# A Case Study of the Radon Hazard at the Boundary of a Coal Minefield
## 3 Results
### Rfd  
RFD ranged from 10 to 160 mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\), with a mean value of \(59.76\pm 2.45\) mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\) and a median value of \(57.43\) mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\). The data distribution is normal. In the study area, there were nine monitoring sites with mean values exceeding 80 mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\). As per the radiation protection standards (NRB-99/2009) [32] for residential buildings, this necessitates a moderate level of protection against geological radon. At 38 monitoring sites, values above 80 mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\) were also observed. The percentage of RFD values above 80 mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\) constituted 0 to 85.7% of all recorded values at each observation point. We found some correlations between RFD, the distance of the observation points from the mines, and the displacement of the Zhurinsky Fault (Table 5). Table 6 represents the descriptive statistics of outside the mine of RFD. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Research Point**} & \multicolumn{6}{c}{**Radon Statistics, mBq\(\cdot\)m\({}^{-2}\)\(\cdot\)s\({}^{-1}\)**} \\ \cline{2-7}  & **RFD** & **SE** & **Median** & **Max** & **Min** & **Interval** & **Percent over 80** \\ \hline
1 & 50.27 & 4.84 & 53 & 84 & 21 & 63 & 6.7 \\
2 & 49.13 & 5.21 & 46 & 83 & 23 & 60 & 0.0 \\
3 & 34.47 & 5.04 & 28 & 85 & 12 & 73 & 6.7 \\
4 & 58.53 & 5.13 & 55 & 99 & 27 & 72 & 20.0 \\
5 & 44.27 & 4.52 & 46 & 69 & 12 & 57 & 0.0 \\
6 & 39.33 & 7.28 & 30 & 101 & 10 & 91 & 20.0 \\
7 & 47.73 & 3.96 & 43 & 73 & 30 & 43 & 0.0 \\
8 & 67.20 & 5.15 & 64 & 95 & 26 & 69 & 33.3 \\
9 & 54.53 & 6.51 & 52 & 102 & 10 & 92 & 13.3 \\
10 & 43.53 & 5.18 & 44 & 72 & 10 & 62 & 0.0 \\
15 & 70.60 & 3.97 & 71 & 98 & 43 & 55 & 26.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Descriptive analysis of RFD outside the mine. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Soil Radon VAR** & **Soil Radon VAR** & **Soil Radon VAR** \\  & **(All Data)** & **(Outside the Mine)** & **(Within the Mine)** \\ \hline T, \({}^{\circ}\)Cav. 1 h & r = 0.41 \({}^{\ast}\) & r = 0.62 \({}^{\ast}\) & No \\ T, \({}^{\circ}\)Cav. 2 h & r = 0.44 \({}^{\ast}\) & r = 0.62 \({}^{\ast}\) & No \\ T, \({}^{\circ}\)Cav. 3 h & r = 0.44 \({}^{\ast}\) & r = 0.61 \({}^{\ast}\) & No \\ \hline \hline \end{tabular} \({}^{\ast}\)Significance \(p\leq 0.01\). \({}^{\ast\ast}\)Significance \(p\leq 0.05\).  
\end{table} 
Table 4: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **RFD** & **Median** & **Max** & **Min** & **Interval** & **Percent over 80** \\ \hline Distance to old mine & r = 0.46 \({}^{\ast}\) & r = 0.45 \({}^{\ast}\) & r = 0.34 \({}^{\ast\ast}\) & r = 0.56 \({}^{\ast}\) & No & r = 0.49 \({}^{\ast}\) \\ Distance to new mine & r = \(-\)0.49 \({}^{\ast}\) & r = \(-\)0.47 \({}^{\ast}\) & r = \(-\)0.43 \({}^{\ast}\) & r = \(-\)0.52 \({}^{\ast}\) & No & r = \(-\)0.50 \({}^{\ast}\) \\ Distance to displacer fault & No & No & No & r = 0.29 \({}^{\ast\ast}\) & r = \(-\)0.40 \({}^{\ast}\) & No \\ Distance to new mine & r = \(-\)0.60 \({}^{\ast}  
RFD ranged from 10 to 144 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\), with a mean value of \(61.96\pm 3.05\) mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) and a median value of 61.84 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\). The data show a normal distribution. There were nine monitoring sites in the study area with an average value above 80 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\). At 22 monitoring sites, measurements exceeding 80 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) were also detected. The percentage of RFD values above 80 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) measured at each observation point varied between 0% and 85.7%.