Abstract
一般核反應器在正常運轉時會釋放一些微量放射性氣體Ar、Kr及Xe，本論文主要探討高純鍺偵檢器(HPGe)作為核能設施現場快速量測放射性氣體之偵檢系統。本實驗之設計乃針對密閉場內及戶外開放空間之均勻瀰漫放射性氣體作一度量，系統由可攜帶式高純度鍺偵檢器及全功能多頻分析儀所組成，可作為移動式偵測系統；且本系統無須利用幫浦抽氣、濾紙吸附等程序，故可達到定性、定量、瞬時、機動之量測。論文概分為二部分：(1) 利用自行製備之氣體射源41Ar、125Xe、133Xe及135Xe均勻瀰漫於密閉室內，對高純度鍺偵檢器作一瀰漫放射性氣體效率校正，再以公式推估不同體積密閉室及開放空間之偵測效率。(2) 利用曝露劑量轉換因子，直接推估瀰漫氣體之有效等效劑量，並由核能設施現場監測所得之偵測極限和可應用範圍作一討論。實驗結果顯示：(1) 效率和能量在對數座標上呈一線性 關係，可看出實驗之準確性，且偵檢系統之現場偵測極限遠低於法規律定之推定空氣濃度及參考濃度，故可應用於核災、核戰等意外事故之放射性氣體偵測，作到機動、快速、定性定量之分析。(2) 由量測之計數率可直接推估現場之曝露劑量，能提供人員防護及事故嚴重程度研判之依據。In the case of normal operations, continuous release ofgaseous radionuclides of trace amount of isotopes ofAr, Kr and Xe form reactor is found. The purpose of thisstudy is to examine the applicability of real- timemonitoring of gaseous radionuclides with a high-purity germaniumdetector (HPGe). The system, consisted of portable HPGe andmultichannel analyzer (MCA), is designed for the measured bothin sealed chamber and in outdoors surrounded withgaseous radionuclides. Besides, quantitative,qualitative, prompt and on-line measurement can bereached with the portable detectors without air sucking pump andfilter paper.The research was divided into two major parts as follows : (1)The HPGe detector was calibrated using artificial gaseousAr-41 and Xe- 125,133,135 released to a sealedchamber. The efficiency in both sealed chamber andoutdoors are formulated from the calibrated volumetricsealed chamber. (2) We can obtain the effective dose equivalentof the gaseous radionuclides using dose rate conversionfactors. Detection limit and possible application in fieldmonitoring are discussed. The results show :(1) linear relationship between efficiency andenergy in log coordinate be obtained, the detector system isavailable for measurement of detection limit (DL) far lessthan legal derived air concentration (DAC),application can be applied to detect the gaseousradionuclides in nuclear accident and nuclear war. (2) The doserate formulated from the counting rate can provide therapid information for personal protection and postaccident assessment.