颗粒可燃毒物空间自屏效应分析研究

可燃毒物被布置于反应堆堆芯中以控制堆芯剩余反应性,颗粒可燃毒物由于空间自屏效应而具有区别于常规均匀弥散可燃毒物的特性,同时颗粒可燃毒物可以增加可燃毒物的使用自由度,通过调整可燃毒物类型、可燃毒物颗粒尺寸以及可燃毒物体积份额以实现堆芯反应性的长期和平稳控制。本文重点研究颗粒可燃毒物的颗粒尺寸对系统反应性以及颗粒内有效核素核子密度变化规律的影响,并解释颗粒可燃毒物由于空间自屏效应而产生的"洋葱"效应,同时对比分析了多种常见可燃毒物不同颗粒尺寸下的中子学规律,对颗粒可燃毒物用于堆芯反应性控制具有重要的指导意义。     

Study of reactivity control method by the application of gadolinium hydride to accelerator-driven system

A reactivity control method for accelerator-driven system (ADS) is studied for its ability to reduce both the maximum beam current and the load on the beam window. A burnable position (BP) assembly (with gadolinium and zirconium hydride pins) is applied to the ADS core for reactivity control, and various BP assembly optimizations (such as pin arrangement, BP assembly loading position, and BP composition) are performed to minimize the burnup reactivity swing. These optimizations lead to a decreased burnup reactivity swing that is as much as 82.5% less than the swing of non-BP-loaded core; furthermore, the maximum beam current is 12.5 mA. The reactor characteristics of the optimized BP-loaded ADS core are also analyzed to investigate how the introduction of BP assembly influences the system. Safety parameters (such as the Doppler coefficient and the coolant void reactivity) worsen with the introduction of BP assembly, and the total minor actinide transmutation amount decreases 30–40 kg because of the moderated neutrons and changed fuel composition.     

MCNP程序在反应堆可燃毒物控制棒计算中的应用

以秦山核电厂一期工程反应堆为例,运用基于蒙特卡罗方法的MCNP程序建立了模拟计算模型,构建出反应堆压力容器内堆芯组件成分及排布,利用MCNP程序中的KCODE卡计算了反应堆中可燃毒物棒数量和位置的变化对有效增值系数Keff值的影响。结果表明,在不考虑控制棒和化学补偿控制对反应堆Keff值影响的情况下,随着可燃毒物棒数量的增多,Keff值呈线性下降的趋势,当毒物棒的布局由密到疏时,Keff值由大变小,这与理论结果一致。     

燃耗信任制中燃耗计算的敏感性因素研究

在OECD/NEA发布的Phase-IA基准题的基础上,采用SCALE程序包对影响燃耗计算结果的因素进行研究。分析堆芯运行参数以及控制棒和可燃毒物对燃耗计算以及乏燃料系统临界安全的影响,给出各因素保守性结论。     

Small,long-life high temperature gas-cooled reactor free from prompt supercritical accidents by particle-type burnable poisons

A design concept for a high temperature gas-cooled reactor without the possibility of a prompt supercritical accident has been proposed by coupling the use of particle-type burnable poison (BP) and criticality control by the core temperature. The combinations of two different BPs, B₄C and Gd₂O₃ particles and B₄C and CdO particles, with the proper particle sizes and the appropriate volume ratio, showed excellent performance in controlling excess reactivity and flattening the reactivity swing. To maintain reactivity at a lower level than the prompt critical state, the reactor was designed to operate in a subcritical mode for a burnup period or for the whole operation cycle. Under subcritical operation during the partial burnup period, the core temperature had to be lowered by at least 164 K for the loading of B₄C + Gd₂O₃ particles and by at least 178 K for the B₄C + CdO particles, which in turn dropped the thermal efficiency from 48% to 42.26% and 41.77%, respectively. On the other hand, under full subcritical operation, a greater decrease of core temperature was required. Remarkable decreases in the core temperatures, approximately 347 K for the B₄C + Gd₂O₃ case and approximately 280 K for the B₄C + CdO case, resulted in the drop of thermal efficiency to only 35.9% and 38.2%, respectively. Therefore, the relative importance of the increase in passive safety and the decrease in thermal efficiency must be considered with regard to their importance in nuclear reactor design.     

