226Ra, 228Ra and 228Th in scale and sludge samples from the Campos Basin oilfield E and P activities

More than 40 scale and sludge samples from the Campos Basin oilfield were analysed in terms of 226Ra, 228Ra and 228Th. Although the exact origin of the samples was not known, scale samples derived from production pipes and sludge samples from water-oil separation units. Reported values ranged from 0.13 to 331 kBq.kg-1 for 226Ra, from 0.10 to 245 kBq.kg-1 for 228Ra and <0.10 to 272 kBq.kg-1 for 228Th in sludge samples. The concentrations in scales were much more regular than in sludges and ranged from 16.2 to 93.2 kBq.kg-1 for 226Ra, from 4.0 to 36.9 kBq.kg-1 for 228Ra and from 4.5 to 18.5 kBq.kg-1 for 228Th. Based on the Safety Standards recommendations and on the derived results, these activities cannot be regarded as exempted and specific procedures should be designed for their radiological control. (author)