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식품류의 토륨 방사능농도와 내부피폭선량 원문보기
Thorium concentrations in foodstuff and their internal dose

  • 저자

    임수경

  • 학위수여기관

    慶北大學校 大學院

  • 학위구분

    국내박사

  • 학과

    물리학과 핵물리학전공

  • 지도교수

  • 발행년도

    2004

  • 총페이지

    128p.

  • 키워드

    토륨 방사능농도 내부피폭선량;

  • 언어

    kor

  • 원문 URL

    http://www.riss.kr/link?id=T10045608&outLink=K  

  • 초록

    In this study, the concentrations of naturally occurring radionuclides ^(228)Th, ^(230)Th and ^(232)Th in foodstuff(milk, meat and grain) were measured, and the annual internal dose due to Th was also estimated. In order to improve the chemical yield of thorium in chemical procedure for foodstuff, the process of oxalic co-precipitation, which removes the phosphate content in food, was added to usual anion-exchange method. The chemical yield of Th was raised to 70% and the measurement of Th concentration was peformed by alpha spectrometry. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in milk were in the range of 0.51∼8.52mBq/kg-fresh, 0.14∼2.45mBq/kg-fresh and 0.01∼2.46mBq/kg-fresh, respectively. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in meat were in the range of 1.57∼103mBq/kg-fresh, 1.22∼13.0mBq/kg-fresh and 0.25∼9.32mBq/kg-fresh, respectively. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in grain were in the range of 2.91∼980mBq/kg-fresh, 0.43∼91.6mBq/kg-fresh and 0.32∼42.2mBq/kg-fresh, respectively. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in vegetables were in the range of 2.41∼163.39mBq/kg-fresh, 0.05∼9.03mBq/kg-fresh and 0.02∼6.76mBq/kg-fresh, respectively. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in fruit were in the range of 3.97∼97.18mBq/kg-fresh, 0.29∼7.41mBq/kg-fresh and 0.20∼9.71mBq/kg-fresh, respectively. The ^(228)Th concentration was higher than concentration of ^(230)Th and ^(232)Th in whole foodstuff because of ingrowth of ^(228)Th from ^(228)Ra and ^(228)Ac. The correction equation for ingowth of ^(228)Th was derived using law of successive disintegration and radioactive equilibrium. In most sample of vegetables and fruits, the ^(230)Th concentration was lineally correlated with ^(232)Th concentration, whereas no lineality was found between concentration of ^(228)Th and ^(232)Th. The concentrations of ^(228)Th, ^(230)Th and ^(232)Th in Korean surface soil were in the range of 19.35∼205.91Bq/kg-dry with an average concentration of 55.4±11.15Bq/kg-dry, 3.32∼88.57Bq/kg-dry with an average concentration of 28.23±5.57Bq/kg-dry and 23.64∼203.91Bq/kg-dry with an average of 63.92±13.01Bq/kg-dry, respectively. The average ratio of ^(230)Th/^(232)Th and ^(232)Th/^(228)Th was 0.51 and 1.19, respectively. The maximum Th concentration was appeared in Gangneung and Chungbuk. From geological viewpoint, this results may due to distribution of granite in Korea. The transfer factor of Th (1)was 4.15×10^(-4) for ^(228)Th, was 1.39×10^(-4) for ^(230)Th and was 2.33×10^(-4) for ^(232)Th in rice; (2)was 1.52×10^(-3) for ^(228)Th, was 1.27×10^(-3) for ^(230)Th and was 1.03×10^(-3) for ^(232)Th in Barley; (3)was 5.95×10^(-2) for ^(228)Th, was 2.58×10^(-2) for ^(230)Th and was 2.85×10^(-2) for ^(232)Th in Chinese cabbage; (4)was 8.60×10^(-3) for ^(228)Th, was 7.54×10^(-3) for ^(230)Th and was 1.06×10^(-4) for ^(232)Th in radish. With the measured Th concentrations, annual consumption of Korean foods and dose conversion factor given by ICRP 72, the annual internal dose for Korean adult men was estimated and presented. The total annual internal doses due to Th in milk, meat, grain, vegetables and fruits were estimated to be 6, 30, 59, 45 and 32nSv/year, respectively. Among them, the internal doses due to rice and chinese cabbage were much larger than that of another samples because of Korean eating habit. The results of this study may be used as environmental radiation research and applied to the safety research of foods and radiation risk of population.


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