COMMEN程序热膨胀模型的开发和验证

堆芯解体事故已成为钠冷快堆安全分析的主要关注点之一。COMMEN程序是中国原子能科学研究院开发的钠冷快堆堆芯解体事故分析程序。该程序耦合了二维的时空中子动力学模块,主要用于计算堆芯丧失原有几何形状之后的事故进程。为改进COMMEN程序,须在现有的中子学模块中添加热膨胀模型。改进后的COMMEN程序计算严重事故时考虑的反应性反馈更全面。为验证该模型,使用改进后的COMMEN程序对中国实验快堆(CEFR)进行建模计算,并将计算结果和SAS4 A程序进行对比。结果表明:添加了热膨胀模型后,COMMEN程序的计算结果得到了很大改善,其结果与SAS4 A符合的很好。     

快堆系统分析程序FASYS堆芯分析模块验证

中国原子能科学研究院自主开发了快堆系统分析程序FASYS,已用于中国实验快堆的调试试验分析,目前正用于中国示范快堆的事故分析。FASYS程序包含堆芯分析模块、一二回路模块、事故余热排出系统模块等,其中堆芯分析模块包括点堆、衰变热、反应性反馈、堆芯通道热工水力模型等。本文采用解析解、DINROS程序、SAS4A/SASSYS-1程序验证FASYS程序的点堆模型;采用SAS4A/SASSYS-1程序验证FASYS程序的衰变热、反应性反馈和堆芯通道热工水力模型,各模型的验证结果均符合良好。对FASYS程序堆芯分析模块各模型的计算偏差和整体计算偏差进行评估,为中国示范快堆的事故分析提供参考。     

快堆系统分析程序FASYS堆芯分析模块验证

中国原子能科学研究院自主开发了快堆系统分析程序FASYS,已用于中国实验快堆的调试试验分析,目前正用于中国示范快堆的事故分析。FASYS程序包含堆芯分析模块、一二回路模块、事故余热排出系统模块等,其中堆芯分析模块包括点堆、衰变热、反应性反馈、堆芯通道热工水力模型等。本文采用解析解、DINROS程序、SAS4A/SASSYS-1程序验证FASYS程序的点堆模型;采用SAS4A/SASSYS-1程序验证FASYS程序的衰变热、反应性反馈和堆芯通道热工水力模型,各模型的验证结果均符合良好。对FASYS程序堆芯分析模块各模型的计算偏差和整体计算偏差进行评估,为中国示范快堆的事故分析提供参考。     

燃料元件瞬态性能分析程序FTPAC验证及应用

为对事故条件下单棒燃料元件热工-力学响应进行研究,本工作开发了燃料元件瞬态性能分析程序FTPAC,主要包括温度模型、力学模型、内压模型和包壳氧化模型。采用FRAP-T6程序例题对FTPAC进行验证,并对NSRR和CABRI反应性引入事故试验的4根燃料元件进行计算。结果表明,FTPAC对未发生破损的燃料元件瞬态响应预测合理。     

钠冷快堆燃料元件性能分析程序的开发与验证

为了评估钠冷快堆氧化物燃料元件稳态、瞬态和事故条件下的性能和行为演化,开发了钠冷快堆燃料元件性能分析程序FIBER。程序采用有限体积法实现燃料元件温度的计算,用有限元方法实现力学、裂变气体释放的计算,并通过时间步长控制模块控制程序的稳定运行。为验证程序的准确性,通过调研得到俄罗斯BN600反应堆辐照数据,与FIBER程序的裂变气体释放、柱状晶粒等计算结果进行对比分析。结果表明,FIBER程序对最大燃耗11.8at%、最大辐照损伤78 dpa的快堆燃料元件的辐照变形、柱状晶区、裂变气体释放性能评价是有效的。     

SARAX程序系统在钠冷快堆瞬态分析中的应用

无保护事故下的瞬态分析是钠冷快堆安全分析的重要内容。基于OECD/NEA发布的MOX-3600和MET-1000基准题,本文利用SARAX程序系统对不同钠冷快堆进行了瞬态计算,分析了堆内各种反应性反馈效应,并计算了无保护失流(ULOF)事故和无保护超功率运行(UTOP)事故下燃料温度和冷却剂温度的变化。计算结果表明：SARAX程序系统在快堆瞬态分析中可给出合理的参数预测结果;ULOF事故对于钠冷快堆是更为严重的事故瞬态,会导致堆内的钠沸腾进而发生严重事故。     

