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Department for Low and Medium Energy Physics (F-2)

National Laboratory for Dosimetry Standards

   The Laboratory for Dosimetry Standards was established at Jozef Stefan Institute in 1992 to offer a high quality metrological support to all institutions in Slovenia working with ionizing radiation, with measurements connected primarily to radiation protection of people and environment.

   The laboratory is authorized by the Ministry of Public Health of Slovenia for testing of radiation monitors under the law regulating radiation protection (Ur. l. SRS st.28/80). To comply with the requirements in the european standard EN 45001, preparations are under way for accreditation by the slovenian Standards and Metrology Institute for calibration of monitors for ionization quantities.

ACTIVITIES:

* Maintenance of the secondary standard for absorbed dose of ionizing radiation in the range of X and gamma rays. The standard is traceable to international standards: the secondary standard at the IAEA (International Agency for Atomic Energy) laboratory in Seibersdorf and primary standard at german PTB (Physikalisch Technische Bundesanstalt).
* Calibrations and testing of all kinds of dosimeters for:
- absorbed dose of ionizing radiation
- absorbed dose rate of ionizing radiation
They are divided by their use into personal dosimeters and survey meters or by technical construction into different types as Geiger-Mueller counters, semiconductor detectors, proportional counters, ionization chambers and termoluminiscent dosimeters.

MEASURING CONDITIONS AND RANGES:

   The calibrations are performed by the comparison of instrument reading with the conventional true value of absorbed dose, which has been calibrated with a secondary standard ionization chamber in the field of different radiation sources. Relative measurement uncertainty in the transfer of measured quantity is 3% at 95% confidence level. Ranges of the calibrated X and gamma sources are as follows:

source energy dose-rate *
60Co 1.25 MeV 1 mSv/h
137Cs 0.661 MeV 11 mSv/h
241Am 59.5 keV 0.3 mSv/h
X-rays ** 33 - 122 keV 40 mSv/h

  * Maximum dose-rates at 1m distance are indicated, lower dose-rates down to 4% of the maximum are achieved at all sources by increasing the distance from the source, and additional decrease at 60Co and 137Cs by combination of filters. The data hold for January 1997 and are changing due to the radioactive decay.

  ** X-ray generator is calibrated for six narrow spectrum qualities N40-N150 by ISO-4037 standard, the table indicates the range of effective energies.

EQUIPMENT:

* irradiation facilities:
- irradiators with radioactive sources 60Co, 137Cs and 241Am
- X-ray generator PANTAK HF 160C with maximum anode voltage 160kV
* measurement equipment:
- secondary standard* ionization chambers with 30, 1000 and 10000 cm3
- standard* electrometers
- accurate positioning system for the dose meters in the ionizing fields
- portable dose-rate meter Reuter-Stokes RS112 with high pressure argon ionization chamber

  * The standards are verified and calibrated at regular time intervals in accredited Slovenian or international laboratories.

IMORTANT DATA:

- J. Stefan Institute,
Jamova 39, 1000 Ljubljana, Slovenija
- +386 (0) 61 177-3900 (Operator)
fax: +386 (0)61 123-2120


Head of the Laboratory: Dr. Matjaz STUHEC
- direct calls: +386 (0)61 177 3841, 177 3651
e-mail: matjaz.stuhec@ijs.si

TEAM:

  1. Dr. Matjaz STUHEC
  2. Gorazd LAKOVIC, B. Sc.
  3. Matjaz MIHELIC, M. Sc.
  4. Marko GERL

Last update June 8, 1998; ms, dgc