TYPE TESTING OF LiF:Mg,Cu,P (TLD-100H) WHOLE-BODY DOSEMETERS FOR THE ASSESSMENT OF Hp(10) AND Hp(0.07).

In this work, the initial results of the type testing of the LiF:Mg,Cu,P (TLD-100H) whole-body personal dosemeters are presented. An assessment of reproducibility, linearity of the response, the residual signal as a function of the dose, energy and angular dependence of the response was performed. In general, the dosemeters show good reproducibility for different dose values and a linear behaviour for a range between 0.1 and 300 mSv. The detection limits obtained are lower than 50 µSv. The system presents a good energy and angular response for different radiation qualities.

FADING EFFECT OF LiF:Mg,Ti AND LiF:Mg,Cu,P Ext-Rad AND WHOLE-BODY DETECTORS.

Thermoluminescence dosemeters are widely used in individual and environmental monitoring. The aim of this work was to compare the thermal stability of dosemeters of the Ext-Rad and whole-body card types with LiF:Mg,Ti and LiF:Mg,Cu,P detectors stored at different temperatures and periods. The dosemeters were stored at 0°C, room temperature and 40°C for periods that lasted 8, 30, 45, 90 and 120 d. In general, TLD-100H detectors present higher TL signal stability than TLD-100 detectors. The intensity of the signal remained constant for both materials for storage periods at 0°C. At RT the same results was observed for TLD-100H. For TLD-100 detectors, a maximum variation of 22 % was registered for the longest period. At 40°C the TL signal decreased with storage time for both detectors. The TL signal of TLD-100H detectors presented maximum variations of 12 % whereas for TLD-100 detectors, larger variations of 25 % were observed.

Evaluation of the performance of two LiF:Mg,Ti and LiF:Mg,Cu,P dosemeters for extremity monitoring.

In this paper, the results aimed at assessing the performance of two varieties of LiF detectors (LiF:Mg,Ti and LiF:Mg,Cu,P) in photon fields relatively to reproducibility, detection threshold and angular dependence as defined in the ISO 12794 standard are presented. The fading properties and the limit of detection were also investigated for both materials. The results suggest that both LiF varieties are well suited for extremity monitoring. However, better fading properties of LiF:Mg,Cu,P when compared with LiF:Mg,Ti, combined with previous results relatively to energy dependence suggests that LiF:Mg,Cu,P dosemeters are better suited for extremity monitoring.

Radioactivity in the environment around past radium and uranium mining sites of Portugal.

Measurements of ambient radiation doses and determination of radionuclide concentrations in mining waste and soils were performed in 60 areas of former radium and uranium mining. In several places, mining waste and low-grade uranium ore left on the surface contain radioactivity above regional background. Most of the former mining sites present no enhanced radionuclide concentrations. However, in the mining facilities where the radioactive ore was chemically extracted, mill tailings contain materials with elevated levels of radioactivity, up to 200 times the levels in unaffected soils of the region. Mud from neutralization ponds used to treat acid mine waters contains also elevated radionuclide concentrations. Furthermore, depending on the type of waste, the radioelement composition varies. Environmental rehabilitation measures shall take these differences into account in order to prevent in the long term the radioactive contamination of agriculture soils and water resources, and to ensure adequate radiological protection to the public and to the environment.