Radioactive Aerosol Standards - Aerosols: Measurement, Dosimetry, and Health Effects - page 534

This part of the study was conducted in order to compare the instruments under such controlled
environmental conditions.
The ield exposure was provided at a former underground uranium mine in Colorado maintained
by BOM in order to compare the instruments under luctuating and uncontrolled conditions.
The National Institute of Standards and Technology (NIST) provided the EPA Radon Laboratory
with multiple spherical glass sample ampules each containing an activity of 222 Rn gas known only
to NIST. The primary radon measurement system used by the EPA Radon Laboratory to determine
radon concentration within the chambers is 0.36 L scintillation cells (also termed Lucas cells).
The BOM facility is a previously operated uranium-vanadium mine, which was used for the
purpose of conducting research. Radon concentrations were in the range of 5,110-15,535 Bq m −3 and
radon decay products concentration varied from about 3.54 to 74.32 μJ m −3 . The mean equilibrium
factor was 14.2%.
Of the six participants who measured radon concentration in the EPA laboratory with charcoal
collectors, four produced results within 8% of the unity for performance ratio. Only one of the four
participants who used alpha-track detectors in EPA laboratory produced results within 11% of unity,
and two participants who used electret ion chamber in EPA laboratory gave results of 10% of unity.
Of the four organizations that measured radon decay product concentrations in EPA laboratory
using grab methods, two produced 10% of unity, and the remaining two within 30%.
The overall conclusion can be made that more international intercomparisons are needed as
there are differences even within the same organizations. This is especially important when mak-
ing interpretations about the health effect, which is the main goal of radon and its decay product
measurements.
In Nezval et al. (1997), intercomparison measurement of soil-gas radon concentration is
presented.
The soil-gas 222 Rn concentration deined as an average radon concentration in the air-illed part
of soil pores in a given volume of soil. This value has a wide range of practical applications:
1. When soil-gas radon is used as indicator for uranium, indoor radon, seismic activity, loca-
tion of sub-service faults, etc.
2. In studies where the focus is on radon itself
From a metrological point of view there are many problems with organizing ield intercomparison
measurement in natural geological environment. Such intercomparisons were previously organized
in 1991 and 1995. This project was organized during the third International Workshop on the
Geological Aspect of Radon Risk Mapping (Praque, Czech Republic, September 1996) measure-
ments. Participants representing 10 organizations from eight countries took part in the intercompar-
ison. The ratio of the standard deviation to the arithmetic mean (SD/mean) was used as a measure
of a spread on intercomparison. For the soil-gas radon concentration the agreement among partici-
pants was very good. If all single values that were obtained over the whole area of the test site were
taken into account, the intercomparison difference, expressed as a ratio SD/mean, was 24%. A more
detailed assessment shows an even smaller number—about 20%. This result has been previously
considered as a reliable target for intercomparison measurements of soil-gas-radon concentration.
20.2.2 a rtiFicial r adioactive a erosols
In Grivaud et al., 1998, the installation for testing radioactive aerosol measurement instruments is
described. The EPICEA laboratory (Laboratoire d'Essais Physiques des Instruments de Mesure
de la Contamination de l'Eau de del'Air), which belongs to the Institute de Protection et de Surete
Nucleaire (IPSN), France, was established to carry out various types of tests on atmospheric con-
tamination monitors under the conditions recommended by the International Electrotechnical
Commission (IEC).