58. Monte-Carlo Modelling and Experimental Study of Radon and Progeny Radiation Detectors for Open Environment

Solid state nuclear track detectors (SSNTDs) have been widely used as sensors of radon and progeny in long-term dosimetry because they exhibit high detection properties while their cost is very low. Alpha-particle energy calculating codes, specific for every incident particle, increase the Monte-Carlo simulation time significantly. The expression of the alpha particle energy as a function of the distance travelled in SSNTD CR-39 was recently introduced as an alternative approximation for the simulation method. This chapter focused on modelling the response of bare CR-39 detectors to alpha-particles emitted by radon and progeny, through Monte-Carlo methods. In order to determine the efficiency of a combined use of bare CR-39 and cup-type detectors in radon measurements, theoretical and experimental CR-39 efficiency factors for alpha-particles were calculated. Modelling rendered calculation of effective volume for CR-39 detector, based on energy and angular distributions of alpha-particles emitted due to decay of radon and progeny. The relationship between equilibrium factor F and the recorded track density values ratio (of bare and cup-enclosed SSNTDs, respectively) R was calculated. The sensitivity factor k _B for bare CR-39 was found equal to k _B = (4.6 ± 0.6) [tracks × cm⁻²]/[kBq × m⁻³ × h] (assuming the Jacobi’s steady-state model), a value not significantly different from the corresponding k _R cup-type value for radon and progeny.