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TLD Radiation Monitoring Network: Previous level TLD Radiation Monitoring Network - Overview

The network of thermoluminescent dosemeters (TLD network) (Figure 1) is one of the most important components of the Czech Radiation Monitoring Network (CRMN). It was started in 1989 to measure photon dose equivalent HX [µSv] in the environment on the republic's territory. Most of the measuring points have been placed outdoors where the dosemeters are exposed in free space geometry; however, some of them have also been installed in adjoining buildings with an intention to obtain information about the shielding effectiveness of inhabitants in case of a radiation accident. In case of a normal radiation situation a three months' monitoring period is used.

At present, there are 184 measuring points distributed on the territory of the Czech Republic forming territorial TLD network. In addition, 90 measuring points are distributed in the surroundings of two Czech nuclear power plants as local TLD networks. The National Radiation Protection Institute (NRPI) operates the territorial TLD network completely, and besides takes part in operation of the local TLD networks. The nuclear power plants operate the local TLD networks.

Figure 1: Territorial TLD Network

click to full size of picture

As for a dosimetric material, cards with three TLD elements of Al2O3:C of Rados production are used. The cards are put into aluminium containers to eliminate energy dependence of the TLD materials. Automatic TLD system Dosacus - Rados is used for measurement (figure 2).

Figure 2: Automatic TLD system Dosacus - Rados

System Dosacus

In case of a normal radiation situation, the measurement is done quarterly. Measured data are processed by special software. The output is mean value of photon dose equivalent rate HX [nSv/h] calculated for each monitoring point. The values of HX [nSv/h] usually don't exceed the range from 70 nSv/h to 270 nSv/h. These results correspond with values of natural radiation background in the environment of the Czech Republic. The limit of 500 nSv/h has never been exceeded.

Figure 3: Distribution of mean values of HX [nSv/h] measured on the territory
of the Czech Republic in the course of 2009

Distribution of mean values of Hx

Regions in the Czech Republic

Praha - Prague, STČ - Central Bohemia, JČ - South Bohemia, ZČ - West Bohemia,
SČ - North Bohemia, VČ - East Bohemia, JM - South Moravia, SM - North Moravia