Table 1.
Comparison of surface radiation dose rates and count rates of contaminated soil when shielded by various materials
| Material | Thickness (mm) | Radiation dose rate (μSv/h) | Count rate (cpm) | ||
|---|---|---|---|---|---|
| Mean ± SD | Reduction coefficient | Mean ± SD | Reduction coefficient | ||
| Contaminated soil | 13.0 ± 0.1 | 1.00 | 7,752 ± 29 | 1.00 | |
| Paper | |||||
| Newspaper (16-sheet) | 1 | 12.0 ± 0.1** | 0.92 | 6,662 ± 121** | 0.86 |
| Corrugated cardboard | 4 | 9.99 ± 0.08** | 0.77 | 5,457 ± 99** | 0.70 |
| Two layers | 8 | 8.46 ± 0.04** | 0.65 | 4,672 ± 559** | 0.60 |
| Magazine | 25 | 4.61 ± 0.03** | 0.35 | 2,094 ± 89** | 0.27 |
| Polystyrene foam board | |||||
| 10 | 8.08 ± 0.14** | 0.62 | 4,658 ± 63** | 0.60 | |
| Two layers | 20 | 5.07 ± 0.09** | 0.39 | 3,254 ± 45** | 0.42 |
| Cloth | |||||
| Polyester:cotton = 65:35 | 0.3 | 12.4 ± 0.1* | 0.95 | 7,326 ± 72** | 0.94 |
| Two layers | 0.6 | 12.4 ± 0.1* | 0.95 | 7,015 ± 22** | 0.90 |
| Four layers | 1.2 | 12.1 ± 0.1** | 0.93 | 6,637 ± 74** | 0.86 |
| Polyethylene | 0.1 | 13.0 ± 0.1 | 1.00 | 7,595 ± 51** | 0.98 |
| Two layers | 0.2 | 12.8 ± 0.1 | 0.98 | 7,469 ± 122* | 0.96 |
| Four layers | 0.4 | 12.6 ± 0.2* | 0.96 | 7,115 ± 24** | 0.92 |
| Ethylene–vinyl acetate | 0.1 | 12.5 ± 0.1* | 0.96 | 7,585 ± 32** | 0.98 |
| Two layers | 0.2 | 12.6 ± 0.1* | 0.96 | 7,549 ± 82* | 0.97 |
| Four layers | 0.4 | 11.7 ± 0.1** | 0.90 | 7,177 ± 63** | 0.93 |
| Cotton:polyurethane = 95:5 | 0.2 | 12.6 ± 0.1* | 0.97 | 7,195 ± 59** | 0.93 |
| Two layers | 0.4 | 12.6 ± 0.1* | 0.97 | 6,996 ± 51** | 0.90 |
| Four layers | 0.8 | 12.2 ± 0.1** | 0.94 | 6,601 ± 79** | 0.85 |
| Cotton | 0.3 | 12.7 ± 0.3 | 0.98 | 7,405 ± 36** | 0.96 |
| Two layers | 0.6 | 12.4 ± 0.2 | 0.95 | 7,164 ± 98** | 0.92 |
| Four layers | 1.2 | 12.2 ± 0.2* | 0.94 | 6,571 ± 175** | 0.85 |
| Wood | |||||
| Cork | 1.3 | 11.7 ± 0.2** | 0.90 | 6,653 ± 91** | 0.86 |
| 6 | 9.55 ± 0.06** | 0.73 | 5,099 ± 445** | 0.66 | |
| 10 | 8.00 ± 0.10** | 0.61 | 4,315 ± 93** | 0.56 | |
| Betula (birch) | 10 | 7.58 ± 0.03** | 0.58 | 4,044 ± 33** | 0.52 |
| Two layers | 20 | 5.25 ± 0.10** | 0.40 | 2,793 ± 43** | 0.36 |
| Aluminum sheet | 3 | 9.32 ± 0.09** | 0.72 | 5,345 ± 61** | 0.69 |
Mean ± standard deviation (SD) is indicated (n = 5); * p < 0.01 and ** p < 0.001 compared with contaminated soil by Student’s t test. The reduction coefficient was calculated by dividing the radiation dose rate and count rate of the model ground surface when shielded with materials by those rates without shielding