226Ra, 228Ra and 40K in scales formed in boilers of industrial installations

Many industrial processes involve the production of steam in boilers, which is sent through pipes to machines and other equipment used in different sectors of the installations. The water commonly used in these processes is groundwater, which generally has high concentrations of calcium and magnesium salts, that can co-precipitate with naturally occurring radioactive elements such as 226Ra and 228Ra creating radioactive scales, which are deposited in pipes, thus decreasing the efficiency of steam production. In addition, 40K that is present in all soils and rocks with a concentration of about 0.012% of natural potassium can also be concentrated in these scales. No data was found in literature relating to radionuclides present in the scales formed on boilers in general. In this context, the purpose of this work was to determine concentrations of 226Ra, 228Ra and 40K, in scales generated inside boilers from different industries in the cities of Caruaru, Paulista and Goiana, Pernambuco. Determination of the radionuclides concentration was performed by gamma spectrometry with an HPGe detector, calculating their specific activities. Activity concentrations of 226Ra were in the range of < 1.4 (Detection Limit) to 1,328.0 ± 23.0 Bq.kg-1 and 228Ra activity concentrations varied from < 1.8 (Detection Limit) to 265.5 ± 8.0 Bq.kg1. Activity concentrations of 40K were in the range of < 14.6 (Detection Limit) to 288.1 ± 11.5 Bq.kg-1. All these activity concentrations were lower than the limits established by the Brazilian Nuclear Energy Commission of for this type of matrix. (author)