核电厂非能动氢气复合器消氢特性试验研究

根据非能动氢气复合器(PAR)的工作状态特点和启动阈值、停止阈值、消氢能力、点火阈值等关键特性参数的要求,设计建立能够模拟安全壳内事故环境条件、在非能动条件下开展PAR关键特性参数验证试验的试验装置,制定相应的试验方法,开展启动阈值试验、启动时间试验、消氢能力试验和点火阈值试验等,获得PAR的关键特性参数。试验结果表明:PAR关键特性在不同的试验参数条件下测试结果也不同;在制定PAR消氢特性参数要求时需要限定试验方法和试验参数条件,以便获得统一的、定量的PAR的消氢特性参数。     

核电厂非能动氢复合器研制

核电厂非能动氢复合器主要用于消除严重事故后安全壳内产生的氢气,避免氢气聚集而产生爆炸。根据H2和O2催化反应消氢的工作原理,设计以Pt、Pd混合配比作为催化剂的催化板,并以此为核心部件,设计制造能够在非能动条件下持续消氢的非能动氢复合器。针对核电厂安全壳严重事故后的消氢要求,开展非能动氢复合器在不同温度、压力、氢气体积分数等条件下的消氢速率试验,不同毒物对消氢效果影响试验以及启动和停止阈值试验。研究结果表明,非能动氢复合器达到了核电厂事故后消氢技术要求,可直接应用于二代堆型核电厂,还可以应用于EPR或AP1000等三代堆型核电厂。     

基于CFD的安全壳局部隔间非能动氢气复合器布置方案研究

非能动氢气复合器用于压水堆核电厂严重事故条件下安全壳内氢气的消除。通过计算流体力学(CFD)方法能够给出事故条件下非能动氢气复合器周围三维流场和温度场的分布。基于CFD程序根据非能动氢气复合器消氢公式,计算非能动氢气复合器进出口的气体流量和气体组分,并作为非能动氢气复合器的边界条件,开展三维空间内非能动氢气复合器消氢速率和氢气分布情况研究。结果表明：简化的非能动氢气复合器模拟方案能很好地模拟非能动氢气复合器样机的消氢效果;对安全壳内局部隔间开展非能动氢气复合器消氢效果研究发现,在相同环境条件下,非能动氢气复合器布置在较高位置与布置在较低位置相比,布置在较高位置时,非能动氢气复合器具有更高的消氢速率,隔间整体氢气浓度较低,但是非能动氢气复合器布置在较高位置时出现隔间底部局部氢气聚集的情况。     

压水堆核电厂消氢装置选用探讨

为消除核电厂在严重事故工况下积聚在安全壳内的氢气,需要在核电厂安全壳内增加消氢装置。本文分析了严重事故工况下目前主要采用的氢气点火器和非能动氢复合器的原理,并结合某核电厂增加非能动氢复合器改造的工程实践,给出了压水堆核电厂消氢装置选用方案。实践结果表明,此最优消氢方案既可以保证电厂安全,又可以节约成本,具有巨大的社会效益和经济效益。     

大亚湾和岭澳核电站安全壳氢气风险及消氢措施有效性分析

使用MAAP程序计算大亚湾和岭澳核电站严重事故条件下安全壳内的相关质能释放和氢气源项;利用TONUS程序建立安全壳集总参数模型,计算分析氢气在安全壳内的分布情况;结合非能动氢复合器消氢性能、现场条件和氢气分布情况,提出氢复合器布置方案;借助TONUS和GASFLOW程序,分别使用集总参数法和CFD法,验证消氢方案的有效性。验证结果表明,安全壳内氢气浓度满足相关法规要求。     

非能动式氢气复合器在田湾核电站的应用

基于福岛核电氢爆事故,文章介绍了非能动式氢气复合器在田湾核电站的应用,分析了非能动式复合器的反应原理、在役试验以及再生试验过程,最后对田湾核电历次非能动式氢气复合器的性能试验数据进行了分析。     

安全壳消氢系统催化板效率试验影响因素分析

本文通过对某核电站安全壳消氢系统(EUH)非能动氢复合器催化板效率试验的试验方法和催化板本身特性的分析,确认对催化板消氢效率试验结果影响较大的因素,并且针对这些影响因素给出相应的应对措施。大修期间的试验数据表明本文给出的各项应对措施是非常有效的,对其他核电项目具有参考意义。     

