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Exposed Workers Dose Measurement

Measurement of personal doses of exposed workers by thermoluminescence method is accredited by the Estonian Accreditation Centre according to the requirements of EN ISO/IEC 17025:2005 since year 2005 (certificate number L175).

Personal doses of exposed workers are measured using thermoluminescent dosemeters (TLD) with LiF detectors.

Personal dosemeter does not emit light or does not protect against ionizing radiation.

Environmental Board Radiation Safety Department uses whole body dosemeters and finger-ring dosemeters.

Thermoluminescence dosimetry method is based on the property of some inorganic materials with additives (LiF, CaF2, Al2O3) to luminescent after irradiation with ionizing radiation and heating. The amount of luminescence is proportional to the original dose of beta and gamma radiation received. On the basis of intensity of luminescence the personal dose equivalent Hp(d) is calculated, which provides an opportunity to assess the effective dose received by the exposed worker.

Hp(d) is the dose equivalent in soft tissue below a specified point on the body at an appropriate depth d. Depths of d=10 mm for strongly penetrating radiation and d=0,07 mm for weakly penetrating radiation are recommended by the ICRP (International Commission on Radiological Protection).

For personal dose measurement of exposed workers Environmental Board, Radiation Safety Department uses thermoluminestcent dosemeters (TLD) with LiF detectors and RADOS TLD measuring system:
area of measurement: beta- and gamma radiation;
  * value of measurement - personal dose equivalent;
  * unit of measurement - mSv (millisievert);
  * range of measurement - 0,01 mSv -10 Sv;
  * energy scale: 30 keV - 2 MeV;
  * minimum detectable level - 0,01 mSv.

Personal monitoring of exposed A category workers shall be systematic. Monitoring of exposed B category workers shall be sufficient to demonstrante that such workers are correctly classified under category B.

Contract on measurement of personal dosemeters
Personal dose monitoring is performed by indefinite contract between the Environmental Board, Radiation Safety Department and the holder of a radiation practice license.
1. The holder of a radiation practice license should fill out an application form ( .odt (15.99 KB, ODT), .doc (20.5 KB, DOC), .pdf (68.45 KB, PDF); NB! All the forms are in Estonian) and send it to the Environmental Board, Radiation Safety Department by e-mail or by mail.
2. Environmental Board, Radiation Safety Department will send the contract for signing as indicated in the application. The contract will be signed by the company's legal representative.
3. Personal dosemeters are issued to the holder of a radiation practice license (to the representative of company or by mail) in accordance with the list of exposed workers. Liabilities of the parties on personal dosemeters issue, use and return are given in appropriate guide (66.35 KB, PDF).
4. The price for the measurement of personal dosemeter is 13 Euros.
5. For the lost and/or broken personal dosemeters contractual penalties apply:
  * lost TLD - 63,91 Euros for 1 piece;
  * missing or damaged dosemeter detector- 9,59 Euros for 1 piece;
  * unfit for use dosemeter- 35,15 Euros for 1 piece;
  * dosemeter covers in unfit technical condition- 7,67 Euros for 1 piece.

Application for changes in the list of exposed workers
To make changes in the list of exposed workers the holder of a radiation practice license shall submit a written application to the Environmental Board, Radiation Safety Department by e-mail or by mail. The holder of a radiation practice license is required to inform the Radiation Safety Department of any changes in the terms of the contract (eg., replacement of a contact person or changes in the contact data of the company).

Notification about the lost personal dosemeter
In the case of loss of the TLD the holder of a radiation practice license shall inform Environmental Board, Radiation Safety Department by written application (.odt, (20.23 KB, ODT) .doc (33 KB, DOC), .pdf (131.7 KB, PDF); NB! All the forms are in Estonian).

In the case of loss of the TLD the holder of a radiation practice license shall estimate the dose value received during the period of measurement and shall ensure the provision of these data. The dose value estimation should be based on the exposed worker's results of previous dose monitoring or on the doses of co-workers or on approved calculation methods.

Estimated dose data should be provided for entering into the State Dose Registry of Exposed Workers.


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