Environmental radiation monitoring of the IRT-2000 research reactor in Sofia. Investigation of plutonium concentrations in soils and plants

The paper estimates the real values of the environmental plutonium contaminations in the vicinity of the IRT-2000 research reactor in Sofia. Soil and plant samples, taken before and after 1986 have been analyzed for plutonium-238, plutonium-239 and plutonium-240 by applying a quite sensitive and selective procedure. An alpha spectrometer with surface-barrier silicon detector has been used. The LLD is 0.0037 mBq.g-1 for soils and 0.0185 mBq.g-1 for plants. For comparison, the same kind of samples, taken from other regions of the country have been analyzed as well. A lichen sample taken before 1986 and a moss sample taken after 1986, both from the Vitosha mountain, have been analyzed as bioindicators. The data obtained demonstrate a complete absence of environmental plutonium contaminations, caused by the Research reactor in Sofia. (author)