Distribution of indoor thoron in dwellings under normal and turbulent flow conditions using CFD simulation technique

Abstract

Ex ten sive work has been car ried out on mea sure ment of ra don and thoron lev els in in door envi ron ment in last three de cades. These stud ies are im por tant from ra di a tion pro tec tion point of view, if one con sid ered the con tri bu tion of ra don, thoron and their de cay prod ucts to to tal in ha la tion dose. Nu mer ous stud ies on ra don mea sure ment well es tab lished the be hav iour of its dis per sion in dwell ings. But the short lives of thoron cause the dif fi culty to un der stand the dis tri bu tion of thoron in dwell ings. The prob lem be comes more com pli cated when thoron dis per sion is stud ied un der dif fer ent in let air flow rate. Dif fer ent air flow pat tern may cause dif fer ent thoron level at dif fer ent point in test dwell ings caus ing un cer tainty in the mea surements. This work uti lized the CFD sim u la tion tech nique for study of in door thoron dis persion in test dwell ings un der nor mal and tur bu lent flow of air. The sim u la tion study for thoron dis tri bu tion in a test room was per formed for air ve loc i ties 0.10 ms-1 , 0.25 ms-1 , 0.50 ms-1 , 1.0 ms-1 , 1.5 ms-1 , and 2.0 ms-1. The re sults show that the thoron dis tri bu tion be comes uniform for the in let ve loc ity more than 0.5 ms-1 and ap pro pri ate to mea sure in door thoron concen tra tion. While in nor mal con di tion the mea sured thoron level var ies de pend ing upon the lo ca tion of do sim e ter. Thoron dif fu sion and mi gra tion length are also in creased with air flow rate.

Measurement of radon in soils of Lima City - Peru during the period 2016-2017

“…Reference radon concentration in the chamber was continuously measured by means of the AlphaGUARD DF 2000 monitor, traceable to the primary Rn standard in Physikalisch-Technische Bundesanstalt (PTB), Braunchweig, Germany. from soil surface decreases exponentially with the distance to the bottom of the hole, in a manner analogous to what happens in front of a wall (Godoya et al, 2002;Hadler & Paulo, 1994;Chauhan et al, 2017) or inside a diffusion chamber (Urosevic et al, 2008;Nikezic & Stevanovic, 2007). Since the main mechanism of gas transport within the PVC tube is diffusion, very few thoron atoms can reach 20 cm from the source because their diffusion length is approximately 2-3 cm for the commonly used air diffusion coefficient values.…”

Evaluation of the gamma dose rate inside Egyptian buildings, utilizing theoretical and experimental techniques

“…Ra dio ac tive equi lib rium is the main as sump tion for all these mod els; al though, it is well known that ra don and thoron es cape from the walls, so that no real equi lib rium in the nat u ral se ries ex ists. In par tic u lar, it was eval u ated that over es ti ma tion by mod els reaches up to 20 % in the case of strong ra don ex ha la tion [14,20,21]. Also, it was ob served that the ef fect of chang ing the po si tion and di men sions of the room causes low vari abil ity of the specific dose rate; while high vari abil ity with wall thick ness and den sity are ob tained [16].…”

Simultaneous measurements of radon, thoron and equilibrium equivalent concentrations in family house - single case study

“…It is con sid ered that the dis tri bu tion of indoor ra don is ho mo ge neous, but thoron con cen tra tion ex po nen tially de creases from its sources in the room (walls, floor etc.) [2,3], even for the high rate of air-flow in side the room [4]. How ever, ra don and thoron prog e nies have sim i lar be hav ior in in door air due to the rel a tively long half-lives.…”