IFBA/WABA可燃毒物元件的燃耗特性分析

针对AP1000反应堆采用的燃料元件表面涂硼毒物(IFBA)和湿式环状可燃毒物棒(WABA),分别采用蒙卡程序MCNP5和组件均匀化计算程序CASMO构建含可燃毒物的燃料组件计算模型,基于MCNP5分析了可燃毒物棒布置方式及数目对组件初始k_(inf)、局部功率分布的影响;基于CASMO分析了不同类型可燃毒物组件的燃耗特性。结果表明:在燃料表面涂硼作为可燃毒物具有良好的燃耗跟踪特性,燃耗寿期内k_(inf)变化较小且几乎没有残留;同时将含IFBA毒物燃料元件交叉布置可获得较小的组件初始k_(inf)值,并能更好地展平组件局部功率分布,但随IFBA涂层变厚,组件k_(inf)的变化率逐渐变小,但温度系数绝对值呈上升趋势。     

Effect of burnup on the neutronic parameters of ITU TRIGA Mark II research reactor

This study aims to estimate burnup of the fuel elements for the Istanbul Technical University TRIGA Mark II Research and Training Reactor using a Monte Carlo-based burnup-depletion code. Effect of burnup on the core neutronic parameters, effective core multiplication factor, fast/epithermal/thermal neutron fluxes, and core-average neutron spectrum, and incoming neutron spectrum of the piercing beam port (PBP), is investigated at the Beginning of Life (BOL) and End of Life (EOL). Operational data peculiar to a selected operation sequence, which contains positions of CRs, power level of the reactor, material temperatures and latest core map, are used to determine the current fuel burnup of fuel elements at the time under consideration. A specific operation sequence is selected for the analysis. Furthermore, all control rods are considered fully withdrawn to assess the excess reactivity. Results are obtained using MONTEBURNS2 with ENDFB/V-II.1 neutron/photon library for a full power of 250 kW. Neutron cross-section libraries at the full-power operating temperatures are generated using NJOY. From the results, the calculated burnup values of the core at the sequence considered and EOL are found to be 420 MWh and 560 MWh, respectively. Remaining excess reactivity is calculated to be less than 0.3 $. It is observed that core average thermal neutron flux reduces by 1 % while the fast and epithermal neutron fluxes remain almost unchanged.     

超临界水冷堆可燃毒物设计与分析

在超临界水冷堆中,为了减少控制棒的使用,采用加入可燃毒物的方式控制初始剩余反应性。目前广泛采用的是稀土氧化物弥散在燃料中的整体型可燃毒物设计。通过对比4种常用的稀土氧化物,选择Er₂O₃作为可燃毒物材料。分析了不同可燃毒物布置方案对组件性能的影响,在不同可燃毒物含量下对组件安全性进行了评价。分析了可燃毒物对堆芯性能的影响,发现加入可燃毒物有利于降低堆芯径向功率峰,但会增大轴向功率峰并使其往堆芯顶部偏移。通过对该现象的分析,提出了降低堆芯底部温度和增大轴向富集度梯度的改进措施。计算结果表明,优化后的堆芯轴向功率峰明显降低,从而降低了最大包壳温度。     

基于遗传算法的可燃毒物设计优化方法研究

可燃毒物可补偿寿期初过剩反应性及展平功率分布,因此对堆芯燃料组件设计具有重要意义。目前传统的优化设计主要依靠设计者的主观经验及判断,复杂耗时,其设计效率及可靠性急待改进。本文将多目标并行遗传算法应用于压水堆组件毒物选型优化,以反应性控制、功率分布和不同时期燃耗剩余等为目标,对可燃毒物材料类型、含可燃毒物燃料棒排列方式、毒物含量、轴向分层等决策变量进行优化,研究了遗传算法在燃料组件毒物多目标优化设计中的理论模型及实现方法。同时将遗传算法与蒙特卡罗粒子输运方法有机结合,应用到压水堆燃料组件设计中,得到了组件可燃毒物优化方案。针对二维和三维燃耗计算,分别筛选了13和40种优化方案。计算结果表明：Er2O3用作毒物的综合效果最好;Gd2O3、Eu2O3和Sm2O3的应用需结合堆芯方案开展进一步研究;HfO2和Dy2O3不适合用作可燃毒物。该结果与通过人工搜索优化得到的结论基本一致。同时,三维轴向分层可为优化提供更多可选的材料种类方案,以部分毒物的分层布置方式可减小功率峰因子。本文研究为堆芯燃料/毒物设计提供了先进方法及工具。     

