Content of plutonium, thorium and protactinium in sea water and recent coral in the North Pacific

  • Toshio Imai
  • Masanobu Sakanoue


The contents of plutonium isotopes (239Pu and238Pu), thorium isotopes (232Th,230Th and228Th) and protactinium-231 in sea water collected in the North Pacific, the East China Sea and the Japan Sea were determined. These nuclides were sequentially analyzed byα-ray spectrometry after separating them mainly with solvent extraction technique. The contents of239Pu in surface sea water ranged from 0.6 to 1.6 pCi/10001,238Pu/239Pu activity ratios being 0.2∼0.7. The228Th/232Th activity ratios for the North Pacific waters varied between 7.6 and 30, whereas the sample from the East China Sea showed the very high value, 65. The contents of231Pa are less than 6 percent of that in equilibrium with its parent235U. Furthermore, the analysis of plutonium isotopes in recent coral from Yoron Island was carried out and it was confirmed that plutonium isotopes have concentrated in recent coral with the concentration factor of about 1∼2×103.


Japan Solvent Extraction Thorium Concentration Factor Extraction Technique 
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Copyright information

© The Oceanographical Society of Japan 1973

Authors and Affiliations

  • Toshio Imai
    • 1
  • Masanobu Sakanoue
  1. 1.Radiochemical Laboratory, Department of Chemistry, Faculty of ScienceKanazawa UniversityKanazawaJapan

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