Correlation of Radon Exhalation Rates from Granites with Radium Contents

1. Correlation of Radon Exhalation Rates from Granites with Radium Contents M. I. Al-Jarallaha, Fazal-ur-Rehmana,b, M. S. Musazaya,A. Aksoyb Department of Physics, b Center for Applied Physical Sciences (CAPS) King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

2. ABSTRACT • Radon exhalation rates for 152 samples of granite tiles used in Saudi Arabia were determined • Active and passive measuring techniques were used in this study. • In the active technique, a PC-based radon gas analyzer with emanation container was used. • In the passive technique, CR-39 nuclear track detectors with the “Can technique” were applied for 30 days. • Radium contents of 21 samples of granite tiles were measured using HPGe-based gamma spectroscopy • The radon exhalation rates measured by the active technique showed a good linear correlation with radium content (R2 = 0.9).

3. Fig. 1. Schematic diagram showing the active set-up used for the exhalation measurements of samples with AlphaGUARD.

4. Fig 2. A PC-based Active Radon Measuring System containing radon gas analyzer type AlphaGUARD 2000 PRQ along with emanation container.

5. Activity (Bq m-3) Fig. 3 Buildup of radon exhaled from a granite sample measured by the active system. The x-axis shows the real time of buildup while the y-axis shows the radon concentration in the container. The bold line shows the log fit. Time (h)

6. Fig. 4. Frequency distribution of radon exhalation rate measurements from the granite tiles using the active technique.

7. Fig. 5. Schematic diagram showing the passive setup where an NTD is placed on the surface of granite tile and surrounded by a sealed vessel

8. Fig. 6 Photograph showing the can technique where two cans, enclosing the NTDs, are placed on two locations of the surface of each granite tile.

9. Fig. 7

10. Fig. 8 Track density in the NTDs is being measured using an optical microscope associated with Image Analyzing System.

11. Fig. 9 Correlation of track production rate (passive technique) and radon exhalation rate (active technique) measurements from granite tiles.

12. Fig. 10 Correlation between activity of radon emanated per unit mass and the actual radium content (Ra + Rn).

13. Table 1: The Increment in the radon concentration (Bq m-3) due to the presence of tiles for maximum and average exhalation rates at ventilation rates of 0 and 0.1 h-1.

14. CONCLUSION • It was found that all building materials exhale radon with a very wide range. 2.Most of granites showed relatively higher radon exhalation rates (<0.12 to 10.6 Bq m-2 h-1). 3. The reproducibility measurements of the radon exhalation rates with both the passive and active techniques for granite tiles were found 7% and 5% respectively. 4. A correlation was found between radon exhalation rate and the radium content(R2 =0.9). • The contribution of building materials of high radon exhalation rates in indoor radon concentration can be significant.up to 470 Bq m-3, for the highest radon exhalation and zero ventilation. • Regular ventilation is very effective in reducing radon concentration ( A ventilation of 0.1 h-1 reduces radon concentration from 470 to 35 Bq m-3). • Most users of granite are unaware of its Uranium content and are unable to measure its radon exhalation rates. Therefore, we suggest adding extra information to the identification of granites, namely its Uranium content and radon exhalation rate and this should be accessible to the users.

15. Thank you