Project development Radioelement mapping

Radioelement mapping

Radioelement Mapping

General

  • Radioactive elements, both naturally occurring isotopes and anthropogenic products, cause particular public concern and their spatial distribution should, therefore, form part of a comprehensive geochemical database;

  • Gamma ray spectrometry enables the abundance of natural and human-made radioactive elements to be determined in a laboratory, in situ, or from a vehicle or aircraft;

  • An aircraft can provide a continuous quantitative profile of radioelement abundance over any type of land surface;

  • Flight-line spacing can be varied according to the sampling density required;

  • Airborne data may be used to provide an inter- and trans-continental Th reference datum to assist in levelling geochemical maps from geographically diverse regions;

  • Methodologies published by the International Atomic Energy Agency (IAEA) should be followed.

 

  Use of Existing Data 

  • Countries should make an inventory of all airborne and carborne gamma ray spectrometric surveys carried out since 1970;

  • If necessary, arrangements should be made through the IAEA to establish radiometric calibration facilities;

  • If necessary, a back-calibration exercise should be carried out to allow the preparation of quantitative maps;

  • For environmental health radiation monitoring purposes, a map of air dose rate (Gy s-1) or effective dose equivalent (mSv a-1), should be produced;

  • Where sufficient data are available, they should be used to prepare an appropriate grid, suitable for the production of a regional or national atlas and ultimately a radioelement map of the world.

 

Collection of New Data

  • Many past radiometric surveys were undertaken with inadequate equipment and insufficient quality control; at best, they were qualitative rather than quantitative; such data are unsatisfactory for baseline purposes;

  • In situ measurements with a field portable gamma ray spectrometer (GRS) should be made at each subsite in the primary 160 x 160 km reference grid wherever a regolith reference sample is collected;

  • Additional information can be obtained by using a portable GRS to obtain a continuous profile whilst in transit in a road vehicle between sample sites (i.e., a carborne survey);

  • Airborne Gamma Ray Spectrometry (AGRS) is the preferred method of obtaining comprehensive radioelement baseline data;

  • To complement the 160 x 160 km primary reference grid, flight-line spacing should be at 80 km, or 40 km or 20 km in populated or contaminated areas;

  • If funding permits, ground sample collection and AGRS may be undertaken as a single combined operation by using helicopter transportation along regularly spaced cross-country profiles;

  • A helicopter-mounted combined operation would provide the fastest way of obtaining comprehensive radiometric global geochemical coverage, at the same time facilitating the linkage of geochemical with aerogeophysical data.