebhah D. , Djeffal S. , Badreddine A. , Madjahed M.
Published: February 2017

The Radiation Protection and Safety Centre in Algiers provides two types of dosemeters, one for monitoring doses to the whole body and skin and the other one for monitoring doses to the extremities of the body. In nuclear medicine services and radiopharmaceutical laboratories, hands and arms are often closer to a given radiation source than the main part of the body and therefore receive greater doses. In this context, extremity doses have been measured by a ring dosemeter and by a fingertip ultra-thin dosemeter. The ring dosemeter consists of a metallic ring with a circular indentation to hold a LiF chip which is covered with a 10 mg.cm-2 shrinkable black polyamide layer. The ultra-thin dosemeter contains a 5 mg.cm-2 LiF element for measuring doses at a depth of 7 mg.cm-2. These extremity dosemeters have been characterised before their use in the field. They have also been tested using radioisotopes of various energies. The doses received by the monitored workers were correlated with the amount of the handled activity. The doses obtained using the fingertip and the ring dosemeters are presented and discussed from a radiological point of view.
Improving the Accuracy of TLD Systems in Clinical Applications
Authors: Toivonen M.J.
Published: February 2017

Conditions are outlined for obtaining routine measurements of the highest precision with a TLD system in clinical applications. A method for studying and specifying the inherent uncertainties in a TLD system is also presented. The principles of optimising reader design are given, as is guidance in optimising partial processes of the measurement (e.g. during annealing or constant dose irradiation). Finally, two alternative TLD processes and a clear-cut calibration procedure are presented, along with instructions for the operator on how to keep systematic errors at an insignificant level. The overall uncertainty of measurement using sintered LiF discs was compared with the required accuracy (to within 3%) for the calibration of therapy units. The conclusion was drawn that, to meet this requirement, the random error of measurements should be very small (1 SD below 0.5%) as it is in the best manual TLD systems. Automatic TL readers seem to be far from this goal, but improvements may be made by redesigning light collection geometries for the specific needs of clinical applications.
Experimental Verification of a Superheated Liquid Droplet (Bubble) Neutron Detector Theoretical Model
Authors: Harper M.J. , Nelson (INVITED) M.E.
Published: February 2017

Superheated liquid droplet ('bubble') neutron detectors utilise thousands of microscopic droplets of freon-based compounds suspended in a viscous matrix material. Neutrons can interact with the atoms of the superheated liquid droplets, resulting in the formation of energetic charged recoil ions. These ions transfer their energy to the liquid in the droplets, sometimes resulting in the droplets vaporising and producing visible bubbles. The basis of bubble detector operation is identical to that of bubble chambers, which have been well characterised by researchers such as Wilson, Glaser, Seitz and others since the 1950s. Each of the microscopic superheated liquid droplets behaves like an independent bubble chamber. This paper presents a theoretical model that considers the three principal aspects of detector operation: nuclear reactions, charged particle energy deposition, and thermodynamic bubble formation. All possible nuclear reactions were examined and those which could reasonably result in recoil ions sufficiently energetic to vaporise a droplet were analysed in detail. Feasible interactions having adequate cross sections include elastic and inelastic scattering, n-proton, and n-alpha reactions. Ziegler's transport of ions in matter (TRIM) code was used to calculate the ions' stopping powers in various compounds based on the ionic energies predicted by standard scattering distributions. If the ions deposit enough energy in a small enough volume then the bubble of vapour that forms will grow to 'critical' size, and spontaneously vaporise the rest of the entire droplet without further energy input. Various theories as to the vaporisation of droplets by ionising radiation were studied and a novel method of predicting the critical (minimum) energy was developed. This method can be used to calculate the minimum required stopping power for the ion, from which the threshold neutron energy is obtainable. Experimental verification of the model was accomplished by measuring the response of two different types of bubble detectors to monoenergetic thermal neutrons, as well as to neutrons from the polyenergetic spectra of bare and moderated californium spontaneous fission sources. The model's predicted response compared favourably with the experimental data.
Role of Neutron Bubble Dosemeters
Authors: Riel G.
Published: February 2017

Bubble dosemeters may determine whether routine dosimetry is required, because they are a credible indicator of the presence or absence of neutrons even in strong gamma ray fields. They can be used, as pocket ion chambers are, to complement a primary dosemeter. They are small and need no phantom to measure neutrons from thermal to 25 MeV, so they can map fields varying rapidly with distance. Spectrometers are made from bubble devices(s) with various thresholds. Bubble dosemeters with electronic counters may serve as area monitors. Such roles use the bubble device's high sensitivity, immediate results, freedom from interference, and flat energy response while avoiding its weaknesses in dynamic range, lifetime, and variation of response with temperature.
The New Panorama of Radioepidemiology - Problems and Possibilities that Emerge in a Changed Europe
Authors: Kellerer (INVITED) A.M.
Published: February 2017

