Radiological characterization, combustion-related enrichment, and screening-level dose assessment of coal and coal...

This study investigated the natural radionuclide contents of coal from the Konya-Karapınar Neogene basin and laboratory-simulated coal ash, their distribution and enrichment characteristics within the coal ash, and the associated radiological risks. To this end, the activities of ²³⁸U, ²³²Th, and ⁴⁰K were determined by gamma spectrometry in 15 coal samples taken from five boreholes and their ash phases, and the enrichment behaviour during combustion was evaluated. The activities of ²³⁸U, ²³²Th, and ⁴⁰K in the coal samples averaged 99.2 ± 8.1, 35.1 ± 2.5, and 313 ± 18 Bq kg^-1 respectively. After combustion, these values increased on average by 3.33, 2.55 and 2.56 times on an ash basis, reaching 328 ± 23, 82.3 ± 6.6 and 710 ± 40 Bq kg^-1. The relative enrichment factor values for ²³⁸U range from 0.71 to 1.47, with an average of 1.06, indicating that uranium is generally retained in the ash. While ²³⁸U is controlled by secondary enrichment in organic matter-rich, sulphidic microenvironments, ²³²Th and ⁴⁰K are associated with detrital/inorganic minerals. Radiological indices revealed that the radium equivalent activity of ash (500.0 Bq kg^-1) exceeds the international safety threshold and that the absorbed gamma dose rate (232.1 nGy h^-1) is approximately four times the global average. In the screening-level modelling conducted with RESRAD-ONSITE (v7.2) for the residential farmer scenario, it was determined that the maximum total dose for uncontrolled surface ash accumulation reached 0.164 mSv y^-1 at year 23.2. Although the elevated natural radioactivity in Karapınar coal ash requires careful management, the estimated doses under the modeled exposure scenario remain within acceptable limits and do not pose a significant risk to public health.