核燃料组件无损检测探测系统设计

燃料组件是反应堆的核心部分,在高温、高压及强中子辐射场等复杂环境条件下,燃料棒中芯块会出现肿胀、变形甚至包壳破裂,严重威胁反应堆的安全运行。为了更好地了解燃料组件在反应堆内的变化,研究高燃耗的燃料组件中燃料棒的中心空洞形成和燃料棒的变形情况,高能X射线无损检测是一种有效的技术手段。由于辐照后核燃料组件自身具有强放射性,探测系统设计中必须考虑减弱燃料组件自身辐射对探测采集的影响,因此组件探测系统中探测器阵列及准直器的优化设计十分必要。经过建模及相关模拟计算,得到了探测器单元最佳尺寸,优化了后准直器的结构设计,为提高燃料组件无损检测系统重建图像的质量提供帮助。     

Detection System for the Fuel Assembly Nondestructive Testing

Fuel assemblies are the central components of a reactor. The core fuel pellets in the fuel pins will swell and deform and the fuel cladding may even break under the complex environment of high temperature, high pressure and intense neutron radiation field, which threats the safety of the reactor. To better understand the changes in the behavior of the fuel assembly in the reactor and study the central void formations and deformations of fuel pins in fuel assemblies to high burn-up, high-energy X-ray non-destructive testing is an effective technical means. Irradiated nuclear fuel assembly has a strong radioactivity, it is necessary to optimize the design of the detector system and the collimator to reduce the effect from gamma rays emitted from the irradiated fuel assembly during detection system designing phase. Through modeling, estimating and optimization, the optimal size of the detector unit is obtained and the collimator design is optimized which can lay the foundation to improve the quality of the reconstructed images of the fuel assembly nondestructive system.     

燃料组件上管座单元件国产化焊接工艺研究

阐述了国产化燃料组件上管座单元件的材料焊接性能及焊接工艺,进行相应的母材熔敷性、均匀性、熔透性以及管座实体焊接试验,摸索出符合技术条件要求的焊接工艺:上管座单元件的焊接接头为无坡口对接形式;采用手工组装点焊+自动焊+微缺陷手工补焊的方法;采用变速焊接,在板簧槽段和收弧段提高焊接速度。采用该工艺开展焊接鉴定,结果均符合技术条件要求。     

AFA 3G燃料组件骨架导向管与格架的压力电阻焊工艺研究

骨架点焊是压水堆燃料组件制造过程中的重要工序。对AFA 3G骨架点焊焊接技术，即格架与变径导向管之间的压力电阻点焊，在我国尚属一个崭新的技术课题。在大量实验的基础上，就不同的焊接规范对焊点质量的影响进行了详细的讨论与研究，包括焊点的剪切力、焊点熔核尺寸以及焊点腐蚀性能，从而获得了比较理想的焊接规范。     

FCM燃料堆内行为模拟及结构设计研究

本文采用二维特征模型模拟不同无燃料区厚度全陶瓷微封装弥散(FCM)燃料的热力学行为,在保证堆芯装载要求的条件下,研究不同结构FCM燃料SiC基体和包覆燃料颗粒SiC层的应力状态。通过优化无燃料区厚度,调整TRISO颗粒间的间距,保证无燃料区和SiC层同时具有较低的应力水平。分析了无燃料区厚度为100～500μm时基体SiC、无燃料区以及SiC层的应力分布,结果表明,基体SiC和SiC层最大应力随无燃料区厚度增大而增大,而无燃料区的最大应力则随其厚度增大而降低。当无燃料区厚度为400μm时,无燃料区和SiC层均处于较低的应力状态,无燃料区SiC基体应力约为400 MPa,而SiC层的最大环向应力约为200MPa,其失效概率约为2.5×10-4。因此,当无燃料区厚度为400μm时,FCM燃料既能维持芯块结构完整,又能保证SiC层具有较低的失效概率。结构优化为FCM燃料的应用提供了基础。     

