The activating field of microtron bremsstrahlung is characterized by sharp recession of intensity in lateral and longitudinal
directions. Therefore, the irradiation of several samples simultaneously results in their different activation which is a
source of systematic error. Evaluation of correction coefficients needed for quantitative analysis by measurement of thin
copper disks placed between the samples does not result in acceptable data. For these purposes a method for 3D-activating
field monitoring and Monte-Carlo simulation for computation of the needed correction coefficients has been developed. The
monitor represents the copper foil wrapped round the sample assembly. The autoradiogram of the irradiated monitor is used
for characterization of the activating field. The Monte-Carlo simulation model involves both the field characteristics and
the results obtained while making single training analysis.