How to assess the sensitivity and related uncertainty of a new solid state passive thoron measuring device

To test the sensitivity of our CR-39 alpha-track detector thoron passive device (ATD-TnPD), a closed-circuit exposure facility, composed by a new thoron source, a small exposure chamber and a new absolute (220)Rn active monitor (TnM), was set up. (220)Rn exposure was evaluated by assessing the TnM response and its combined uncertainty. The ATD-TnPD's sensitivity was determined by three thoron exposures, tested at different etching times. A non-linear relationship on etching conditions was obtained, with values in the range 1.54-1.76 (tracks cm(2))(kBq h m(-3))(-1).