未来核电机组安全壳消氢系统的工艺方案研究

本文立足于新版HAF法规的要求，参考大田湾核电站、秦山三期和岭澳二期的安全壳消氢系统设计，对用于未来核电机组安全壳内可燃气体控制的安全壳消氢系统的设计功能、消氢设备选择配置及系统运行方案进行初步研究，重点对非能动氢复合器（PAR）和点火器这两种消氢设备的特点进行比较，并针对未来核电机组提出PAR＋点火器的系统初步工艺方案。     

基于DLL的GOTHIC 8.0程序氢气复合器模拟方法研究

非能动氢气复合器已广泛应用于核电厂氢气威胁的缓解和消除。本文通过对GOTHIC 8.0程序进行二次开发,采用外部动态链接库（DLL）编译、调用的方式,精确模拟了非能动氢气复合器的实际消氢能力,进而将采用该方法计算得到的消氢结果分别与公式计算、MAAP5程序算例计算结果进行比较,结果符合度高,验证了该方法的合理性。本文提供的模拟方法不仅为安全壳氢气风险缓解分析提供了新方法,也为GOTHIC程序开发提供了新思路。     

一个换料周期前后非能动消氢复合器催化片消氢效率对比试验

从设备功能、设备组成、现场布置、在役试验方法和周期等方面介绍秦山第二核电厂3、4号机组使用的非能动消氢复合器。对经过1个换料周期使用前后的4组催化片进行消氢效率对比试验,对比分析调试与生产过程中容易发生的锈蚀、油污等问题对催化片消氢效率的影响。试验结果表明:经过1个换料周期后,由于受油污、灰尘等因素的影响,催化片的消氢成功时间与初始结果相比略有延长;少量锈蚀和油污对催化片的消氢效率未产生显著影响,但锈蚀容易造成催化片穿孔、破损,油污板片试验过程中产生的烟气容易对消氢过程产生干扰。     

Effect of spray on performance of the hydrogen mitigation system during LB-LOCA for CPR1000 NPP

During the course of the hypothetical large break loss-of-coolant accident (LB-LOCA) in a nuclear power plant (NPP), hydrogen is generated by a reaction between steam and the fuel-cladding inside the reactor pressure vessel (RPV). It is then ejected from the break into the containment along with a large amount of steam. Management of hydrogen safety and prevention of over-pressurization could be implemented through a hydrogen mitigation system (HMS) and spray system in CPR1000 NPP. The computational fluid dynamics (CFD) code GASFLOW is utilized in this study to analyze the spray effect on the performance of HMS during LB-LOCA. Results show that as a kind of HMS, deliberate igniter system (DIS) could initiate hydrogen combustion immediately after the flammability limit of the gas mixture has been reached. However, it will increase the temperature and pressure drastically. Operating the DIS under spray condition could result in hydrogen combustion being suppressed by suspended droplets inside the containment. Furthermore, the droplets could also mitigate local the temperature rise. Operation of a PAR system, another kind of HMS, consumes hydrogen steadily with a lower recombination rate which is not affected noticeably by the spray system. Numerical results indicate that the dual concept, namely the integrated application of DIS and PAR systems, is a constructive improvement for hydrogen safety under spray condition during LB-LOCA.     

Analysis of hydrogen depletion using a scaled passive autocatalytic recombiner

Hydrogen depletion tests of a scaled passive autocatalytic recombiner (PAR) were performed in the Surtsey test vessel Germany) at Sandia National Laboratories (SNL). The experiments were used to determine the hydrogen depletion rate of a PAR in the presence of steam and also to evaluate the effect of scale (number of cartridges) on the PAR performance at both low and high hydrogen concentrations.     

