Statistical prediction of environmental external gamma radiation doses of Perak, Malaysia
Abstract
ABSTRACT
Concentrations of Natural Occurring Radioactive Material (NORM) and terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. An attempt was made to statistically predict and validate environmental gamma radiation dose rates based on limited number of actual field measurements using sodium iodide (NaI(Tl)) detector. Statistical analysis including the correlations between the actual and predicted dose were made based on 32 different lithology and soil type combinations. Results of field measurements, have shown that more than 50% of the predicted data were not significantly different from the actual measured data. The interpolation method in GIS was used to produce an isodose map based on the prediction equation. A correlation of multiple regression on the predicted versus lithology and soils dose rates gave relationships of DP = 0.35 DL + 0.82 DS – 0.02, r2 = 0.736. A predicted isodose map was subsequently plotted base on 4 dose rates classes, ranging from 0.1 – 0.3 μSvhr-1.
ABSTRAK
Kepekatan NORM dan aras sinar gama terestrial menunjukkan bahawa ia dipengaruhi oleh litologi dan jenis tanih tertentu. Satu kajian telah dilakukan dengan meramal secara statistik dan mengesahkan kadar dos sinaran gama sekitaran berdasarkan bilangan pengukuran sebenar di lapangan yang terhad dengan menggunakan pengesan natrium iodide (NaI(Tl). Analisis statistik termasuk korelasi di antara dos sebenar dan dos ramalan dilakukan berdasarkan 32 kombinasi litologi dan jenis tanih yang berlainan. Hasil yang diperoleh dari pengukuran lapangan, menunjukkan bahawa lebih daripada 50% dari dos ramalan tidak berbeza dengan bacaan sebenar. Kaedah interpolasi dalam GIS telah digunakan untuk menghasilkan peta isodos berdasarkan persamaan ramalan. Korelasi bagi regresi berganda ramalan bagi litologi dan jenis tanih memberikan hubungan DP = 0.35 DL + 0.82 DS – 0.02, r2 = 0.736. Seterusnya peta dos ramalan telah diplot berdasarkan 4 kelas kadar dos dengan julat 0.1 – 0.3 μSvj-1.
