高通量工程试验堆80盒元件堆芯研究

通过理论分析和运行结果比较了高通量工程试验堆８０盒、６０盒工件堆芯性能。结果表明，ＨＴＦＴＲ８０盒元件堆芯在允许功率、材料辐照和单晶硅掺杂、钼锝同位素生产等方面与６０盒元件堆芯性能相同。８０盒元件堆芯更有利于５００ｋＷ回路入堆后堆的运行，有利于大幅度提高高比度＾６０Ｃｏ医疗源产量和元件利用率。     

熔融物堆芯冷却滞留特性研究

The severe accident analysis model of the small modular reactor ACP100 is built using MELCOR code, and the core heat removed process through the barrel and wall of reactor pressure vessel (RPV) is analyzed by the cavity injection system (CIS). The collapse behavior of the fuel assemblies is estimated by the fuel rod degradation model, and the failure behavior of the lower core plate is estimated by ANSYS program. The results show that the fuel assemblies in the core center melt and collapse to form the core melting pool, while the structure of the fuel assemblies surrounding the core melting pool remains intact, and the core lower plate supports the core melting pool and un-collapsed fuel assemblies all the time, and no creep rupture phenomenon occurs; the core heat can be removed by CIS and the debris in-vessel retention successfully avoids the formation of molten pool in the lower head.     

堆芯燃料组件流阻特性模块式与整体式三维数值模拟方案比较

组件的阻力特性影响堆芯不同类型组件的流量分配，对堆芯的设计起到至关重要的影响。为提高验证堆芯燃料组件特性的求解精度及效率，本文针对燃料区6类燃料组件中的两类进行模块式及整体式三维数值模拟，获得了两类组件的流阻特性，并用相同条件下的全组件试验结果进行了对比。结果表明：推广至堆芯所有燃料组件流阻特性预测，模块式所需计算时间约为整体式的1/6，但整体式三维数值模拟所得压降与试验结果吻合度高，误差较模块式小。最后深入研究了流速及温度变化对流阻特性的影响。该研究为后续各类组件的流阻特性研究方法选取提供技术支持。     

熔融物堆芯冷却滞留特性研究

以模块式小型堆ACP100为分析对象，建立MELCOR程序严重事故分析模型，分析了堆芯衰变热依次经过吊篮、压力容器壁面然后进入堆腔注水系统（CIS）的传热行为。采用燃料棒失效模型评价燃料组件坍塌行为，并通过ANSYS程序蠕变断裂模型评价堆芯下板失效行为。分析结果表明，严重事故后堆芯中心燃料组件坍塌形成堆芯熔融池，堆芯周围燃料组件保持完整结构状态，堆芯下板支撑堆芯熔融池和未坍塌的燃料组件且未发生蠕变断裂失效；CIS冷却压力容器外壁面并导出堆芯衰变热，最终实现熔融物堆芯滞留，避免下封头内形成熔融池。      

MOX燃料组件装入现役M310堆芯对堆芯核设计的影响研究

国际上的MOX燃料技术目前已较为成熟,且已有在压水堆中运行的工程经验。本文对MOX燃料组件的中子学性能进行了分析,对其在我国现役M310堆芯应用的可行性进行了研究,得到了M310堆芯由全部使用UO2燃料组件向使用30%的MOX燃料组件过渡的堆芯燃料管理方案,并对使用MOX燃料组件的堆芯的部分中子学参数进行了初步分析。结果表明:使用30%的MOX燃料组件的堆芯可达到与全UO2堆芯相当的循环长度;堆芯反应性控制能力可满足要求;慢化剂温度系数、Doppler温度系数、Doppler功率系数、氙和钐的动态特性均趋向使堆芯运行更加安全和稳定。本文的研究结果可为MOX燃料在M310堆芯中应用的进一步研究提供参考。     

华龙一号“177堆芯”特点分析

华龙一号（HPR1000）压水堆核电厂最显著的技术特征是反应堆采用由177个燃料组件构成的堆芯（简称“177堆芯”）,具有完全的自主知识产权。为深入分析其特点,本文介绍了“177堆芯”的主要技术特征,并在燃料组件及控制棒组件数目方面与157个燃料组件构成的堆芯（简称“157堆芯”）进行了对比分析;对2种典型反应堆堆芯（“177-A堆芯”与“177-B堆芯”）装载方案的异同进行了叙述和评价。结果表明,与“157堆芯”相比,“177堆芯”在安全性和经济性方面更有优势;2种典型堆芯的首循环装载布置各有所长,在可燃毒物选材上,“177-B堆芯”优于“177-A堆芯”。最后,从取消堆芯中央位置控制棒组件、设置堆芯径向金属反射层、实施无中子源启动、分批装载自主化燃料组件以及优化堆芯活性段长度等5个方面给出了HPR1000反应堆堆芯的优化建议。      