The political change in the former Soviet Union and its sphere of influence has brought into the open information on various situations involving the radiation exposure of large populations, and has thus widened the field of radioepidemiological investigations that need to be performed. Three issues are considered. The consequences of the Chernobyl accident are still largely unresolved, and the hopes for radioepidemiological investigations have been gravely disappointed due to the lack of coordinated efforts. The steep increase of childhood thyroid carcinoma rates in Belarus is the only observed late effect so far; but even in the face of this alarming situation there is little readiness to accept help with regards to medical treatment and to scientific investigations. The attempts to block all information after the reactor accident in the former Soviet Union must be seen against the background of earlier occurrences that were successfully hidden for decades, and a particularly grave issue was the large scale contaminations in the Southern Urals of the River Techna and adjacent villages. An epidemiological study on the affected population has led to first results; it may develop into a major body of knowledge on radiation risks from protracted exposures. A third broad task in the years to come will be the analysis of the health effects in the underground miners of the Wismut AG, the former Soviet-German uranium mining enterprise. Exposure data and health information on several 100,000 miners will need to be analysed, and this may further the knowledge of the effects of radon exposures.
Generalised Microdosimetric Calculations of Cell-to-Cell Variance
Authors: Brenner D.J. , Sachs R.K.
Published: February 2017

The cell-to-cell variance of an endpoint gives extra information, which is highly model dependent and thus potentially useful for distinguishing between possible mechanisms. Some years ago, Virsik and Harder calculated variances of dicentric chromosome aberrations using two assumptions: first, that dicentrics are produced independently by different radiation tracks, and second, that the dicentric yield due to a single track is Poisson distributed. It is shown that the formalism can be generalised so that the Poisson assumption is dropped. This affects predictions of neutron induced variances quite markedly. For lesions formed directly, such as immediate, irremediable chromosomal breaks, the formalism is general. For lesions formed by pairwise damage interaction, such as exchange-type chromosomal aberrations, the first assumption (single track action) limits the applicability of the results to high LET or low dose situations. In general, therefore, estimating variances requires the use of spatially inhomogeneous models.
Calculation of Neutron Energy Deposition in Nanometric Sites
Authors: Morstin K. , Olko P.
Published: February 2017

Simulations of charge particle tracks in water vapour were used to build a parametric model enabling the calculation of ionisation distributions in spherical targets, including the influence of straggling and d rays. The model has been applied to assess neutron energy deposition in nanometric sites in tissue. Emission and slowing down spectra of charged particles from neutron interactions and of photo-induced electrons were combined with the model. All kinds of ionisation events were taken into account, although in such small sites crossers and touchers definitely predominate. The approach has been coupled with macroscopic radiation transport calculations, thus allowing for biophysical modelling of realistic radiobiological situations.
Kerma Associated with High Energy Neutrons
Authors: Binns P.J. , Hough J.H.
Published: February 2017

The kerma for monoenergetic neutrons of nominal energies 27, 42 and 63 MeV was measured with commercial tissue-equivalent and carbon proportional counters. By operating the detectors in helix mode and exposing them to pulsed beams of quasi-monoenergetic neutrons, time-of-flight (TOF) techniques enabled the unambiguous identification of pulse height events associated with the neutron energies of interest. The microdosimetric spectra so obtained were used to derive gas-to-wall dose conversion factors for the TE gas filled carbon proportional counter. Subsequently the kerma ratios for carbon to A-150 plastic at the three nominal neutron energies were determined with the monoenergetic data. The results concur with other published data using different techniques.
Microdosimetry and Cellular Radiation Effects of Radon Progeny in Human Bronchial Airways
Authors: Hofmann W. , Nösterer M. , Ménache M.G. , Crawford-Brown D.J. , Caswell R.S. , Coyne J.J.
Published: February 2017

