생태재료의 라돈 방출 특성에 대한 실험적 연구 - 황토 Mock up 실험체를 중심으로
Experimental Research on the Radon Emission Characteristic of Ecological Materials : the Hwang-toh Mock up
초록/요약
국 문 초 록 현대인은 하루 일과의 80% 이상을 실내에서 생활하는 만큼 실내공기질은 재실 자의 건강과 직결되는 문제라 할 수 있다. 세계보건기구(WHO)의 조사에 따르면 2012년 실내공기오염으로 인한 사망자 수는 430만 명에 달하며, 최근 중국에서는 하루 평균 300명이 건물 내 유해물질로 인해 사망한다는 통계가 발표되기도 하였 다. 국내 역시 새집증후군(Sick Building Syndrome), 화학물질과민증(Multi Chemical Sensitivity)과 같은 환경성 질환이 해마다 증가하는 등 전 세계적으로 실내공기질 악화에 대한 우려의 목소리가 높아지고 있다. 그 중에서도 라돈은 방사능 중 유일한 기체로서 국제암연구센터(IARC)에서 매년 약 2만 1천 명이 장기적인 라돈 노출로 인한 폐암으로 사망하는 것으로 추산하는 등 위험도가 매우 높은 유해 물질이라 할 수 있다. 일반적으로 실내 중 라돈의 약 85%는 건물 바닥이나 벽의 갈라진 틈새를 통해 유입된 토양가스에 기인한 것으로 서 토양과 근접한 저층건물일수록 라돈에 특히 취약한 것으로 알려져 왔다. 그러나 최근 대다수의 고층건물에서도 기준치 이상의 라돈이 검출되면서 라듐을 포함하고 있는 토양이나 암석으로 제작된 건축 자재를 사용할 경우에도 고농도 라돈에 노출 될 수 있다는 위험성이 제기되고 있다. 이러한 배경 하에 본 연구의 목적은 대표적인 친환경 생태재료이자 광물성 재 료인 황토의 라돈 방출 특성을 확인하고 기후조건(온·습도, 압력 등)과 라돈 방출 량 사이의 상관관계를 확인하는 것이다. 이를 위해 먼저 황토 사용량을 달리한 실 물크기의 Mock up 실험체를 구축하였으며, 연속 모니터링을 통해 기후조건 변화 에 따른 황토의 라돈 방출 특성을 확인하였다. 본 연구의 결과는 다음과 같다. 1) 대표적인 생태재료이자 광물성 재료인 황토를 이용하여 실물 크기의 Mock up 구축한 후 황토에서 발생하는 라돈 방출량을 연속 모니터링 한 결과, 최대 10.1 pCi/L의 라돈이 방출되는 것을 확인하였다. II 이는 세계보건기구(WHO)의 권고기준인 4.0 pCi/L의 2.5배에 달하는 높은 수치 로서 황토 재료에서 고농도의 라돈이 방출됨을 알 수 있었다. 2) 황토의 사용량 및 구조(지하층의 유무)를 달리한 실험체의 라돈 방출 특성을 비교 분석한 결과, 황토의 사용량이 증가함에 따라 라돈의 최대 방출 농도도 증가 함을 알 수 있었다. 또한, 지하층의 유무와 관계없이 모든 실험체에서 일정한 라돈 농도를 보이는 점 등을 통해 황토 자재 자체에서 라돈이 방출됨을 확인하였다. 3) 황토 실험체 내부의 라돈 농도분포를 확인하기 위하여 CFD(Computational Fluid Dynamics) 프로그램을 이용하여 전산해석을 실시하였다. 수직 단면상의 시 뮬레이션 결과에 따르면, 밀도가 약 9.7g/L로 공기보다 9배가량 무거운 라돈 가스 는 주로 바닥에 집중적으로 분포하고 있다. 따라서 서구와 달리 좌식생활을 주로 하는 우리나라의 생활 방식은 고농도의 라 돈에 노출될 위험이 높은 것으로 판단된다. 그러므로 실내 활동 시에는 호흡기가 라돈 가스에 노출되지 않도록 일정 높이를 유지하는 등의 주의가 필요할 것이다. 4) 라돈의 이동 및 확산은 온도, 습도, 압력 등 기후적 요인과 밀접한 관련이 있 다. 온도와 라돈 방출량과의 상관관계를 분석한 결과, 모든 실험체에서 실내 온도 가 낮아짐에 따라 실험체 내 라돈 농도가 증가하는 추세를 보였다. 황토 Mock up 의 경우 온도 11~12℃의 낮은 온도에서 10.1pCi/L의 최대 라돈 농도를 보였으며, 황토마감 Mock up 또한 온도가 낮아질수록 기준치를 초과하는 라돈이 자주 측정 되었다. 이를 통해 온도와 라돈 방출량 사이에는 음(-)의 상관관계가 있음을 알 수 있다. 5) 습도와 라돈 방출량과의 상관관계를 분석한 결과, 모든 실험체에서 실내 습도 가 높아짐에 따라 실험체 내 라돈 농도가 증가하는 추세를 보였다. 두 실험체 모두 실내 습도가 약 82%로 높은 구간에서 각각 10.1pCi/L, 7.4pCi/L의 최대 라돈 방 출강도를 나타냈으며, 이를 통해 습도와 라돈 방출량 사이에는 양(+)의 상관관계 가 있음을 알 수 있다. III 황토는 광물성 생태재료로 채취 지역에 따라 다량의 라듐을 포함하고 있을 수 있으므로, 라돈 저감화를 위한 고려 없이 건축물에 적용할 경우 고농도의 라돈을 방출할 위험이 있다. 또한 건축재료의 라돈 방출량은 다공성, 두께, 라듐 함량에 따라 달라지므로 계획 초기부터 재료에 의한 실내 오염을 최소화하기 위한 자재 선택이 중요하다. 마지막으로 라돈은 온도가 낮아짐에 따라, 습도가 증가함에 따라 방출량이 증가하므로 기후 조건 변화에 따른 적절한 환기 계획이 필요한 것으로 판단된다. 키워드 : 라돈, 황토, 실내공기질, CFD, 시뮬레이션, Mock up
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목 차
국 문 초 록
제 1 장 서 론
1.1 연구의 배경 및 목적 ··········································································································1
1.2 연구의 내용 및 방법 ··········································································································3
1.3 선행 연구 고찰 ··················································································································5
제 2 장 라돈의 특성 및 관리현황
2.1 라돈의 물리적 특성 ············································································································7
2.1.1 라돈의 생성 및 물리적 특성 ··················································································7
2.1.2 라돈가스의 유입경로 ································································································8
