The Slanic-Prahova (ROMANIA) underground low-background radiation laboratory.

A low-background radiation laboratory was constructed and fully commissioned in 2006 in the former Unirea (Slanic-Prahova) salt mine at 208 m below surface (estimated to 560 m water equivalent). Preliminary measurements showed a global reduction of the absorbed dose due to natural factors of about 39 times compared to level on the surface, reaching inside the mine 1.17+/-0.14 nGy/h. The total gamma background spectrum between 40 KeV and 3 MeV was 100 times smaller at laboratory level with respect to the same spectrum recorder at surface, in open field. All these experimental facts recommend the Slanic-Prahova low-background radiation laboratory, at present time fully operational, as very suitable for various measurements needing a low background.

Slanic-Prahova low background calibration facility.

The reduced background of 2 nSv h(-1) of the Slanic-Prahova Low Background Radiation Laboratory allowed installing a calibration stand for low-dose-rates dosimetry. The stand is provided with (60)Co, (137)Cs and (241)Am low activity sources. A Physikalisch-Technische Bundesanstalt-calibrated AUTOMESS 6150 AD-6 dose rate meter with a 6150 AD-b/H external probe was used to check to what extent this stand could serve as a low background calibration facility. A detailed analysis of possible uncertainties in measuring dose rates evidenced an extended uncertainty related to the certified calibration as well as instrument readings of about 3 % for a confidence level of 95 %. In these conditions, the experimentally determined dose rates for all three gamma ray sources and for source-to-probe distances varying between 0.3 and 2.0 m confirmed a good correlation between the calculated and measured dose rates. At the same time, dose rates perfectly obey to an inverse squared distances law.

Results obtained in the metrological certification of a commercially available radionuclide calibrator.

The paper presents the results obtained at IFIN-HH during a metrological certification of the commercially available radionuclide calibrator, the CURIEMENTOR2. Its performance was tested for the radionuclides: 57Co, 99mTc, 131I and 137Cs. The calibration factors determined by the manufacturer and those obtained at IFIN-HH differed by less than 3.5%. New calibration factors were determined for 60Co and 188Re, which have, until now, not been distributed by the manufacturer to the users. Furthermore, the linearity of instrument response and the dependence of measuring geometry were checked and found in accordance with the international accepted standards and legal requirements.

Low and high dose measurement by Agfa personal monitoring film and FD-III-B badge dosimeter system.

This paper presents the measurement of the dose equivalent Hp(10) to low (0.005-1) mSv and high (20-1000) mSv doses by exposure at (241)Am and (173)Cs radiation sources of the halide film with FB-III-D dosimeter system. Accuracy of measurements, standard error of the dose mean value (SEM) and some comments about ability to reread of dosimetric films were determined. A good accuracy was obtained over the important dose ranges. In the low dose range, under 0.1 mSv, the SEM values of the (241)Am doses, recorded on the film under plastic filter, are between -21.36% and +47.51%. For 0.1-500 mSv (137)Cs dose range the SEM values are from -9.55% to +7.24%.

External dose rate in Unirea salt mine, Slanic-Prahova, Romania.

The distribution of the external dose rate within the former Unirea salt mine, host of the Low-Level Background Laboratory was determined and compared with calculated values based on the experimentally determined content of natural radioactive elements in the mine walls. The average external dose rate was found to be 1.3+/-0.3 nSv h(-1), close to calculated one of 1.4+/-0.2 nSv h(-1).