Study On Measurement Of²²⁰Rn Concentration And Spatial Distribution Of²²⁰Rn Equilibrium Factor In Dwellings Structure With Soil

The dose contribution from radon, thoron and their decay products accounts formore than50%in all kinds of natural radiations.²²⁰Rn（Thoron） is one of naturalisotopes of²²²Rn （Radon）,and existing with it in air always. Instead of only focusingon²²²Rn among all radon isotopes in the past, the importance of²²⁰Rn is causing moreand more attention in recent decades. Survey in China and other countries and regionsindicates that dose from²²⁰Rn and its progeny should not be ignored. High thoron andits progeny concentration may be a character of China natural radiation for232Thactivity in natural soil and building materials are higher than word average. It isimportant study on the level of²²⁰Rn progeny and to evaluate its contribution topublic dose in China. This study mainly focused on measurement, change anddistribution of²²⁰Rn and its progeny, distribution of equilibrium factor.Because lack of corresponding criterion of²²⁰Rn and its progeny measurementat recently,instruments used in this work is compared with other instrument andmethods, the paper analyzed the dependability of measurement data for differentinstruments to ensure the veracity and validity of the data. Passive method andpositive measurement were used to measure²²⁰Rn and its progeny, and equilibriumfactors of²²⁰Rn for different distances from different sources were calculated based onthe measurement.Distribution of²²⁰Rn and its progeny from the data of passive method asfollows: the spatial distribution of²²⁰Rn concentration decreases from the distance ofsource. While the distance from roof and floor is far more than70cm,²²⁰Rnconcentration isn’t detected.²²⁰Rn concentration appears decreases exponentially fromthe distance of the wall. the spatial distribution of²²⁰Rn progeny is accordant,whilethe distance from source is far more than20cm.The level of²²⁰Rn and its progeny concentration are similarity in summer and autumn. From10am to23pm on June,²²⁰Rn concentration appears first up and then falling,²²⁰Rn concentration is higher inthe afternoon, and lower in the morning and night.²²⁰Rn progeny concentrationchange slow, but the concentration level are different everyday,²²⁰Rn progeny is lowin night and high in daytime. For the measurement on June, typical measurement timeone day of²²⁰Rn is from10am to16pm, for²²⁰Rn progeny is from14pm to19pm.The equilibrium factor between²²⁰Rn and its progeny is dependant on thedistance from source. Studying distribution of²²⁰Rn equilibrium factor found that²²⁰Rn equilibrium factor increases exponentially or linearity from the wall（thedistance from the wall is far than10cm）...