SARAX程序系统在钠冷快堆瞬态分析中的应用

无保护事故下的瞬态分析是钠冷快堆安全分析的重要内容。基于OECD/NEA发布的MOX-3600和MET-1000基准题,本文利用SARAX程序系统对不同钠冷快堆进行了瞬态计算,分析了堆内各种反应性反馈效应,并计算了无保护失流(ULOF)事故和无保护超功率运行(UTOP)事故下燃料温度和冷却剂温度的变化。计算结果表明:SARAX程序系统在快堆瞬态分析中可给出合理的参数预测结果;ULOF事故对于钠冷快堆是更为严重的事故瞬态,会导致堆内的钠沸腾进而发生严重事故。     

铅基快堆氧化物燃料性能分析程序FUTURE开发与初步验证

为了对铅基快堆氧化物燃料元件稳态工况下的服役性能和行为演化进行模拟计算,本文基于串行的半隐式耦合求解方法开发了铅基快堆氧化物燃料性能分析程序FUTURE。程序采用两步分析法实现了铅基快堆氧化物燃料棒全域热力分析与局部行为模型的多物理场耦合计算。通过各计算模块与模型算例、基准公式和现有程序的对比分析,对FUTURE程序进行了各分离效应的初步验证。结果表明,FUTURE程序能准确模拟铅基快堆稳态工况条件下氧化物燃料元件内部的温度演化、结构变形、应力分布和相互作用,并实现对燃料重构、氧和钚元素的迁移、裂变气体释放和服役期内液态铅铋腐蚀等内容的计算模拟。     

铅基快堆氧化物燃料性能分析程序FUTURE开发与初步验证

为了对铅基快堆氧化物燃料元件稳态工况下的服役性能和行为演化进行模拟计算,本文基于串行的半隐式耦合求解方法开发了铅基快堆氧化物燃料性能分析程序FUTURE。程序采用两步分析法实现了铅基快堆氧化物燃料棒全域热力分析与局部行为模型的多物理场耦合计算。通过各计算模块与模型算例、基准公式和现有程序的对比分析,对FUTURE程序进行了各分离效应的初步验证。结果表明,FUTURE程序能准确模拟铅基快堆稳态工况条件下氧化物燃料元件内部的温度演化、结构变形、应力分布和相互作用,并实现对燃料重构、氧和钚元素的迁移、裂变气体释放和服役期内液态铅铋腐蚀等内容的计算模拟。     

基于CFD的池式快堆多物理耦合分析方法研究

基于临界/次临界点堆中子动力学模型、燃料棒传热模型、热交换器和多孔介质等辅助热工水力模型,采用显式迭代和动态链接库技术（DLL）,利用商用计算流体力学（CFD）程序FLUENT的用户自定义函数（UDF）实现中子动力学、燃料棒热传导等和快堆堆池冷却剂流动换热的耦合计算,开发池式快堆多物理耦合计算程序CFD/PF。采用CFD/PF开展小型自然循环铅铋快堆SNCLFR-10无保护超功率事故（UTOP）模拟,并与国际知名快堆多物理耦合分析程序SIMMR-III的计算结果开展Code-to-Code对比分析。研究结果表明:CFD/PF与SIMMER-III的分析结果吻合良好,耦合程序的开发取得了初步成功,可用于分析池式快堆堆池内的复杂三维流动和换热现象。      

燃料棒破损热力学模块开发及在严重事故分析程序中的应用

包壳肿胀和破损是严重事故早期阶段的重要现象。包壳形变不仅会造成局部流动堵塞,同时,水蒸气会从破裂处进入包壳气隙,增加包壳被蒸汽氧化的表面积。广泛使用的一体化严重事故分析程序不能分析早期事故过程中燃料棒的热力学行为,判断包壳破裂也只是基于简单的参数模型。本文开发了分析燃料棒热力学行为的FRTMB模块,并集成在严重事故分析程序ISAA中。使用开发的耦合系统ISAA FRTMB分析了CAP1400反应堆直接注射（DVI）管线小破口事故过程中燃料棒的热力学行为,并预计了包壳破裂时间及相应的失效温度。计算结果整体验证了ISAA FRTMB分析瞬态事故过程中燃料棒热力学行为以及判断包壳破裂的适用性和可靠性。     

REA analysis of the Iranian VVER-1000 core by modification of PRORIA code for annular pellets

The PRORIA code and its recent modifications are described here. The PRORIA code analyzes the transient response of the core against the reactivity increase caused by the control rod rapid withdrawal. The code solves and analyzes neutronic and thermal–hydraulic equations simultaneously. The code is designed for western PWR-type reactor performance. The equations representing thermal–hydraulic and neutronic should be modified to use the code to analyze VVER-1000 reactor core transients, because The VVER-1000 reactor fuel has a central hole in the fuel pellet. In a cylindrical solid fuel pellet, operation of an oxide fuel material at high temperature alters its morphology and the inner region is restructured to form a void at the center surrounded by a dense fuel region. Most of the restructuring occurs within the first few days of operation with slow changes afterward. Hence, the effects of a central hole in mathematical equations and in the transient are investigated. After the code modification, three accident scenarios with control rod ejection are simulated. The results are in good agreement with those reported in the plant’s FSAR. The results show that the peak fuel temperature in the hot fuel pin is lower than what the original code predicts by 150–500 °C. Furthermore, the Doppler reactivity effect, when the fuel pellet has a central hole, is higher than the solid fuel pellet.     

