Evaluation of efficiency calibration parameters of the LR-115 radon detector.

Measurement of 222Rn is an important research concern because of the high-energy alpha emission of its 218Po and 214Po progeny. The LR-115 passive detector is the basis of a solid-state nuclear track detector (SSNTD) whose use for radon measurements has been well established. The usage of the SSNTD technique requires calibration by comparison. The aim of this work is to evaluate the efficiency calibration parameters for the radon measurement system that three steps: (1) irradiation conditions, (2) etching conditions, and (3) track counting. The following parameters were evaluated: breakdown and counting voltages for the spark counter, detector thickness, etching time, temperature and NaOH concentration as etching conditions for the LR-115 detector. Calibrating factors of 0.035 and 0.028 tracks cm-2 Bq-1 m3 d-1 for the open- and closed-chamber radon monitors, respectively, were determined considering the best efficiency calibration parameter values.