Methods of Measuring Radioactivity in the Environment

In this thesis a variety of sampling methods have been utilised to assess the amount of deposited activity, mainly of Cs-137, from the Chernobyl accident and from the nuclear weapons tests. Starting with the Chernobyl accident in 1986 sampling of air and rain was used to determine the composition and amount of radioactive debris from this accident, brought to southern Sweden by the weather systems. The resulting deposition and its removal from urban areas was then studied through measurements on sewage sludge and water. The main part of the thesis considers methods of determining the amount of radiocaesium in the ground through soil sampling. In connection with soil sampling a method of optimising the sampling procedure has been developed and tested in the areas of Sweden which have a comparatively high amount of Cs-137 from the Chernobyl accident. This method was then used in a survey of the activity in soil in Lund and Skåne, divided between nuclear weapons fallout and fallout from the Chernobyl accident. By comparing the results from this survey with deposition calculated from precipitation measurements it was found possible to predict the deposition pattern over Skåne for both nuclear weapons fallout and fallout from the Chernobyl accident. In addition, the vertical distribution of Cs-137 has been modelled and the temporal variation of the depth distribution has been described