A comparative study between the dynamic method and passive can technique of radon exhalation measurements from samples

Building material radon emanation and exhalation rate: Need of a shared measurement protocol from the european database analysis

In this paper the authors present a collection of radon emanation and exhalation rate data of about 2000 samples of building materials used in Europe. The data analysis highlighted some critical issues, such as the use of different units to express radon exhalation rate, the use of different measurement techniques and the general lack of information about density and thickness of samples. In many cases these differences of type and amount of information make difficult a reliable comparison of the obtained data. In the light of these considerations, the need arises to start, at both national and European level, a research activity aimed to develop a shared protocol for measuring the radon exhalation rate based on widely used and reliable measurement techniques. At European level, this protocol could support in forthcoming EU Member States national radon action plans, to take into account the contribution of building materials to the indoor radon concentrations.

COMPARISON OF RADON MASS EXHALATION RATE MEASUREMENTS FROM BUILDING MATERIALS BY TWO DIFFERENT METHODS

The aim of this study is to measure the radon mass exhalation rate from common granite building materials used in the east and northeast part of Portugal. Twelve cubic shaped samples were measured. Nine of them without any coating and three coated with different materials (varnish, hydrorepellent and liquid silicone). The radon measurements were performed with two different techniques: one using passive detectors and other using an active detector. For the passive method, CR-39 solid-state nuclear track detectors were used. The active method used the RAD7 DURRIDGE detector. Radon mass exhalation rates obtained from both methods present relatively low values in the 11-45 mBq kg-1 h-1 range for the analysed samples. Concerning the coated samples, the measured values are on average four times lower than the ones without coating. Overall, the measured values for both methods present a good agreement.

A WALK-IN TYPE CALIBRATION CHAMBER FACILITY FOR 222Rn MEASURING DEVICES AND INTER-COMPARISON EXERCISES

A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.

RADIUM AND RADON EXHALATION RATE IN SOIL SAMPLES OF HASSAN DISTRICT OF SOUTH KARNATAKA, INDIA

The radon exhalation rate was measured in 32 soil samples collected from Hassan district of South Karnataka. Radon exhalation rate of soil samples was measured using can technique. The results show variation of radon exhalation rate with radium content of the soil samples. A strong correlation was observed between effective radium content and radon exhalation rate. In the present work, an attempt was made to assess the levels of radon in the environment of Hassan. Radon activities were found to vary from 2.25±0.55 to 270.85±19.16 Bq m^-3 and effective radium contents vary from 12.06±2.98 to 1449.56±102.58 mBq kg^-1 Surface exhalation rates of radon vary from 1.55±0.47 to 186.43±18.57 mBq m^-2 h^-1, and mass exhalation rates of radon vary from 0.312±0.07 to 37.46±2.65 mBq kg^-1 h^-1.

A note on "an erroneous formula in use for estimating radon exhalation rates from samples using sealed can technique"

In this note, we point out a serious fallacy in a formula that has appeared in literature for calculating the (222)Rn exhalation rates using the Solid-State Nuclear Track Detector (SSNTD) based sealed can technique. It is shown that this formula underestimates true exhalation rates by a factor of more than 10(6). Several publications have used this formula instead of the well-known Abu-Jarad formula and have reported unrealistically low (µBq/m(2)/d) surface exhalation rates for normal materials.

Radon as a tracer of daily, seasonal and spatial air movements in the Underground Tourist Route "Coal Mine" (SW Poland)

The surveys of radon concentrations in the Underground Tourist Route "Coal Mine" were carried out using passive and active measurement techniques. Passive methods with application of Solid State Nuclear Track Detectors LR115 were used at 4 points in years 2004-2007 and at 21 points in year 2011. These detectors were exchanged at the beginning of every season in order to get information about seasonal and spatial changes of radon concentrations. The average radon concentration noted in this facility was 799 Bq m(-3) and is consistent with radon concentrations noted in Polish coal mines. Seasonal variations, observed in this underground tourist route, were as follows: the highest radon concentrations were noted during summers, the lowest during winters, during springs and autumns intermediate but higher in spring than in autumn. The main external factor that affected seasonal changes of radon concentrations was the seasonal variation of outside temperature. No correlation between seasonal variations of radon concentrations and seasonal average atmospheric pressures was found. Spatial variations of radon concentrations corresponded with air movements inside the Underground Tourist Route "Coal Mine". The most vivid air movements were noted along the main tunnel in adit and at the place located near no blinded (in the upper part) shaft. Daily variations of radon concentrations were recorded in May 2012 using RadStar RS-230 as the active measurement technique. Typical daily variations of radon concentrations followed the pattern that the highest radon concentrations were recorded from 8-9 a.m. to 7-8 p.m. and the lowest during nights. The main factor responsible for hourly variations of radon concentrations was the daily variation of outside temperatures. No correlations were found between radon concentration and other meteorological parameters such as atmospheric pressure, wind velocity or precipitation. Additionally, the influence of human factor on radon concentrations was noticed. As human factor, we consider open entrance door during restorations works carried out inside the underground facility. Comprehensive surveys of radon concentrations in the Underground Tourist Route "Coal Mine", which included hourly, seasonal and spatial measurements, have revealed that radon can be the excellent tracer of air movements inside the underground facilities that are not equipped with mechanical ventilation system. The main external factor that affects hourly, seasonal and even spatial changes of radon concentrations inside Underground Tourist Route "Coal Mine" is the variation of outside temperature. The maximum effective dose received by employees during 2000 working hours in a year was 5.8 mSv y(-1) and the minimum was 3.5 mSv y(-1). Tourist guides, who usually spend underground about 1000 h y(-1), received effective dose from 1.7 mSv y(-1) to 2.3 mSv y(-1). According to Polish Law, employees, receiving effective dose for occupational exposure higher than 1 mSv y(-1) but below 6 mSv y(-1), are allocated to category B of workers and the level of radiation in their place of work should be controlled and continuously monitored. The radiation monitoring system in the Underground Tourist Route "Coal Mine" does not exist. None of Polish tourist routes or caves has installed radiation monitoring system although effective doses received by employees, in some of them, exceed values defined by law. Effective dose received by tourist during one trip was lower than 0.001 mSv y(-1) and risk of cancer induction was lower than 0.00001%. The probability, that tourists inside the Underground Tourist Route "Coal Mine" receive effective dose exceeding allowable annual limit for members of the public of 1 mSv y(-1) does not exist. The Underground Tourist Route Coal Mine is a safe place for tourists from radiological point of view.