Methods for the experimental study of 220Rn homogeneity in calibration chambers

Krasimir Mitev (1) , Philippe Cassette (2) , D. Pressyanov (3) , S. Georgiev (3) , Chavdar Dutsov (4) , Nathalie Michielsen (5) , Benoît Sabot (2)

1 St. Clement of Ohrid University at Sofia
2 LNHB (CEA, LIST) - Laboratoire National Henri Becquerel (CEA, LIST)
3 Université de Sofia
4 Sofia University "St. Kliment Ohridski"
5 IRSN/PSE-ENV/SEREN/BERAD - Bureau d'étude et d'expertise du radon

This work presents two experimental methods for the evaluation of 220Rn homogeneity in calibration chambers. The first method is based on LSC of the 220Rn decay products captured in silica aerogel. The second method is based on application of solid state nuclear track detectors facing the air of the calibration chambers. The performances of the two methods are evaluated by dedicated experiments. The repeatability of the method, estimated as relative standard deviation of the LSC measurements of ten silica aerogel samplers exposed under the same conditions is found to be 1.6%. Both methods are applied to study thoron homogeneity in a 50 L empty AlphaGuard emanation and calibration container with its fan turned on, and it was found that the 220Rn distribution is homogeneous within 10%. Both methods are also applied to test the thoron homogeneity in the BACCARA chamber at IRSN during a thoron calibration exercise. The results show that, at the centre of the chamber where the inputs of the sampling systems of the instruments were put close to each other, the thoron inhomogeneity is less than 10%. However, regions of higher thoron concentrations are clearly identified near the walls and the upper part of the chamber, with 220Rn concentrations being up to 60% higher compared to the concentration at the reference point. These results highlight the importance of the control and assessment of thoron homogeneity in thoron calibrations and in the cases when radon monitors are checked for thoron influence.

Mots clés: Thoron (220Rn); Thoron calibration; Thoron homogeneity; LSC; nuclear track detectors; nuclear instrumentation; instrumentation; radioactivity; ionizing radiation; calibration; detector; Decay data measurement

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Physique Nucléaire Expérimentale [nucl-ex]

Krasimir Mitev, Philippe Cassette, D. Pressyanov, S. Georgiev, Chavdar Dutsov, et al.. Methods for the experimental study of 220Rn homogeneity in calibration chambers. Applied Radiation and Isotopes, 2020, 165, pp.109259. ⟨10.1016/j.apradiso.2020.109259⟩. ⟨hal-02928806⟩