This study examined correlations between radon, thoron and thoron progeny concentrations based on surveys conducted in several different countries. For this purpose, passive detectors developed or modified by the National Institute of Radiological Sciences (NIRS) were used. Radon and thoron concentrations were measured using passive discriminative radon-thoron detectors. Thoron progeny measurem...

Although thoron (2201Zn) was recognized as a potential source of radiation exposure in homes twenty yearsago, only a few homes in the United States have been measured for thoron. Early indoor surveys suggested that thoron concentrations would generally be low, highly variable, and make a poor surrogate for thoron pro eny dose. Howeyer, 522 recent reports of significant thoron interference with ...

INTRODUCTION Although a lot of studies on radon have been done for a long time, there are few reports on thoron. It was considered that the presence of thoron could be negligible because of its own quantity compared to that of radon. However, recent studies have shown high thoron levels in our living environment (1-4). In particular, high thoron concentrations were occasionally observed in some...

A new thoron reference ((220)Rn) in air measurement system is developed at the LNE-LNHB with the collaboration of the IRSN. This measurement system is based on a reference volume with an alpha detector which is able to directly measure thoron and its decay products at atmospheric pressure. In order to improve the spectrum quality of the thoron progenies, we have applied an electric field to cat...

To consider the total exposure to indoor radon and thoron, a concept of equivalent radon concentration for thoron is introduced, defined as the radon concentration that delivers the same annual effective dose as that resulting from the thoron concentration. The total indoor exposure to radon and thoron is then the sum of the radon concentration and the equivalent radon concentration for thoron....

Several case-control studies have indicated an increased risk of lung cancer linked to indoor radon exposure. For a precise evaluation of radon-related lung cancer risk, however, contribution of thoron should be considered. There are a lot of studies in which passive type radon detectors are used without thoron discrimination techniques. Therefore, these passive type radon detectors may be stro...

The importance of (220)Rn (thoron) progeny for human exposure has been widely recognised in the past decades. Since no stable equilibrium factor was found between indoor thoron and its progeny, and the concentration of thoron progeny varies with time, it is necessary to develop detectors for long-term measurement that directly sample and detect thoron progeny. However, power supply of this kind...

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. (222)Rn (radon gas) and (220)Rn (thoron gas) are the most common isotopes of radon. In order to assess thoron contribution to indoor radon and thoron exposure, a survey of residential radon and thoron concentrations was initiated in 2012 with ∼4000 homes in the 33 census metropolitan areas of Canada. The...

Recently there has been an increased interest in the measurement of airborne ""Rn (thoron). Such measurements are particularly targeted in areas rich in thorium, and in facilities processing thorium compounds and associated radioactive wastes. Standard electret ion chambers @-PERMSR)* designed for making indoor and outdoor "^Rn (radon) measurement have very little response to "¡R (thoron). How...

Thoron 220Rn is one of four naturally occurring radon isotopes. It has a half-life T1/2 equal to 55 s. Radon isotopes are chemically inert radioactive gases that occur in the environment as a result of the decay of radioactive elements in soil and minerals. While radon 222Rn results from the decay chain of uranium 238U, thoron 220Rn results from the decay of thorium 232Th. Both uranium and thor...