DOE OSTI2016
The impacts on the ocean of releases of radionuclides from the Fukushima nuclear power plants remain unclear. Korean people worry about radioactive contamination of Japanese and Korean sea products. Radioactive contamination of processed foodstuffs, livestock, sea products, farm products imported from Japan and fishes caught in coastal oceans of Korea has become an important social issue. Recently, there are also needs of inspection system for monitoring of public meals such like school feedings of kindergarten, elementary/middle/high school and university. Radioactivity inspections of food materials have been executed manually with portable measuring instruments or at labs using their samples. But, it's very important the radioactivity inspection should be performed at the field of feeding facilities. To protect the health of people from radioactivity contained in Japanese marine products imported to Korea, a system to inspect radioactivity in real time has been developed. The system is to measure the radioactivity level of farm and marine products and public meals continuously and automatically at inspection sites of an agency checking radiation of imported foodstuffs or school. The performance test of NaI(Tl) detector was examined using the quantified Cs-137 source 10 Bq/kg, 30 Bq/kg, 50 Bq/kg, 300 Bq/kg and 900 Bq/kg at Korea Research Institute of Standards and Science(KRISS). Source was put in a box and radioactivity was measured in the middle of the box. First of all, Background was measured and calibration was performed using the Cs-137 300 Bq and Ba-133 3700 Bq for 60 minutes. After setting the background and calibration data, tests of the Cs-137 10, 30, 50, 300, 900 Bq/kg were executed for 10 minutes. A peak-shaped graph is shown at the location of 662 KeV (80∼100 channel). This is due to the gamma radiation energy with 662 KeV emitted by the Cs-137. Because through KRISS examination, the MDA (minimum detectable activity) is about 23 Bq/kg, it is reasonable Cs-137 10 Bq/kg cannot be measured. And in cases of Cs-137 300 Bq/kg and 900 Bq/kg, there are some peak movement on the graph. It can be adjusted by controlling gain or high voltage. The examination was identified through the performance test (Cs-137 10, 30, 50, 300, 900 Bq/kg) at KRISS. In order to increase the measurement efficiency of Cs-137 and the system performance, database will be built up based on radioactivity measurement results from 10 to 300 Bq/kg with the unit 10. Thus, Cs-137 concentration of food materials can be identified below the maximum permissible concentration of 100 Bq/kg on a basis of the spectrum characteristic of Cs-137. Also, anxiety about radioactive contamination of foods after the Fukushima nuclear accident will be eased and trust of the radioactive inspection is expected definitely. (authors)
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