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通过蒙特卡罗程序MCNP(Monte Carlo N Particle Transport Code)建立了海洋γ谱连续监测的测量模型,模拟计算不同能量γ射线在海水中的衰减情况和有效探测距离。根据我国近岸海域海水中天然放射性核素活性浓度,模拟得到不同晶体尺寸NaI探测器连续监测的本底谱,分析能量分辨率对全能峰本底计数率的影响并探讨了影响NaI探测器能量分辨率的因素。最后针对我国核电厂周围海域中重点关注的人工放射性核素,并假设不同尺寸NaI晶体在能量662 keV处分辨率保持7.0%不变的条件下,分别计算了不同尺寸NaI晶体探测器在海洋γ谱连续监测中的探测效率、本底计数率和最小可探测活性浓度等技术参数。模拟结果为海洋或其它水体中γ谱连续监测方法的应用提供技术参考。
The Monte Carlo N Particle Transport Code (MCNP) was used to establish a continuous monitoring model of marine gamma spectrum, and the attenuation of the different energy γ rays in seawater and the effective detection distance were simulated. Based on the active concentrations of natural radionuclides in the seawater of coastal areas in China, the background spectra of continuous monitoring of NaI detectors with different crystal sizes were simulated and the effect of energy resolution on the background count rate of all-around peaks was analyzed. The effects of NaI detector energy Resolution factor. Finally, for the artificial radionuclides that are the focus of attention in the sea area around the NPPs in our country and assuming that the resolution of the NaI crystals with different sizes remains unchanged at the energy of 662 keV, the resolution of the NaI crystals with different sizes in the ocean γ Spectrum continuous monitoring of detection efficiency, the background count rate and the minimum detectable concentration and other technical parameters. The simulation results provide a technical reference for the application of γ-ray continuous monitoring method in marine or other water bodies.