I.K. Bailiff

The pre-dose technique

Abstract The pre-dose technique has found applications in dating and authentication, accident dosimetry and heat treatment studies. It is a technique requiring considerable experimental effort to yield dose estimates, primarily due to the complexity of the pre-dose effect on which it is based. Nonetheless it has important potential in the dating of ceramics of the last two millennia, in accident dosimetry and in the study of the role of defects in thermoluminescence processes. This paper examines recent uses of the technique including current research problems and wider implications of the results of pre-dose studies, in particular the study of the effect in minerals other than quartz. Several questions raised in recent papers on the basis of measurements with synthetic and natural alpha quartz and related to assumptions made in the use of the technique for dose evaluations are also discussed.

The First International Intercomparison of EPR-dosimetry with Teeth: First Results

Intercomparison of EPR-dosimetric techniques using tooth enamel had been performed in order to check whether the results produced by different laboratories are consistent and accurate. Participants were supposed to evaluate doses applied to pulverized enamel samples, using routine techniques from their laboratories. The intercomparison has demonstrated a great variety of methods used for dose reconstruction. Peculiarities of experimental approaches are discussed systematically in terms of procedure for recording the EPR-spectra, determination of the amplitude of the radiation induced signal, determination of the dose, and error propagation.

Retrospective dosimetry with ceramics

Abstract This paper reviews recent progress that has been made in the application of luminescence techniques with ceramic materials to the problem of dose reconstruction at: Hiroshima and Nagasaki; areas downwind of the Nevada Test Site; regions of Belarus, the Russian Federation and the Ukraine contaminated by fallout from Chernobyl; settlements along the Techa River affected by releases from the Mayak facility at Chelyabinsk; Kiisa, Estonia where a stolen 137 Cs irradiator source was discovered. Luminescence has an increasingly important role in radiological health studies at such sites because of the ability of the method to measure dose retrospectively in areas where radiation monitoring was lacking or sporadic following the incident. Commonly produced ceramics such as brick, tile and porcelain fittings and artefacts have been used to determine the integrated external gamma radiation dose (the transient dose). Evaluation of the reliability and accuracy with which the transient dose can be estimated when it approaches and drops below the level of the integrated natural background dose (

Determination of trap depths associated with TL peaks in synthetic quartz (350–550 K)

Abstract The thermoluminescence of annealed synthetic quartz has been investigated in the temperature region 350–550 K; the trap parameters for a number of TL peaks within this region of the glow curve have been determined using the fractional glow technique. The experimentally obtained values of thermal trap depth have been corrected for the effect of thermal quenching; the new correction accommodates an arbitrary form of internal thermal quenching behaviour that is assumed to be appropriate for quartz. Radioluminescence measurements were also performed to evaluate the variation in luminescence with sample temperature.

Characteristics of infrared-stimulated luminescence from a feldspar at low temperatures

Abstract The characteristics of infrared-stimulated luminescence (IRSL) from a sample of potassium feldspar at low temperatures are presented. These studies extend the previous work from this laboratory on the optical bleaching characteristics and emission spectra of feldspars at room temperature and recent measurements of the stimulated spectrum for a sample of potassium feldspar at room temperature. Stimulation spectra have been measured at 290, 160 and 145 K. By fitting Gaussian functions to the spectra, the peak position is shown to shift to higher photon energies at lower temperatures and the full-width half-maximum of the peak to reduce with decreasing temperature. The variation of IRSL intensity with temperature for several stimulating wavelengths has been determined and the form of the IRSL decay curve measured at 290 and 160 K. No substantial differences were observed in the form of the decay curves at each temperature.

Interlaboratory beta source calibration using TL and OSL on natural quartz

Abstract Laboratories using luminescence methods for dose reconstruction have to make interlaboratory source calibrations—initially this will be a single isotope beta or gamma source using one particular reference material. The procedure requires not only the administration of exact doses to the material but also the uniform handling of the dosimetric material and standardization of the procedures. An interlaboratory calibration of an Sr-90 beta source was recently carried out by our five laboratories which are involved in a retrospective project. The reference material was quartz but there were difficulties finding sufficient suitable quartz. Five different batches were obtained from the Merck company and tested for sensitivity, linearity and stability of the 340°C peak, the 1992 batch was found to be the most appropriate. The irradiations were performed at the Secondary Standard Dosimetry Laboratory at GSF using a Co-60 source as well as the in situ measurements with an ionization chamber, calibrated to the primary standards of PTB Braunschweig. Irradiated and unirradiated quartz was distributed to the five laboratories and although different procedures were used for thermoluminescence and optically stimulated luminescence, the source calibrations for the different laboratories agreed within ±3% compared to the previous calibrations of the laboratories.