This microdosimetric interaction model simulates individual interactions of alpha particles with nuclei of sensitive target cells in human bronchial airway generations 2, 4, 6 and 10. For a normalised source density of 218Po and 214Po alpha particles, number of hits, microdosimetric spectra and related parameters for cell nuclei located at various depths in bronchial epithelium are calculated. The lineal energy spectrum in a spherical nuclear target is then converted into probabilities for cell killing, mutation and transformation by multiplying the single event chord length distribution with event specific probabilities per unit track length as a function of LET. These effect probabilities are finally weighted by the depth-density distributions of basal and secretory cells. The predicted transformation probability is compared with other physical indicators of lung cancer risk, such as dose, dose equivalent, biologically weighted dose, mean lineal energy, and number of alpha particle hits.
Radon Mitigation in Schools Utilising Heating, Ventilating and Air Conditioning Systems
Authors: Fisher G. , Ligman B. , Brennan T. , Shaughnessy R. , Turk B.H. , Snead B.
Published: February 2017

As part of a continuing radon in schools technology development effort, EPA's School Evaluation Team has performed radon mitigation in schools by the method of ventilation/pressurisation control technology. Ventilation rates were increased, at a minimum, to meet the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) standard Ventilation for Acceptable Indoor Air Quality (ASHRAE 62-1989). This paper presents the results and the preliminary evaluations which led to the team's decision to implement this technology. Factors considered include energy penalties, comfort, indoor air quality (IAQ), building shell tightness, and equipment costs. Cost benefit of heat recovery ventilation was also considered. Earlier results of the SEP team's efforts have indicated a severe ventilation problem within the schools of the United States. An integrated approach to radon mitigation in schools and other large buildings which control radon as well as improve overall IAQ should be the goal of radon remediation where practical. Two case studies are presented where HVAC technology was implemented for controlling radon concentrations. One involved the installation of a heat recovery ventilator to depressurise a crawl space and provide ventilation to the classrooms which previously had no mechanical ventilation. The other involved the restoration of a variable air volume system in a two-storey building. The HVAC system's controls were restored and modified to provide a constant building pressure differential to control the entry of radon. Pre-mitigation and post-mitigation indoor air pollutant measurements were taken, including radon, carbon dioxide (CO2), particulates, and bio-aerosols. Long-term monitoring of radon, CO2 building pressure differentials, and indoor/outdoor temperature and relative humidity is presented.
Radon: Occupational or Domestic Carcinogen?
Authors: Monchaux G. , Masse (INVITED) R.
Published: February 2017

An association between an excess risk of lung cancer and exposure to radon and its daughters has been demonstrated in uranium miners and in other miners. In various countries, radon measurements in dwellings showed that indoor radon concentrations are in the same range as in underground mines. Geographical epidemiological studies do not show an excess risk of lung cancer in people living in radon rich areas and case-control studies of domestic exposures lead to conflicting results. A joint study allowing meta-analysis of the results from 19 epidemiological studies carried out throughout the world should provide reliable data by and after 1995. Experimental data and biological data from radon-induced human tumours might allow the identification of tumours induced by irradiation compared with tumours induced by other agents. Until now, the role of domestic exposure in the occurrence of lung cancer remains unclear and therefore the usefulness of remedial actions questionable.
Lung Cancer Risk at Low Doses: What Can Cellular Radiobiology Tell Us?
Authors: Hofmann W.
Published: February 2017

The inevitable interaction of confounding factors limits the validity of any epidemiological estimate of lung cancer risk at low, environmental exposures to radon progeny. The present study therefore investigates how the functional form of the dose-effect relationship can be derived from in vitro radiobiological observations at the cellular level relevant for radiation carcinogenesis. The way by which the initial cellular response may be modified by the specific in vivo exposure conditions of individual cells in an organised tissue structure is then discussed.
Radon Sources, Radon Ingress and Models
Authors: Scott (INVITED) A.G.
Published: February 2017

Information available 20 years ago suggested that unusual soil conditions were needed to produce high radon concentrations in houses. Based on this belief, simple models were developed to predict house radon concentrations based on estimates of soil radium concentration and soil type (related to permeability). Recent radon-in-housing surveys show that clay soils, which cover much of North America, are radon-prone. The permeability of these soils is not controlled by the soil type, but by the fracture patterns that develop as the soil dries out. Realistic prediction models must take the macroscopic soil structure into account. They must also deal with the effect of the rapid variations in driving force produced by wind velocity variations. The interaction between house and soil is complex, and simple models cannot give realistic results. Many people live in apartment buildings, and are exposed to radon released from building materials. Better models are needed for this source to help develop better controls. Many radon-prone areas have been identified by house surveys, so modelling is now needed only to explain what we know. The priority task today is not prediction, but encouraging production of low-radon dwellings in known high-radon areas.
Models for Determining the Response of Passive Alpha Particle Detectors to Radon and Its Progeny in Cylindrical Detecting Volumes
Authors: McLaughlin J.P. , Fitzgerald B.
Published: February 2017

