Intrinsic dosimetry of glass containers used to transport nuclear materials: Potential implications to the fields of waste management and nuclear forensics

Thermoluminescence (TL) and Electron Paramagnetic Resonance (EPR) dosimetry were used to measure dose effects in borosilicate glass with time, from 10 min to 60 days following exposure to a dose of up to 100 Gy. TL and EPR results were consistent and performed similarly, with both techniques capable of achieving an estimated limit of detection of between 0.5 and 1 Gy. Three peaks were identified in the TL glow curve at roughly 110 °C, 205 °C, and 225 °C. The intensity of the 205 °C peak was the dominant peak over the time period of this study. The stability of all of the peaks with time since irradiation increased with their corresponding temperature and no significant variation was observed in the glow curve response to a specified total dose attained at different dose rates. The intensity of the 205 °C peak decreased logarithmically with time regardless of total dose. Based upon a conservative limit of detection of 3.3 Gy, a 100 Gy dose would still be detected 2.7E3 years after exposure. Here, we introduce the concept of intrinsic dosimetry, the measurement of the total absorbed dose received by the walls of a container containing radioactive material. The foreseen advantage of intrinsic dosimetry comes from considering the measured absorbed dose received by containers in concert with the characteristics (amount, type) of the source of that dose, the radioactive material contained within the walls of the container, in order to provide enhanced information about the history of an unknown sample in question. Three hypothetical scenarios are presented to introduce this method and to illustrate how intrinsic dosimetry might benefit the fields of nuclear forensics and waste management.     

Sonochemical dosimetry: A comparative study of Weissler,Fricke and terephthalic acid methods

Acoustic cavitation and sonochemical reactions play a significant role in various applications of ultrasound. A number of dosimetry methods are in practice to quantify the amount of radicals generated by acoustic cavitation. In this study, hydroxyl radical (OH) yields measured by Weissler, Fricke and terephthalic acid dosimetry methods have been compared to evaluate the validities of these methods using a 490 kHz high frequency sonochemical reactor. The OH yields obtained after 5 min sonication at 490 kHz from Weissler and Fricke dosimetries were 200 µM and 289 µM, respectively. Whereas, the OH yield was found to be very low (8 µM) when terephthalic acid dosimetry was used under similar experimental conditions. While the results agree with those reported by Iida et al. (Microchem. J., 80 (2005) 159), further mechanistic details and interfering reactions have been discussed in this study. For example, the amount of OH determined by the Weissler and Fricke methods may have some uncertainty due to the formation of HO₂ in the presence of oxygen. In order to account for the major discrepancy observed with the terephthalic acid dosimetry method, high performance liquid chromatography (HPLC) analysis was performed, where two additional products other than 2-hydroxy terephthalic acid were observed. Electrospray ionization mass spectrometry (ESI-MS) analysis showed the formation of 2,5-dihydroxyterephthalic acid as one of the by-products along with other unidentified by-products. Despite the formation of additional products consuming OH, the reason for a very low OH yield obtained by this dosimetry could not be justified, questioning the applicability of this method, which has been used to quantify OH yields generated not only by acoustic cavitation, but also by other processes such as γ-radiolysis. The authors are hoping that this Opinion Paper may initiate further discussion among researchers working in sonochemistry area that could help resolve the uncertainties around using these dosimetry methods.     

A peak structure in isothermal luminescence signals in quartz: Origin and implications

Isothermal heating is commonly used in luminescence dosimetry and trap parameter studies. It is often observed that the isothermal luminescence signal has a peak shape instead of a monotonous decay form. We provide here evidence that this peak shape in quartz may equally result from a ‘thermal lag’ problem in contrast to the earlier propositions of non first-order kinetics. Temperature modelling suggests that the peak-shaped signal contains elements of both the ramped — and isothermal — thermoluminescence (TL). The modelled changes in the peak movement as a function of isothermal temperature and the ramp-rate show an excellent agreement with those obtained experimentally. This understanding of thermal lag is extended to optically stimulated luminescence (OSL) measurements for which the effects of isothermal TL contamination and changing thermal assistance during thermal equilibration are discussed. Appropriate methods are suggested to identify thermal lag on the basis of the peak structure, and to circumvent this effect in isothermal methods.     

