Radioactivity and ionizing radiation is all around us. We are irradiated by cosmic radiation, by radionuclides from soil, also our body contains radionuclides (mainly it's kalium). Although these sources have been irradiating us since the beginning of human being, there is an endeavour to reduce irradiation (because of its negative effects like malign tumours and genetic damages).
Radon is responsible for about 50% of total irradiation of population.
Radon is radioactive gas, which arises by uranium decay. Uranium is contained
in soil since Earth rise, radon gets from the soil to the atmosphere.
In the open area there is a low concentration of radon, so it's not necessary
to be affraid of it. Situation is worse in buildings with insufficient
ground isolation, where the radon can be accumulated. Breathing radon
and his decay products causes higher probability of lung cancer rise
(something like smoking). This was verified by lot of epidemiological
studies. There are estimates, that inhalation of radon causes in CR about
900 new disorders by lung cancer per year. This is caused by insufficient
isolation of buildings.
It is estimated, that there are about 60 000 buildings with higher radon
concentration in CR. 16 000 of these buildings have been found by
nation-wide investigation. This investigation is financed by state.
In buildings with higher radon concentration it's suitable to do
detailed radon prospection. Aim is to detect main sources and radon
entries in the building. Results of this prospection are used by designer to propose
effective anti-radon measures. Nowadays, about 2000 houses and 200 school
buildings have been repaired. Radon concentration have been decreased in more
then 260 water suppliers (water is one of the way how radon gets into
the building).
How is there ensured not to build new buildings with high radon concentration?
This problem is solved by law No. 18/1997 ("nuclear law"). Before building
works start, the radon investigation on building
site have to be done. On the basis of measured
values proposes designer suitable ground isolation according to
ÈSN 73 0601 "Building protection against penetrating radon from soil".
Quality of realized isolation is verified by radon measurement in completed
building. One of the possible source of radon in building is a building
material, so producers have to do control measurement and to give
results to State office for nuclear safety (SUJB). Nowadays it's practically
impossible to buy high radioactive building material in the shop. That's not valid
in the case you make your own materials and use non-measured materials like
dross or ash. Water suppliers also have to check periodically radionuclides concentration
in supplied water, in the case of exceeding limits they have
to adopt a measure leading to decrease amount of radionuclides. It is recommended
to do the measurements also in the case of individual wells.
These measures ensure not to build new buildings with high amount of radon
and to keep amount of radon and other radionuclides in supplied water in norm.
Accepting of regulations is ensured by inspectors of SUJB and workers of
surveyor's offices.
Nuclear law and regulation also ensure not to introduce other radionuclides
into environment (not only radon and natural radionuclides). For example
there's going on discarded sources of radiation used in industry and in
medicine which must be liquidated according to law. But sometimes the
source of radiation gets into the scrap iron and deteriorates it. So it's
necessary for heads of smelting works to check radioactivity of incoming
scrap iron and meltage. The majority of customers requires document which
proves that amount of radionuclides in supplied materials is in norm.
In the case of food stuff import, some states require document, that the
limits for concentration of radionuclides in imported food stuff aren't
exceeded.
In the workplaces, where higher irradiation of workers caused by natural
sources occurs (mines, caves, filter plants, coal cleaning plant, processing
of phosphate sources, corrosion-resistant materials, noble earths, ...),
measurement and annual effective dose calculation for workers must be done.
These calculations enable to qualify the level of worker's irradiation.
If it's necessary, employer is obliged to adopt measures leading to decrease
irradiation of workers.
It's necessary to do all the measurements with statued devices according to law about metrology No.505/1990 and to verify these devices periodically at State metrological centres. Licence for measurements joined with ionizing radiation is given by SUJB to persons with proper knowledges after passing exams. List of licence holders is on internet pages www.sujb.cz.