Neutron-physical and thermohydraulic calculations of VVR-SM with high-and low-enrichment uranium fuel assemblies

The VVR-SM reactor at the Institute of Nuclear Physics of the Academy of Sciences of Uzbekistan is being converted from fuel assemblies with high-enrichment uranium (36% ²³⁵U) to fuel assemblies with low-enrichment uranium (19.7% ²³⁵U). During the conversion process consisting of nine cycles, the IRT-3M fuel assemblies with high-enrichment uranium, which are removed at the end of each cycle, will be replaced with IRT-4M fuel assemblies with low-enrichment uranium. This will require increasing the core size up to 20 fuel assemblies and increasing the power of the reactor to 11 MW. The methods used for and the results of neutron-physical calculations (burnup, power distribution, subcriticality), thermohydraulic analysis, and calculations of the kinetic parameters of a stable state are described for a core with high-enrichment uranium, a mixed core, and the first full core with low-enrichment uranium. __________ Translated from Atomnaya énergiya, Vol. 104, No. 5, pp. 269–273, May, 2008.     

Calculation of the thermohydraulic parameters of a core comprised of unjacketed fuel assemblies

A computer program for calculating the thermohydraulic parameters of a core with jacketless fuel assemblies as a single mass of fuel elements is developed on the basis of the Kedr program for the channelwise computation. The Kedr-A program algorithm employs the principle of decomposition (partition) to the computed region of the core (1/12th part). The computational space is divided into a definite number of subregions – symmetry elements with repeatable geometric structure of the lattice of fuel elements and other structural components of the core. The thermohydraulic parameters of the cells in each section of the core are calculated iteratively over the symmetry elements of the jacket-less fuel assemblies of 1/12th part of the core of a nuclear reactor with water coolant. The symmetry elements are interrelated by the conditions at the boundaries connecting theses regions. The computational algorithm is checked by comparing with experimental data on the mixing of the coolant obtained on a technological stand consisting seven jacketless fuel assemblies.     

Transport of Fresh MOX Fuel Assemblies for the MONJU Initial Core

Abstract

Transport of fresh MOX fuel assemblies for the prototype FBR MONJU initial core started in July 1992 and ended in March 1994. As many as 205 fresh MOX fuel assemblies (109 assemblies for an inner core, 91 assemblies for an outer core and 5 assemblies for testing) were transported in nine transport missions. The packaging for fuel assemblies, which has shielding and shock absorbing material inside, meets IAEA regulatory requirements for Type B(U) packaging including hypothetical accident conditions such as the 9 m drop test, fire test, etc. Moreover, this packaging design features such advanced technologies as high performance neutron shielding material and an automatic hold-down mechanism for the fuel assemblies. Every effort was made to carry out safe transport in conjunction with the cooperation of every competent organisation. This effort includes establishment of, the transport control centre, communication training, and accompanying the radiation monitoring expert. No transport accident occurred during the transport and all the transport missions were successfully completed on schedule.     

Letter to the Editor

Abstract

Transport of fresh MOX fuel assemblies for the prototype FBR MONJU initial core started in July 1992 and ended in March 1994. As many as 205 fresh MOX fuel assemblies (109 assemblies for an inner core, 91 assemblies for an outer core and 5 assemblies for testing) were transported in nine transport missions. The packaging for fuel assemblies, which has shielding and shock absorbing material inside, meets IAEA regulatory requirements for Type B(U) packaging including hypothetical accident conditions such as the 9 m drop test, fire test, etc. Moreover, this packaging design features such advanced technologies as high performance neutron shielding material and an automatic hold-down mechanism for the fuel assemblies. Every effort was made to carry out safe transport in conjunction with the cooperation of every competent organisation. This effort includes establishment of the transport control centre, communication training, and accompanying of the radiation monitoring expert. No transport accident occurred during the transport and all the transport missions were successfully completed on schedule.     