Performance comparison of OSLD (Al2O3:C) and TLD (LiF:Mg,Cu,P) in accreditation proficiency testing

The U.S. Navy uses a dosimetric system, which employs the LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs), developed and produced by Thermo Fisher Scientific. Every two years, the Naval Dosimetry Center (NDC) performs proficiency testing to maintain its national accreditation. Since 2007, the U.S. Navy has also tested InLight Basic - OSLN Optically Stimulated Luminescence Al₂O₃:C dosimeters (OSLD) manufactured by Landauer. In 2011 and 2013, the Naval Dosimetry Center performed proficiency testing for both systems. Here we present a comparison of the performance of TLDs (LiF:Mg,Cu,P) and OSLDs (Al₂O₃:C) in five categories of proficiency testing. The testing included irradiation with photons, neutrons, beta particles and selected mixtures of these radiations. All irradiations were performed at the Pacific Northwest National Laboratory (PNNL). The delivered doses were not reported to the NDC. The official comparison of delivered and reported doses was conducted by PNNL in terms of dose bias and its standard deviation for each category of accreditation. In total, the NDC reported to the PNNL doses for 147 dosimeters of each type (TLD and OSLD). Both NDC tested dosimetric systems have passed established limits. The comparison of OSLD and TLD system performance in each category is discussed. Advantages and disadvantages of both systems are analyzed.     

Evaluation of TL response and intrinsic efficiency of TL dosimeters irradiated using different phantoms in clinical electron beam dosimetry

The TL response of LiF:Mg,Ti microdosimeters and CaSO₄:Dy dosimeters were studied for 12 MeV electron beams using PMMA, liquid water and solid water (SW) phantoms. The different phantom materials affect the electron spectrum incident on the detector and it can alter the response of dosimeters to different radiation types, so this fact should be considered in clinical dosimetry. The dosimeters were irradiated with doses ranging from 0.1 up to 5 Gy using a Varian Clinac 2100C linear accelerator of Hospital Israelita Albert Einstein – HIAE using a 10 × 10 cm² field size and 100 cm source-phantom surface distance, with the dosimeters positioned at the depth of maximum dose. The TL readings were carried out 24 h after irradiation using a Harshaw 3500 TL reader. This paper aims to compare the TL response relative to ⁶⁰Co of the dosimeters for different phantoms used in radiotherapy dosimetry. CaSO₄:Dy dosimeters presented higher TL sensitivity relative to ⁶⁰Co and intrinsic efficiency than microLiF:Mg,Ti dosimeters for all phantoms.     

Preliminary TL Studies of K2GdF5:Dy3+ exposed to photon and neutron radiation fields

Results of the investigation concerning thermoluminescence (TL) responses to X, gamma and neutron radiation fields for crystals of complex fluoride K₂GdF₅ undoped and doped with varying concentrations of Dy³⁺ ions are presented. Crystals doped with 5.0 at% Dy³⁺ have shown the most efficient TL response, with a linear response to doses for all the radiation fields. In the X rays range, the maximum TL response has been found to be 15 times more than the response for gamma. The fast and thermal neutron TL outputs were evaluated for K₂Gd_0.95Y_0.05F₅ and the contribution of the gamma component in the TL curve was estimated.     

Photon dosimetry methods outside the target volume in radiation therapy: Optically stimulated luminescence (OSL), thermoluminescence (TL) and radiophotoluminescence (RPL) dosimetry

