후쿠시마 원자력발전소 사고에 따른 국내 식품(버섯)의 방사능 영향

Abstract

The concerns about environmental radioactivity is increasing due to Hukushima nuclear power plant accident caused by tsunami in 2011. Environmental radioactivity is classified into natural radioactivity nuclide and artificial radioactivity nuclide. Natural radioactivity has been existing ever since the earth was created and great amount of artificial radioactivity nuclide has been released because of numerous nuclear bombing experiment implemented between 1950 to early 1960s and Chernobyl nuclear power plant accident in Russia in 1986. These artificial radioactive substance causes internal exposure after being taken into the body through various paths. The regulation of pollution of imported and exported foods was reinforced to prevent foods polluted by artificial radioactivity released into environment from being distributed. The pollution of surrounding nuclear facilities is watched by Korea Institute of Nuclear Safety, Korea Hydro & Nuclear Power Co. and Ltd., private observation center, university research center and etc. in Korea and the imported foods are managed by tentative allowable standards set by Korea Food & Drug Administration. Regulation of radioactivity pollution changed into foods originated from Japan and the rest area after Hukushima Nuclear Power Plant accident and the standard of Cesium has been strengthened from 370 Bq/kg to 100 Bq/kg.(2013.09.06) The radioactivity of homegrown mushrooms (shiitake) were gathered and analyzed after Hukushima Nuclear Power Plant accident in this study. The shiitake mushrooms were chosen since there has been continuous report on radioactivity detection and the influence of radioactivity of the rest mushrooms that are grown in facilities can not be found thus the shiitake mushrooms grown outdoor with rain-proof methods were selected for sample to analyze radioactivity in this study. About 4kgs of these shiitake mushrooms were gathered from 8 points of the whole country. The methods of experimenting harmful substance among foods in chapter 10 of book 2 of standard of foods (Food fair) according to clause 7 of Food Sanitation Act were referred for drying methods since shiitake contains lots of moisture and they were dried with heated air drier of 105℃ after being dried with wind for 1~2 days until they are easily pulverized then they were powered using blender before they reabsorb moisture, put into measuring container (450ml Marinelli Beaker), pressed to minimize the volume with equal distribution, weighed and measured with high purity germanium gamma nuclide analyzer for 10,000 and 80,000 seconds. The measuring equipment should be able to evaluate precisely and correctly in analyzing and evaluating gamma nuclide. Thus standardized nuclide were used for measuring by detection device of measuring equipment which Korea Research Institute of Standards & Science keeps radioactivity standards for correction of the equipment and the substance used for correction is standard radioactivity source. Effective correction should be performed since the efficiency of measurement of the equipment differs according to gamma rays energy and the radioactivity concentration was calculated and applied after sample measurement by calculated effective correction formula based on each geometry. The correction result was fine with the error range of all within ±5% when the radioactivity certified value of mixed gamma rays source according to each geometry and the measured value of analyzing instrument were compared after energy and efficiency correction. Only tiny amount of Cs-13 that can not reach the radioactivity allowable standard was detected from all the samples. 0.0106±1.1(Bq/kg-fresh) was detected from rice, 0.0272±3.0(Bq/kg-fresh) was detected from chinese cabbage in national environment radioactivity inspection of Korea Institute of Nuclear Safety in 2012. Imported and distributed foods and homegrown foods were purchased and preprocessed to analyze the gamma nuclide rays in radioactivity pollution among foods inspection ( inspection and research of Korea Atomic Energy Research Institute 2007) Average of 39.40Bq/kg was detected from chaga mushrooms as a result Radioactivity pollution of imported and homegrown foods was inspected in establishing radioactivity analyzing methods and inspecting pollution among foods ( report of Mistry of Food and Drug Safety 2008) I-131, Cs-134, 137 which are gamma nuclide of food fair were not detected, and chaga among foods, blueberry jam and blueberry powder among fruits contained comparatively more than other foods but with much lower level than radioactivity allowable standard(370Bq/kg). The concentration is similar or lower than the past report like above results. There is almost no influence on the body assuming that ordinary person took in that detected radioactivity concentration for a year and calculated the effective amount 8.99E-02 mSv/yr is the amount which is much lesser than 1.0 mSv of intake limit of ordinary person according to item 4 of clause 2 of Nuclear Safety Reinforcement Act. It is concluded that there is almost no influence of Hukushima nuclear power plant accident since there is no Cs-134 detected.