R&D on high temperature components

Experimental studies were carried out to confirm the structural integrity of the key high temperature components, which are necessary to commercialize the HTGR, that is, an intermediate heat exchanger (IHX) and a coaxial hot gas duct. As for the IHX, the following tests were conducted: (1) creep collapse of tube against external pressure, (2) creep fatigue of tube against thermal stress, (3) seismic behavior of tube bundles, (4) thermal hydraulic behavior of tube bundles and (5) in-service inspection technology of tube with full-scale models. As for the coaxial hot gas duct, the thermal insulation performance as well as the structural integrity was investigated with the HENDEL-loop.     

Design and experiment of hot gas duct for the HTR-10

A horizontal coaxial double-tube hot gas duct is a key component connecting the reactor pressure vessel and the steam generator pressure vessel for the 10 MW High Temperature Gas-cooled Reactor—Test Module. Hot helium gas from the core outlet flows into the steam generator through the liner tube, while helium gas after being cooled returns to the core through a passage formed between the inner tube and the duct pressure vessel. Thermal insulation material is packed into the space between the liner tube and the inner tube to resist heat transfer from the hot helium to the cold helium. The thermal compensation structure is designed in order to avoid large thermal stress because of different thermal expansions of the duct parts under various conditions. According to the design principal of the hot gas duct, the detailed structure design and strength evaluation for it has been done. A full-scale duct test section was then made according to the design parameters, and its thermal performance experiment was carried out in a helium test loop. With helium gas at pressure of about 3.0 MPa and a temperature over 900 °C, the continuous operation time for the duct test section lasted 98 h. At a helium gas temperature over 700 °C, the cumulative operation time for the duct test section reached 350 h. The duct test section also experienced 20 pressure cycles in the pressure range of 0.1–3.4 MPa, 18 temperature cycles in the temperature range of 100–950 °C. Thermal test results show an effective thermal conductivity of the hot gas duct thermal insulation is 0.47 W m⁻¹ °C⁻¹ under normal operation condition. In addition, a hot gas duct depressurization test was carried out; the test result showed that the pressure variation occurred on the liner tube was not more than 0.2 MPa for an assumed maximum gas release rate.     

高温气冷堆热气联箱内部流场数值模拟

以高温气冷堆热气联箱为研究对象，在实验研究基础上，采用流体力学计算程序CFX5对热气联箱和热气导管内部流场进行数值模拟，以获得热气联箱和热气导管内的速度场、压力场和温度场，为高温气冷堆热气联箱的设计和实验研究提供参考。数值计算结果表明：热气联箱内气流发生剧烈搅混，加速了不同温度气流间的热传递，有利于高温和低温气流间的温度混合，存在肋片的区域未发生剧烈的气流搅混，不利于气流间的热传递；热气导管内温度混合率随其长度的增加逐渐增大，当热气导管长度为2.5m以上时，温度混合率达到99％以上。     

Thermal and hydraulic tests of test sections in the helium engineering demonstration loop

The helium engineering demonstration loop (HENDEL) has been constructed and operated to test the large-scale components of the high temperature engineering test reactor (HTTR) under simulated reactor operating conditions. The fuel stack test section (T₁) of HENDEL simulates the fuel stack of the HTTR core and is used to investigate thermal and hydraulic performance. Hot tests with 1000°C helium gas have been conducted using simulated fuel rods having uniform, exponential and cosine axial heat flux distributions. The test results agreed with previously proposed correlations, although the simulated fuel rods had various heat flux distributions and high heat flux rates.

The in-core structure test section (T₂) also was installed in the HENDEL to verify the performance of the core bottom structure of the HTTR. The tests show that good performance was obtained. Examination of the thermal mixing characteristics indicated that mixing started at the location where the hot helium gas flowed into the hot plenum and that complete mixing was achieved during the downward flow in the outlet hot gas duct. The seal performance testing indicated no change of the leakage flow rate after 4000 hours of operation. The temperature of the metal portion of the structure was below 500°C and uniform around circumferential cross-sections due to the good performance of the thermal insulation blocks.     

