The measurement performances of in vivo monitoring vehicles were studied
considering an increase in the radiological background in areas where the population is
not evacuated after a nuclear accident. The study focused on 137Cs and 131I Detection Limits (DLs) and
corresponding doses, for adults and one-year-old children. These DLs for ground
contamination were obtained experimentally using a grid of point sources. Then, the DLs
and doses were calculated using the experimental data and a safety factor for two accident
scenarios. For these scenarios the 137Cs DL corresponds to a committed effective dose of
0.02 mSv. The 131I
DL corresponds to committed equivalent thyroid doses of 3 mSv (adult) and 30 mSv
(one-year-old child). To guarantee a 45 mSv thyroid equivalent dose assessment for the
child the surface activity of 131I +
132I +
133I should be below 1.6 MBq/m2. This study shows that the
vehicles can operate in a contaminated area where the population is not evacuated.
However, in such a case, the contamination level outside and inside the vehicle should be
kept stable to guarantee efficient body counting.