高温气冷堆舱室抗商用飞机撞击的耦合数值分析

本文建立了大型商用飞机撞击典型高温气冷堆核电站反应堆舱室的非线性有限元模型，计算中混凝土舱室直接采用工程用钢筋混凝土的损伤塑性本构模型，飞机结构采用Johnson-Cook本构模型。对飞机高速撞击高温气冷堆核电站反应堆舱室非线性撞击过程进行模拟计算，得出正面和侧面撞击条件下的撞击载荷曲线、撞击位移云图、反应堆舱室混凝土破坏情况等结果。评估表明，反应堆舱室结构在撞击条件下的整体损伤微小，可为保护内部关键设备提供重要的屏障功能。     

高温气冷堆舱室抗商用飞机撞击的耦合数值分析

本文建立了大型商用飞机撞击典型高温气冷堆核电站反应堆舱室的非线性有限元模型,计算中混凝土舱室直接采用工程用钢筋混凝土的损伤塑性本构模型,飞机结构采用Johnson-Cook本构模型。对飞机高速撞击高温气冷堆核电站反应堆舱室非线性撞击过程进行模拟计算,得出正面和侧面撞击条件下的撞击载荷曲线、撞击位移云图、反应堆舱室混凝土破坏情况等结果。评估表明,反应堆舱室结构在撞击条件下的整体损伤微小,可为保护内部关键设备提供重要的屏障功能。     

飞机撞击下高温气冷堆乏燃料厂房损伤研究

本文针对典型高温气冷堆乏燃料厂房在双发商用飞机撞击载荷下的响应及结构完整性开展研究，并探讨结构特性对撞击损伤的影响。对乏燃料厂房及飞机分别建立有限元模型，通过弹体-目标相互作用分析模拟了飞机撞击过程，综合IAEA与NRC的评价准则对乏燃料厂房在飞机撞击下的损伤程度进行评估。数值结果表明：厂房上对应于机身及发动机的撞击位置发生可接受的局部损伤；乏燃料贮存井墙体对于提高构筑物抗飞机撞击能力有重要作用。此外，构筑物外形对损伤有很大影响，圆柱形壳体的抗飞机撞击能力显著强于方形厂房，是核电厂厂房设计的优化方向之一。     

飞机撞击下高温气冷堆乏燃料厂房损伤研究

本文针对典型高温气冷堆乏燃料厂房在双发商用飞机撞击载荷下的响应及结构完整性开展研究,并探讨结构特性对撞击损伤的影响。对乏燃料厂房及飞机分别建立有限元模型,通过弹体-目标相互作用分析模拟了飞机撞击过程,综合IAEA与NRC的评价准则对乏燃料厂房在飞机撞击下的损伤程度进行评估。数值结果表明:厂房上对应于机身及发动机的撞击位置发生可接受的局部损伤;乏燃料贮存井墙体对于提高构筑物抗飞机撞击能力有重要作用。此外,构筑物外形对损伤有很大影响,圆柱形壳体的抗飞机撞击能力显著强于方形厂房,是核电厂厂房设计的优化方向之一。     

基于ANSYS/LS-DYNA的抗飞机撞击结构非线性动力分析

APC壳是核电站抵御飞机撞击的主要屏障,本文运用非线性有限元程序LS-DYNA对某核电站燃料厂房APC壳进行了分离式建模,并对大型商用飞机的撞击进行了数值计算,对APC壳的动力响应及弹塑性特性进行了研究分析,提出了大型商用飞机撞击局部效应的观点,为APC壳的设计计算提供参考。     

基于ANSYS/LS-DYNA的抗飞机撞击结构非线性动力分析

APC壳(Air Plane Crash Shell)是核电厂抵御飞机撞击的主要屏障,本文运用非线性有限元程序LS-DYNA对某核电厂燃料厂房APC壳进行了分离式建模,并对大型商用飞机的撞击进行了数值计算,对APC壳的动力响应及弹塑性特性进行了研究分析,提出了大型商用飞机撞击局部效应的观点,为APC壳的设计计算提供参考。     

AP1000钢筋混凝土屏蔽厂房抗大型商用飞机撞击分析

针对建设中的三门、海阳AP1000钢筋混凝土(RC)屏蔽厂房,开展抵抗大型商用飞机撞击的分析研究。分析中采用我国核安全导则(HAD)推荐的总质量约90 t的大型窄体商用飞机作为撞击飞机,选取屏蔽厂房筒身中部、进气口区域和屋顶锥屋面作为撞击目标,并采用LS-DYNA显式有限元分析软件使用"飞机-标靶相互作用法"进行3种工况模拟。结果表明:AP1000的RC屏蔽厂房可以抵抗这种级别飞机的撞击。     

飞机撞击核岛屏蔽厂房的有限元分析

采用经典的显式有限元动力程序LS-DYNA,模拟商用大型飞机对核岛屏蔽厂房的撞击,混凝土有限元动力模型采用Holmquist-Johnson-Cook模型,用来模拟混凝土在大应变、高应变率下的非线性性能,同时评估屏蔽厂房的抗飞机撞击能力。     

