Internal dosimetry

Introduction

The assessment of doses from internal contaminations requires monitoring by direct or indirect measurements.

  • Direct measurements consist of the measurement of retained activity in the body by gamma-ray spectrometry.
  • Indirect measurements evaluate the activity present in urinary or fecal excretion.

The results of these measurements, retained or excreted activity, can be related to the intake taking into account the time of intake and the retention/excretion functions published by ICRP. Knowing the intake, the committed effective dose (the effective dose that will be delivered to the body over the next 50 years) can be calculated taking into account the biokinetic model of the considered radionuclide.

Main activities

Our research mainly focusses on the improvement of the efficiency for direct measurements by the use of computational phantoms for calibration.

  1. First objective is the optimization of the measurement geometry to obtain the best possible efficiency.
  2. Secondly, by calculating person specific calibration curves for Whole Body, Lung or Thyroid counting uncertainties on measured activities can be lowered.

Besides this research we also do efforts to extend our measurement capacity for incident monitoring. In the case of incidents where a large number of persons is involved, it will be necessary to monitor people on a more convenient location than at the laboratories of SCK•CEN. Therefore, and to account for the small number of dedicated measurement setups readily available in the country, efforts are being done to investigate the possibility to use measurement equipment that is originally not meant to be used for internal contamination monitoring.

Other work comprises the study of monitoring methods and dose assessment for workers handling Ac-227 samples. Also SCK•CEN is involved in a project to study health effects of uranium workers in Europe.

Applications

The use of Monte Carlo code to simulate in vivo measurement geometries offers a wide range of applications. Besides the possibility to calculate person specific calibrations, it also provides a tool to calculate relatively fast the efficiency for any non standard measurement geometry for example the measurement of an organ or a distribution of activity in the body.

Hopefully our mobile equipment for emergency situation will never need an application but preparedness is essential to be able to respond adequately to any incident or accident where internal contamination of a large number of persons can not be excluded. These instruments can be used for triage to reassure not-contaminated persons and to indicate which individuals need to be followed up. As such these measurements will help to evaluate the possible health consequences of an accident.

Projects

  • The laboratory is involved in the European Radiation Dosimetry Group EURADOS within WG7 for internal dosimetry research.
  • A physical modular phantom for WBC was developed and manufactured.
  • A library of female and male computational phantoms was developed for calibration of WBC setups of SCK•CEN and the KC Doel power plant.
  • A library of realistic female torso phantoms containing internal organs was developed for the calibration of lung actinides measurement setup.
  • A wide range of nuclear measurement equipment was evaluated and calibrated to be used as thyroid monitor in case of emergency monitoring.

Contact

Anne Laure Lebacq, Filip Vanhavere

dosimetry@sckcen.be