In the Laboratory of Nuclear Spectroscopy several analysis methods using ionizing radiation for environmental studies are developed. By using high-resolution spectrometric and radiometric methods the following topics are developed and studied:
The main research is based on the application of high resolution spectrometric methods of low-background HPGe gamma spectrometry, gamma-induced X-ray emission spectrometry and Mössbauer spectrometry. As additional supporting tools both laboratory and in-situ radiometric and dosimetric measurements, radon and area gamma monitoring are used.
The basic equipment is of a modern Western production (1-7 years old). In the analytical practice contemporary methods and calibration standards are used. The analysis methods were successfully tested in several international intercalibration exercises in 1994-1997. In Estonia most of the present facilities and methods are unique. The equipment is used both for research and for teaching/practicing of students.
The significant support from the Swedish Radiation Protection Institute (SSI), Icelandic Radiation Protection Institute, Finnish Centre of Nuclear and Radiation Safety (STUK) and STUDSVIK AB (Sweden) is gratefully acknowledged.
A low-background coaxial HPGe detector GEM-35200 (p-type, with an efficiency of 42 % and a FWHM of 1.7 keV at 1.3 MeV) in a special low-background LN2 cryostat and a 10 cm Pb + 0.2 cm Cu housing ensure a low background count-rate and low LLD values for radionuclide analysis. Gamma spectra in the range of energies from 40 to 3000 keV are recorded using a 16K multichannel buffer 92x SPECTRUM MASTER equipped with an on-line PC. Spectrum analysis is performed using several specific software packages (MAESTRO-WIN, GANAAS (IAEA), GAMMA_WIN (STUK), etc.). The calibration of efficiency and energy scale is performed using the IAEA/RG-SET certified reference materials and a MULTIGAMMA standard. According to its parameters this spectrometer is the best of its kind in Estonia.
A HPGe planar detector BDRG-32 of 800 mm2 selective area and FWHM of 0.6 keV (at 122 keV) in a 15 cm Fe + 10 cm Pb + 0.2 cm Cu shield is used for the analysis of low-energy gamma emitting radionuclides (210Pb, 234Th/238U, 239Pu, 241Am) in the energy range of 5 .. 300 keV. The NIM-type power supply and amplifier with a 4096 channel ORTEC-ACE-4K MCA computer-card buffer and an on-line PC are used to record the spectra.
The spectrometer consists of a basic scintillation module BDBS3-1eM with a set of various scintillators (NaI(Tl), incl. a well-type Ø 63 x 63 mm3 and a large-volume Ø 200 x 120 mm3 versions, CsI(Tl), stilbene, plastic etc.), of a 5 cm lead shield, NIM modules and a CMCA-2000 MCA with an on-line PC. Moderate resolution (10 .. 17 %) spectra are recorded with a high efficiency. It is a simple and inexpensive apparatus for the preliminary analysis using various kinds of ionizing radiation.
A universal Mössbauer spectrometer used for the analysis and study of gamma resonant 57Fe, 119Sn, 151Eu containing solids, incl. environmental samples. Parameters: digital reference generator for Doppler velocities in the range of 0 .. 300 mm/s with a preset frequency of 1 .. 100 Hz; velocity calibration using a HeNe laser-interferometer with an accuracy of ± 0.05 %, a fast Kr-filled proportional counter, 3 x (256 4096) channel MCA CMCA-2000 with a RS232 computer interface and an on-line PC for spectrum storage and analysis; software packages SIRIUS and NORMOS; LHe cryostat MD526 (OXFORD INSTRUMENTS, USA) for sample temperature range of 4 .. 350 K. At present Mössbauer sources 57Co(Rh) ja 151SmF3 are available. It is the only modern Mössbauer spectrometer in Estonia.
Automatic continuous monitor for beta and gamma background dose rate with 9 preset alarm levels, a built-in 864 memory register, on-line PC, automatic self-check and UPS-backed power supply. The monitor has been continuously in operation from 1992.
Measurement of radon concentration in air and in soil in the range from 1 106 Bq/m3 using electrostatic deposition of radon progeny 218Po ja 214Po with high resolution -ray spectrometry. The monitor has an internal pump, printer, RS232 output and can also be used for long-term radon monitoring, for radon leak detection or for the determination of emanation coefficients of materials. Either 218Po-based "fast" or 218Po + 214Po-based "slow" recording options are selectable. Measurement intervals can be preselected within 5 min up to 24 h. Calibrated in the Radon Chamber of the Swedish Radiation Protection Institute.
A simple counter with a NaI(Tl) scintillation detector for an express analysis of the concentration of 137Cs in food, grain, etc. Specific activities from 10 Bq/kg can be measured.
An active-shielded detector with a large sensitive area and a
multichannel (256 channels) counter for analysis of -emitting
radionuclides (e.g., 90Sr, 137Cs ) with
a LLD of 1 Bq. A built-in microprocessor calculates the results
using user-defined methods for background stripping, for efficiency
compensation, etc. and displays the results both numerically and
graphically on a LCD screen.
A sensitive fast (< 3 s) dose-rate meter for and radiation exposure in the range 0.01 Sv/h 10 mSv/h with a large energy-compensated plastic scintillation detector.
A portable and ray dosimeter with a microprocessor (32 kB of program memory and 8 kB of data memory) and a 1000 channel memory for the dose-rate range of 0,05 Sv/h 10 Sv/h and dose range of 0.1Sv 10 Sv.
A sensitive hand-held counter with a programmable microprocessor (48 kB of program and 8 kB of data memory, 2 x 512 EEPROM) and with a large area (21 x 11 cm2) Xe proportional counter for and ray detection.
A light-weight pump (25 L/h) with both aerosol and carbon filter for air sampling and for radioactive pollution assessment.