THE INFLUENCE OF THE RADON VARIABILITY ON DOSE ASSESSMENT
VLADIMIR UDOVIČIĆ1, ALEKSANDAR DRAGIĆ1, RADOMIR BANJANAC1, DEJAN
JOKOVIĆ1, BOJANA GRABEŽ1, JELENA FILIPOVIĆ2, ZORA S. ŽUNIĆ2
1Institute
2Institute
of Physics, University of Belgrade, Serbia, udovicic@ipb.ac.rs
of Nuclear Sciences “Vinča”, ECE LAB, University of Belgrade, Serbia, ecelab@vinca.rs
Abstract. The radon dose assessment is based on the recommended formula proposed by UNSCEAR and ICRP.
There is still some misunderstanding in the two different approaches on radon dose assessments regarding how to
transform radon concentration to the radon dose. One model is based on epidemiological assessments (ICRP) and the
other one is evaluated from physical dosimetry (UNSCEAR). Also, it is very important to evaluate accurate annual
radon concentration due to very complex indoor radon behavior. This task is not trivial and mostly come up from the
radon variability. The aim of this work is to investigate the influence of the radon variability on dose assessment. For
this purpose, we used the data sets from the indoor radon measurements performed in one-family dwelling house in
Serbia.
Key words: Radon dose, Variability
Introduction: Radon is a unique natural element
since it is a gas, noble and radioactive in all of its
isotopes. The radon contribution to the annual effective
dose from all natural radioactive sources is significant
(about 55%). It is very important to get accurate radon
dose estimation. The radon dose assessment is based
on the recommended formula proposed by UNSCEAR
and ICRP. There is still some misunderstanding in the
two different approaches on radon dose assessments
regarding how to transform radon concentration to the
radon dose [1]. Indoor radon concentration can vary
significantly due to a large number of factors which
include the local geology, soil permeability, building
and lifestyle characteristics and meteorological
parameters. Based on the measurements worldwide,
there are two main periodicities in the indoor radon
behavior, the daily and seasonal variability [2]. The
influence of the radon variability to the radon dose
assessments is the subject of the research in many
countries [3], [4], [5], [6]. The aim of this work is to
investigate the influence of the daily radon variability
on dose assessment. For this purpose, we used data
sets from the indoor radon measurements performed
in one-family dwelling house in Serbia.
Short-term indoor radon measurements:
The radon concentration, as a physical quantitate has a
one of the largest number of the methods to measure.
All of them may be divided in the two groups. One is
the long-term measurements, mostly performed with
passive integrated measuring devices based on the
nuclear track detectors, which is due to their low cost,
simplicity and characteristics have ability to collect
information from a large number of the measurement
points at the same time, so they are used in the large
radon mapping projects. The second group of the
radon measurements methods are short-term
measurements This type of measurements are
performed with much more complex and expensive
passive or active (pump air sampling) continuous
measuring devices.
The radon monitor is used to investigate the daily
variations in the radon concentrations. For this type of
short-term measurements the SN1029 radon monitor
was used (manufactured by the Sun Nuclear
Corporation, NRSB approval-code 31822). The device
consists of two diffused junction photodiodes as a
radon detector, and is furnished with sensors for
temperature, barometric pressure and relative
humidity. The user can set the measurement intervals
from 30 min to 24 h. The radon monitor device records
radon and atmospheric parameters readings every one
hour in the one-family dwelling house in Belgrade,
Serbia. The data are stored in the internal memory of
the device and then transferred to the personal
computer. The data obtained from the radon monitor
for the temporal variations of the radon concentrations
over a long period of time enable the study of the shortterm periodical variations.
The selected house is a typical one-family dwelling
house building with standard construction materials
such as blocks of brick, concrete, mortar. The house is
thermally insulated with Styrofoam. In the summer
time, the house is naturally ventilated. Air conditioning
device is used during the hottest part of summer. The
indoor radon measurements were done in the living
room and the bedroom. The usually lifestyle means
staying in the living room for a period of 16 up to 24
hours in the working days of the week. The sleeping
time is from 24 to 08 hours. In the summer, the stay in
the house is reduced. The opposite situation is in the
autumn and winter, when the most of the time,
inhabitants stay in houses. The measurements were
performed in the August and September for the three
days in each room separately.
Results and discussion: The time-series of the
indoor radon measurements performed in the living
room and bedroom in the August and September for
the three days in the one-family dwelling house in
Belgrade are shown in Figures (see Fig. 1 and Fig. 2).
other side, there is positive correlation between radon
concentration and the relative humidity. The Pearson
correlation coefficients between radon concentration
and relative humidity are 0.47 and 0.67 for the living
room and bedroom, respectively.
Fig. 2 The short-term indoor radon measurements performed
in the August and September for the three days in the
bedroom
The special attention was made to the results of the
mean radon concentrations based on the short-term
measurements. The results are shown in Table 1.
Table 1 Title of table (Style Table title)
Fig. 1 The short-term indoor radon measurements
performed in the August and September for the three days in
the living room
The short-term measurements have shown that
there are temporal variations on daily basis. The
differences between minimum and maximum value are
more intensive in the September than in the August.
Also, it is obvious that daily variations of the indoor
radon concentrations may be extreme (up to 600 Bqm3, see Fig. 1). The SN1029 radon monitor has sensors
for temperature, barometric pressure and relative
humidity. The Pearson correlation coefficient between
radon concentration and the indoor temperature in
both rooms is -0.5, which shows anticorrelation
between two parameters, as it present in [7]. On the
2
Month
Living room
Bedroom
Mean/Averaged
Mean/Averaged
from 16 to 24 hours from 24 to 08 hours
August
50.50/58.71
64.96/58.98
September
150.05/66.26
210.74/278.48
Besides the mean radon concentrations, it is also
obtained the radon concentration averaged over 16 to
24 hours for the living room and 24 to 08 hours for the
bedroom. The results show a big difference between
mean radon concentrations in the September and
August in both rooms, due to seasonal radon variability
(the ratio is about three). Also, there is a deviation
from the mean value of the radon concentrations
averaged over different period of the day due to
lifestyle. In the all short-term measurements, the radon
concentration has maximum in the morning (07:30)
and minimum in the afternoon (16:30).
Conclusions: Indoor radon concentration varies
daily and seasonally, mainly due to the changes of the
atmospheric parameters (temperature, atmospheric
pressure and relative humidity) and the exchange rate
between indoor and outdoor air. For this reason, it is
important to investigate short-term variations of the
indoor radon concentrations because the short-term
variation during the day may be extreme. Also, in the
laboratory with the the system for radon reduction and
under controlled experimental conditions (indoor–
outdoor air exchange rate was constant; the influence
of the behaviour of the people, for example opening
and closing the door of the laboratory, was minimized),
. there is significant one day radon periodicity [8], [9]
The results present in this work show that it is
difficult to estimate the annual radon concentration
due to very complex indoor radon behavior. This task is
not trivial and mostly come up from the radon
variability. In many recent published articles, this issue
is the subject of the research [10], [11]. One of the
conclusions is that must be used the correction factors
for determination of annual average radon
concentration resulting from seasonal and also daily
variability, based on the database of the short and longterm indoor radon measurements
4.
5.
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10.
Acknowledgement: The paper is a part of the
research done within the project 43002 of the Ministry
of Education and Science of the Republic of Serbia.
11.
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