Journal of Radiation Protection and Research

The Korean Association for Radiation Protection (대한방사선방어학회)
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Neutron Dose Measurements Using TLDs in a 252Cf Neutron Field

252Cf 중성자장에서 열형광선량계(TLD)를 이용한 중성자 방사선량 측정

  • Chang, Insu (Health Physics Department, Korea Atomic Energy Research Institute) ;
  • Kim, Sang In (Health Physics Department, Korea Atomic Energy Research Institute) ;
  • Lee, Jung Il (Health Physics Department, Korea Atomic Energy Research Institute) ;
  • Kim, Jang Lyurl (Health Physics Department, Korea Atomic Energy Research Institute) ;
  • Kim, Bong Hwan (Health Physics Department, Korea Atomic Energy Research Institute)
  • 장인수 (한국원자력연구원 방사선방호팀) ;
  • 김상인 (한국원자력연구원 방사선방호팀) ;
  • 이정일 (한국원자력연구원 방사선방호팀) ;
  • 김장렬 (한국원자력연구원 방사선방호팀) ;
  • 김봉환 (한국원자력연구원 방사선방호팀)
  • Received : 2013.02.25
  • Accepted : 2013.03.15
  • Published : 2013.03.30
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Abstract

In case of neutron dose measurement using TLDs (thermo-luminescence dosimeters), because the neutron energy dependence of the TLD is very high, the calibration of the energy response according to the characteristics of the neutron spectrum of workplace is required. In the present study, the ambient dose equivalent rates inside and around the Long-Counter (neutron detector) with narrow and complex inside in the neutron field of $^{252}Cf$ were evaluated. The calibration factors to account for the neutron energy dependence of TLDs were established for both the bare and $D_2O$ modulated $^{252}Cf$ neutron beams, respectively. The values of the TLD's measurement were compared with the computational results of the MCNPX (Monte Carlo N-Particles transport code). When using the two calibration factors of the TLD than a single calibration factor, the measured and the calculated values at the point of verification outside and inside the Long-Counter were in more good agreement. This results show that TLD should be calibrated in the reference neutron field similar to workplace situation.

TLD를 이용하여 중성자 선량을 측정할 경우, TLD는 중성자 에너지에 대한 반응도 차이가 크기 때문에 현장 중성자장의 스펙트럼 특성에 맞는 에너지 반응도 보정이 반드시 필요하다. 본 실험에는 소형으로 가공된 TLD 소자를 사용하여 $^{252}Cf$ 중성자장에 설치된 내부구조가 복잡하고 좁은 Long-Counter (중성자 검출기) 내외부에서의 중성자 주위선량당량(ambient dose equivalent)을 측정하였다. 측정결과는 입자수송해석코드(MCNPX)를 이용한 계산결과와 비교하였다. 기존의 TLD 교정 선원인 $D_2O$ 감속 $^{252}Cf$만으로 교정하여 판독한 결과값은 전산모사 계산값과 많은 차이를 보였다. 그러나 bare 및 $D_2O$ 감속 $^{252}Cf$ 선원을 사용하여 생산한 두 교정인자를 혼용한 판독값은 계산값과 비슷하였다. 결과적으로, TLD 소자는 사용 현장과 비슷한 특성을 가지는 중성자장에서 교정되어야지만 올바른 선량평가가 가능함을 확인하였다.

Keywords

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