Development of dosimetry for radon daughter decay products

The contribution of radon into the total human exposure from all the sources of ionizing radiation is a widely known fact. But what one ...

The contribution of radon into the total human exposure from all the sources of ionizing radiation is a widely known fact. But what one specifically should be aware of when planning and implementing radiation protection programs in Ukraine is so that at least the past two decades, the average individual dose from radon only are significantly higher than exposure from sources of Chornobyl origin. Whatever sedition it may sound, even in sadly memorable 1986 the collective dose to the population of Ukraine from radon and external natural radiation was higher than the collective dose from the Chornobyl disaster.

About a half of the average dose without exception from all the sources of ionizing radiation falls on radon including its daughter decay products (DDP), and for irradiation at home radon is the dominant source.

Nevertheless the paradox is in fact that though the radon DDP are considered a major source of human exposure, the exposure valuation is performed via gaseous radon. That is explained plainly by general practice of integrated passive measurement techniques use, which is based largely on solid state nuclear track detectors (SSNTD).

So according to modern ideas about formation of effective dose, the main contribution to human exposure is accounted for DDP of radon rather than for radon itself. Namely, the dose conversion coefficient (DCC) for 222Rn is 0.33, and for its DDP - 80 mSv·year-1·Bq-1·m3, i.e. the contribution of radon alone to the dose is very small (about 1%) as compared to its DDP.

It is explained by the difference between physical and chemical properties of radon (noble gas) and its DDP (non-gaseous), which leads to significant differences in mechanisms of penetration into the human body through various barriers as well as, that is most important, the dose forming patterns. Therefore, the study of these mechanisms and patterns for the radon DDP can directly allocate critical exposure factors and hence build an effective protection system.

Two publications below are actually dedicated to the aforementioned issues (these are a Ukrainian-English-Russian remake of two earlier publications now created on MediaWiki):
The following issues are highlighted and justified in these publications in detail:
  • alternative approaches to the calculation of the effective dose from radon and its DDP;
  • special units of radon DDP exposure;
  • physical dose factors, namely the distribution of aerosol DDP carriers in size, the ventilation effect, filtering ability of respirators;
  • requirements for radiation monitoring instrumentation;
  • principle of registration of nuclear radiation using solid state track detectors;
  • physical characteristics and limitations of the SSNTD alpha spectrometry.
Sources:

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