Demonstrative testing of honeycomb passive autocatalytic recombiner for nuclear power plant

Passive autocatalytic recombiners (PAR) are widely being used as hydrogen control device in the current and advanced light water reactors (ALWRs). The PARs lend themselves to very effective means of circumventing buildup of combustible or detonable hydrogen gas mixtures in the reactor containment. Korea Nuclear Technology Inc. has recently developed a new PAR system with high porous catalyst material in the shape of honeycomb. The honeycomb PAR catalyst has a design characteristic of improved hydrogen removal performance by increasing the surface area and enhancing the flow rate through the catalyst at the same time, without increasing PAR size compared to the conventional PARs. The experimental study was focused on the development of the hydrogen depletion rate correlation of the honeycomb PAR. Two different sizes of PARs, KPAR-40 and KPAR-T2, have been employed in the tailor-made Integral Test Facility and Performance Test Facility. Multiple tests were conducted in various conditions of pressure, temperature, and hydrogen concentration. The hydrogen depletion rate correlation and the PAR performance constant were determined from the experimental results, which can be applied to the honeycomb PAR system. Also determined was the scale effect due to the PAR size, i.e., the number of catalysts in a PAR.     

Modeling of the Helium-Heated Steam Reformer for HTR-10

In this study, based on the pseudo-homogeneous one-dimensional model, a steady-state model of the helium-heated steam reformer planned to be connected with the 10 MW high temperature gas cooled reactor (HTR-10) has been developed. Good agreement is shown between the simulating results and experimental data. The influence of main process parameters on the performance with respect to the methane conversion and the hydrogen yield is investigated and discussed. The performance increases remarkably with the increase in the inlet helium temperature when it is lower than 1,000°C. Whereas, the effect becomes weak when the temperature is higher than 1,000°C. The influence of the inlet helium flow rate is not as evident as that of the temperature. The inlet helium pressure and inlet process gas temperature have almost no influence on the performance. The performance increases with the decrease in the inlet process gas pressure. The influence of the inlet process gas flow rate and steam-to-carbon ratio (S/C) is complicated. Optimal values should be chosen for them to obtain a high performance.     

超临界水堆全系统启动特性研究

为研究超临界水堆（SCWR）全系统启动特性,以SCTRAN程序为计算工具,基于中国超临界水堆（CSR1000）堆芯参数、高性能轻水反应堆（HPLWR）热力循环回路和日本SCWR再循环启动回路,建立了SCWR完整再循环启动系统模型。通过与HPLWR热力循环回路的稳态参数对比,验证了完整回路模型的正确性。分析在控制系统控制下的CSR1000再循环启动过程,得到了启动过程中堆芯、汽鼓、汽轮机、各级抽汽、再热器、各级回热器的瞬态响应曲线。计算结果表明,启动序列和启动过程各热工参数的变化符合预期,系统稳定启动;堆芯始终处于单相状态;汽轮机入口为超临界蒸汽;经过高压和低压回热器后堆芯入口温度能够达到280℃;高压缸入口压力维持恒定;在启动的过程中最大燃料包壳表面温度低于限值温度650℃,整个启动过程安全可靠。      

高温气冷堆甲烷蒸汽重整制氢系统重整器性能数值分析

甲烷转化率和产氢量是反映重整器性能的重要指标。本文对匹配高温气冷堆HTR-10的蒸汽重整器性能进行数值分析。设定重整器氦气入口流量不变，研究不同氦气入口温度、压力，不同工艺气入口温度、压力、流量，以及不同水碳比对重整器性能的影响。在所研究的范围内，结果表明：氦气的入口温度对重整器性能有明显的影响；氦气的入口压力、工艺气的入口温度和压力对重整器性能影响较小；提高工艺气流量，甲烷转化率降低，但产氢量增加，而提高水碳比则有相反的变化关系。     

The Efficiency of Noble Metals in Reducing the Corrosion Potential in the Primary Coolant Circuits of Boiling Water Reactors Operating under Hydrogen Water Chemistry Operation

