Unattached Fraction of Radon Decay Products as a Crucial Parameter for Radon Dosimetry in Postojna Cave

Janja Vaupotič, Ivan Kobal

DOI: https://doi.org/10.3986/ac.v33i1.317

Abstract

V letih od 1998 do 2001 smo v zraku Postojnske jame na najnižji točki merili koncentracijo radona (CRn) in radonovih kratkoživih razpadnih produktov (CRnDP), ravnotežni faktor (F), delež nevezanih radonovih razpadnih produktov (fun), zračni tlak (P), relativno vlažnost zraka v jami (RH) in temperaturo zraka v jami (Tin) ter zunaj (Tout). Poseben poudarek je bil na fun in na njegovi odvisnosti od vremenskih razmer. Vrednosti fun so bile v širokem razponu, od 0,10 do 0,68. Z uporabo novega dozimetrijskega modela smo na osnovi izmerjenih vrednosti fun izračunali dozne pretvorbene faktorje in ugotovili, da so bili znatno višji od 5 mSv/WLM, to je vrednosti, ki jo priporoča metodologija ICRP-65. Tako so dejanske doze, ki jih prejmejo jamski vodiči, v povprečju za faktor 8 poleti in za faktor 2,7 pozimi višje od vrednosti, ki jih dobimo po dosedanji metodologiji ICRP-65.

Short-term summer and winter monitoring was carried out at the lowest point in Postojna cave, on air concentrations on radon (CRn) and radon decay products (CRnDP), the equilibrium factor (F) and unattached fraction of radon decay products (f un ), barometric pressure (P), relative air humidity in the cave (RH) and air temperature outside (T out ) and in the cave (T in ), with the emphasis on f un . Dose conversion factors (DCF) for mouth and nasal breathing were calculated from the f un values (ranging from 0.10 to 0.68) and effective doses for the employees in the cave were obtained. These signifi cantly exceed the doses based on the ICRP-65 methodology now in use.

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DOI: https://doi.org/10.3986/ac.v33i1.317

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