Retrospective luminescence dosimetry: development of approaches to application in populated areas downwind of the Chernobyl NPP

Estimation of 'dose-depth' profile in the surface layers of a quartz-containing tile from the former Hiroshima University building indicates the possible presence of beta-irradiation from residual radioactivity after A-bombing

The problem of differentiating between primary irradiation and exposure due to residual radioactivity following A-bombing (including beta-exposure), is the subject of special attention and discussions in order to understand the health effects following the Hiroshima and Nagasaki A-bombings, especially among newcomers to cities soon after the detonations. In this work, the method of single quartz grain luminescence retrospective dosimetry was applied for a retrospective estimation of the 'dose-depth' profile in a quartz-containing tile extracted from the building of former Hiroshima University (HU), which was a 'witness' of the Hiroshima atomic bombing on the 6 August 1945. It has been shown that results of retrospective estimates of the 'dose-depth' profile using the method of optically stimulated luminescence (OSL) from inclusions of quartz grains in very thin layers of the sample, in combination with the calculations of the 'dose-depth' profile using the Monte Carlo method, indicates the possible presence of beta irradiation of thin layers of the sample located near the surface of the tile facing the air, where there is no electronic equilibrium from gamma radiation.

Comparison of the thermoluminescence kinetic parameters for natural alkali-rich aluminosilicates minerals

Natural alkali-rich aluminosilicates minerals from Harmancık/Bursa/Turkey and Kepsut/Balıkesir (Turkey) were characterised by X-ray diffractometry (XRD), X-ray fluorescence (XRF) and investigated the blue thermoluminescence (TL) emission of the samples. The TL glow curves exhibited a very complex structure that were analyzed via computerized glow curve deconvolution (CGCD), initial rise (IR) and variable heating rate (VHR) techniques. It could be appreciated how the kinetic parameters (trap depth -E_a-, kinetic order -b- and frequency factor -s- for each electron trap levels) were consistent regardless of the analytical method used.

TLD characteristic of glass, feldspathic and lithium disilicate ceramics

Thermoluminescence (TL) emission of dental ceramics could be potentially used for retrospective dosimetry purposes as this allows a quick and reliable dose assessment in case of nuclear accident or bad use of a nuclear attack. This paper reports on the chemical and luminescence characterization of glass, feldspathic and lithium disilicate glass ceramic (LS₂ ). Swedish and Turkish dental ceramics supplied by Vivadent Ivoclar considering: (i) the dose response in the range 10 Gy to 6.9 kGy which displays a linear dose-response at low dose values up to 36 Gy (glass and feldspathic ceramics) and shows sublinear behavior from 12 Gy to 6 kGy (lithium disilicate glass ceramics), (ii) a reproducibility of the TL signal in which the area under the glow curve increased about 25% after 10 cycles for glass and lithium disilicate ceramics and increased about 30% after seven cycles for feldspathic ceramics, (iii) stability of the luminescence emission with the elapsed time and (iv) effect of the heating rate. Glass, lithium disilicate and feldspathic ceramics display a complex UV-blue glow emission that can be respectively fitted to five and four groups of components assuming first-order kinetics behavior.

Radiation effect on cathodoluminescence and thermoluminescence emission of Ca-rich oxalates from the human body

The radiation effect of luminescence emission of Ca-rich oxalate biogenic materials (gallbladder and renal calculi) and a commercial standard sample (CaC₂ O₄ ·H₂ O) is reported. The samples were characterized by environmental scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric and differential thermal analyses, display complex cathodoluminescence (CL) and thermoluminescence (TL) glow emissions. CL spectra (in the UV-infrared range) displayed non-well defined peaks, and exhibited emission at: (i) higher energies (300-490 nm) mainly associated with non-bridging oxygen hole centers, oxygen-deficient centers and peroxy intrinsic defects, regardless of the sample; and (ii) higher, narrow and sharp wavebands, in the red region, probably induced by the presence of traces of Sm³⁺ (⁴ G_5/2 →⁶ H_9/2 transition) and/or Tb³⁺ (⁵ D₄ →⁷ F₃ transition) only for mineral-like materials in the human body. The UV-blue TL emission showed low-intensity maxima in which it was possible to distinguish at least four groups of components in each sample.