Design of an overmoderated fuel and a full MOX core for plutonium consumption in boiling water reactors

The use of uranium–plutonium mixed oxide fuel (MOX) in light water reactors (LWR) is nowadays a current practice in several countries. Generally 1/3 of the reactor core is loaded with MOX fuel assemblies and the other 2/3 with uranium assemblies. Nevertheless the plutonium utilization could be more effective if the full core could be loaded with MOX fuel. In this paper the design of a boiling water reactor (BWR) core fully loaded with an overmoderated MOX fuel design is investigated. The design of overmoderated BWR MOX fuel assemblies based on a 10×10 lattice are developed, these designs improve the neutron spectrum and the plutonium consumption rate, compared with standard MOX assemblies. In order to increase the moderator to fuel ratio two approaches are followed: in the first approach, 8 or 12 fuel rods are replaced by water rods in the 10×10 lattice; in the second approach, an 11×11 lattice with 24 water rods is designed with an active fuel length very close to the standard MOX assembly. The results of the depletion behavior and the main steady state core parameters are presented. The feasibility of a full core loaded with the 11×11 overmoderated MOX fuel assembly is verified. This design take advantage of the softer spectrum comparable to the 10×10 lattice with 12 water rods but with thermal limits comparable to the standard MOX fuel assembly.     

Modelling of PWR cladding corrosion in mixed core situations

In this paper a thermal-hydraulic model for cladding corrosion recently developed in ABB Atom and used in the code is presented. The features of the model are a subchannel geometry which consists of a 3 × 3 matrix of rods, and modelling of coolant cross-flow and coolant enthalpy mixing. The thermal-hydraulic model is benchmarked against the code, which is a 3D code for analysing the thermalhydraulics of a reactor core. In addition, results of model calculations are compared with corrosion data obtained in mixed core situations, i.e. situations where the fuel assemblies in the core have different designs (e.g. different grid and nozzle designs). Fuel assembly components in assemblies of different designs usually have unequal flow resistances. These differences result in transverse pressure gradients, which in turn increase the lateral flow velocity and thus affect the cociant mass flow rate distribution. Two different situations where this type of mismatch between fuel assemblies in the Ringhals 3 core have occurred are studied in this paper. In the first case a reload batch of fuel assemblies, with Zircaloy mixing vane grids, inserted in a core where the resident fuel assemblies have Inconel mixing vane grids is considered. In the second case cladding tubes from the same manufacturing lot that have been irradiated for the same period of time but have been situated in fuel assemblies with Zircaloy mixing vane grids of different designs are considered. The results manifest the capability of the code to model the effects of flow resistance on cladding corrosion.     

Accuracy of nuclear design of fast and thermal neutron coupled core by SRAC

Supercritical-pressure light water cooled fast reactor adopts the blanket fuel assemblies with depleted uranium fuel and zirconium hydride layer in the core for negative coolant void reactivity. Thermal neutrons are generated in the core of fast reactor. It is called “fast and thermal neutron coupled core”. The purpose of the present study is to examine the accuracy of assembly and core calculations including preparation of the macroscopic cross sections with the SRAC code system for “fast and thermal neutron coupled core” in comparison with the Monte Carlo codes, MVP and MVP-BURN. Accuracy of the neutron multiplication factor and coolant void reactivity calculation has been evaluated in four types of cores of different fractions of the blanket fuel assembly with zirconium hydride rods. The conventional analysis is based on the macroscopic cross sections which are prepared with infinite lattice. The conventional SRAC calculation underestimates the neuron multiplication factor for all types of cores. Other findings are that the conventional SRAC calculation overestimates coolant void reactivity for the cores without zirconium hydride rods, and underestimates coolant void reactivity for the core of all blanket fuel assemblies having zirconium hydride rods. To overcome these problems, it has been proposed that the macroscopic cross sections of seed fuel assembly are prepared with the model that a seed fuel assembly is surrounded by blanket fuel assemblies in order to take into account the effects of the surrounding fuel assemblies. Evaluations show that accuracy of the neutron multiplication factor by the SRAC calculation can be improved by the proposed method.     

