Dosimetry research

Research and development areas:

• Environmental and personal dosimetry(10^-6 Sv - 1 Sv)

• Accidental and reactor dosimetry (0.01 Gy - 10 kGy)

• Radiation processing dosimetry (1 Gy - 1 MGy)

• Investigation and characterization of new dosimeter materials

• Environmental and personal dosimetry (10^-6 Sv - 1 Sv)

The purpose is to develop methods to measure the dose of mixed low and high LET (alpha, electron, gamma and neutron) radiation fields by using passive thermoluminescent (TL) dosimetry systems with high sensitivity and/or LET selectivity in the following areas:

- monitoring of aircraft personnel (troposphere, 8-10 km) by using Polish LiF, (MTS-N) TL dosimeters.

- dose measurements in the stratosphere (10-60 km) by using Al₂O₃:C, CaSO₄:Tm, TL dosimeters.

- monitoring of spacecraft personnel (ionosphere, 200-250 km) by using various LiF (TLD-100, MTS-N, Austrian LiF-F) TL dosimeters. [M. Osvay and S. Deme, Radiation Protection Dosimetry 85, 469-72, 1999].

• Accidental and reactor dosimetry (0.01 Gy - 10 kGy)

The purpose is to measure absorbed dose at room- and high temperature (up to ~ 110 ^oC) and in difficult-to-access areas, such as the "hermetic" zone in nuclear power plants. The TL dosimeter used is the ceramic Al₂O₃:Y, Mg pellet developed at the Institute. The TL system has negligible neutron sensitivity up to 6 MeV neutron energy compared to gamma sensitivity and proper high temperature TL peak suitable for dose measurements up to about 110 ^oC in the dose range of 0.01 - 10 kGy. [M. Osvay and T. Bíró: Aluminium Oxide. In: Thermoluminescent Materials (Prentice Hall Inc. USA), 1993].

• Radiation processing dosimetry (1 Gy - 1 MGy)

Research and development of aqueous and organic liquid and solid phase systems for dosimetry measurements in electron and gamma radiation processing (i.e. for facility characterization, product and process validation as well as for routine dose control in radiation sterilization of medical products, polymer processing, food irradiation and at environmental technologies using ionizing radiation), in environmental monitoring, radiation protection dosimetry and in medicine.

Research and development of organic and inorganic dosimetry systems (dose range: 10 Gy - 300 kGy) and the corresponding analytical instrumentation (based on spectrophotometric, reflectometric, optically stimulated luminescence, conductometric and oscillometric evaluation).

Dosimetry methods developed and in routine use:

- ethanol-monochlorobenzene dosimeter solution (ISO/ASTM 51538), applicable in the 1 - 300 kGy dose range by using the non-destructive oscillometric evaluation method(applied in about 18 countries worldwide) [Horváth, Zs., Bányai, É., Földiák, G.: Radiochimica Acta, 13, 150-152, 1970; Kovács A., Miller A.: Use of ethanol-monochlorobenzene dosimeter at electron accelarators. Radiation Physics and Chemistry, 36, 709 - 712 (1990)].

- dosimetry characterization and development of fluorimetric and spectrophotometric evaluation methods for the LiF/PE Sunna dosimeter film developed at the Sunna Systems Co. (Richland, WA, USA) applicable in the dose range of 10 Gy - 300 kGy. [Kovács A., Baranyai M., Fuochi P.G., Lavalle M., Corda U., Miller S.D., Murphy M.K., O�Doherty J.: The application of Sunna dosimeter film for process control at industrial gamma- and electron beam irradiation facilities.: Radiation Physics and Chemistry, 71, 329 - 333 (2004)].

- tetrazolium based radiochromic films evaluated by spectrophotometry and reflectometry, applicable in the dose range of 1 - 100 kGy. [Kovács, A., Baranyai, M., Wojnárovits, L., Slezsák, I., McLaughlin, W.L., Miller, A., Moussa, A.: Radiat. Phys. Chem., 57, 711-716, 2000].

Other dosimetry systems in use:

Routine application of Fricke solution, Perspex (PMMA), FWT-60, B3, GafChromic, cellulose triacetate dosimetry systems and water, graphite and polystyrene calorimeters for dose mapping and routine dose control at ⁶⁰Co gamma irradiation facilities as well as at 2-10 MeV electron accelerators.

• Investigation and characterization of new dosimeter materials

Several new materials - Lithium tetraborate doped with different activators - were synthetized for future dosimetric applications. Optical absorption spectroscopy, steady-state and time-resolved photoluminescence spectroscopy, radioluminescence (RL) and thermoluminesce (TL) techniques are used for the characterization of the luminescence properties of these new materials. Dependence on the dopant concentration and on the crystalline structure (single crystal, polycrystalline, glassy) is also investigated as well as the effect of the irradiation with ionizing radiation of different doses. Dosimetric properties, mainly as TL detectors, of these materials are also investigated.

An original measuring method and system was elaborated for the characterization of the energy storing capabilities of the TL dosimeter or other luminescent materials. With performing consecutive RL and TL measurement we can determine the RL/TL ratio that can be modified by changing the activator concentration or by using special heat treatment.

Cooperations:

• Croatian Academy of Sciences
• Serbian Academy of Sciences
• Italian Research Council
• National Institute of Standards and Technology, USA
• Environmental Measurement Laboratory, USA
• NASA, USA
• Sunna Systems Co., USA
• Risø National Laboratory, Denmark
• Institute of Surface Chemistry of NASU, Kyiv, Ukraine
• International Atomic Energy Agency
• Scientific and Technological Co-operation Programme with Portugal, Turkey and Argentina

Fuente: Institute of Isotopes