Study of a remediated coal ash depository from a radiological perspective

H*(10) was 290 (130-525) nSv/h at the covered depository; CRa-226 was 1997 Bq/kg, 960 Bq/kg and 104 Bq/kg for the ash, cover layer and background soil respectively. CRn-222 in the soil was 25-161 kBq/m3, and soil gas permeability K was between 6.4E-13 and 1.80E-11 m2. The radon exhalation of the uncovered and covered depository was 259-1100 mBq/m2s. The exhalation and emanation coefficients of the samples were 0.05-0.32 mBq/kgs and 8-22%. The effects of vegetation on the migration of radon were also examined. The results show that the Ajka coal ash depository involves higher radiological risk than that reported by previously published studies on depositories. The applied cover layer halved the field radon exhalation; in addition, the vegetation reduced the convective airflow and, with this, the migration of Rn.