Characterization of Ivoclar Vivadent Dental Restoration Material for 137CS Retrospective Radiation Dosimetry

Retrospective dosimetry is the method of using materials on or near a person who is exposed to ionizing radiation to determine the amount of radiation received by the person. A possible candidate material for retrospective dosimetry is Ivoclar Vivadent IPS e.max® CAD ceramic dental restoration material, which exhibits radiation-induced thermoluminescence when exposed to gamma- and x-ray radiation from a Cs source. The purpose of this paper is to characterize the material and study the behavior of the thermoluminescence signal with radiation dose and with delay time between radiation exposure and thermoluminescence measurement. The first glow peak is well-modeled by a first-order glow curve deconvolution formula. The height of the first glow peak is approximately linear with dose. The fading of the signal with time is approximately described by a power law curve with cutoff. The material appears to be suitable for retrospective radiation dosimetry.

Comparison of calculated beta- and gamma-ray doses after the Fukushima accident with data from single-grain luminescence retrospective dosimetry of quartz inclusions in a brick sample

To estimate the beta- and gamma-ray doses in a brick sample taken from Odaka, Minami-Soma City, Fukushima Prefecture, Japan, a Monte Carlo calculation was performed with Particle and Heavy Ion Transport code System (PHITS) code. The calculated results were compared with data obtained by single-grain retrospective luminescence dosimetry of quartz inclusions in the brick sample. The calculated result agreed well with the measured data. The dose increase measured at the brick surface was explained by the beta-ray contribution, and the slight slope in the dose profile deeper in the brick was due to the gamma-ray contribution. The skin dose was estimated from the calculated result as 164 mGy over 3 years at the sampling site.

Dose Deposition Profiles in Untreated Brick Material

In nuclear forensics or accident dosimetry, building materials such as bricks can be used to retrospectively determine radiation fields using thermoluminescence and/or optically stimulated luminescence. A major problem with brick material is that significant chemical processing is generally necessary to isolate the quartz from the brick. In this study, a simplified treatment process has been tested in an effort to lessen the processing burden for retrospective dosimetry studies. It was found that by using thermoluminescence responses, the dose deposition profile of a brick sample could be reconstructed without any chemical treatment. This method was tested by estimating the gamma-ray energies of an Am source from the dose deposition in a brick. The results demonstrated the ability to retrospectively measure the source energy with an overall energy resolution of approximately 6 keV. This technique has the potential to greatly expedite dose reconstructions in the wake of nuclear accidents or for any related application where doses of interest are large compared to overall process system noise.

Investigation of Optically Stimulated Luminescence and Signal Fading Properties of Several Materials

Optically stimulated luminescence (OSL) dosimetry involves the illumination of an irradiated sample on an appropriate material to produce a stimulated emission of light, whose intensity is indicative of the radiation dose. This technique is currently used for personnel dosimetry, environmental dosimetry, and geological dating applications. While a great deal of published research focusing on α-Al2O3:C and natural materials used for geological dating exist, relatively little is known about the OSL properties of thermoluminescent (TL) materials. This paper reports the results of an experiment conducted to characterize the OSL behavior of KBr, CaSO4:Tm, CaSO4:Dy, CaSO4:Dy+P, LiF:Mg,Cu,Na,Si, and LiF:Mg,Cu,Si. The OSL signal responses to seven excitation wavelengths from 625 nm to 455 nm for each material were measured at 12 time periods post-irradiation from 6 h to 120 d. The magnitude and fading characteristics of the OSL response of each material were then analyzed. The data demonstrated that significant OSL responses exist for CaSO4:Tm, LiF:Mg,Cu,Na,Si, and LiF:Mg,Cu,Si. In addition, it was found that the fading rates of OSL signals depend on the excitation wavelength used to elicit the signals and that these fading rates and the corresponding excitation wavelengths correlate well with the material's TL behavior. Thus, the various fading rates with respect to the excitation wavelengths could be used to obtain temporal dose information.

