共查询到18条相似文献,搜索用时 93 毫秒
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AP1000等非能动压水堆核电厂依靠自然的原理清除事故后安全壳气空间内的放射性气溶胶,可靠性较高,但对其进行分析较为复杂。事故后安全壳内气溶胶的主要运动形式有凝聚、重力沉降、扩散泳及热泳等,本文研究确定了合适的机理模型、假设条件和主要参数等,完成了AP1000核电厂的分析。分析结果表明,AP1000核电厂LOCA后,主要气溶胶去除机制中扩散泳贡献最大,其次是热泳和重力沉降;安全壳内气溶胶自然去除系数约为0.4~0.9h~(-1),堆芯裸露5h后变化较小;基于RG1.183源项、包络大气弥散因子及本文给出的安全壳气溶胶自然去除系数,计算得到的LOCA后厂外及主控室人员所受剂量可满足10CFR50中规定的限值要求。 相似文献
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发生频率较大的安全壳旁通事故对严重事故的放射性后果有较大贡献。在AP1000的概率安全评价(PSA)分析中,采用MAAP4.0.4程序计算安全壳旁通事故的源项。MAAP4.0.4未考虑蒸汽发生器二次侧复杂流道结构对气溶胶的沉积效应,在国外相关实验的基础之上,开发了复杂流道结构下气溶胶的沉积模型,并修改MAAP4.0.4源程序中蒸汽发生器二次侧的气溶胶沉积模型,最后对安全壳旁通释放类的源项进行了重新评价,结果表明:采用改进后二次侧气溶胶沉积模型计算比采用原模型计算气溶胶的质量释放份额有所减少。这也为今后AP1000的概率安全评价分析中计算安全壳旁通事故源项提供一个参考。 相似文献
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拟建桃花江AP1000核电站LOCA 131I源项分析 总被引:1,自引:0,他引:1
针对核电厂事故工况下放射性物质的大气弥散问题,运用CALPUFF空气质量模型,模拟了桃花江核电厂冷却剂丧失事故(LOCA)工况下典型气载放射性物质131I的大气弥散过程,并对计算结果进行辐射剂量的估计,结果表明:1)事故开始后数小时内,源下风向8 km左右,高程与释放源有效高度相当,且海拔明显高于上风向海拔的地形区域,极易形成131I地面空气积分浓度峰值。2)三种化学形态的碘中,元素碘最易沉积。计算区域内地面沉积浓度与空气积分浓度呈现相同的分布规律。3)131I内照射造成的最大剂量当量比外照射高4个数量级,因而事故情况下防止放射性物质从呼吸道、口腔、伤口及皮肤进入人体,能极大降低131I的辐射剂量当量。 相似文献
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基于微机的核设施环境评价软件包—NGAS,NLIQ,NACC,NRED 总被引:1,自引:1,他引:0
本文介绍了基于微机的核设施环境评价软件包的主要内容、设计原则和特点。该软件包包括:核设施气态流出物常规和事故释放环境评价程序、核设施液态流出物常规和事故释放环境评价程序以及核设施环境数据库。核设施气态流出物常规和事故释放环境评价程序,用于大气弥散计算和公众剂量算,给出了核设施周围放射性核的空气浓度、地面沉积浓度和动物物产品中的浓度,并进而估算核设施周围的集体剂量和最大个人剂量。 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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反应堆发生严重事故时,堆芯释放出的吸湿性气溶胶会在潮湿的安全壳内增大,从而影响其自然去除过程。本文理论推导了吸湿性气溶胶的增大模型并通过多种方法对其进行了验证。模型计算结果表明,气溶胶的增大过程由于受到溶解度的限制而存在临界湿度值,在该临界值以下时气溶胶不发生吸湿,但这未被其他严重事故分析程序所考虑。同时,基于某三代先进压水堆的特定严重事故工况,本文分析了干颗粒半径及湿度对气溶胶的平衡半径和自然去除系数的影响。结果表明:气溶胶的自然去除系数随干颗粒半径的增大将先减小后增加,并在1 μm时达到最小值;相同湿度下,干颗粒半径对气溶胶半径的最大增大比例的影响不大;湿度的增加对不同干颗粒半径气溶胶去除系数的影响不同。 相似文献
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J.M Mäkynen J.K Jokiniemi P.P Ahonen E.I Kauppinen R Zilliacus 《Nuclear Engineering and Design》1997,178(1):74
Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m3 total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compared to high RH. Thus at high RH (96–97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs. Experimental results were also compared with calculations obtained by severe accident computer codes. These calculated results will be presented in a later paper. 相似文献
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Thermal-hydraulic and aerosol containment phenomena modelling in ASTEC severe accident computer code 总被引:1,自引:0,他引:1
Ivo Kljenak Maik Dapper Luis E. Herranz Joan Fontanet 《Nuclear Engineering and Design》2010,240(3):656-667
Transients in containment systems of different scales (Phebus.FP containment, KAEVER vessel, Battelle Model Containment, LACE vessel and VVER-1000 nuclear power plant containment) involving thermal-hydraulic phenomena and aerosol behaviour, were simulated with the computer integral code ASTEC. The results of the simulations in the first four facilities were compared with experimental results, whereas the results of the simulated accident in the VVER-1000 containment were compared to results obtained with the MELCOR code. The main purpose of the simulations was the validation of the CPA module of the ASTEC code. The calculated results support the applicability of the code for predicting in-containment thermal-hydraulic and aerosol phenomena during a severe accident in a nuclear power plant. 相似文献
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本文通过对福岛核事故期间应急监测工作的总结,发现了应急监测期间气溶胶样品γ核素分析结果需修正。样品中短半衰期核素,特别是采样时间和测量时间较长的样品需进行衰变修正,给出了采样、放置、测量时间衰变修正因子。在分析气溶胶样品中放射性核素活度浓度时,需考虑滤膜收集效率修正,文中采用双滤膜法给出了两种常用滤膜的收集效率。针对气溶胶中137Cs的分析,介绍了有干扰峰的γ能谱解谱方法,并提出了分析气溶胶样品时降低干扰的措施。本文对气溶胶样品γ核素分析结果的修正方法,可为全国性核事故应急监测提供参考。 相似文献
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Radioactive aerosols as one of the most important products in serious nuclear reactor accidents are generated from leakage of solid fission products and condensation of gaseous fission products. Bubbly scrubbing is an effective way to deposite radioactive aerosols. It is of great significance for post-accident source term control and accident analysis and evaluation to accurately grasp its filtration efficiency. In this paper, an in-depth basic research was carried out on the aerosol deposition characteristics in rising bubbles. With the help of advanced particle size spectrum analysis technology, the influence of parameters such as liquid submersion depth and apparent gas phase velocity on the deposition efficiency of submicron aerosols was studied to explore the deposition mechanism of aerosols in rising bubbles. The research results of this project can be used to verify the aerosol deposition efficiency model, so as to improve the uncertainty of the analysis results of source term concentration under severe accident conditions. 相似文献