Analysis of 766 keV Gamma Peak from NPP Environmental Samples

원전주변 환경시료의 766 keV 감마선에너지 피크에 대한 해석

  • Kim, Wan (Radiation Science Research Institute, Kyungpook National University) ;
  • Lee, Hae-Young (Radiation Science Research Institute, Kyungpook National University) ;
  • Yang, He-Sun (Korea Hydro & Nuclear Power CO. LTD Ulchin Nuclear Power Site,) ;
  • Park, Hae-Soo (Korea Hydro & Nuclear Power CO. LTD Ulchin Nuclear Power Site,) ;
  • Kim, Bong-Kuk (Korea Hydro & Nuclear Power CO. LTD Ulchin Nuclear Power Site,) ;
  • Park, Hwan-Bae (Department of Physics and Energy Sciences, Kyungpook National University) ;
  • Kim, Hong-Joo (Department of Physics and Energy Sciences, Kyungpook National University) ;
  • Lee, Sang-Hoon (Department of Physics and Energy Sciences, Kyungpook National University)
  • 김완 (경북대학교 방사선과학연구소) ;
  • 이해영 (경북대학교 방사선과학연구소) ;
  • 양희선 (한국수력원자력 울진원자력본부) ;
  • 박해수 (한국수력원자력 울진원자력본부) ;
  • 김봉국 (한국수력원자력 울진원자력본부) ;
  • 박환배 (경북대학교 물리및에너지학부) ;
  • 김홍주 (경북대학교 물리및에너지학부) ;
  • 이상훈 (경북대학교 물리및에너지학부)
  • Published : 2009.12.30

Abstract

Gamma spectral results for macroalgae samples taken from the environment of Ulchin nuclear power plants in Korea (east coast), showed 766 keV peaks, which were identified as $^{95}Nb$ by several research institutes. After the enhancement of liquid radioactive waste disposal facility at Ulchin NPP site, the $^{95}Nb$ amount in the liquid radioactive waste outflow has drastically reduced, but the expected reduction in $^{95}Nb$ specific activity from environmental samples did not actually show up on gamma spectroscopy. Detailed re-investigation revealed that along with 766 keV peak, other peaks (63, 92 and 1001 keV) from $^{234}Th-^{234}mPa$ decay series were also detected on spectroscopy, and that the measured half lives of the four peaks were very close to known half life of $^{234}Th-^{234}mPa$ decay series, which is 24.1 day. The measured gamma yield ratios of 766 keV peak to 1001 peak were very close to known ratio 0.35 for $^{234}mPa$. It is concluded that 766 keV peaks on gamma spectroscopy of Ulchin NPP environmental samples were mainly from $^{234}mPa$, which is one of naturally occurring radionuclides.

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