中文摘要：

为研制用于海洋放射性监测（特别是核电海域）的海水中就地7能谱仪，利用MonteCarlo程序MCNP，采用分层抽样、结果加权叠加的方法，模拟了海水中NaI（T1）、HPGe、CdZnTe、LaBr等探测器在理想状况下对几种有关7射线的能谱，并分析计算出以上各探测器对海水中137CS、60Co、56Mn、40K等放射性核素的探测效率、有效探测距离。结果表明，各探测器对γ放射性核素的有效探测距离约为20～40cm，具体数值与探测器种类和γ射线能量有关。综合探测效率和能量分辨率而言，LaBr探测器具有最好的实际应用价值。该结果为实际的海水中就地γ能谱仪的探测器选择和应用提供了重要参考。

英文摘要：

To develop in-situ 7 spectrometer used in seawater for marine radioactivity monitoring （especial- ly in areas around nuclear power plants）, with the means of stratified sampling and summing by weights, the general-purpose Monte Carlo code MCNP was utilized to simulate the energy spectra of several rele- vant 7 rays recorded by NaI, HPGe, CZT and LaBr detectors immersed in seawater. The detection effi- ciency and the effective detection distance of these detectors to the radionuclides of 137 Cs, 50 Co, 54 Mn and 40 K dispersed in seawater were calculate＆ The results show that the effective detection distance of these detectors to 7 radionuclides is about 20~40cm and the specific value is related with the detector type and γ-ray energy. Concerning detection efficiency and energy resolution, the LaBr detector has the best prac- tical application value. The results will provide an important reference to detector selecting and application of practical in-situ γ spectrometer used in seawater.