Measurement of Seasonal and Spatial Variation of Indoor Radon and Development of a Passive Dosimeter for Thoron’s Progeny

Abstract

Radon has long been recognized as one of the indoor air problems. There is a strong relation between radon and lung cancer. It is the second leading cause of the lung cancer after cigarette smoking. The present research work concerning the Measurement of seasonal and spatial variation of indoor radon and development of a passive dosimeter for thoron’s progeny is divided into two parts. The first part deals with the field and laboratory measurements which were performed using the passive radon dosimeters and in the second part laboratory experiments were carried out to develop a new passive thoron progeny dosimeter. Chapter 1 gives a brief introduction to radon, its health effects, measurement techniques and the instruments used for the measurement of indoor radon concentration. Different dose conversion relations and excess lung cancer reports have also been discussed in this chapter. Chapter 2 describes different types of equipments and materials used in the research work. Information about the geology, climatic conditions and building characteristics of the houses surveyed have also been given in this chapter. It also includes procedure of the samples preparation for the measurement of radioactivity and radon exhalation rate in the laboratory using active and passive detectors. In chapter 3 reviews reported studies conducted in Pakistan concerning the measurement of natural radioactivity and indoor. Chapter 4 discusses the results and discussion of the present work concerning radon measurement performed throughout the years in four cycles which has covered all the seasons. Seasonal correction factor, weighted average indoor radon levels excess lung cancer risk and the dose delivered to the inhabitants using the local occupancy factor have also been included in this chapter. Chapter 5 deals with the results and discussions about the radon exhalation from the soil, sand and brick samples which were collected from the selected area. Effect of moisture contents on the radon exhalation rate using a closed can technique has also been presented in the chapter. The effect of back diffusion on the radon exhalation has also been studied and included in this chapter. Measurement of the natural radioactivity in the soil and other building materials, 1like sand, brick, marble and cement samples which were collected form the selected area has been dealt with in chapter 6. Research work performed at the University of St., John University USA has been included in chapter 7 and 8. These chapters include experiments performed in the exposure room using the electret ion chambers. Radon concentration in the exposure room was measured using both short term and long term electrets. It also includes the results of the performance factor for the alpha contamination chambers using the electrets as radon progeny dosimeter. Experiments were performed using both short term high sensitivity and long term (low sensitivity) electrets. Development of a new passive thoron progeny dosimeter using the principle of the surface deposition has been discussed in chapter 8. This chapter includes an introduction about the different types of active and passive equipments used for the measurement of thoron. It also discusses the calibrations of different types of active detectors for the measurements of surface deposited activities on the glass surfaces. Finally chapter 9 concludes the present research work and includes future recommendations.