宁德核电站一号机组首循环启动物理试验结果分析

宁德核电站一号机组作为世界首例首循环采用钆作为可燃毒物的大型商用压水堆,堆芯首次启动物理试验是检验堆芯设计的重要依据。本文叙述了宁德核电站一号机组反应堆首次启动物理试验理论分析模型、程序和计算结果与测量值的比较。结果表明,理论预计值与实测结果符合良好,偏差均满足验收准则。     

轻水堆含钆燃料棒稳态辐照行为分析

国内外的压水堆燃料组件最新设计中,广泛采用钆燃料（UO₂-Gd₂O₃）作为可燃毒物来控制初始反应性和展平堆芯功率分布。钆燃料棒的性能与普通燃料棒存在较大差异,本文利用燃料元件性能分析程序FRAPCON-3.5对BR3堆内含钆燃料棒性能进行计算,并与实验测量值进行比较。结果表明：FRAPCON-3.5对含钆燃料棒的计算结果与实验测量值符合较好;含钆燃料棒在辐照初期强化了燃料棒自屏效应,对燃料的径向功率分布影响显著;在平均功率密度相同的情况下,燃料中加入钆会导致热导率降低,芯块温度升高;钆含量不同,裂变气体释放及燃料和包壳的变形略有差异。     

球床高温气冷堆使用可燃毒物的方案探讨

为改善球床高温气冷堆在特定情况下功率分布的形状和峰值,可在燃料球内添加可燃毒物。本文分析两种可燃毒物的添加方式,燃料球石墨基体均匀添加可燃毒物和燃料球内添加可燃毒物颗粒。由于¹⁰B的强吸收性能,均匀添加可燃毒物的消耗速度过快,不易控制,而通过添加不同尺寸的可燃毒物颗粒可优化燃耗速度,有效改善堆芯功率分布的形状和峰值。     

长寿期压水堆板状燃料组件可燃毒物选型研究

可燃毒物在长寿期压水堆中起着至关重要的作用,板状燃料组件在长寿期压水堆中具有较好的应用前景。本文开展长寿期压水堆板状燃料组件可燃毒物选型及中子学特性研究,对含不同可燃毒物的板状燃料组件进行输运-燃耗计算,筛选出中子学性能较好的可燃毒物。结果表明,采用富集同位素157Gd、167Er和B4C作为可燃毒物时,几乎无反应性惩罚;当采用PACS-J和231Pa作为可燃毒物时,因其自身特性,在寿期末不仅未造成反应性惩罚,且延长了组件寿期,提高了燃料利用率;PACS-J与慢燃耗可燃毒物组合,可获得更优的反应性曲线。由本文结果可知,板状燃料组件可以选用富集同位素157Gd、富集同位素167Er、B4C、231Pa和PACS-J作为可燃毒物,可燃毒物组合可以选用PACS-Er和PACS-Pa两种组合方案。     

关于深燃耗堆芯的反应性测量

介绍了在实验性PWR堆上完成的深燃耗条件下测量反应性概况。用实验结论剖析了在国外核电站堆芯上应用噪声分析法对慢化剂温度系数作全燃耗期监测研究中出现的测量结果与常规方法相差2～5倍的现象。从测量公式和堆芯扰动模型图入手所作的分析结果说明,没有消除随燃耗不断增长的强自发裂变中子源干扰是产生差异的根本原因。事实说明:在多种噪声分析技术中,只有能够清除自发裂变中子源干扰的方法才能成功地应用于燃耗后堆芯的反应性测量。     

Gas releases and rod internal pressure of BN-added UO2 fuel

Gadolinium (Gd), in the form of gadolinia (Gd₂O₃), has been used as integral burnable absorber to UO₂ fuel by different companies. Recently, alternative burnable absorber materials are under investigation. In this paper, the results of the study on the use of boron mixed in UO₂ as an integral burnable absorber are presented. Boron nitride was selected as the form of B to be added to UO₂ fuel based on the stability of B during sintering. Fuel performance analysis code FRAPCON-UNI, which is based on FRAPCON code and has the modifications for boron and helium generation and gasses release models, was used for the calculation of fuel performance. Helium generation was calculated using a model and the result was verified against ORIGEN calculation results. Gas release calculation was based on Forsberg Massih model and different characteristics of the gasses were considered. Power histories of maximum burnup rods (B rod, no B rod, and Gd rod) were selected from reactor physics data. The results indicated significant increases in rod internal pressure by 500 ppm boron addition at the end of life with minimum influence of a grain boundary boron fraction due to high diffusivity of helium and nitrogen.     

