Quantification of 37Ar emanation fractions from irradiated natural rock samples and field applications.

Musy, S; Casolaro, P; Dellepiane, G; Berger, A; Braccini, S; Purtschert, R (2022). Quantification of 37Ar emanation fractions from irradiated natural rock samples and field applications. Journal of environmental radioactivity, 251-252, p. 106966. Elsevier 10.1016/j.jenvrad.2022.106966

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Underground-produced 37Ar can be used for underground nuclear explosions (UNE) detection and for groundwater dating. The quantification of the emanation, that is the fraction of activity produced in the rock that escapes to the pore space, is essential for predicting the background activity expected in natural environments. We propose an experiment in which artificial CaCO3 powder and natural rock particles are irradiated with neutrons in a routinely operated medical cyclotron, whose energy spectrum is experimentally measured. The produced activity was quantified and compared with the emanated activity to determine the emanating fraction. The results showed consistent and reproducible patterns with a dominance of the recoil process at small scales (<2 mm). We observed emanation values ≤1% with a dependency on the grain size and the inner geometry of particles. Soil weathering and the presence of water increased the recoil emanation. The atoms produced that were instantaneously recoiled in the intra- or inter-granular pore space left macroscopic samples by diffusion on timescales of days to weeks (Deff = 10-12 - 10-16 m2 s-1). This diffusive transport determines the activity that prevails in the fluid-filled pore space accessible for groundwater or soil gas sampling.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)
08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP)
08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Musy, Stéphanie Lisa; Casolaro, Pierluigi; Dellepiane, Gaia; Berger, Alfons; Braccini, Saverio and Purtschert, Roland

Subjects:

500 Science > 530 Physics
500 Science > 550 Earth sciences & geology

ISSN:

0265-931X

Publisher:

Elsevier

Language:

English

Submitter:

Pubmed Import

Date Deposited:

12 Aug 2022 08:27

Last Modified:

05 Dec 2022 16:22

Publisher DOI:

10.1016/j.jenvrad.2022.106966

PubMed ID:

35939879

Uncontrolled Keywords:

(37)Ar CTBT Emanation fraction Irradiated rocks Medical cyclotron Neutron activation

BORIS DOI:

10.48350/171808

URI:

https://boris.unibe.ch/id/eprint/171808

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