Autoradiography

Uraniferous concretion showing internal colour-banding from the Permian Littleham Mudstone Formation, south Devon
Digital autoradiograph recorded from a similar nodule showing the distribution of radioactivity from bands of uranium mineralization

The BGS has over 40 years of experience in the use of autoradiography to evaluate and quantify the distribution of radioactivity and understand the behaviour of radioactive elements in geological and environmental materials.

Originally this involved conventional plastic detector methods (CR-39 for alpha autoradiography, and LEXAN for U235 fission-track registration), in which damage induced in the polymer material by bombardment with radioactive particles is chemically etched to reveal the particle tracks. Photographic methods can also be used for ? and ? autoradiography. These techniques are still available but the facility now routinely uses modern digital autoradiography employing Eu-doped BaFBr storage phosphor imaging plate (IP) technology.

The IP cumulatively detects α-, β- and γ-radiation (as well as background cosmic radiation) by storing the energy imparted from energetic particles or ionising radiation within an excited state of the phosphor's crystal lattice. This energy is released as light when the phosphor is irradiated with laser light (photostimulated luminescence or PSL). The PSL signal released is proportional to the amount and energy of the incident ionising radiation and provides sensitive, quantitative and flexible analysis with very rapid recording times (typically <1 hour to 5 days, depending on sample activity), compared to conventional techniques (typically requiring exposure times of months).

Autoradiography analyses can be undertaken on a wide variety of geological and environmental samples and sample formats, including flat cut rock and concrete surfaces, soils, unconsolidated sediments, core walls, fracture surfaces and polished (uncovered) petrographic thin sections. In addition, the system allows direct "whole core surface" imaging of the curved cylindrical surfaces of core samples.

Autoradiography and fission-track registration analysis are integrated with high-resolution petrographical and microchemical analysis in order to identify specific radioactive elements and their host minerals and chemical phases.

Equipment

  • GE Amersham BioSciences STORM 860 digital autoradiography and laser-stimulated fluorescence scanner, with capability for red (635 nm) and blue (450 nm) fluorescence excitation imaging.
  • General purpose (polyurethane-coated) Eu-doped BaFBr Storage Phosphor Imaging Plates in 23 x 25 cm and 35 x 43 cm size formats for use with digital autoradiography for the general purpose detection, analysis and imaging of ?-, ?- and ?-radiation.
  • Uncoated ("Tritium") Eu-doped BaFBr Storage Phosphor Imaging Plates with 20 x 25 cm format for use with digital autoradiography for detection, analysis and imaging of ?- and low-energy ?-radiation (e.g. tritium).
  • GE Amersham Biosciences ImageQuantTL (v2005) digital image processing and analysis software package.

Applications

  • Evaluation of the distribution of anthropogenic radioactivity and radionuclide contamination in rocks and soils from radioactively-contaminated areas at nuclear licensed sites.
  • Natural analogue studies of radionuclide migration in the geosphere for the radioactive waste management research.
  • Distribution of natural radioactivity in geological samples.

Staff and facilities are also in constant demand for direct consultancy analysis and interpretation by external clients including: radioactive waste management companies and university departments.

Contact

Please contact Antoni Milodowski for further information