Dosimetry methods outside the target volume are still not well established in radiotherapy. Luminescence detectors due to their small dimensions, very good sensitivity, well known dose and energy response are considered as an interesting approach in verification of doses outside the treated region. The physical processes of thermoluminescence (TL), radiophotoluminescence (RPL) and optically stimulated luminescence (OSL) are very similar and can be described in terms of the energy band model of electron-hole production following irradiation.This work is a review of the main dosimetric characteristics of luminescence detectors which were used in experiments performed by EURADOS Working Group 9 for in-phantom measurements of secondary radiation (scattered and leakage photons). TL LiF:Mg,Ti detectors type MTS-7 (IFJ PAN, Poland), types TLD-100 and TLD-700 (Harshaw), OSL Al₂O₃:C detectors type nanoDot™ (Landauer Inc.) and RPL rod glass elements type GD-352M (Asahi Techno Glass Coorporation) are described. The main characteristics are discussed, together with the readout and calibration procedures which lead to a determination of absorbed dose to water.All dosimeter types used show very good uniformity, batch reproducibility and homogeneity. For improved accuracy, individual sensitivity correction factors should be applied for TL and OSL dosimeters while for RPL dosimeters there is no need for individual sensitivity corrections.The dose response of all dosimeters is linear for a wide range of doses.The energy response of GD-352M type dosimeters (with Sn filter) used for out-of-field measurements is flat for medium and low energy X-rays.The energy dependence for TLDs is low across the range of photon energies used and the energy correction was neglected. A significant over response of Al₂O₃:C OSLDs irradiated in kilovoltage photon beams was taken into account. The energy correction factor f_en was calculated by using the 2006 PENELOPE Monte Carlo code.With suitable calibration, all dosimeter types are appropriate for out-of-field dose measurements as well as for the in-phantom measurements of radiotherapy MV X-rays beams.     

U and Th thin film neutron dosimetry for fission-track dating: application to the age standard Moldavite

Neutron dosimetry based on U and Th thin films was used for fission-track dating of the age standard Moldavite, the central European tektite, from the Middle Miocene deposit of Jankov (southern Bohemia, Czech Republic). Our fission-track age () agrees with a recent ⁴⁰Ar/³⁹Ar age, , based on several determinations on Moldavites from different sediments, including the Jankov deposit. This result indicates that the U and Th thin film neutron dosimetry represents a reliable alternative for an absolute approach in fission-track dating.     

Radiotherapy out-of-field dosimetry: Experimental and computational results for photons in a water tank

The first objective of this work was to check and select a set of four kinds of passive photon, dosimeters (two thermo-luminescence dosimeter (TLD) types, one radiophotoluminescence (RPL) dosimeter and one optically stimulated luminescence (OSL) dosimeter) together with a common measurement protocol. Dosimeters were calibrated in a reference clinical linear acccelerator beam in a water tank at a reference facility at the Laboratoire National Henri Becquerel (CEA LIST/LNE LNHB, Saclay. Radiation qualities of 6, 12 and 20 MV were used with standard calibration conditions described in IAEA TRS 398 and non-standard conditions. Profile and depth dose ion chamber measurements were also made to provide reference values. Measurements were made in a water tank into which pipes could be inserted which held dosimeters in pre-determined and reproducible positions. The water tank was built to enable investigation of doses up to 60 cm from the beam axis. A first set of experiments was carried out with the beam passing through the tank. From this first experiment, penumbra and out-of-field dose profiles including water and collimator scatter and leakage were found over three orders of magnitude. Two further sets of experiments using the same experimental arrangement with the beam outside the tank, to avoid water scatter, were designed to measure collimator scatter and leakage by closing the jaws of the collimator. Depending on the energy, typical leakage and collimator scatter represents 10–40% and 30–50% of the total out-of-field doses respectively. It was concluded that all dosimeters can be used for out-of-field photon dosimetry. All show good uniformity, good reproducibility, and can be used down to low doses expected at distances remote from the subsequent radiotherapy target volume.     

A survey of the signal stability and radiation dose response of sulfates in the context of adapting optical dating for Mars

The Martian landscape is currently dominated by eolian processes, and eolian dunes are a direct geomorphic expression of the dynamic interaction between the atmosphere and the lithosphere of planets. The timing, frequency, and spatial extent of dune mobility directly reflects changing climatic conditions, therefore, sedimentary depositional ages are important for understanding the paleoclimatic and geomorphologic history of features and processes present on the surface of the Earth or Mars. Optical dating is an established terrestrial dosimetric dating technique that is being developed for this task on Mars. Gypsum and anhydrite are two of the most stable and abundant sulfate species found on the Earth, and they have been discovered in Martian sediments along with various magnesium sulfates and jarosite. In this study, the optical dating properties of various Ca-, Mg-, and Fe-bearing sulfates were documented to help evaluate the influence they may have on in-situ optical dating in eolian environments on Mars. Single-aliquot regenerative-dose (SAR) experimental procedures have been adapted to characterize the radiation dose response and signal stability of the Martian sulfate analogs. Jarosite was dosimetrically inert in our experiments. The radiation dose response of the Ca- and Mg-sulfates was monotonically increasing in all cases with characteristic doses ranging from ∼100 to ∼1000 Gy. Short-term signal fading also varied considerably in the Ca- and Mg-sulfates ranging from ∼0% to ∼40% per decade for these materials. These results suggest that the OSL properties of Ca- and Mg-sulfates will need to be considered when developing protocols for in-situ optical dating on Mars, but more enticingly, our results foreshadow the potential for gypsum to be developed as a geochronometer for Mars or the Earth.     

