Measurement of radioactive effluent in a coastal environment
The discharges of radioactive materials from the Windscale Fuel Processing Plant have resulted in the build up of radionuclides in the accreting mud banks of adjacent estuaries. A mathematical model has been developed which can successfully predict the activity profile of each radionuclide in the sediment. Laboratory experiments have shown that the distribution coefficient for caesium depends on a number of variables such as sediment particle size, salinity, initial radionuclide concentration and time. The model described can be used to predict likely changes in the activity profiles in the sediment if the waste discharge rates are altered. Measurements of the effect of salinity on the adsorption of caesium onto sediment would indicate that a change in the salinity of the discharges might reduce the uptake of activity onto particulate matter in the immediate vicinity of the discharge pipe and consequently reduce the amount of activity building up in the mud banks. Three types of adsorption site on the sediment have been established with quite different characteristics. The construction of two types of alpha spectrometer is discussed. It is shown that the chemistry of an "extractive scintillation" method can be used to prepare samples for counting on a surface barrier detector. The feasibility of using a large area gridless pulse ionisation chamber for environmental alpha spectrometry is discussed and the spectrum of the instrument built showed to have a resolution of 64 KeV.