Radon concentration variations at the Yangyang underground laboratory

TL;DR

This study measures radon levels over 18 years in an underground lab, revealing seasonal variations linked to external temperature and ventilation, with implications for underground experiments.

Contribution

It provides long-term radon concentration data and identifies seasonal patterns influenced by surface temperature, improving understanding of underground radon dynamics.

Findings

Average radon levels: 53.4 and 33.5 Bq/m3 in two areas

Radon levels correlate with external temperature (r=0.22 and 0.70)

Peak radon concentration occurs annually around August 31

Abstract

The concentration of radon in the air has been measured in the 700 m-deep Yangyang underground laboratory between October 2004 and May 2022. The average concentrations in two experimental areas, called A6 and A5, were measured to be 53.4$\pm$0.2 Bq/m3 and 33.5$\pm$0.1 Bq/m3, respectively. The lower value in the A5 area reflects the presence of better temperature control and ventilation. The radon concentrations sampled within the two A5 experimental rooms' air are found to be correlated to the local surface temperature outside of the rooms, with correlation coefficients r = 0.22 and r = 0.70. Therefore, the radon concentrations display a seasonal variation, because the local temperature driven by the overground season influences air ventilation in the experimental areas. A fit on the annual residual concentrations finds that the amplitude occurs each year on August, 31$\pm$6 days.