Sensitivity analysis of fuel pin failure performance under slow-ramp type transient overpower condition by using a fuel performance analysis code FEMAXI-FBR

The FEMAXI-FBR is a fuel performance analysis code and has been developed as one module of core disruptive evaluation system, the ASTERIA-FBR. The FEMAXI-FBR has reproduced the failure pin behavior during slow transient overpower. The axial location of pin failure affects the power and reactivity behavior during core disruptive accident, and failure model of which pin failure occurs at upper part of pin is used by reflecting the results of the CABRI-2 test. By using the FEMAXI-FBR, sensitivity analysis of uncertainty of design parameters such as irradiation conditions and fuel fabrication tolerances was performed to clarify the effect on axial location of pin failure during slow transient overpower. The sensitivity analysis showed that the uncertainty of design parameters does not affect the failure location. It suggests that the failure model with which locations of failure occur at upper part of pin can be adopted for core disruptive calculation by taking into consideration of design uncertainties.     

Analysis of fuel pin behavior under slow-ramp type transient overpower condition by using the fuel performance evaluation code ‘FEMAXI-FBR’

FEMAXI-FBR has been developed as the one module of the core disruptive accident analysis code ‘ASTERIA-FBR’ in order to evaluate the mixed oxide (MOX) fuel performance under steady, transient and accident conditions of fast reactors consistently. On the basis of light water reactor (LWR) fuel performance evaluation code ‘FEMAXI-6’, FEMAXI-FBR develops specific models for the fast reactor fuel performance, such as restructuring, material migration during steady state and transient, melting cavity formation and pressure during accident, so that it can evaluate the fuel failure during accident. The analysis of test pin with slow transient over power test of CABRI-2 program was conducted from steady to transient. The test pin was pre-irradiated and tested under transient overpower with several % P ₀/s (P ₀: steady state power) of the power rate. Analysis results of the gas release ratio, pin failure time, and fuel melt radius were compared to measured values. The analysis results of the steady and transient performances were also compared with the measured values. The compared performances are gas release ratio, fuel restructuring for steady state and linear power and melt radius at failure during transient. This analysis result reproduces the measured value. It was concluded that FEMAXI-FBR is effective to evaluate fast reactor fuel performances from steady state to accident conditions.     

Mathematical description of WAFER-1, a three-dimensional code for LWR fuel performance analysis

This article describes in detail the mathematical formulation used in the WAFER-1 code, which is presently used for three-dimensional analysis of LWR fuel pin performance. The code aims at a prediction of the local stress-strain history in the cladding, especially with regard to the ridging phenomenon. To achieve this, a clad model based on shell theory has been developed. This model interacts with a detailed finite difference pellet model which treats radial and transversal cracking in the pellet in a deterministic way, based on certain assumptions with respect to the cracking pattern. Pellet and clad creep are taken into account. The inner core of the pellet, bounded by a specified isotherm, may be treated as a viscous material. Axial force exchange between pellet and clad is also included. The axial loading is distributed on the pellet end face with due regard to any pellet dishing. An arbitrary power history may be used as input to the model.     

基于CFD的池式快堆多物理耦合分析方法研究

Based on the critical/subcritical point kinetics model, the fuel pin heat transfer model, and the auxiliary thermal hydraulic models such as the heat exchanger model and the porous media model, a multi-physical coupling code CFD/PF was developed by means of the explicit iteration method, dynamic link library technique (DLL) and user-defined functions (UDF) of FLUENT. The CFD/PF was used to carry out the simulation of SNCLFR-100 unprotected transient of over power (UTOP) of a small natural circulation LBE cooled fast reactor, and the code-to-code comparison analysis was conducted with the renowned multi-physical coupling code SIMMER-III. The results indicated that the CFD/PF simulation results are in a good agreement with SIMMER-III calculation results, and the multi-physical analysis method and code development have been achieved initial success, which can be used to analyze the complex three-dimensional flow and heat transfer phenomena in pool-type fast reactors.