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38
ST 1.1 –
Dosimetría interna
INTERNAL CONTAMINATION SCREENING WITH DOSE RATE METERS
Hunt, John*; Fonseca, Telma
IRD/CNEN, Brasil.
* Autor responsable, email: john@ird.gov.br
Assessing the intake of radionuclides after an accident in a nuclear power plant or after the
intentional release of radionuclides in public places allows dose calculations and triage actions
to be carried out for members of the public and for emergency response teams. High energy
gamma emitters in the lung, thyroid or the whole body may be detected and quantified by
making dose rate measurements at the surface of the internally contaminated person. In an
accident scenario, quick measurements made with readily available portable equipment are a
key factor for success. In this paper, the Monte Carlo program Visual Monte Carlo (VMC) is
used in conjunction with voxel phantoms to calculate the dose rate at the surface of a
contaminated person due to internally deposited radionuclides. A whole body contamination
with
137
Cs and a thyroid contamination with
131
I were simulated and the calibration factors in
µSv/h per kBq were calculated. The calculated calibration factors were compared with real data
obtained from the Goiania accident in the case of
137
Cs and the Chernobyl accident in terms of
the 131I. The successful comparison of the calculated and real measurements indicates that the
method may be applied to other radionuclides. Minimum detectable activities are discussed.