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为准确评估小型动力堆海上严重核事故后释放的气载核素造成的海洋放射性污染水平,以小型动力堆断电诱发的严重核事故为例,建立核素在大气和海洋中扩散的计算模型,计算事故后大气和海洋中137Cs的放射性污染水平,并分析了气载核素释放高度、大气稳定度对沉降核素海洋扩散的影响。结果表明,在一定的释放高度下,源下风轴线上表层海水中核素的时间积分浓度随下风向距离的增大呈先升高后下降的变化规律;在离源一定距离内,释放位置越高,表层海水中核素的时间积分浓度越小;在离源一定距离外,大气越不稳定,表层海水中核素的时间积分浓度越小。 相似文献
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放射性液体泄漏事故是后处理设施典型的事故,泄漏事故通常发生在设备室。高放废液贮槽泄漏后气载放射性核素生成包括两个过程:一是在泄漏放射性液体的过程中惰性气体从溶液中释放,以及与空气、地板相互作用产生的气溶胶;二是泄漏后的蒸发过程(包括冲洗前稀释前和稀释后)。气溶胶在设备室内生成后会发生沉积,同时随着设备室排风系统,经过滤后向环境排放。本文给出了一种放射性溶液贮槽泄漏事故源项估算方法,实现了事故泄漏质量、泄漏活度、设备室气载放射性活度浓度及积分浓度、环境释放源项估算,为事故应急决策和响应行动提供数据支持。 相似文献
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在分析无外中子源照射条件下核部件中裂变产物的来源及其释放缓发γ射线机理基础上,提出了应用CINDER90程序计算核部件中裂变产物活度的方法,计算并分析了裂变产物的种类、活度及其随辐照时间和冷却时间的变化规律,继而根据裂变产物β-衰变释放的特征γ射线的能量与分支比数据,计算得到了核部件中裂变产物缓发γ射线源项,并应用蒙特卡罗方法计算了核部件释放的缓发γ能谱随辐照时间和冷却时间的变化,分析了缓发γ能谱的时间演化行为。结果表明:核部件缓发γ能谱中强度最大的γ射线是裂变核素140La β-衰变发射的1 596 keV射线,且该γ射线的强度在部件组装一定时间后保持稳定,该结果与文献结果符合一致。本文提出的裂变产物缓发γ能谱模拟计算方法和结果可为核部件γ能谱的测量与分析提供参考。 相似文献
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根据AST方法建立了AP1000LOCA放射性核素活度计算模型,研究事故后安全壳及环境中放射性核素活度的变化。结果表明:事故后安全壳气空间内各核素的放射性活度呈先增大后减小的趋势,40min时达到最大。根据核素性质,将其分为不考虑母核衰变的核素和考虑母核衰变的核素。事故发生40min后,前者在安全壳内的活度指数减小,典型核素有131~135I、83 Krm等,后者由于母核衰变的影响导致其在安全壳内的活度减小趋势放缓,典型核素有85 Kr、133 Xem、133 Xe和135 Xe等。I和Cs由于受自然去除机制的去除作用,事故几小时后其向环境的累积释放量增长非常缓慢;对于Kr和Xe,半衰期较长的核素向环境的累积释放量不断增大,半衰期较短的核素在事故几小时后向环境的累积释放量趋于平衡。 相似文献
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为提高全身计数器γ能谱分析精度,开展了基于能谱重建技术的γ能谱分析方法研究。首先建立方法的原理框架;然后进行应用实验,使用一台立式NaI型全身计数器测量含放射性的BOMAB人体模型,并通过建模和蒙特卡罗模拟计算测量矩阵;最后使用boosted-Gold算法求解出射能谱,并将结果与Genie 2000软件进行比较。结果显示,boosted-Gold算法在参数p取1~10时能准确重建出理论的核素出射能谱,实现对所有核素的准确识别,且每种核素的活度计算误差均小于10%,这一结果显著优于Genie 2000软件。 相似文献
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介绍了航空伽玛能谱谱线校正的方法,并且对经过校正航空伽玛能谱数据进行数据窗口的重组.对航空能谱仪谱漂产生的原因和航空伽玛能谱数据的处理方法进行了介绍,根据我国自主研制的航空伽玛能谱仪谱线采集的特点和谱线合成方式,提出了采用变尺度校正的方式对谱线数据进行校正,并且根据航空伽玛能谱测量的要求,对窗口数据进行重组.实验结果表... 相似文献
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在天然辐射环境下,无法找到仅含单一天然放射性系列的近似无限大地层用于获取航空γ谱仪的响应谱,这是导致无法利用最小二乘法解析航空γ能谱的关键问题所在。本文基于介质互换原理、地层模块化与分能区多次模拟的思想,通过构建Monte Carlo组合模型,从而获得了含不同放射性物质的任意形状地层上空航空γ谱仪的响应谱。依据航空γ能谱测点上γ辐射来源与石家庄动态带分析,建立了一套可靠的最小二乘法航空γ能谱解析模型。通过对野外10 km测线分析发现,当地层含量大于4×10~(-6)时,该方法与标准方法分析结果相当。同时该方法为人工放射性核素响应谱的剥离提供参考。 相似文献
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Katsunori Ueno Takahiro Tadokoro Takuya Fukumoto Satoshi Okada 《Journal of Nuclear Science and Technology》2019,56(9-10):822-830
ABSTRACTFor decommissioning the Fukushima Dai-ichi Nuclear Power Station, information on the radiation environment such as dose rate and radionuclides inside the primary containment vessel (PCV) is crucial. The authors have developed a fiber optic-type compact dosimeter and demonstrated it for a basement investigation inside the PCV of Unit 1. The dosimeter consisted of a Nd:YAG crystal that emitted infrared photons of 1064 nm by gamma-ray irradiation, an optical fiber as signal transmitter, and a measurement instrument for pulse height analysis. The dose rate linearity of the dosimeter was evaluated in the dose rate range from 0.01 to 8760 Gy/h by using gamma rays emitted from Co-60. The Nd:YAG crystal installed in a sensor unit was placed in a shape changing robot, PMORPH2, and dose rate distributions were obtained at 10 measurement points. The dose rate increased gradually when the sensor unit was close to the surface of some sediment. A comparison of measured dose rate attenuations obtained at two measurement points and calculated results showed that Cs-137 might stay on the surface or inside the sediment as the dominate radionuclide. 相似文献