高温气冷堆螺旋管式直流蒸汽发生器热工水力学

高温气冷堆蒸汽发生器具有一次侧氦气工质、二次侧直流、螺旋管结构、工作温度高等特点,其热工水力特性与传统压水堆自然循环蒸汽发生器存在很大区别。针对高温气冷堆蒸汽发生器的特点,对其基础热工水力及特有热工水力学问题进行了阐述,主要包括螺旋管内单相及两相流阻及换热计算、横掠螺旋管束流阻及换热计算、温度均匀性及两相流不稳定性等。同时介绍了清华大学核能与新能源技术研究院针对高温气冷堆蒸汽发生器热工设计、温度均匀性及两相流不稳定性等热工水力学问题所开发的一维稳态程序、一维瞬态程序、二维分析程序和方法,并对分析结果和结论进行了讨论。相关研究方法、程序和结论对其他相似参数螺旋管和直管式直流蒸汽发生器具有参考和借鉴意义。     

高温堆热气联箱内部流场分析

以高温堆热气联箱为研究对象,在实验研究的基础上,采用流体力学计算程序CFX5对热气联箱和热气导管内部流场进行了数值模拟,以获得热气联箱和热气导管内的速度场、压力场和温度场,为高温堆热气联箱的设计和实验研究提供参考.数值计算结果表明:热气联箱内气流发生剧烈搅混,加速了不同温度气流间的热传递,有利于高温和低温气流间的温度混合.但存在肋片的区域没有发生剧烈的气流搅混,不利于气流间的热传递.热气导管内温度混合率随其长度的增加逐渐增大,热气导管长度2.5m以上时,温度混合率达到99%以上.     

Numerical investigations of thermal mixing performance of a hot gas mixing structure in high-temperature gas-cooled reactor

A numerical simulation study was performed to clarify the thermal mixing characteristics of coolant in the core bottom structure of the high-temperature gas-cooled reactor(HTR). The flow field and temperature field in the hot gas chamber and the hot gas duct of the HTR were obtained based on the commercial computational fluid dynamics(CFD) program. The numerical simulation results showed that the helium flow with different temperatures in the hot gas mixing chamber and the hot gas duct mixed intensively, and the mixing rate of the temperature in the outlet of the hot gas duct reached 98 %. The results indicated many large-scale swirling flow structures and strong turbulence in the hot gas mixing chamber and the entrance of the hot gas duct, which were responsible for the excellent thermal mixing of the hot gas chamber and the hot gas duct. The calculated results showed that the temperature mixing rate of the hot gas chamber decreased only marginally with increasing Reynolds number.     

Transient thermal–hydraulic simulations of direct cycle gas cooled reactors

This work concerns the design and safety analysis of gas cooled reactors. The CATHARE code is used to test the design and safety of two different concepts, a High Temperature Gas Reactor concept (HTGR) and a Gas Fast Reactor concept (GFR). Relative to the HTGR concept, three transient simulations are performed and described in this paper: loss of electrical load without turbo-machine trip, 10 in. cold duct break, 10 in. break in cold duct combined with a tube rupture of a cooling exchanger. A second step consists in modelling a GFR concept. A nominal steady state situation at a power of 600 MW is obtained and first transient simulations are carried out to study decay heat removal situations after primary loop depressurisation. The turbo-machine contribution is discussed and can offer a help or an alternative to “active” heat extraction systems.     

模块式高温气冷堆非能动余热排出系统分析与研究

非能动的余热排出系统是高温气冷堆固有安全性的重要体现之一。本文介绍了模块式高温气冷堆余热排出系统热工水力计算方法,并给出了不同工况、不同环境温度下余热排出系统的运行参数,为余热排出系统的设计和运行提供了参考。对事故工况下舱室混凝土温度分布进行了数值分析,结果表明混凝土最高温度低于安全限值。     

高温气冷堆热气导管中石墨粉尘沉积特性分析

高温气冷堆中石墨粉尘的运动规律对反应堆安全具有重要意义。本工作采用计算流体力学方法得到热气导管中的温度场分布,在此基础上分析了热气导管中热泳沉积与湍流沉积的规律。结果表明,随着颗粒粒径的增大,热泳沉积率下降,而湍流沉积率则先减少后增大。通过比较30%FP及100%FP两种反应堆功率下的计算结果发现：反应堆功率为30%FP时对应的热泳沉积率更高,而反应堆功率为100%FP时,湍流沉积率增长更加迅速。当颗粒粒径较小时,热泳沉积与湍流沉积作用相当,颗粒粒径较大时,湍流沉积明显占主导地位。最后,采用最可几分布的粒径计算了热气导管中石墨粉尘总的沉积量,计算结果表明石墨粉尘沉积总量有限。     

