Stef. Charalambous

Radiation measurements and radioecological aspects of fallout from the cherbonyl reactor accident

Fallout from the Chernobyl reactor accident has been monitored for about one year in Thessaloniki in Northern Greece. Fifteen different short-lived, three relatively long- and one long-lived fission products were identified in air, precipitation, soil, grass and milk samples. The iodine-131 and cesium-137 concentrations in air reached 6·5 and 3 Bq m−3 respectively, on 6 May, 1986. The external exposure dose rate rose to five times the normal background level. It was estimated that the accumulated dose equivalent to the adult thyroid from inhaled iodine-131 averaged 96 μSv, while the body burden from inhaled radiocesium nuclides averaged 2 μSv, 1000 times lower than that corresponding to the estimated dose equivalent from ingestion of foodstuff, which averaged 2 mSv for the first year after the accident.

Heating rate effects on the TL glow-peaks of three thermoluminescent phosphors

Abstract The maximum temperature, the integral and the full width at half maximum of the thermoluminescence glow-peak as a function of the heating rate were studied. The glow-peaks studied are the 110°C glow-peak of Norwegian quartz, the 210°C glow-peak of LiF:Mg,Ti (TLD-700) and the 250°C glow-peak of natural CaF2:MBLE. The heating rate ranges from 2 up to 70°C s . The experimental results are compared with theoretical calculations in order to test the theory.

Superlinearity of synthetic quartz: Dependence on the firing temperature

Abstract In the present work, the sensitivity and thermoluminescence (TL) dose response behaviour of glow-peaks of synthetic quartz are studied as a function of the firing temperature between 300°C and 900°C in steps of 100°C. Complete TL dose response curves in the dose region, 0.1 up to 170 Gy were obtained at each firing temperature. Each TL dose response curve consists of two dose regions, which on a log–log scale have different slopes, k, indicating two different degrees of superlinearity. In the case of the glow-peak at 110°C, the TL dose response curves were fitted with an analytical expression. From the fitting procedure the superlinearity index g(D) was evaluated as a function of dose. The results show that the firing temperature influences the TL dose response behaviour of all glow-peaks. However, the effects are more profound on the glow-peak at 110°C. The superlinearity index g(D) is strongly reduced as the firing temperature increases.

The thermoluminescence behaviour of LiF(TLD-100) for doses up to 10 MRad

Abstract The behaviour of the thermoluminescence of LiF (TLD-100) was studied, for doses up to 10M Rad. At these doses, peaks appear, grow and disappear. The total TL between 60°C and 600°C was found to increase for doses up to 105 Rad and to decrease by up to a factor of 2 for higher doses. Changes in the shape of the peaks were observed as well as a shift of their maxima on the temperature scale. In particular, a peak at about 480°C was investigated. The results are discussed and possible explanations of the phenomena are offered.

Anomalous fading in apatite

Abstract The anomalous fading (AF) in natural fluoroapatite vs storage time at room temperature is studied as a function of (a) grain size between 40 and 200 μm; (b) annealing temperature between 500 and 1000°C; (c) pre-dose from 500 Gy up to 20 kGy; and (d) irradiation temperature (Tirr) from liquid nitrogen temperature (LNT) up to 200°C. It was found that the above conditions do not influence the appearance of the phenomenon, but in some cases cause only a change in the fading rate. The results show quantum mechanical tunnelling as a probable mechanism responsible for the anomalous fading in apatite.

Thermoluminescence dose response of quartz as a function of irradiation temperature

The thermoluminescence (TL) response of pure Norwegian quartz as a function of irradiation temperature (Tirr) and dose has been investigated. The TL response of the (150-230 degrees C) and (230-350 degrees C) glow curve intervals shows a strong dependence on Tirr between 77 and 373 K in the dose range from 54 to 8.4*104 Gy. Both glow curve intervals also show temperature dependent dose response properties. The 150-230 degrees C interval is supralinear from the lowest dose (54 Gy). Its maximum supralinearity factor appears at Tirr=293 K. The 230-350 degrees C interval shows sublinear behaviour below Tirr=193 K, while at Tirr>or=273 K it shows the well known dose response curves. Its maximum supralinearity factor appears at Tirr=323 K. The linear response is extended up to 460 Gy at Tirr=273 K and falls to 80 Gy at Tirr=373 K.

Temperature dependence of Doppler broadening of the annihilation line in a high Tc superconductor

Abstract Positron annihilation measurements in the high Tc superconductor YBa2Cu3O6+χ have been performed. The S parameter decreases with temperature in two steps. That is an indication of a two-step superconducting transition.

Dose rate effects on CR-39 SSNT detector

Abstract Dose rate effects on CR-39 SSNTDetector were observed for doses from 0 up to 1 Mrad. The dose rate region examined was 10 2 –10 6 rad/min. The behavior is strongly dependent on the irradiation in vacuum or in open air. The contribution of degradation and recombination mechanisms is discussed.

Silver-110 m and 125Sb in chernobyl fallout

Measurements of the two unusual nuclides 110mAg and 125Sb in soils and grass, derived from fallout, were made in Greece after the Chernobyl reactor accident. The 110mAg concentrations ranged from 4.5 to 46.1 Bq kg-1 (average 14.3 Bq kg-1) in soils and from 0.2 to 1.5 Bq kg-1 (average 0.8 Bq kg-1) in grass. The 125Sb concentrations ranged from 15.7 to 284.6 Bq kg-1 (average 105.0 Bq kg-1) in soils and from 1.1 to 19.6 Bq kg-1 (average 4.4 Bq kg-1) in grass.

A simple device for measuring radon exhalation from the ground

Abstract A special device was developed for measuring radon exhalation from the ground in the earthquake prediction research. A solid state nuclear track (SSNT) detector (CA 80-15) has been used as a probe. The thoron registration is reduced by a factor of 103. Several problems concerning field measurements (e.g. humidity) were solved.