A study of selected parameters affecting the radiation dose from radionuclides in drinking water downstream of the Hanford project

Studies of some parameters affecting radiation doses received from consumption of water derived from the Columbia River downstream of the Hanford production reactors were performed. Included were measurement of radionuclides in (1) water entering and leaving the water treatment plants at Richland and Pasco, Washington; (2) sanitary (municipal) water at a number of points in Richland; and (3) coffee brewed from sanitary water. The removal efficiencies for the alum-floc water treatment plants studied ranged from 80% for rare-earth nuclides to 10% for Cr-51. The relative concentration of radionuclides (principally Na-24, As-76, Sb-122, Np-239) found within the Richland distribution system was used to estimate the average dose to residents consuming the water. Average GI tract doses calculated for persons residing at each of six locations within the city were 1/3–1/2 of those calculated for consumption of water leaving the treatment plant. The average dose received, calculated by weighing these six individual doses by the population distribution, yielded 45% of that calculated for consumption of water leaving the treatment plant. Since coffee represents a major liquid intake mode for adults, the volume of coffee consumed and the potential removal of radionuclides during coffee brewing was studied. The average drinkable volume of coffee per cup was 200 ml. The concentrations of radionuclides in the water and coffee brewed from it were not significantly different for those radionuclides contributing the most to the GI tract dose, and hence those doses were not significantly reduced.