高温气冷堆用碳毡材料导热系数测量及反问题计算

碳纤维材料已成为核能、航天等领域不可或缺的重要功能材料,在高温气冷堆及其相关实验中需要使用大量碳纤维保温材料。但由于目前测试方法的限制,相关材料物性参数测量数据严重不足,尤其是缺乏高温1000℃以上的热物性参数,致其使用受到限制。为此,清华大学核能与新能源技术研究院研制了模拟高温气冷堆温度、环境氛围的材料测试装置,可提供1600℃以下的材料性能测试。根据该装置一次典型实验过程的测量数据,详细介绍了采用非线性导热反问题方法确定材料温度相关导热系数的完整过程和具体算法。提出了一种依据稳态、非稳态热传导原理求解反问题的简明算法,该方法既可单独使用,也可为其他反问题算法提供良好的迭代初值。实验确定了高温气冷堆用碳毡保温材料在1600℃以下的导热系数,将为高温气冷堆相关实验和其他特高温条件下的应用提供重要参考。     

Calcium oxide/carbon dioxide reactivity in a packed bed reactor of a chemical heat pump for high-temperature gas reactors

The thermal performance of a chemical heat pump that uses a calcium oxide/carbon dioxide reaction system was discussed as a heat storage system for utilizing heat output from high temperature gas reactors (HTGR). Calcium oxide/carbon dioxide reactivity for the heat pump was measured using a packed bed reactor containing 1.0 kg of reactant. The reactor was capable of storing heat at 900 °C by decarbonation of calcium carbonate and generating up to 997 °C by carbonation of calcium oxide. The amount of stored heat in the reactor was 800–900 kJ kg⁻¹. The output temperature of the reactor could be controlled by regulating the carbonation pressure. The thermal storage performance of the reactor was superior to that of conventional sensible heat storage systems. A heat pump using this CaO/CO₂ reactor is expected to contribute to thermal load leveling and to realize highly efficient utilization of HTGR output due to the high heat storage density and high-quality temperature output of the heat pump.     

Utilization of high temperature heat from nuclear reactor using inorganic chemical heat pump

A new chemical heat pump designed to utilize high-temperature heat generated from high-temperature gas reactor (HTGR) is discussed. The calcium oxide / lead oxide / carbon dioxide reaction system was found to be a suitable reaction system for the desired heat pump from experimental survey of inorganic oxide / carbon dioxide reaction systems. The proposed heat pump using the reaction system was expected to be heat storage and heat transform system for HTGR. To demonstrate the validity of the heat pump, equilibrium relationship and kinetics of the reaction system was studied experimentally. The practical operation conditions of the heat pump were revealed from the experiment. This system was available to store heat above 800°C and transform it to higher temperature under a thermal driving condition. The heat output of the heat pump was valued enough compared to a common system. The applied system of the heat pump combined with HTGR was proposed to show the way of effective utilization of HTGR.     

Transient Behaviors of Gas in Thermal Insulation Media at Rapid Depressurization

Thermal insulation systems are often used to high-temperature gas cooled reactors.

In this paper, transient behavior of the gas flow in thermal insulation media was systematically analyzed in the case of sudden decrease in a coolant pressure. The structure of these systems is capable of substituting for the simplified model that the gas in a containment filled with porous insulation media exhausts from a balancing hole to main flow duct. In the case of rapid depressurization, these behaviors were calculated by using equations of continuity and motion based on the Darcy flow model with area ratio of a balancing hole and permeability of porous insulation media as parameters. The transient pressure difference of a hot liner wall between the main flow helium and the insulation layer induced at depressurization was numerically analyzed. It was revealed from analytical results that transient behaviors were strongly influenced by prescribed parameters, and experimental results can be explained by using the analytical model.     

HTR-PM热气导管结构强度的分析与计算

500 MW高温气冷堆示范电站(HTR-PM)的反应堆压力容器与蒸汽发生器通过热气导管连接,热气导管是反应堆堆芯出口氦气导入蒸汽发生器的主要通道.热气导管是安全三级、抗震Ⅰ类部件,根据ASME规范,要求热气导管能在地震条件下保持结构的完整性.为验证热气导管在反应堆寿期内的安全可靠性,本文建立了热气导管有限元计算模型,计算了热气导管在绝热纤维压力、压力边界失压的压差、自重以及地震载荷等多种载荷作用下,内衬管、锥管与外管的应力分布状况.计算结果表明,热气导管各部分强度有较大裕度,可承受运行载荷、失压载荷以及地震载荷.     

