https://doi.org/10.1140/epjs/s11734-025-01755-0
Regular Article
A remarkable small local natural radiation anomaly in Poços de Caldas, Brazil
1
, Vienna, Austria
2
Graduate School of Health Sciences, Hirosaki University, Hirosaki, Japan
3
CNEN / LAPOC, Poços de Caldas, MG, Brazil
4
UNIFAL-MG, Poços de Caldas, MG, Brazil
5
IFSULDEMINAS, Poços de Caldas, MG, Brazil
6
CNEN/CDTN, Belo Horizonte, MG, Brazil
7
Center of Applied Geosciences/Geological Survey of Brazil, Rio de Janeiro, RJ, Brazil
8
INCA, Rio de Janeiro, RJ, Brazil
9
SÚRO, Prague, Czech Republic
Received:
28
September
2024
Accepted:
16
June
2025
Published online:
8
July
2025
Natural radiological anomalies occur in nature as a result of geological and geochemical variability. They can indicate mineral resources, but can also represent a hazard. In this contribution, we report results of the radiometric investigation of a small but intense radiation anomaly that was detected in the course of a regional survey of ambient dose rate in the outskirts of the city of Poços Caldas, Minas Gerais, Brazil, and discuss its radiological significance. The anomaly is only a few meters large and boasts a dose rate up to 
5 µSv/h above the local background values, typically 0.1 µSv/h. As part of a workshop organized by the International Atomic Energy Agency (IAEA), a field measurement exercise was performed at the location, aimed at training participants and conducting a closer investigation of the anomaly. The overall result is that most likely the spot is due to the circulation of a hydrothermal fluid on the fracture system intruding uranium-bearing phases (not determined at this moment) within an otherwise radiologically unsuspecting sedimentary rock. The extension of the anomaly could be delineated to be less than about 5 m, with local soil radon concentration in the order of some MBq/m3. We report the data of the detailed evaluation and show maps of the anomaly. The appropriateness of the chosen measurement methods for the purpose is addressed. We also discuss possible consequences of such findings regarding radioprotection and their suitability for training under field conditions.
P. Bossew Retired
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