GASFLOW应用于HTR-PM冷却剂排放事故分析

模块式高温气冷堆(HTR-PM)在冷却剂排放事故下的舱室承压能力是反应堆安全分析的重要对象。通过对FLUENT、GASFLOW和RELAP5的计算结果进行对比分析,发现GASFLOW因其兼顾计算效率与计算结果合理性的特性,最适合反应堆舱室在冷却剂排放事故下的承压计算。     

“华龙一号”核岛厂房防御外部事件设计改进

"华龙一号"是由中核集团和中广核集团共同开发,具有完整自主知识产权的百万千瓦级压水堆核电机组,"华龙一号"核岛厂房外部事件防护设计按照现行核安全法规要求进行了技术改进。在抗震设计方面,建立核岛厂房三维实体有限元模型,在提高抗震设计加速度水平下采用多组地基参数进行包络分析,提高了核岛厂房抗震设计的安全性和适用性;采用流固耦合动力非线性分析方法计算安全相关重要水池和水箱中水体在地震作用下的晃动效应。遵照新版HAF102的要求,将大型商用飞机撞击作为一种超设计基准外部事件进行评估。     

Structural analysis of aircraft impact on a nuclear powered ship

As part of a general safety analysis, the reliability against structural damage due to an aircraft crash on a nuclear powered ship is evaluated. This structural analysis is an aid in safety design. It is assumed that a Phantom military jet-fighter hits a nuclear powered ship. The total reaction force due to such an aircraft impact on a rigid barrier is specified in the guidelines of the Reaktor-Sicherheitskommission (German Safety Advisory Committee) for pressurized water reactors.This paper investigates the aircraft impact on the collision barrier at the side of the ship. The aircraft impact on top of the reactor hatchway is investigated by another analysis. It appears that the most unfavorable angle of impact is always normal to the surface of the collision barrier. Consequently, only normal impact will be considered here. For the specific case of an aircraft striking a nuclear powered ship, the following two effects are considered: Local penetration and dynamic response of the structure.The local penetration occurs at points where the engines or other rigid objects hit the structure. It is assumed that the aircraft engine is a rigid body projectile and the side wall of the ship is the target. The applied steel penetration formulae for projectiles were empirically derived for military applications, where both the projectile and the target are unlike those of an impact of an aircraft engine. For this reason it is expedient to calculate the upper and the lower limit values of the penetration depths. The results show that the highest penetration depth is less than the sum of all wall thicknesses of the collision barrier.The solution of the dynamic analysis is obtained by using the finite element method. The results are the eigenmodes, the eigenfrequencies, the displacements of the nodes, and the stresses in the applied plane stress elements. It is shown that the maximum stress which only appears in one element is on the same level as the yield stress of the St. 42 steel. The structural analysis shows that the collision barrier is a sufficient safeguard against the perforation of the engine and against the cracking of the structure as a result of the dynamic response to an aircraft impact.     

Collapse of chimney caused by earthquake or by aircraft impingement with subsequent impact on reactor building

The behaviour of a typical chimney stack of a nuclear-power plant subjected to earthquake and impact loads is examined. The explicit integration procedure using convected coordinates is adopted to perform the transient analyses with large displacements and material nonlinearities of the concrete stack, of the impinging aircraft and of the soil. Thanks to the favourable effect of the partial separation of the base mat from the soil (lifting-off), the chimney does not collapse for realistic accelerations of the earthquake. Force-time relationships of the aircraft impinging on the chimney are developed. The impact of aircraft debris causes only local damage of the chimney. The direct impingement of an aircraft, however, may lead to partial collapse or total overturning of the chimney. The resulting motion, including the impact of the chimney on the reactor building, is studied. The response of the structure being hit and of the equipment located within will in many cases govern their design.     

A review of procedures for the analysis and design of concrete structures to resist missile impact effects

Concrete containment walls and internal concrete barrier walls are often required to withstand the effects of missile impact. Potential missiles include external tornado generated missiles (steel rods, steel pipes, wooden poles, and automobiles), aircraft crash, and internal accident generated missiles (turbine blade, and steel pipe missiles resulting from pipe break). Impacting missiles can be classified as either ‘hard’ or ‘soft’ depending upon whether the missile deformability is small or large relative to the target deformability. This paper only deals with the effects of ‘hard’ missile impact. Missile velocities between 100 and 1500 ft/sec are emphasized. ‘Hard’ missile impact results in both local wall damage and in overall dynamic response of the target wall. Local damage consists of spalling of concrete from the front (impacted) face and scabbing of concrete from the rear face of the target together with missile penetration into the target. If damage is sufficient the missile may perforate or pass through the target. This paper reviews the various empirical procedures commonly used for determining penetration depth, perforation thickness, and scabbing thickness for concrete targets subjected to ‘hard’ missile impact. Results obtained from these procedures are compared with test data results for low velocity impacts (200–1500 ft/sec). Design recommendations to prevent detrimental local wall damage are presented. Overall dynamic response of the target wall consists of flexural deformations and a potential flexural or shear failure if the strain energy capacity of the wall does not exceed the kinetic energy input to the wall by the striking ‘hard’ missile. Simplified procedures are defined for determining the dynamic response of the target wall and for preventing overall failure of the wall. Included are procedures for defining the effective target mass to be used in determining the fraction of the total missile kinetic energy which is transferred or ‘input’ into the target wall. Also included are procedures for defining the total strain energy capacity of the target wall as determined from the moment and rotational capacities of flexural yield hinges and the yield line deformation pattern of the wall. Lastly, criteria for preventing a premature shear failure are presented.     