Dosimetric feature of natural biotite mineral

A thermoluminescence (TL) study relevant to radiation dosimetry has been carried out for X-ray irradiated biotite mineral under un-annealed and different annealed (473, 573, 673 and 773 K) conditions. Some significant variations in dosimetric characteristics have been observed with annealing treatment. Due to generation of an additional shallow trap level at depth 0.78 eV in 673 and 773 K annealed samples, the dose response is found to improve. For the 773 K annealed sample, a linear dose response has been observed from 10 to 1100 mGy. The fading is ∼13% within 5 d after irradiation and onward it reduces to 7% up to 60 d. Reproducibility of this (773 K) sample is excellent. After 10 recycles the coefficient of variations in the results for the 60, 180 and 1000 mGy dose-irradiated samples are found to be 0.97, 1.31 and 1.03%, respectively. The potential use of biotite as a natural X-ray dosemeter is discussed.

Comparison of thermoluminescence (TL) and cathodoluminescence (ESEM-CL) properties between hydrothermal and metamorphic quartzes

This paper reports on the Thermoluminescence (TL) and Cathodoluminescence (CL) emission of well-characterized hydrothermal milky quartz specimens from Hakkari in Turkey, labeled THQ, and Madrid in Spain, labeled SHQ, and metamorphic quartz from Madrid, in Spain, labeled SMQ. Both hydrothermal and metamorphic quartz samples display similar UV-IR CL spectra consisting of five groups of components centered at 330 nm and 380 nm linked to [AlO(4)]° centers, 420 nm due to intrinsic defects such as oxygen vacancies, lattice defects, and impurities which modify the crystal structure, 480 nm associated with [AlO(4)]° centers of substitutional Al(3+), and a red broad band related to the hydroxyl defects in the quartz lattice as precursors of non-bridging oxygen hole centers (NBOHC) and substitutional point defects. The Turkish quartz specimen exhibits higher CL intensity in the UV region (up to 330 nm) than the Spanish specimens probably linked to the presence of Ca (0.95% in THQ and less than 0.1% in SHQ and SMQ). At wavelengths greater than 330 nm, SMQ (formed at high pressure 6000 bars and temperatures over 500-600°C) shows higher intensity than the hydrothermal (growth at 2000 bars and temperatures 200-300°C) samples associated with the formation process. The natural blue TL glow curves of both THQ and SHQ display a weaker TL intensity than the SMQ, attributable to the Al (0.32%), Ti (0.14%), K (0.01%) and Zr (76 ppm) content. It is shown that mineralogical formation, crystallinity index and the content of the impurities seem to be the main parameters of influence in the shape intensity of the CL and TL glow curve emission.

Optically stimulated luminescence dosimetry with gypsum wallboard (drywall)

Gypsum wallboard (drywall) represents an attractive target for retrospective dosimetry by optically stimulated luminescence (OSL) in the event of a radiological accident or malicious use of nuclear material. In this study, wallboard is shown to display a radiation-induced luminescence signal (RIS) as well as a natural background signal (NS), which is comparable in intensity to the RIS. Excitation and emission spectra show that maximum luminescence intensity is obtained for stimulation with blue light-emitting diodes (470 nm) and for detection in the ultraviolet region (290-370 nm). It is necessary to decrease the optical stimulation power dramatically in order to adequately separate the RIS from the interfering background signal. The necessary protocols are developed for accurately measuring the absorbed dose as low as 500 mGy and demonstrate that the RIS decays logarithmically with storage time, with complete erasure expected within 1-4 d.

Luminescence dosimetry using building materials and personal objects

There is a growing public awareness of the risk of accidental radiation exposure due to ageing nuclear power installations, illegal dumping of nuclear waste and terrorist activities, and of the consequential health risks to populations in addition to social and economic disturbance extending beyond national boundaries. In the event of catastrophic incidents where no direct radiation monitoring data are available, the application of retrospective dosimetry techniques such as luminescence may be employed with materials from the immediate environment to confirm values of cumulative gamma dose to compare with or augment computational modeling calculations. Application of the method to post-Chernobyl studies has resulted in the development of new procedures using fired building materials with the capability to measure cumulative doses owing to artificial sources of gamma radiation as low as 20 mGy. Combined with Monte Carlo simulations of photon transport, values of cumulative dose in brick can be presented in a form suitable for use in dose-reconstruction efforts. Recent investigations have also shown that certain types of cementitious building material, including concrete, mortar and plaster, and personal objects in the form of telephone cards containing microchips and dental ceramics have the potential to be used for retrospective dosimetry. Examples of the most recent research concerning new materials and examples of application to sites in the Former Soviet Union are discussed.