Transfer, pathways, enrichment, and discharge of 137Cs and 90Sr in the pulp industry

Natural and artificial radionuclides are transferred from terrestrial ecosystems via the forest industry to coastal sea water. The material processed, i.e., wood, fresh water, and bark, have low levels of radionuclides, but large amounts of raw materials are processed annually. Thus the annual flux of radionuclides is substantial. The purpose of this investigation was to study transfer, redistribution, enrichment, and discharges of 137Cs and 90Sr in pulp industry employing the sulphate process. 137Cs and 90Sr were measured by means of Ge-detectors and a low level liquid scintillation spectrometer, respectively. 137Cs was highly enriched in the recovering process for sodium, while 90Sr was enriched in the recovering system for calcium compared to concentration levels in raw materials. The concentrations of 137Cs and 90Sr in bark were almost ten times the concentration level in conifer wood. No 137Cs or 90Sr could be identified in atmospheric discharges from the combustion processes. The products contained very low levels of these radionuclides. Only 5% of the annual input of 137Cs and 90Sr were found in the products. Discharges of radionuclides from this particular pulp production plant is nearly 40% of the annual 137Cs and 90Sr input. The contribution of 137Cs and 90Sr to coastal seawater is probably of minor importance providing that wood or fresh water from highly contaminated areas are not utilized.