Pergamon Radiation Measurements, Vol. 27, No. 2, pp. 389-392, 1997 © 1997ElsevierScienceLtd. All rights reserved Printed in Great Britain PII: S1350-4487(96)00119-9 1350-4487/97 $17.00+ 0.00 ACCIDENT DOSE ESTIMATION USING PORCELAIN. A COMPARISON BETWEEN DIFFERENT THERMOLUMINESCENCE METHODS GRZEGORZ ADAMIEC*.% DOREEN STONEHAM* and YETER GOKSUt *Research Laboratory for Archaeology and the History of Art, 6 Keble Road, Oxford OX1 3QJ, U.K. and #Institut f'tir Strahlenschutz GSF-Forschungszentrum Neuherberg, Postfach 1129, D-85758 Obersehlei#heim, Germany Abstract--Accident dose estimation using the pre-dose technique on the 110°Cpeak in porcelain has been used since 1984. The disadvantage of this technique is that the reservoir traps appear to begin to saturate for doses around 1 Gy. This has limitations in regions of high fallout doses such as the contaminated settlements in the Chernobyl Exclusion Zone with fallout doses often above 1 Gy. When doses are added to measure the growth curve the total absorbed dose falls into the saturation region. Samples of porcelain fitments were collected from such settlements and it was observed that the 230°C peak in the thermoluminescence (TL) glow-curvefor some of them was strong enough to carry out the simple additive dose procedure. In addition, the 230°C peak pre-doses in a similar way. This enabled us to carry out three dose evaluations on each sample. It was observed that both pre-dose evaluations yielded a similar result. The results of the simple additive dose in most cases are in agreement within error limits with the results obtained using pre-dose techniques, although in some cases some discrepancies were observed. © 1997 Elsevier Science Ltd I. INTRODUCTION Accident dosimetry using porcelain from fallout regions was first used on samples from Hiroshima (Stoneham, 1984). In regions of high fallout from the Chernobyl accident, it was found that low-fired materials, such as bricks, sometimes absorbed radionuclides from rainwater deposition. Since then, porcelain has been the preferred material and method for dose evaluation. The pre-dose method exploits thermally activated sensitivity changes in quartz, related to the absorbed dose, first reported by Fleming (I 969). Its application for accident dosimetry was proposed by Fleming and Thompson (1970) and applied to samples from regions affected by the Nevada bomb tests by Haskell et al. (1988). The two pre-dose methods for dose evaluation are multiple activation (MA) and additive dose (AD) techniques, described by Bailiff (1994). Although it requires several aliquots to produce a growth curve, the AD technique is the one used as only a single heating is involved. 2. EXPERIMENTAL METHOD The dose determinations were performed on slices of porcelain from electrical insulators and lamp holders collected in Belarus and Ukraine in 1995. The samples were cored with diamond coring drills under running water (Stoneham, 1986). The diameter of the cores was 2.8 or 7.8 mm depending on the size of the sample. Subsequently the cores were mounted with cyanoacrylate glue in Tufnol TM tubes and cut into slices of 200/~m thickness using a low speed saw with a diamond coated blade. All measurements were carried out on slices placed in platinum cups using an automated Riso TL reader (Botter-Jensen, 1988) fitted with an EM1 9635Q PM tube and two calibrated ~Sr-~Y beta sources delivering 22.5 and 3.2 mGy s-'. Prior to measure- ment the oven was evacuated and all measurements carried out in an atmosphere of nitrogen. The heating rate used was 5 K s- '. In the light detection system, the Corning 7-59 filter was used (transmission in the ~310-460 nm with peak at 370 nm). Thermal activation characteristics (TAC) were carried out in order to determine the optimum activation temperature for each sample (Bailiff, 1991). An example of a TAC for the 110 and 230°C peak is presented in Fig. 1. In order to be able to obtain all three dose estimates from one set of 24 slices the following measuring sequence was used: 1. Thermal wash to 140°C in order remove the signal which might have been induced by cutting (no effect was observed). 2. Irradiation with additive beta doses depending on the accrued dose predicted from a TAC for a natural and irradiated sample. aPermanent address: Institute of Physics, Silesian Technical University, ul. Krzywoustego 2, 44-100 Gliwice, Poland. 389