Abstract
In the present study, 222Rn activity concentrations in a newly formed underground tourist route under Książ castle, Poland, were investigated for periods undisturbed and disturbed by construction works. This preliminary assessment is based on the almost 3-year long continuous measurements (28 Oct. 2016–02 Jul. 2019) done with an SRDN-3 instrument. In detail described are radon concentrations for periods of renovation (11 Aug. 2018–10 Oct. 2018), opening (15 Oct. 2018–10 Apr. 2019) and operation and monitoring (11 Apr. 2019–02 Jul. 2019) of the facility. It was observed that after the termination of construction work, when natural ventilation returned to the state preceding this work, the absolute values of radon activity concentration decreased. The mean annual radon concentrations were higher than the reference level of radon concentration in underground spaces recommended by IAEA, ICRP, and by the EU Council Directive for workplaces. They reached 1179 Bq/m3 and 943 Bq/m3 in 2017 and 2018, respectively. Cyclically recurring daily changes in radon concentrations occurred only in April and October (so-called transitional periods) and only outside the period of construction work. The results confirmed; however, that these changes need not be considered when planning the work in the tunnel. The minimum effective dose rate from radon exposure occurs in colder periods of the year, from November to the end of March, where the mean effective dose rate value was found to be 0.0003 mSv/h. In contrast, the maximum dose rate of 0.014 mSv/h was observed from April to August.
Highlights
In Poland, like in other countries, the increased ionising radiation in underground spaces is related to the accumulation of radon—a radioactive gas
In the context of the present study, seasonal changes in 222Rn activity concentration occurred throughout all measurement periods, but their course was varied in years disturbed (2018) and undisturbed (2017) by construction works, respectively (Figs. 4 and 5)
At the first stage of tourist route creation (11 August 2018 to 14 October 2018), the course of changes in 222Rn activity concentration was largely influenced by a change in the intensity and volume of the air stream flowing through the underground complex
Summary
In Poland, like in other countries, the increased ionising radiation in underground spaces is related to the accumulation of radon—a radioactive gas Existing and newly opened underground facilities of various types and functions are becoming workplaces for a growing number of people These sites are very often restored historic sites (including technological or military heritage sites like underground fortresses, tunnels, shelters, pyramids, tombs, castles, wineries) where underground tourist routes are organized. More and more people— mainly service staff and guides, sometimes speleologists or researchers—are working in conditions of increased exposure to ionising radiation from radon (mainly from the radioisotope 222Rn) and its, radioactive, progeny
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