共查询到20条相似文献,搜索用时 62 毫秒
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基于蒙特卡罗均匀化理论与有限体积方法,建立了适用于瞬发临界事故分析的三维扩散时空动力学模型。将三维扩散时空动力学模型与非稳态传热模型、辐照裂解气泡模型耦合,对计算程序GETAC-S进行了升级,使其具备了对溶液系统任意几何与材料条件下的瞬态分析能力。使用国际上已有的瞬态装置TRACY的实验数据对GETAC-S进行了验证,结果符合良好。使用GETAC-S对日本的JCO临界事故进行了事故进程反演,证明GETAC-S具备了对复杂溶液系统下的临界事故后果进行评价与反演的能力,为核临界事故的预防、评估和屏蔽提供了理论支持。 相似文献
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日本JCO临界事故的辐射监测 总被引:2,自引:0,他引:2
1999年 9月 3 0日 1 0 :3 5日本核燃料处理公司 ( JCO)的 3名工作人员在将约 1 6.6kg浓缩铀溶液直接倒入沉淀池内时引发临界事故。事故的核裂变总数为 2 .5× 1 0 1 8,释放出大量中子和 γ辐射 ,3名当事人都受到严重中子和 γ照射 ,表现出厌食、恶心、呕吐、腹泻等典型的急性辐射综合症。当天 1 5:0 0东海地方当局实施半径 3 50 m范围内 2 0 0人避迁撤离措施 ,1 0月 1日 6:0 0链式反应终止 ,1 0月 2日 1 8:3 0日本政府宣布解除对该地区的警戒。事故发生后日本有关部门和机构对事故处理、事故分析、应急监测、事故影响评价、公众沟通等方面做了大量工作。这次事故在国际核事故分级表上列为 4级 ,场外无明显放射性污染 ,临近公众受到轻微照射。本文介绍 JCO临界事故的事故序列、事故响应、事故监测和剂量估算。 相似文献
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对瞬态临界事故的准确模拟是核燃料溶液系统临界安全评估的关键因素。现有的辐解气体模型经验参数较多,导致功率特性预测存在较大偏差。为提高模拟精度和避免对模型中经验参数取值的依赖,需对辐解气体模型进行改进。基于对溶液中辐解气体行为的分析和简化假设,建立了包含辐解气体浓度、辐解气泡单位体积物质量和气泡数量密度的守恒模型,并将其与点堆中子动力学模型和二维导热模型相耦合,开发了溶液系统二维瞬态分析程序,通过日本TRACY实验进行了验证。结果表明,程序模拟值与实验数据符合较好,程序模型能够准确模拟溶液系统临界事故的功率变化。 相似文献
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日本JCO有限公司临界事故及值得思考的问题 总被引:1,自引:0,他引:1
1999年9月30日,日本JCO有限公司一座铀转化设施的辅助工厂发生了一起核临界事故。本文主要依据国际原子机构(IAEA)派往日本的一个专家组了解事故情况后相应的报告,简要介绍了事故发生的经过,所采取的应急响应措施,环境监测和初步的剂量评价结果。文中着重分析了事故的原因、性质和对环境的影响,指出该事故主要是由严重违反安全原则的人为错误引起的。文章最后还讨论了从这次事件中应吸取的教训和新闻媒体等有关方面值得思考的问题。 相似文献
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核临界安全分析是保证乏燃料后处理厂安全性的关键技术,而现有核临界安全事故分析程序中,或在几何适用范围上受限,或由于计算效率低而工程实用性差。因此,亟需研发一套适用范围大、计算精度高的临界安全分析方法,提高对核临界事故的分析精度,为乏燃料后处理厂提供技术保障。为此,本文针对乏燃料溶液系统特性,基于零维超细群截面制作与全问题并群方法、预估-校正准静态中子动力学计算方法和二维轴对称热工-辐解气体模型,开发了相应的计算程序模块,最终形成了一套具备并行功能的三维乏燃料溶液系统临界安全分析程序hydra-TD。进一步利用该程序对法国SILENE实验装置进行了验证,结果显示:第一裂变功率峰、倍增时间、总裂变次数等关键参数的误差较小,证明hydra-TD程序正确模拟了燃料溶液系统临界过程中的多物理过程,具备临界安全分析的能力。 相似文献
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Yoshitaka Naito Toshihiro Yamamoto Tsuyoshi Misawa Yuichi Yamane 《Journal of Nuclear Science and Technology》2013,50(11):1045-1061
Since the early 1960s, many studies on criticality safety evaluation have been conducted in Japan. Computer code systems were developed initially by employing finite difference methods, and more recently by using Monte Carlo methods. Criticality experiments have also been carried out in many laboratories in Japan as well as overseas. By effectively using these study results, the Japanese Criticality Safety Handbook was published in 1988, almost the intermediate point of the last 50 years. An increased interest has been shown in criticality safety studies, and a Working Party on Nuclear Criticality Safety (WPNCS) was set up by the Nuclear Science Committee of Organisation Economic Co-operation and Development in 1997. WPNCS has several task forces in charge of each of the International Criticality Safety Benchmark Evaluation Program (ICSBEP), Subcritical Measurement, Experimental Needs, Burn-up Credit Studies and Minimum Critical Values. Criticality safety studies in Japan have been carried out in cooperation with WPNCS. This paper describes criticality safety study activities in Japan along with the contents of the Japanese Criticality Safety Handbook and the tasks of WPNCS. 相似文献
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Yuichi Yamane 《Journal of Nuclear Science and Technology》2013,50(11):1425-1435
A simple equation for the first peak power in a criticality accident due to instantaneous reactivity insertion into nuclear fuel solution system has been developed to improve the accuracy in the estimation of the first peak power keeping the easiness of calculation.The equation is based on the assumption that temperature feedback reactivity is a second-order function of an increase in fuel temperature. Peak power estimated using the equation was in a range between about a half and twice of experimental value. Its applicability to a wide range of initial reactivity and accuracy of estimation have been confirmed in the comparison to one-point kinetics numerical calculation.The expression suggests the first peak power increases with the square of small initial reactivity and three-halves power of large initial reactivity. 相似文献