In order to promote the effectiveness of hydrogen water chemistry (HWC) and to achieve a more effective reduction in electrochemical corrosion potential (ECP) in the primary coolant circuits of boiling water reactors (BWRs), the technology of noble metal chemical addition (NMCA) was brought into practice about 10 years ago. NMCA aims at enhancing the oxidation of hydrogen on metal surfaces and lowering the concentrations of the oxidants (oxygen and hydrogen peroxide) via recombination with hydrogen on the catalyzed surfaces, and therefore reducing the corrosion potentials of the structural alloys in a BWR primary heat transport circuit. Previous research indicates that the effectiveness of NMCA in combination with a low HWC might be evaluated via model predictions of the hydrogen-to-oxidant molar ratio (M_H/O) in the primary coolant circuit. If the M_H/O at a certain location is calculated to be greater than 2, it is justified that the NMCA would be effective in reducing the ECP to much below the critical potential for Intergranular Stress Corrosion Cracking (IGSCC), E_IGSCC, of --0.23 V_SHE. However, this statement is true only when the recombination efficiency of hydrogen with oxygen and/or hydrogen peroxide at the location of interest is 100%. Otherwise, significant amounts of oxidants may still be present, even with a stoichiometric M_H/O of greater than 2. With the aid of a computer model DEMACE, we explored the impact of incomplete recombination and found that the ECP might be reduced under given circumstances, but not to a great extent, and might remain well above E_IGSCC. Accordingly, considerable caution should be exercised upon using the M_H/O as a sole indicator for evaluating the effectiveness of NMCA with low HWC as a means of mitigating IGSCC in a BWR. An important finding of this study is that it is necessary to quantify the recombination efficiencies of hydrogen with oxygen and/or hydrogen peroxide on the noble metal treated stainless steel surfaces in order to qualify the use of M_H/O as an indicator for NMCA effectiveness in the primary coolant circuit of a BWR.     

Environmental controls for higher temperature direct-cycle light water reactors

Radiolysis modeling is used to estimate the minimum hydrogen concentration to activate platinum catalysts and reduce the electrochemical corrosion potential in light water reactors. Platinum catalysts are used in boiling water reactors to catalyze hydrogen and oxygen recombination, which reduces the corrosion potential and the susceptibility of austenitic structural materials to intergranular stress corrosion cracking. Two environmental challenges for material performance in higher temperature light water reactors are the increased susceptibility of austenitic materials to stress corrosion cracking and the higher production rate of oxidizing radiolytic species. For a reference supercritical water reactor, a hydrogen addition rate of 2 standard cubic feet per minute is needed to significantly reduce the susceptibility of austenitic materials to stress corrosion cracking. Also, for a reference higher temperature boiling water reactor, a hydrogen addition rate of 10 standard cubic feet per minute of hydrogen reduces the stress corrosion crack susceptibility of austenitic materials located in the lower portion of the reactor vessel.     

Study of hydrogen mitigation for safe storage of spent cesium adsorption vessels

Hydrogen mitigation is one of the important issues for safe storage of spent cesium adsorption vessels that were used in the contaminated-water treatment facility at the Fukushima Daiichi Nuclear Power Station because the production and accumulation of hydrogen is induced by the radiolysis of residual water in the vessel. In the present study, an experimental examination was performed using a miniature acrylic vessel to simulate an upper section of the vessel using particle image velocimetry to clarify the internal flow of hydrogen-mixed gas and to verify the analytical results by the ANSYS Fluent code. As a result, weak upflow and circulating flow at the stepped section were successfully visualized, and the validity of the analytical results was confirmed by the flow patterns. Additionally, the practicality of a recombination catalyst for hydrogen and oxygen was considered as a passive autocatalytic recombiner in hydrogen mitigation. A catalytic reaction test was conducted to evaluate its effectiveness. The results showed that the catalyst retains activity under the humid condition assumed in the real vessel.     

Thermal and Stability Considerations of Super LWR during Sliding Pressure Startup

The feasibility of the sliding pressure startup of a high-temperature supercritical-pressure light water reactor (super LWR, SCLWR-H) is assessed from both thermal and stability considerations. In the sliding pressure startup, nuclear heating starts at subcritical pressure and the reactor is pressurized to supercritical pressure at a low power and high enough flow rate. The reactor power and flow rate are then raised gradually to the rated normal values at constant supercritical operating pressure. During startup, the maximum cladding surface temperature must not exceed 620°C. For two-phase flow at subcritical pressures, the homogeneous equilibrium model is used. The thermal-hydraulic and coupled neutronic thermal-hydraulic stabilities during pressurization and power-raising are investigated by a frequency-domain linear analysis for both supercritical-pressure and subcritical-pressure operating conditions. The same stability criteria as those of BWRs are used. From the analysis results, a sliding pressure startup procedure is proposed for super LWR. The thermal criteria are satisfied by keeping the core power between the maximum allowable limit and minimum limit required for turbine startup and operation. The thermal-hydraulic stability and coupled neutronic thermal-hydraulic stability can be maintained by applying an orifice pressure drop coefficient at the inlet of fuel assembly and by controlling the power and flow rate during startup.