he aim of this paper was to estimate radioactive contamination of wood in Lithuania and evaluate radiation exposure to a population and workers at wood production factories, due to discharge to environment from wood fuel combustion energy power plants, to evaluate effective dose of the population due to living in houses made from radioactively contaminated wood. Radioactive contamination of forests was caused by global fallout from nuclear weapons testing in the atmosphere in the northern hemisphere. Another source of contamination was Chernobyl nuclear accident which resulted in significant contamination of thousands of square kilometers of forested areas with mixture of radionuclides including long lived fission products such as Cs-137 and Sr-90. Part of this radioactivity non-uniformly contaminated territory of Lithuania. The radiological investigation of timber and wood products from different regions of Lithuania was done in 1997-2006. The activity concentration of Cs-137 was very low – ranging from MDA (less than minimum detectable activity) to 4 Bq/kg, the average was 1.30.3 Bq/kg. Later, in 2008-2011, Cs-137 and Sr-90 concentrations were measured in wood fuel from the local markets, manufacturers and energy power plants. Activity concentrations of Cs-137 were in range of 0.3-7.0 Bq/kg, Sr-90 – 0.8-6.0 Bq/kg. Average of Cs-137 activity concentration in ash was 103±54 Bq/kg and Sr-90 – 22±15 Bq/kg. Contamination of timber and wood fuel products imported from Ukraine and Belarus were also investigated. Measured activity concentrations were higher in comparison with Lithuanian wood.
Measurements of activity concentration of Cs-137 were performed by gamma spectrometry using IEC 1452:1995 method. Sr-90 activity concentration in the wood was determined after radiochemical separation by counting the Cherenkov radiation of high energetic particles (2.27MeV) radiated by Y-90 in a liquid scintillation counter Quantulus.
Exposure of the population due to contaminated wood depends on activity concentrations of radionuclides in wood and different application of wood products. Modelling of gamma dose rate due to wood contaminated with Cs-137 was performed using Visplan-3D ALARA suite 4.0 planning tool and the effective dose to the population was estimated.
Keywords: wood radioactive contamination, Cs-137, Sr-90, activity concentration, exposure, effective dose
Authors
Ladygienė R.
Department of Expertise and Exposure Monitoring, Radiation Protection Centre, Kalvarijų, Vilnius
Orentienė A.
Department of Expertise and Exposure Monitoring, Radiation Protection Centre, Kalvarijų, Vilnius
Pilkytė L.
Department of Expertise and Exposure Monitoring, Radiation Protection Centre, Kalvarijų, Vilnius
Skripkienė A.
Department of Expertise and Exposure Monitoring, Radiation Protection Centre, Kalvarijų, Vilnius
Login to download the PDF