Radioactive elements in the forest industry

Ash from 16 different biofuel powered plants in Sweden collected in 2-week intervals over half a year were analyzed for the activity concentration of radiocesium, potassium and radiostrontium. The flux of radionuclides at different steps in a pulp mill process were also studied. The gamma emitting radionuclides such as 137Cs and 134Cs are of prime interest when considering current dose rates on a biofuel waste deposit. Measurements of the absorbed dose to superficial tissue using TL-dosimeters showed a clearly increasing trend for the dose rate (+5 nGy/year) as a function of time when measure 1 m above different locations on the dump corresponding to deposits made from 1987 to 1990. The present investigation shows that besides the potential increase in absorbed doses to a rather limited population, waste products must be considered from a radiological point of view due to the involved concentration processes. The radionuclides might play an important role in the understanding of the effects of using waste products as fertilizers.