Absorbed dose evaluations in retrospective dosimetry: methodological developments using quartz

Abstract Dose evaluation procedures based on luminescence techniques were applied to 50 quartz samples extracted from bricks that had been obtained from populated or partly populated settlements in Russia and Ukraine downwind of the Chernobyl NPP. Determinations of accrued dose in the range ∼30–300 mGy were obtained using TL (210°C TL and pre-dose) and OSL (single and multiple aliquot) procedures. Overall, good inter-laboratory concordance of dose evaluations was achieved, with a variance (1 σ ) of ∼±10 mGy for the samples examined.

Characteristics of time-resolved luminescence in quartz

Abstract Time-resolved luminescence measurements were performed with samples of synthetic quartz (Sawyer Premium Q) and granular quartz extracted from ceramics and sediment samples under pulsed (∼5 ns) laser stimulation (OPO). The luminescence was detected in the UV region using colour glass filters (FWHM 280–380 nm). The time-resolved spectrum is dominated by a single exponential decay that remains substantially unaltered when the stimulation wavelength is changed from 600 to 450 nm indicating that the same recombination process is being observed. The lifetime measured at room temperature was 40±0.6 μs for the synthetic quartz; at elevated temperatures the measured lifetime is reduced in a manner that is consistent with a competitive non-radiative recombination process (thermal quenching). An average lifetime of 33±0.3 μs was obtained for seven samples of granular quartz, indicating a common recombination process in these natural samples that differs from the value for synthetic quartz.

A preliminary study of time-resolved luminescence in some feldspars

Abstract A new time-resolved optically stimulated luminescence system has been assembled. It has a stimulation range from 400 nm to > 2 μm and has a temporal resolution of 5 ns thus permitting measurements of lifetimes down to the order of tens of nanoseconds. Measurements with a set of six feldspars (orthoclase, albite, sanidine and oligoclase) have been made using 850 nm stimulation during which recombination luminescence is observed. Strong similarities, but also marked differences, were found between the samples. Lifetimes range from a few tens of nanoseconds to tens of μs. Measurements of these samples have also been made three different detection regions from 300 to 600 nm, appearing to reveal associations between some of the emission bands and particular lifetimes. Investigations of the dependence upon sample temperature have also been performed.

The application of retrospective luminescence dosimetry in areas affected by fallout from the semipalatinsk nuclear test site: an evaluation of potential.

Luminescence retrospective dosimetry techniques have been applied with ceramic bricks to determine the cumulative external gamma dose due to fallout, primarily from the 1949 test, in populated regions lying NE of the Semipalatinsk Nuclear Test Site in Altai, Russia, and the Semipalatinsk region, Kazakhstan. As part of a pilot study, nine settlements were examined, three within the regions of highest predicted dose (Dolon in Kazakshstan; Laptev Log and Leshoz Topolinskiy in Russia) and the remainder of lower predicted dose (Akkol, Bolshaya Vladimrovka, Kanonerka, and Izvestka in Kazakshstan; Rubtsovsk and Kuria in Russia) within the lateral regions of the fallout trace due to the 1949 test. The settlement of Kainar, mainly affected by the 24 September 1951 nuclear test, was also examined. The bricks from this region were found to be generally suitable for use with the luminescence method. Estimates of cumulative absorbed dose in air due to fallout for Dolon and Kanonerka in Kazakshstan and Leshoz Topolinskiy were 475 ± 110 mGy, 240 ± 60 mGy, and 230 ± 70 mGy, respectively. The result obtained in Dolon village is in agreement with published calculated estimates of dose normalized to 137Cs concentration in soil. At all the other locations (except Kainar) the experimental values of cumulative absorbed dose obtained indicated no significant dose due to fallout that could be detected within a margin of about 25 mGy. The results demonstrate the potential suitability of the luminescence method to map variations in cumulative dose within the relatively narrow corridor of fallout distribution from the 1949 test. Such work is needed to provide the basis for accurate dose reconstruction in settlements since the predominance of short-lived radionuclides in the fallout and a high degree of heterogeneity in the distribution of fallout are problematic for the application of conventional dosimetry techniques.