Dependence of the dose estimate on the time pattern of intake by the example of tritiated water intakes

Titre du congrès : 6th Workshop on Internal Dosimetry of Radionuclides
Ville du congrès : Montpellier
Date du congrès :02/10/2006
Titre de la revue : Radiation Protection Dosimetry 127 issue 1-4 Pages : 387-391

The uncertainties related to activity measurement and time pattern of intake in routine monitoring of internal exposure are considered through the example of tritiated water intakes. For this purpose, a combination of intake-to-bioassay and bioassay-to-intake calculations with Monte Carlo integration technique is introduced as a method of investigation. The time pattern of intake and the measured activity are defined as random input quantities. The probability density functions (PDFs) of the input quantities are defined and a Monte Carlo integration is performed to obtain the PDF of the output quantity which is either the value of intake estimated from a measured value of activity or the estimated activity from a given value of intake. Different possible estimates of the intake are considered: some represent the parameters of the PDF of the output quantity, others are derived from the commonly used constant chronic, ICC, and mid-point, I1/2, methods. The combinations of activity and intake estimates that would provide a stable estimate of the initial intake in intake-to-bioassay and bioassay-to-intake calculations were studied. Several intake estimates satisfying this requirement can be chosen depending on the task to be solved by adjusting the proper activity estimate.