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FACULTY OF PHYSICS

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2026-06-11 23:58

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Conference: Bucharest University Faculty of Physics 2026 Meeting

Section: Nuclear and Elementary Particles Physics

Title:

Evolution of the radon concentration in the MicroBq laboratory from Unirea Mine, Slănic Prahova

Authors:

Alexandru-Nicolae BRĂGARIN (1,2), Ana-Maria BLEBEA-APOSTU (2), Claudia-Mariana GOMOIU (2), Bogdan CROITORU (2)

^*
Affiliation:

1) Faculty of Physics, University of Bucharest

2)Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering

E-mail

alexandru.bragarin@nipne.ro

Keywords:

radon concentration, AlphaGUARD, Unirea Salt Mine, MicroBq, underground laboratory

Abstract:

Radon is a noble gas produced in the decay chains of 238U, 235U, and 232Th, with a half-life of 3.82 days. Due to its radioactive nature and its proven link to lung cancer, radon represents an important environmental and occupational health concern, being the second leading cause of lung cancer after smoking. Monitoring radon levels is therefore essential, especially in underground environments where accumulation may occur. This study investigates the evolution of radon concentration in the MicroBq underground laboratory located in the Unirea Salt Mine, Slănic Prahova, Romania. The mine is excavated in a large salt deposit approximately 5 km long, 3 km wide, and 500 m thick, with the laboratory situated at a depth corresponding to more than 600 m water equivalent. The underground salt environment provides extremely low natural radioactivity and strong shielding against cosmic radiation, making the site suitable for ultra-low background radiation measurements. Radon concentration measurements were performed in the gamma spectrometry laboratory (Room D) using an AlphaGUARD D2000 radon monitor. The instrument recorded radon activity in air with a sampling cycle of 3600 seconds (one hour). Measurements were carried out during several monitoring campaigns: March–April 2018, May–December 2020, December 2022–May 2023, and July–October 2025. The results highlight the temporal variation of radon concentration within the underground laboratory and contribute to the characterization of the radiological environment of the MicroBq facility. Understanding radon behavior in this ultra-low background setting is essential for maintaining optimal experimental conditions for high-sensitivity nuclear radiation measurements and for ensuring accurate low-activity detection in environmental and biological samples.

References:

1.R. M. Margineanu et al,External dose rate in Unirea salt mine, Slanic-Prahova, Romania

2.R. M. Margineanu et al,The Slanic-Prahova (ROMANIA) underground low-background radiation laboratory

3.M. Calin et al, Radon levels assessment in some Northern Romanian salt mines

Acknowledgement:

This work was supported by the Romanian National Nucleus Programme, project PN 23 21 02 02, “Interdisciplinary applied research and development of new theoretical and experimental models dedicated to life and environmental physics studies”, carried out within the Department of Life and Environmental Physics , IFIN-HH.