Many radon detectors exist in the form of a planar disc shaped alpha particle detector mounted in one end of a small cylindrical chamber. Models have been developed to determine the sensitivity of such detectors to radon exposure. A model, adapted from the Jacobi-Porstendorfer room models, is used to determine the partitioning of short-lived radon progeny between airborne and surface deposited states within the detecting volume. This is used in conjunction with Monte Carlo simulation to obtain the radon sensitivity. The use of these models with passive alpha track detectors is highlighted although they are of general applicability to passive detectors using other alpha detecting media. Using these models it is possible to design passive detectors with dimensions such that the alpha track densities may be optimised to a chosen radon exposure range. Validation of the modelling is presented in the form of comparisons between predicted and experimentally determined sensitivities of CR-39 alpha track detectors.
Regional Variations in Occupational Exposure to Radon and the Resulting Regulatory Action
Authors: Ross B.C. , Atkinson M.R. , Dixon D.W.
Published: February 2017

Measurements in over 3000 workplaces throughout Great Britain show that radon concentrations in about 10% of these premises exceed the level at which the Ionising Radiations Regulations 1985 may apply. Most of the measurements and high results are in Cornwall and Devon, but high results have also been obtained in other counties, particularly Derbyshire, Northamptonshire and Somerset. The data for workplaces are supplemented by the results of measurements in about 100,000 homes suitably transposed to indicate the likely impact of the Regulations where workplace data are scarce. These findings have been used to develop advisory and regulatory strategies for workplaces.
Mechanism of Non-Linear TL Response Characteristics of Thermoluminescence Phosphors - Competing Quasi-Continuous TL Trap Distribution Model
Authors: Srivastava J.K. , Supe S.J.
Published: February 2017

A new TL model, namely a competing quasi-continuous trap distribution model, has been proposed for explaining the physical mechanism of TL processes. It takes into account the capture reaction mechanism of TL traps (activation energy) and the effect of the trap distribution on the accompanied competition processes. The model is quite general in nature and it has been examined for a number of TL phosphors with diverse trap distribution characteristics e.g. CaSO4:Dy, CaF2:Dy, Li2B4O7:Mn and Li2B4O7:Cu.
Phosphate Glass Energy Compensation Filters for the Measurement of Operational Dose Quantities
Authors: Burgkhardt B. , Röber H.G. , Piesch E.
Published: February 2017

Different perforated energy compensation filters have been developed using a D-7 phosphate glass dosemeter, 16 x 16 x 1.5 mm3 in size, with common and laser UV excitation for the measurement of the effective dose equivalent and the dose equivalent in tissue depths of 10 mm, 3 mm and 0.07 mm.
Development of an Australian TLD Personal Monitoring Badge Based on CaSO4:Dy
Authors: Boas J.F. , Martin L.J. , Mika J.F. , Murray A. , Young J.G.
Published: February 2017

The TLD personal monitoring badge developed by the Australian Radiation Laboratory for use by workers in the uranium mining industry uses two CaSO4:Dy-Teflon discs. One of these is unshielded and the other is shielded by 2.5 mm copper. The factors involved in the calculation of the whole body dose are considered. Further development of the filter to enable the badge to be used at photon energies down to 20 keV is described.
Thermoluminescence of Borate Glass Containing Copper
Authors: Fukuda Y. , Okuno T. , Takeuchi N.
Published: February 2017

Thermoluminescence (TL) of X ray irradiated borate glass containing copper (0.01 to 1.0 mol%) has been studied. Samples were made from mixtures of B2O3 and CuCl2. They were melted at 1100 oC for 1 hour in a platinum crucible followed by annealing in a brass mould. Samples were irradiated with various doses of X rays at room temperature. The samples containing CuCl2 showed a much stronger TL response than pure B2O3 glass. The kinetic orders for the TL peaks in CuCl2 doped samples were always about 1.5, while those in undoped glass obeyed 2nd order kinetics. The sample doped with 0.05 mol% CuCl2 had the strongest TL response. The TL emission spectra for samples containing CuCl2 showed a maximum at 2.77 eV (448 nm) for all temperatures during the TL measurements. The emission is possibly due to the recombination reaction: Cu+ + hole ® Cu2+* ® Cu2+ + h?. Thermally stimulated current (TSC) for X ray irradiated glass showed maxima in the temperature region 90 ~ 100 oC when a bias voltage was applied to the sample. The TSC is thought to be related to the TL.