Feasibility study on the applicability of a diffusion-welded compact intermediate heat exchanger to next-generation high temperature gas-cooled reactor

The development of an intermediate heat exchanger (IHX) transferring high temperature heat to a process heat application is of prime importance for a next-generation high temperature gas-cooled reactor (HTGR). The IHX needs high structural integrity and reliability over 900°C for a long duration. A plate fin type compact heat exchanger (PFCHX) has a large heat transfer area per heat exchanger volume and is expected to be used as the IHX. However, the brazing for connecting fins and plate is not reliable when existing PFCHXs are used in a high temperature condition for a long time. We have proposed a concavo-convex plate type compact heat exchanger (CPCHX) which consists of concavo-convex plates (CPs) welded by solid state diffusion and made of nickel-based superalloy Hastelloy XR. In our study, first, an optimized condition for the solid state diffusion welding between the CPs of the CPCHX was found by experiments using test pieces made of Hastelloy XR. Second, small-scale diffusion-welded CPCHXs were designed, manufactured and installed in a test loop to investigate the reliability of the diffusion welding. As a result of leakage tests, it was confirmed that the reliability of the solid state diffusion welding between the CPs of the small-scale CPCHX is sufficient. A thermal performance test revealed that the thermal conductance of the small-scale CPCHX was better than calculated. In addition, a design study for the CPCHX was performed to investigate the feasibility of the diffusion-welded CPCHX to the IHX in a next-generation HTGR.     

Optimization of Hot Gas Chamber in High Temperature Reactor

The flow field in the hot gas chamber of the High Temperature Gas Cooled Reactor (HTGCR) was studied with the Computational Fluid Dynamics (CFD) program CFX5. On the basis of the experimental studies, the velocity field, pressure field and temperature field in the hot gas chamber and hot gas duct were obtained, and the simulation's accuracy and reliability were validated by comparison with the results of previous experiments. Two other design schemes of the hot gas chamber were calculated in order to determine which hot gas chamber would be optimal for minimizing temperature differences at the inlet of the heat exchanging components. The results indicated that there was much highly turbulent twisting flow in the hot gas chamber, which was responsible for the excellent temperature mixing effect of the hot gas chamber. But the flow in the rib region was calm, and this fact hindered the heat transfer between the hot and cold gas. The temperature mixing coefficient increases with the increase of the hot gas duct's distance from the hot gas chamber. The hot gas chamber without ribs was more beneficial to the heat transfer between air flows with different temperatures, so the hot gas chamber without ribs was indicated as the optimal design.     

HTR-PM蒸汽发生器绝热层支撑结构的设计与分析

为提高HTR-PM高温气冷堆蒸汽发生器的热交换效率并分隔冷热氦气的通路,必须在蒸汽发生器中设置绝热装置.在围绕换热管放置的钢制围筒上铺设一定厚度的绝热纤维,用多块覆盖板将绝热纤维压紧,在每块覆盖板中心与四角,用中间填充绝热纤维的螺栓将覆盖板定位并紧固,组成绝热层支撑结构.使用有限元方法对绝热层支撑结构在绝热材料压力、蒸汽发生器失压、地震等多种载荷的综合作用下的应力分布情况进行计算,计算结果表明:支撑结构在多种载荷的作用下仍能保持绝热层功能的可靠性与结构的完整性.     

Thermal mixing characteristics of helium gas in high-temperature gas-cooled reactor, (I) thermal mixing behavior of helium gas in HTTR

The future high-temperature gas-cooled reactor (HTGR) is now designed in Japan Atomic Energy Agency. The reactor has many merging points of helium gas with different temperatures. It is needed to clear the thermal mixing characteristics of helium gas at the pipe in the HTGR from the viewpoint of structure integrity and temperature control. Previously, the reactor inlet coolant temperature was controlled lower than specific one in the high-temperature engineering test reactor (HTTR) due to lack of mixing of helium gas in the primary cooling system. Now, the control system is improved to use the calculated bulk temperature of reactor inlet helium gas. In this paper, thermal–hydraulic analysis on the primary cooling system of the HTTR was conducted to clarify the thermal mixing behavior of helium gas. As a result, it was confirmed that the thermal mixing behavior is mainly affected by the aspect ratio of annular flow path, and it is needed to consider the mixing characteristics of helium gas at the piping design of the HTGR.     

核能制氢技术的发展

氢是清洁能源,有非常好的应用前景.但氢是二次能源,需要利用一次能源来生产.以可持续的方式(原料来源丰富、无温室气体排放)实现氢的大规模生产是实现氢广泛利用的前提.核能是清洁的一次能源,核电已经成为世界电力生产的主要方式之一.正在研发的第四代核能系统除了要使核电生产更经济和更安全之外,还要为实现核能在发电之外的领域的应用...