Cesium- 134 and Cesium- 137 radioactivity levels in Sri Lankan sea water after recent nuclear power plant accident in Fukushima, Japan.
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Date
2014
Authors
Wickramasooriya, P. L.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
The major radioactive contaminants released to the Pacific Ocean as a result of the recent nuclear power plant accident took place in Fukushima Japan in March 2011 were 134CS , 137Cs and 1311. It is important to estimate the levels of 137 Cs in seawater because of its long half life. This particular research was conducted to check whether there was an impact of Fukushima Nuclear Power Plant (FNPP) accident on marine water of Sri Lankan Sea and to choose the most efficient and effective method to determine the radioactive cesium in sea water.
Ion-exchange method and co-precipitation with Ammonium Molybdophosphate (AMP) method were used to pre-concentrate sea water samples and to compare the effectiveness of technique. About 100 L-150 L samples were brought to the laboratory and they were pre-concentrated using the AMP co-precipitation technique. Sampling was done from September 2011 to April 2013. The co-precipitates were measured for 72,000 seconds (20 hours) using a hyper pure germanium detector system (HPGe). The radioactive isotopes of 137Cs was detected in trace levels whereas 134 Cs isotopes was not found in detectable levels in all sea water samples analyzed. The levels of 137Cs ranged from 0.76 ± 0.12 to 1.72 ± 0.15 rnBq/L (MDA, Minimum Detectable Activity was 0.42 mBq/L). The recovery of AMP co-precipitation method was 86%.
The recovery of 137 Cs in AMP method was much larger than in ion-exchange chromatography method. Therefore co-precipitation with AMP found to be the most effective method of analysis for cesium isotopes in sea water for us. Non-detection of 134Cs by this preliminary study reveals that the ocean around Sri Lanka has not been contaminated by radioactive traces released due to FNPP accident. However all the samples analyzed had shown the presence of a trace amount of radioactive 137 Cs suggesting the occurrence of background levels of 137 Cs in sea water. This could possibly be due to the different inputs of 137 Cs into the environment that had occurred in the past such as nuclear-weapon testing and nuclear power plant accidents. However , the finding of this study will definitely be ·of immense use in the future as no such recorded data available for 137 Cs and 134Cs in sea water of Sri Lanka. Therefore the present data could be utilized as baseline values immense use in the future as no such recorded data available for 137Cs and 134Cs in sea water of Sri Lanka. Therefore, the present data could be utilized as baseline values to estimate whether there is any increase of radioactive Cesium in seawater due to an accidental release into the environment in future.
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Keywords
Cesium , Radioactivity , Sea water