CEFR组件替换反应性价值试验测量与计算分析

组件替换反应性价值定义为测量位置组件替换成相应组件时引入的反应性变化。中国实验快堆物理启动试验中组件替换反应性价值测量试验方案中,试验测量了8个典型位置,其中6个位置为燃料组件替换成不锈钢组件,另外两个为不锈钢组件替换成燃料组件。测量结果显示,燃料组件替换反应性价值由内至外依次减少,内圈燃料组件替换反应性价值约-980 pcm,外圈燃料组件替换反应性价值约-470 pcm,补偿棒棒组测量和单根补偿棒测量的结果差别微小。使用CITATION程序对试验方案进行了理论计算,结果表明,计算结果与实验值符合良好,检验了CITATION程序的工程设计实用性。     

Conceptual designing of reduced-moderation water reactor with heavy water coolant

The conceptual designing of reduced-moderation water reactors, i.e. advanced water-cooled reactors using plutonium mixed-oxide fuel with high conversion ratios more than 1.0 and negative void reactivity coefficients, has been carried out. The core is designed on the concept of a pressurized water reactor with a heavy water coolant and a triangular tight lattice fuel pin arrangement. The seed fuel assembly has an internal blanket region inside the seed fuel region as well as upper and lower blanket regions (i.e. an axial heterogeneous core). The radial blanket fuel assemblies are introduced in a checkerboard pattern among the seed fuel assemblies (i.e. a radial heterogeneous core). The radial blanket region is shorter than the seed fuel region. This study shows that the heavy water moderated core can achieve negative void reactivity coefficients and conversion ratios of 1.06–1.11.     

A nuclear reactor core fuel reload optimization using artificial ant colony connective networks

The core of a nuclear Pressurized Water Reactor (PWR) may be reloaded every time the fuel burn-up is such that it is not more possible to maintain the reactor operating at nominal power. The nuclear core fuel reload optimization problem consists in finding a pattern of burned-up and fresh-fuel assemblies that maximize the number of full operational days. This is an NP-Hard problem, meaning that complexity grows exponentially with the number of fuel assemblies in the core. Moreover, the problem is non-linear and its search space is highly discontinuous and multi-modal.     

田湾核电厂长周期混合堆芯稳态热工水力分析

田湾核电厂1、2号机组计划自2014年开始向长周期燃料循环过渡,在AFA型燃料组件组成的堆芯中逐步装入TVS-2M新型燃料组件,经过3个燃料循环的过渡,堆芯将全部装载TVS-2M型燃料组件,以实现长周期燃料循环。燃料组件结构的改变使原堆芯热工水力分析不再适用。本文以长周期燃料循环过渡时期的5种典型堆芯组成情况为例,介绍了VVER机组稳态热工水力分析的程序和方法,对混合堆芯的稳态热工水力特性进行了重新分析。结果表明,混合堆芯稳态设计仍满足热工水力设计准则。     

An economically optimum PWR reload core for a 36-month cycle

Cycle length extension in currently operating PWRs may be economically interesting if the benefits stemming from capacity factor improvement offset the higher fuel costs of the longer cycle. A PWR reload core is presented that meets current physics and fuel performance design limits for a cycle of 33.9 EFPM or 36 calendar months when operating at a capacity factor of 94.1%. Fuel is enriched to 6.5% U-235 and selected pins use gadolinia as burnable absorber mixed with UO₂. The power is evenly distributed over a broad region of the core by including pins with two different concentrations of gadolinia in the assemblies. The core periphery is loaded with reused assemblies. The rest of the assemblies are discharged after one cycle in the core. The fuel performance is acceptable, although the parameters analyzed are closer to the limits than in a contemporary reference 18-month cycle multibatch loading strategy. The 36-month core is economically competitive with an 18-month reference core under certain operational conditions. Potential reductions in fuel enrichment costs would make the 36-month cycle cost competitive with the 18-month reference cycle under a wide range of conditions.     

高通量工程试验堆考验回路功率分布重组及堆芯热点因子计算研究

利用精细注量率重组和注量率形状因子的乘积方法对高通量工程试验堆的考验回路和堆芯燃料组件内的功率分布进行重组 ,并给出全堆芯的热点因子及其出现的时间 (燃耗步 )、组件位置、轴向位置、径向环位置和环向角度     

径向倒料式驻波堆堆芯概念设计

本工作在综合分析日本CANDLE堆和美国TerraPower公司设计的TP-1堆的基础上,提出沿径向倒料的驻波堆堆芯设计初步方案,通过高、低富集度组件在堆芯的混合布置展平功率,降低了堆芯的功率峰因子和组件的最大燃耗深度。通过倒换料,实现了增殖 燃耗波的传递。为能有效地利用行波堆增殖产生的易裂变核素,采用更换包壳的新技术,实现核燃料的持续利用。