FCM燃料堆内行为模拟及结构设计研究

The thermal mechanical performance of the fully ceramics microencapsulated fuel (FCM) with different non-fuel part size was simulated using two-dimensional characteristic unit. When the fissile loading meet the requirements of the reactor core, the stress condition of SiC matrix and SiC layers were investigated for FCM pellets with different structures. Non-fuel parts and SiC layers suffered relative lower stress by optimizing FCM pellet structure and adjusting distance between different TRISO particles. The stress distribution of matrix, non-fuel part and SiC layer was discussed for the FCM pellets with non-fuel part size from 100 μm to 500 μm. The results indicate that, the maximum hoop stress of the matrix and SiC layer increased with the increasing of non-fuel part size, while the non-fuel parts exhibited crosscurrent. Non-fuel parts and SiC layer possessed lower stress when the non-fuel part was 400 μm. The stress of non-fuel part was about 400 MPa, and the maximum hoop stress of the SiC layers were about 200 MPa. The failure probability was 2.5×10-4. The structure integrity was maintained for the pellets with 400 μm non-fuel part, at the same time the failure probability SiC layer was low. Structural optimization is the basis for the application of FCM pellet.     

核燃料包装容器桶体缝焊工艺可靠性建模

从缝焊工艺的质量要求出发，详细分析了缝焊工艺可靠性的影响因素，针对焊透率与重叠量建立了工艺可靠性概率模型，给出了工艺可靠性试验方案与工艺可靠度计算步骤。     

堆内考验燃料组件设计

4×4—4压水堆燃料组件用于验证国产化燃料棒的堆内性能。燃料组件中包括了目前压水堆标准化燃料棒、高性能燃料棒和双金属定位格架。高性能燃料棒采用了衬锆包壳管和环形芯块,以便减小芯块-包壳相互作用和降低燃料温度,从而降低裂变气体释放率。预计标准化燃料棒中,最高棒平均燃耗可达到45GW·d/tU,高性能燃料棒达到60GW·d/tU。     

CF系列燃料组件落棒性能综合评价

核电压水堆燃料组件中导向管主要功能是为控制棒组件的快速下插提供通道,并且依靠导向管下部缓冲段结构减缓控制棒下落速度,减小冲击力,保证燃料组件结构完整。首先运用落棒时程分析程序(CIGAL)计算得到CF系列燃料组件落棒时间,再利用落棒缓冲分析程序(SAM)计算CF系列燃料组件中缓冲过程冲击力。结果表明:CF3相对于CF2,随着导向管内径减小以及轴肩螺钉孔长度增加,落棒时间变长;落棒过程中缓冲段内压强最大值增大;控制棒组件对燃料组件上管座冲击力最大值减小;控制棒组件撞击之前控制棒在缓冲段内运动时间变长。     

Out-of-pile and In-pile Perfomance of Advanded Zirconium Alloys (HANA) for High Burn-up Fuel

The performance of the advanced Zr alloys (HANA) for a high burn-up fuel has been evaluated in the out-of-pile and in-pile conditions. The corrosion resistance of the HANA claddings was superior to Zicaloy-4 in a PWR-simulating loop condition. The improved corrosion resistance of the HANA claddings was attributed to the fine distribution of the precipitate. HANA claddings showed a higher creep resistance as compared to Zircaloy-4 from the thermal creep test. The deformation behavior of HANA in a LOCA condition was similar to Zircaloy-4. Threshold ECR value of HANA was higher than the conventional value of 17% in Zircaloy-4, which is mainly due to the fact that the Nb decreases the oxidation rate as well as the hydrogen pickup. Fretting wear test revealed that HANA claddings have a similar wear resistance to Zircaloy-4. From the irradiation test up to burn-up of about 12 GWd/MtU, HANA claddings showed a better corrosion resistance as well as a better creep resistance than Zircaloy-4. The in-pile corrosion resistance of the HANA claddings was improved by 40–50% as compared to Zircaloy-4 on the basis of the oxide thickness measurements.     

5MW THR燃料组件

本文介绍了5MW THR 燃料组件的设计原则、设计特性及其结构。并对其性能进行了分析与评价。     

燃料组件压紧部件分析研究

燃料组件压紧部件是核反应堆燃料组件的重要部件,其性能影响到燃料组件的完整性乃至安全性,是核电厂安全审查中关注的重点之一.结合燃料组件压紧部件的要求,计算板状弹簧压紧部件全寿期内的压紧力,针对压紧力不足的风险进行了原因分析,并给出了应对措施及建议.     

3×3-2回堆考验组件辐照后检验

文章涉及3×3-2可拆卸组件和相应热室检验装置的设计及热室内组件的远距离再组装和拆卸;组件检验及平均燃耗(以金属铀计,全文同)为30.9 GW*d/t和6.5 GW*d/t燃料棒的非破坏性检验和破坏性检验;室温和高温下的燃料棒检漏.主要结果是可拆卸组件及相应热室检验装置的设计合理,热室内远距离操作可行;经堆内考验后组件结构完整,但格架辐照弹簧松弛量较大;燃料棒性能完好,环脊明显,棒径减小显著;采用多种方法检漏,未发现破损的燃料棒.     

