Comparison Study of in-vivo and in-vitro Techniques for the Assessment of Internal Exposures of Actinides

In-vivo measurements of actinides are carried out in the CIEMAT Whole Body Counting facility, using a Low Energy germanium detection system (LE Ge) to evaluate the Activity of Am in lungs and skeleton. The sensitivity of the LE Ge detection system in the assessment of the Americium retained in the body is associated to the Minimum Detectable Activity (MDA) estimated in the different available in-vivo counting geometries (lung, skull, knee); inherent difficulties found and solved in these estimations will be discussed. An appropriate QA (Quality Assurance) methodology is applied to guarantee the good performance and sensitivity of the LE Ge system in routine monitoring. Alpha Spectrometry is the most widely used technique for measurement of activity in excreta samples for monitoring of occupational exposure to actinides. The in-vitro Bioassay Laboratory of CIEMAT has been participating in intercomparison exercises since 1998. The results obtained represent the validation of the radiochemical separation methods and the measurement techniques. On the other hand, a study on the MDA reached in routine measurement of actinides is also discussed. In the case of excreta samples, this study is carried out in urine samples corresponding to the monitoring of personnel involved in the decommissioning of a nuclear power plant in Spain. The sensitivity and applications of in-vivo and in-vitro techniques in case of internal exposures of actinides are compared, especially in the case of occupational inhalation of Am The aim of this comparison study is to provide adequate occupational monitoring programmes. These programmes are established in the perspective of the application of ICRP78 recommendations and fulfilling the Spanish Regulations.