STUK supervises STUK supervises

STUK supervises

STUK supervises

Radon in underground mines and at excavation sites

Radon in underground mines and at excavation sites

The Radiation and Nuclear Safety Authority (STUK) regulates the radon concentration at workplaces. According to the Radiation Act (section 145), the responsible party shall notify the Radiation and Nuclear Safety Authority (STUK) of any mining as referred to in the Mining Act and any excavation work or other work carried out in a subterranean passageway or tunnel, in which a single worker’s combined working hours per year is more than 100 hours. The notification must be submitted in writing prior to the commencement of such practice.

The reference value for the radon concentration at the workplace is 300 becquerels per cubic metre in a space where people work for 600 hours or more per year. The reference value for occupational exposure to radon is 500,000 becquerel hours per cubic metre (Bq h/m3) per year. Exposure is calculated as the sum of the exposures in all work spaces during the year. The reference value for occupational exposure to radon is not applied if the worker only works in a space where the radon concentration is lower than the reference value for the radon concentration in indoor air at the workplace.

According to the STUK regulation, the radon concentration must be measured as follows:

  1. at underground excavation sites: every six months; however, if the result of two consecutive measurements is lower than 100 Bq/m3 at all measurement stations, the radon measurement interval can be extended to one year
  2. in underground mines: every other year; however, if the result of three consecutive measurements is lower than 100 Bq/mat all measurement stations, the radon measurement interval can be extended to five years.

In underground mines, at excavation sites and in tunnels, measurements are conducted:

  • ends where excavation is being carried out;
  • in underground maintenance facilities and break rooms used; and
  • other underground work sites that are constantly used.

Radon measurements are also conducted during post-excavation construction and finalisation work.

Often, it is not possible to conduct a radon measurement that lasts at least two months in underground mines and at excavation sites. Consequently, the radon concentration is often measured from air samples collected at the work site.

When the action level is exceeded, the radon concentration must be reduced as far as possible considering the circumstances. The most effective ways to reduce the radon concentration is to improve ventilation and to reduce the leakage of water.

With the exception of radiation safety, the safety of mines is supervised by the Finnish Safety and Chemicals Agency (Tukes).