Conceptual design of a small nuclear reactor for large-diameter NTD-Si using short PWR fuel assemblies

A design of a small nuclear reactor for a large-diameter NTD-Si using a conventional Pressurized Water Reactors (PWR) full-length assembly was proposed in previous works. The height of the full-length assembly was 400 cm, and the overall size of the reactor and reflector around the core became large. In addition, the irradiation channel became very long, making handling of the Si ingots in the channel more difficult. The use of a short PWR fuel assembly, with a height of 100 cm, was considered in the current work. With the shorter assembly, the design of the reactor became compact and more practical. Gd₂O₃ and control rods were used to suppress excess reactivity. Criticality, neutron transport, and core burn-up calculations were performed using the MVP/GMVP II code and MVP-BURN code. Steady-state single-channel thermal hydraulic analyses were also performed. The calculation results showed that the reactor could be critical over 1200 days, and that heat removal from core was possible under 1 atm operating pressure. Large-diameter ingot up to 20 cm in height could be doped with sufficient uniformity. The reactor semiconductor production rate was estimated, and varied between 48 tons/year and 70 tons/year for the 50 Ω cm target resistivity depending on the position of the control rod.     

AC—600堆芯设计

本文叙述了 AC-600的堆芯核设计、热工水力和屏蔽设计.为了改善燃料利用和提高反应堆的安全性,在堆芯设计中,采用了低功率密度堆芯、较大的负反应性温度系数、机械谱移控制、钆可燃毒物、灰棒及不锈钢反射层等先进技术。     

西南反应堆工程研究设计院APWR开发研究工作简介

本文简要地介绍了西南反应堆工程研究设计院在先进压水堆方面所做的跟踪和开发研究工作,介绍了具有中国特色的先进压水堆核电厂(AC-600)的设计目标、初步方案的特点和今后工作的设想。AC-600的优点是工程投资少,固有安全性好,可靠性高,工期短,并能很好地与我国已建造的或正准备建造的压水堆核电厂相衔接,是我国发展核电厂的主要方向。     

Design simplification of a small nuclear reactor for large-diameter neutron transmutation doping silicon using control rods

A design concept for a small nuclear reactor for neutron transmutation doping silicon (NTD-Si) using a Pressurized Water Reactor (PWR) full-length fuel assembly was proposed in our previous work. The excess reactivity was suppressed by a combination of Gd₂O₃ and soluble boron, which results in a flatter flux profile over the core than with control rod insertion; however, the soluble boron system for reactivity control is quite complex and expensive. The removal of this system would make the design much simpler. In the current work, the removal of soluble boron is considered. Criticality, neutron transportation and core burn-up calculations were performed using the MVP/GMVP II code and MVP-BURN code. The calculation results show that the insertion of control rods in five of the nine assemblies is enough to suppress reactivity. The thermal hydraulic analysis showed that heat removal from the core was possible under 1 atm operating pressure. Silicon ingots up to 30 cm in diameter could be irradiated with sufficient uniformity in the irradiation channels.     

长寿期压水堆颗粒弥散可燃毒物中子学设计与分析

为实现长寿期压水堆的低硼运行,对颗粒弥散可燃毒物进行了中子学设计与分析,颗粒弥散可燃毒物的自屏效应可通过颗粒半径进行调节,能实现可燃毒物消耗和燃料燃耗的较优匹配。本文选取目前压水堆常用的快燃耗可燃毒物B、Gd为对象,研究了颗粒弥散可燃毒物不同颗粒半径和填充份额对组件中子学特性的影响。结果表明,颗粒弥散可燃毒物能实现长期稳定的反应性控制,其中BISO含硼弥散颗粒符合长寿期压水堆低硼运行的要求,适合作为长寿期压水堆的候选可燃毒物进行下一步研究。