陶瓷球床组件堆内辐照在线产氚物理计算分析

对陶瓷球床组件的堆内辐照情况进行物理计算分析有助于改进辐照装置的设计,完善辐照方案。按照堆内辐照陶瓷球床组件的实验技术要求,采用MCNP程序对陶瓷球床组件在不同孔道内的辐照情况进行了产氚量、产氚速率、发热量等计算。计算结果表明：采用天然丰度⁶Li的陶瓷球床组件在考验孔道内以半功率辐照能满足实验技术要求;如要采用满功率辐照,则需将组件中心位置提升至活性区中平面以上23 cm处。     

Long-Cycle and High-Burnup Fuel Assembly for the VHTR

For a prismatic VHTR fuel assembly, a physics study has been performed to maximize the fuel performance in terms of the cycle length and the discharge burnup for a given fuel enrichment. The relationship between the fuel performance and the fuel configurations has been investigated in terms of the TRISO packing fraction, diameter of the fuel kernel, fuel management, and moderating power of the fuel block. Both a typical low-enrichment uranium fuel (LEU) and a fuel made of transuranics (TRU) from LWR spent fuel are considered in this paper. It is shown that in order to obtain a long refueling cycle and a high burnup at the same time, the fuel loading needs to be increased together with the moderating power of the fuel block. Three ways are considered for a higher moderation of the fuel block: a larger pitch of the coolant hole pattern, an extra graphite thickness in the fuel block, and a higher graphite density. The impact of the increased pitch on the fuel temperature is also evaluated with a thermal analysis code. We have shown that long refueling cycles and high burnups can be achieved simultaneously for both LEU and TRU fuels.     

燃料组件修复过程中单根燃料棒损坏影响分析

以核电厂燃料组件修复过程中单根燃料棒损坏释放的放射性物质为分析对象,就放射性物质释放对组件修复的工作人员产生的累积有效剂量进行评估,对向环境释放的气态流出物的放射性总活度进行计算,并对气态流出物排放监测的影响开展分析。分析结果表明单根燃料棒损坏后,执行燃料组件修复的每位工作人员接受的累积有效剂量为12.2 mSv,低于GB 18871—2002规定的工作人员职业照射年平均有效剂量限值20 mSv;向环境释放的气态流出物中惰性气体与碘的放射性总活度分别为3.51×10¹¹ Bq和2.17×10⁸ Bq,远小于GB 6249—2011规定的年排放控制值6.0×10¹⁴ Bq和2.0×10¹⁰ Bq。燃料棒损坏后40 min烟囱排气惰性气体测量仪的读数小于1.0×10¹¹ Bq/h,核电厂无需进入应急待命状态。     

国外压水堆燃料组件的发展动向

基于反应堆的运行经验,压水堆燃料组件自问世以来一直在不断地发展,最新一代燃料组件的设计批平均卸料燃耗（以金属铀计）已达５２０００ＭＷ．ｄ／ｔ。文章就高燃耗下压水堆燃料组件所出现的问题及目前世界上４家较大的核燃料供应商所推出的高性能压水堆燃料组件作一概要介绍。     

电磁爆炸压接焊工艺研究

电磁爆炸压接焊,是一种新型的焊接方法。本文介绍了此种焊接新技术的工作原理、试验装置概况、压接工艺及检测方法等。与此同时,分析讨论了影响电磁爆炸压接焊的各种因素。对电磁爆炸压接焊的优越性和发展前景也作了一定的描述。     

高通量工程试验堆燃料元件进一步加深燃耗研究

本文通过三维网程序对所选择的高通量工程试验堆参考堆芯作了三维计算，通过已知的实验结果论证了计算结果的准确性。从物理计算分析的角度看，ＨＦＥＴＲ元件在不超过最大燃耗为６７％这个限制值的提前下，盒平均燃耗限值可以由４５％和提高到５０％，同时元件的安全性能不变。     

用切伦科夫计数法确定破损元件组件

本文介绍了切伦科夫计数原理，分析了反应堆冷却剂中活化产物，裂变产物的放射性特性；讨论了用切伦科夫计数确定反应堆破损元件组件的可行性。