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No currently available, single leak-detection method combines optimal leakage detection sensitivity, leak-locating ability, and leakage measurement accuracy. Technology is available to improve leak detection capability at specific sites by use of acoustic monitoring. However, current acoustic monitoring techniques provide no source discrimination (e.g., to distinguish between leaks from pipe cracks and valves) and no leak-rate information (a small leak may saturate the system).Seven cracks, including three field-induced IGSCC specimens and two thermal-fatique cracks, have been installed in a laboratory acoustic leak detection facility. The IGSCC specimens produce stronger acoustic signals than the thermal-fatigue cracks at equivalent leak rates. Despite significant differences in crack geometry, the acoustic signals from the three IGSCC specimens, tested at the same leak rate, are virtually identical in the frequency range from 300 to 400 kHz. Thus, the quantitative correlations between the acoustic signals and leak rate in the 300–400 kHz band are very similar for the IGSCC specimens. Also, acoustic background data have been acquired during a hot functional test at the Watts Bar PWR. With these data, it is now possible to estimate the sensitivity of acoustic leak detection techniques. 相似文献
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Small perturbations of the environmental radiation field by artificial radionuclides have been successfully quantified using high pressure ionization chambers and in situ semiconductor detector gamma-ray spectra. The calibration and use of these instruments for the detection of ground-deposited and airborne sources of activity is described and general methods for data interpretation are discussed. Specific examples are given in which the exposure rate from fallout radionuclides deposited on the soil surface and from noble gases released by nuclear facilities are determined and unambiguously separated from variations in the underlying background. 相似文献
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《核技术(英文版)》2016,(3):109-118
NaI(T1) scintillation detectors have been widely applied for gamma-ray spectrum measurements owing to advantages such as high detection efficiency and low price.However,the mitigation of the limited energy resolution of these detectors,which detracts from an accurate analysis of the instrument spectra obtained,remains a crucial need.Based on the physical properties and spectrum formation processes of NaI(T1) scintillation detectors,the detector response to gamma photons with different energies is represented by photopeaks that are approximately Gaussian in shape with unique full-width-at-half-maximum(FWHM) values.The FWHM is established as a detector parameter based on resolution calibrations and is used in the construction of a general Gaussian response matrix,which is employed for the inverse decomposition of gamma spectra obtained from the detector.The Gold and Boosted Gold iterative algorithms are employed to accelerate the decomposition of the measured spectrum.Tests of the inverse decomposition method on multiple simulated overlapping peaks and on experimentally obtained U and Th radionuclide series spectra verify the practicability of the method,particularly in the low-energy region of the spectrum,providing for the accurate qualitative and quantitative analysis of radionuclides. 相似文献
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提出了一种新的自然伽玛能谱测井的方法,该方法仅探测低能伽玛射线,选定~(214)Bi的609.3keV和~(208)Tl的583.2keV特征峰分别作为铀道和钍道的计数窗口.采用HPGe伽玛谱仪对测井模型进行实验测量,获得的铀道、钍道测井曲线效果很好,验证了该方法的可行性,表明基于HPGe探头的铀矿伽玛测井研究前景诱人. 相似文献