Optically stimulated luminescence in Ag doped Li2B4O7 single crystal and its sensitivity to neutron detection and dosimetry in OSL mode

Optically stimulated luminescence (OSL) measurements have been carried out on single crystals of Ag doped Li₂B₄O₇ (LTB:Ag) after exposure to various nuclear radiations. The time integrated OSL intensity is found to be linear in the range from 0.1 Gy to 500 Gy. Fading of the OSL signal was found to be around 36% in 48 h. The presence of ⁶Li and ¹⁰B has been gainfully utilized to measure doses of thermal neutrons. Further, the large difference between the wavelength of the stimulation source (∼460 nm) and emission from the LTB:Ag at 270 nm has enhanced the signal-to-noise ratio in a simple OSL set-up with suitable filters. The high sensitivity of the LTB:Ag to thermal neutrons will be useful in variety of applications including personal dosimetry in mixed-fields and imaging devices for neutron radiography.     

Investigation of the optical absorption dose response of LiF:Mg,Ti (TLD-100) and the role of V centers in F center (5.08 eV) bleaching

The optical absorption (OA) dose response of irradiated LiF:Mg,Ti has been measured over the dose range from 100 Gy to 1.4 M Gy. Measurements at high dose indicate that the 4.0 eV band is actually a composite band at 3.84 eV and 4.3 eV. Bleaching experiments at 5.08 eV (F band) support the participation of V₃ centers in the relaxation mechanisms following the bleach. The results are interpreted in the framework of a spatially correlated trapping center/luminescent center giving rise to composite peak 5 in the glow curve.     

A pulsed EPR method to determine distances between paramagnetic centers with strong spectral anisotropy and radicals: The dead-time free RIDME sequence

Methods to determine distances between paramagnetic metal centers and radicals are scarce. This is unfortunate because paramagnetic metal centers are frequent in biological systems and so far have not been employed much as distance markers. Successful pulse sequences that directly target the dipolar interactions cannot be applied to paramagnetic metal centers with fast relaxation rates and large g-anisotropy, if no echos can be detected and the excitation bandwidth is not sufficient to cover a sufficiently large part of the spectrum. The RIDME method Kulik et al. (2002) [20] circumvents this problem by making use of the T₁-induced spin-flip of the transition-metal ion. Designed to measure distance between such a fast relaxing metal center and a radical, it suffers from a dead time problem. We show that this is severe because the anisotropy of the metal center broadens the dipolar curves, which therefore, only can be analyzed if the full curve is known. Here, we introduce five-pulse RIDME (5p-RIDME) that is intrinsically dead-time free. Proper functioning of the sequence is demonstrated on a nitroxide biradical. The distance between a low-spin Fe(III) center and a spin label in spin-labeled cytochrome f shows the complete dipolar trace of a transition-metal ion center and a spin label, yielding the distance expected from the structure.     

Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams

Radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon-doped aluminum oxide crystals can be used for medical dosimetry in external beam radiotherapy and remotely afterloaded brachytherapy. The RL/OSL signals are guided from the treatment room to the readout instrumentation using optical fiber cables, and in vivo dosimetry can be carried out in real time while the dosimeter probes are in the patient. The present study proposes a new improved readout protocol based solely on the RL signal from Al₂O₃:C. The key elements in the protocol are that Al₂O₃:C is pre-dosed with ∼20 Gy before each measurement session, and that the crystals are not perturbed by optical stimulation. Using 6 and 18 MV linear accelerator photon beams, the new RL protocol was found to have a linear dose-response from 7 mGy to 14 Gy, and dosimetry in this range could therefore be performed using a single calibration factor (∼6 × 10⁶ counts per Gy for a 2 mg crystal). The reproducibility of the RL dosimetry was 0.3% (one relative standard deviation) for doses larger than 0.1 Gy. The apparent RL sensitivity was found to change with accumulated dose ((−0.45 ± 0.03)% per 100 Gy), crystal temperature ((−0.21 ± 0.01)%/ °C), and dose-delivery rate ((−0.22 ± 0.01)% per 100 MU/min). A temporal gating technique was used for separation of RL and stem signals (i.e. Cerenkov light and fluorescence induced in the optical fiber cable during irradiation). The new readout protocol was a substantial improvement compared with the combined RL/OSL protocol, that required relatively long readout times and where the optical stimulation greatly affected the RL sensitivity. The only significant caveat was the apparent change in RL-response with accelerator dose-delivery rate.     

Thermoluminescence in two varieties of jadeite: Irradiation effects and application to high dose dosimetry

The thermoluminescence properties of white (WJ) and green (GJ) mineral jadeite have been investigated with a view to be of use in high dose dosimetry. WJ presented glow curve with 110, 190 and 235 °C peaks. All these peaks grow with radiation dose. The glow curve of GJ the green variety has TL peaks at 140, 210, 250 and 330 °C. We also observed that there is a difference between the TL glow curves for both samples, irradiated with gamma and electron. As expected the green jadeite can be used for measurement of dose as high as 50 kGy.     

A pQCD-based approach to parton production and equilibration in high-energy nuclear collisions

A pQCD-based model for parton production and equilibration in ultrarelativistic heavy-ion collisions is reviewed. The model combines pQCD processes including initial and final state radiations together with string phenomenology for nonperturbative soft processes. Nuclear effects on the initial parton production, such as multiple parton scattering and nuclear shadowing of parton distribution functions are considered. Comparisons with existing data are made and further tests of the model to constrain model parameters are proposed. With the obtained space-time history of the parton production, evolution of the minijet gas toward a fully equilibrated parton plasma is studied. Direct probes of the early parton dynamics, such as pre-equilibrium photon and dilepton production, open charm production, J/ψ suppression and jet quenching are also reviewed.     

Slow-motion theory of nuclear spin relaxation in paramagnetic low-symmetry complexes: A generalization to high electron spin

The slow-motion theory of nuclear spin relaxation in paramagnetic low-symmetry complexes is generalized to comprise arbitrary values of S. We describe the effects of rhombic symmetry in the static zero-field splitting (ZFS) and allow the principal axis system of the static ZFS tensor to deviate from the molecule-fixed frame of the nuclear-electron dipole–dipole tensor. We show nuclear magnetic relaxation dispersion (NMRD) profiles for different illustrative cases, ranging from within the Redfield limit into the slow-motion regime with respect to the electron spin dynamics. We focus on S = 3/2 and compare the effects of symmetry-breaking properties on the paramagnetic relaxation enhancement (PRE) in this case with that of S = 1, which we have treated in a previous paper. We also discuss cases of S = 2, 5/2, 3, and 7/2. One of the main objectives of this investigation, together with the previous papers, is to provide a set of standard calculations using the general slow-motion theory, against which simplified models may be tested.     

A new method for quantitation of spin concentration by EPR spectroscopy: application to methemoglobin and metmyoglobin

A new method of EPR spectral analysis is developed to quantitate overlapping signals. The method requires double integration of a number of spectra containing the signals in different proportions and the subsequent solution of a system of linear equations. The result gives the double integral values of the individual lines, which can then be further used to find the concentrations of all the paramagnetic species present. There is no requirement to deconvolute the whole spectrum into its individual components. The method is employed to quantify different heme species in methemoglobin and metmyoglobin preparations. A significantly greater intensity of the high-spin signal in metmyoglobin, compared to methemoglobin at the same heme concentration, is shown to be due to larger amounts of low-spin forms in methemoglobin. Three low-spin types in methemoglobin and two in metmyoglobin are present in these samples. When their calculated concentrations are added to those of the high-spin forms, the results correspond to the total heme concentrations obtained by optical spectroscopy.