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It has been found that the pressure in the reactor coolant system (RCS) remains high in some severe accident sequences at the time of reactor vessel failure, with the risk of causing direct containment heating (DCH).Intentional depressurization is an effective accident management strategy to prevent DCH or to mitigate its consequences. Fission product behavior is affected by intentional depressurization, especially for inert gas and volatile fission product. Because the pressurizer power-operated relief valves (PORVs) are latched open, fission product will transport into the containment directly. This may cause larger radiological consequences in containment before reactor vessel failure. Four cases are selected, including the TMLB' base case and the opening one, two and three pressurizer PORVs. The results show that inert gas transports into containment more quickly when opening one and two PORVs,but more slowly when opening three PORVs; more volatile fission product deposit in containment and less in reactor coolant system (RCS) for intentional depressurization cases. When opening one PORV, the phenomenon of revaporization is strong in the RCS. 相似文献
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Kosuke Tanaka Shuhei Miwa Isamu Sato Takashi Hirosawa Shin-ichi Sekine Masahiko Osaka 《Journal of Nuclear Science and Technology》2014,51(7-8):876-885
As a first step for obtaining experimental data on the effects of high-temperature chemical interaction on fission product release behavior, we focused on the dissolution of irradiated uranium plutonium mixed oxide (MOX) fuel by molten zircaloy (Zry) and carried out a heating test under the reducing atmosphere. Pieces of an irradiated MOX fuel pellet and cladding were subjected to the heating test at 2373 K for five minutes. The fractional release rate of cesium (specifically 137Cs) was monitored during the test and its release behavior was evaluated. The observation of microstructures and measurements of elemental distribution in the heated specimen were also performed. We demonstrated experimentally that the fuel dissolution by molten Zry accelerated the release of Cs from the fuel pellets. 相似文献
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Naoya Miyahara Shuhei Miwa Naoki Horiguchi Isamu Sato Osaka Masahiko 《Journal of Nuclear Science and Technology》2019,56(2):228-240
In order to improve LWR source term under severe accident conditions, the first version of a fission product chemistry database named ‘ECUME’ was developed. The ECUME is intended to include several datasets of major chemical reactions and their effective kinetic constants for representative severe accident sequences. It is expected that the ECUME can serve as a fundamental basis from which fission product chemical models can be elaborated for use in the severe accident analysis codes. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system from 300 to 3000 K. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate fission product chemistry in Cs-I-B-Mo-O-H system under LWR severe accident conditions, where kinetics effects should be considered. 相似文献
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介绍并分析了ACP100设计的独特性对事故源项和应急计划区产生的影响,比较了可选择源项、机理源项和混合源项的适用性,给出了制定ACP100混合源项与应急计划区划分方法的建议。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(3):344-348
The crystallization process has been developed as a part of the advanced aqueous process, NEXT (New Extraction System for TRU recovery) for fast reactor (FR) cycle. In this process, a large part of U is separated from dissolver solution by crystallization as UO2(NO3)2.6H2O. The U crystallization test was carried out with real dissolver solution of irradiated FR fuel to investigate the influence of cooling rate on the crystal size and the behavior of fission product (FP) compared with that of Pu(IV). In regard to the influence of the cooling rate, it was confirmed that the crystal size was smaller as the cooling rate is faster. Although it was expectable that the decontamination performance was improved by diminishing the specific surface of the crystals, it was suggested that a large crystal produced by crystallization was not always high purity. Concerning the behavior of FPs, Eu behaved similarly to Pu(IV). Cs accompanied with U into the crystals under the condition in this test. 相似文献
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基于国际先进的核设计与安全分析计算程序SCALE,针对我国自主研发的先进压水堆乏燃料贮存水池,建立恰当的计算模型,并选取合理的保守假设,计算乏燃料水池正常贮存及事故工况下的反应性,评估计算模型的临界安全,分析该程序对我国先进反应堆乏池计算的适用性。计算结果表明该先进压水堆乏燃料贮存水池正常贮存工况及事故工况的有效增值因子均小于0.95,处于次临界状态。该设计模型可确保燃料堆内贮存区域临界状态安全可控。SCALE计算程序适用于我国自主研发的先进压水堆乏燃料水池临界安全计算。 相似文献