2.2 라돈의 위해성 ····················································································································11
2.3 국내‧외 연구상황 및 라돈의 관리기준 ·········································································15
2.3.1 국내‧외 연구상황 ·······································································································15
2.3.2 라돈의 연구기준 ········································································································18
제 3 장 생태재료의 특성 분석
3.1 생태재료의 정의 ················································································································21
3.2 생태재료 황토의 특성 분석 ····························································································22
3.2.1 생태재료 황토의 물리적 특성 ················································································22
3.2.2 생태재료 황토의 사용현황 ······················································································23
3.2.3 생태재료 황토의 실내공기질 특성 ········································································24
제 4 장 Mock Up 실험체를 통한 라돈 방출 특성 연구
4.1 황토 Mock Up 실험체 계획 ··························································································28
4.1.1 황토 Mock Up 실험체 개요 ··················································································28
4.1.2 황토 Mock Up 실험체 디테일 계획 ····································································32
4.1.3 황토 Mock Up 실험체 시공 ··················································································34
4.2 비교 Mock Up 실험체 계획 ··························································································36
4.2.1 황토마감 Mock Up 실험체 개요 ··········································································36
4.2.2 황토마감 Mock Up 실험체 디테일 계획 ····························································40
4.3 Mock Up 실험 계획 ········································································································42
4.3.1 Mock Up 실험 개요 ································································································42
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4.3.2 실험체 측정항목 및 모니터링 시스템 구축 ··························································43
4.3.3 실험방법 및 실험일정 ································································································46
제 5 장 Mock Up 실험 결과 분석
5.1 Mock Up 별 라돈 방출 농도 비교 ··············································································50
5.1.1 황토 Mock Up 실험 결과 분석 ············································································50
5.1.2 황토미장 Mock Up 실험 결과 분석 ····································································53
5.1.3 CFD 시뮬레이션을 이용한 라돈 농도분포 확인 ···············································56
5.1.4 소결 ····························································································································61
5.2 기후조건에 따른 라돈 방출 특성 분석 ········································································63
5.2.1 온도에 따른 라돈 방출 특성 분석 ········································································63
5.2.2 습도에 따른 라돈 방출 특성 분석 ········································································66
5.2.3 소결 ······························································································································68
