Reload Index (ZRiChK UMCS)

STUDY ON RADON DETERMINATION IN THE BOGDANKA COAL MINE

Andrzej KOMOSA, Stanisław CHIBOWSKI

DEPARTMENT OF RADIOCHEMISTRY AND COLLOID CHEMISTRY

A source of radioactive gas – radon (222Rn) is a radium isotope from the uranium series. Radon decays by alpha emission with a half-life of 3.8 days producing the charged particles of short-living daughters. They attach rapidly to atmospheric aerosols and can enter respiratory tracts of human body. In 1998 inhabitants of Poland obtained an equivalent dose of 3.3 mSv. About a half of this dose come from radon and its decay products intake.The importance of radon monitoring is supported by the Directive of European Communities (from 1996) and is reflected in the Polish Atomic Law in force [1,2].

This study is concerned with radon determination in the underground part of Bogdanka Coal Mine. The mine is situated in central-east part of Lublin region, about 10 km away from the Łęczna town. Radon concentration was determined at the underground level of 960 m, where carrying gangways and various workshops were situated. The masurements were performed in places of the lowest airflow rate of ventilation. Two different methods were used: passive one (which allows to determine average gaseous radon concentration after 24 hours of exposition) and active one (to measure a momentary concentration of short-living radon progeny). The passive method included the Pico-Rad detectors (Niton, Canberra) and liquid scintillation for radioactivity measurement. Active measuring method relies on using the 4S-Radon-Thoron-Daughter-Concentration-Meter with an alpha radiation silicon detector and membrane filter for air aerosol collection.

Results obtained with Pico-Rad detectors showed a low concentration of radon in examined places (5.2–65 Bq/m3). Prolonged cyclic measurement of radon daughter concentration revealed also that average radon concentration (at the equilibrium factor 0.5) was equal to 123 Bq/m3 (arithmetic mean), 83 Bq/m3 (geometric mean), and 68 Bq/m3 (median). Such low concentration is the result of a good ventilation system in the underground galleries and a type of rock (clump). The values of radon concentration follow a log-normal distribution; thus geometric mean better describes the average value of radon radioactivity. There were two different distributions of the results in the range of 20–60 Bq/m3 and above 60 Bq/m3.

 The important information was obtained after gamma-spectrometric determination of a precipitate formed by underground water on the gallery wall surface. The concentration of 226Ra, the radon parent, found in the sample was small, reaching 20 Bq/kg, what is consisted with radon concentration measured.

References:

[1]   Directive 96/29 Euratom, Official Journal, European Communities, L 159 (1996).

[2]   Prawo Atomowe, ustawa z 29 listopada 2000, Dz.U. 2001 nr 3, poz.18.