Author index to volume 55

The behaviour of a typical chimney stack of a nuclear-power plant subjected to earthquake and impact loads is examined. The explicit integration procedure using convected coordinates is adopted to perform the transient analyses with large displacements and material nonlinearities of the concrete stack, of the impinging aircraft and of the soil. Thanks to the favourable effect of the partial separation of the base mat from the soil (lifting-off), the chimney does not collapse for realistic accelerations of the earthquake. Force-time relationships of the aircraft impinging on the chimney are developed. The impact of aircraft debris causes only local damage of the chimney. The direct impingement of an aircraft, however, may lead to partial collapse or total overturning of the chimney. The resulting motion, including the impact of the chimney on the reactor building, is studied. The response of the structure being hit and of the equipment located within will in many cases govern their design.     

Damage evaluation of 500 MWe Indian Pressurized Heavy Water Reactor nuclear containment for aircraft impact

Safety assessment of Indian nuclear containments has been carried out for aircraft impact. The loading time history for Boeing and Airbus categories of aircrafts is generated based on the principle of momentum transfer of crushable aircrafts. The case studies include the analysis of BWR Mark III containment as a benchmark problem and analyses of Pressurised Heavy Water Reactor containment (inner and outer containment) for impulsive loading due to aircraft impact. Initially, the load is applied on outer containment wall model and subsequently the load is transferred to inner containment after the local perforation of the outer containment wall is noticed in the transient simulation. The analysis methodology evolved in the present work would be useful for studying the behavior of double containment walls and multi barrier structural configurations for aircraft impact with higher energies. The present analysis illustrates that with the provision of double containments for Indian nuclear power plants, adequate reserve strength is available for the case of an extremely low probability event of missile impact generated due to the commercial aircrafts operated in India.     

Structural integrity analysis of an Ignalina nuclear power plant building subjected to an airplane crash

Recent terrorist attacks using commandeered commercial airliners on civil structures have raised the issue of the ability of nuclear power plants to survive the consequences of an airliner crash. The structural integrity analysis due to the effects of an aircraft crash on an Ignalina nuclear power plant (INPP) accident localization system (ALS) building is the subject of this paper. A combination of the finite element method and empirical relationships were used for the analysis. A global structural integrity analysis was performed for a portion of the ALS building using the dynamic loading from an aircraft crash impact model. The local effects caused by impact of the aircraft's engine on the building wall were evaluated independently by using an empirical formula.The results from the crash analysis of a twin engine commercial aircraft show that the impacted reinforced concrete wall of the ALS building will not have through-the-wall concrete failure, and the reinforcement will not fail. Strain-rate effects were found to delay the onset of cracking. Therefore, the structural integrity of the impacted wall of the INPP ALS building will be maintained during the crash event studied.     

Response of equipment to aircraft impact

After discussing the state of the art of the development of equivalent force-time relationships for aircraft impact, the results of the so-called Riera model and of a lumped-mass model are compared for rigid and deformable targets. The importance of adequate modelling of structures to enable the calculation of response spectra also in the high-frequency range is demonstrated using a typical reactor shield building and a reactor auxiliary building. For an adequate model, the influence of the aircraft-structure interaction, of the material nonlinearly, of the damping and of the mass on the response of equipment is examined.     

Diagnosis of steam generator by estimating an unobserved important state variable

In this study, a technique has been developed for diagnosing in on-line the state of the steam generator of the fast-breeder reactor (FBR) “Monju” by estimating an unobserved important state variable from observed data. The secondary coolant of liquid sodium faces to water/steam across a thin metal tube wall in the steam generator. Therefore, it is very important to detect a small anomaly of the wall of heat transfer tubes at an early stage. The aim of this study is to develop a technique for diagnosing in on-line a state of the steam generator by estimating an overall heat transfer coefficient, which is an unobserved important state variable, from observed data. This study shows simplified mathematical models of superheater and evaporator to estimate the overall heat transfer coefficient. The applicability of the technique is confirmed by configuring state observer with the mathematical model and noise filter and estimating using simulated data. As the results of the estimations, relative errors of the overall heat transfer coefficient of the superheater and the evaporator are less than ±0.5%.