用氢同位素估算氚在熔盐堆结构材料中的渗透

熔盐堆产生的氚在高温下透过结构材料管壁进入大气环境。为降低此危害,研究氚在堆结构材料中的渗透过程十分必要。针对熔盐堆常用的结构材料Hastelloy N、GH3535、Hastelloy C230、Hastelloy C276,本研究采用压力差驱动法,在400-700 oC和5-40 k Pa的试验条件下,获得了氕、氘的渗透系数,并初步估算氚在该结构材料中的渗透。结果表明:氕、氘在镍基合金中的渗透通量与气体压力的平方根成正比,渗透系数随温度增大,与温度倒数的关系符合阿伦尼乌斯公式;氕、氘在成分相似的GH3535和Hastelloy N中渗透系数接近,与其它两种合金材料中渗透系数都在一个数量级内,在相同温度下两者渗透系数比值接近1.4,符合经典扩散理论;在400-700 oC内,氚在4种镍金合金中渗透过程的指前因子为1.1×10-7-1.6×10-7 mol·m-1·s-1·Pa-1/2,活化能为59-62 k J·mol-1。     

氢在FLiNaK(LiF-NaF-KF)熔盐中的渗透行为

FLiNaK(LiF-NaF-KF)熔盐在高温熔盐堆或聚变堆的应用中面临着氚扩散渗透的问题。研究H2在FLiNaK熔盐中的渗透行为,能够为FLiNaK熔盐中氚的控制提供依据。氢同位素在熔盐中的扩散渗透特性测试系统主要用于测定熔盐中氢同位素的渗透行为,以获得氢同位素在熔盐中的扩散系数和溶解度常数等相关参数。通过该系统,本文对FLiNaK熔盐中H2的渗透、扩散和溶解等行为进行了研究。结果表明,受实验装置和实验方法的限制,H2在FLiNaK熔盐中的渗透主要以氢原子(或离子)的方式进行。在500-700°C时,FLiNaK熔盐中H2的扩散系数与温度的关系满足:DFLiNaK-H=1.12×10-4exp(-66.40×103/RgT)(m2·s-1),其扩散活化能为66.40kJ·mol-1。而对于FLiNaK熔盐中H2的溶解常数,其与温度的关系可表述为:KFLiNaK-H=2.1×10-5exp(-0.94×103/RgT)(mol·m-3·Pa-1/2)。     

S22合金钢的氘扩散渗透行为

在分别采用光学显微镜和辉光放电光谱仪获得S22合金钢的金相显微组织和元素成分的基础上,利用已经过氘渗透速率定量标定的渗透实验装置,研究了S22合金钢在400~600℃下的氘扩散渗透行为,得到了氘在S22合金钢中的渗透率和扩散系数。对比分析了500℃时纯D2和He+1%D2下S22合金钢的氘渗透数据,结果表明,随氘分压的降低,氘在S22合金钢中的扩散渗透孕育期增加,氘渗透速率降低,但即使在较低氘分压下依然有氘渗透现象。该结果可为高温气冷堆、快堆等先进反应堆在使用S22合金钢时进行必要的氚渗透防护及其安全分析提供理论与数据支持。     

氚老化对钯钇合金膜氢渗透性能的影响

在聚变堆燃料循环系统中,钯合金膜将被用于氢同位素与杂质气体间的渗透分离以及含氚杂质中氚的催化回收。长期连续的氚操作将使合金膜体内因氚衰变而累积3He,产生氚老化效应。本工作研究了贮氚老化对Pd8.5Y0.19Ru（原子百分数）合金膜的氕、氘渗透性能的影响。研究结果表明：对于膜内体氦浓度He/M为0.042的氚老化膜,在573～723K温度范围内,氕、氘渗透率被严重降低,膜的氕氘渗透分离系数则有所提高。     

氘在Incoloy800H合金材料中的扩散渗透行为

采用气相渗透技术研究了氘在Incoloy800H合金材料中的扩散渗透行为,利用高温气相渗透实验装置和四极质谱仪测定了450～600 ℃温度范围内、氘压110 kPa下氘的渗透实验曲线,计算得到了氘在Incoloy800H合金材料中的渗透率和扩散系数。结果表明,渗透扩散过程为扩散控制,得到的渗透率、扩散系数与温度的关系式均符合Arrhenius关系。     

氢同位素在一些材料中的溶解度系数、扩散系数和渗透率

研究了氚在金属材料、陶瓷材料、玻璃、弹性材料和聚合材料中的溶解度系数、扩散系数和渗透率;介绍了国外一些作者关于氢同位素在一些材料中的溶解度系数、扩散系数和渗透率及这些参数随温度变化的经验公式;论述了氚在金属材料、陶瓷材料和玻璃中的扩散渗透视理;总结了氚和氢在316L不锈钢中的扩散系数和渗透率。     

氢同位素在一些材料中的溶解度系数、扩散系数和渗透率

研究了氚在金属材料、陶瓷材料、玻璃、弹性材料和聚合材料中的溶解度系数、扩散系数和渗透率;介绍了国外一些作者关于氢同位素在一些材料中的溶解度系数、扩散系数和渗透率及这些参数随温度变化的经验公式;论述了氚在金属材料、陶瓷材料和玻璃中的扩散渗透机理;总结了氚和氢在316L不锈钢中的扩散系数和渗透率。     

低活化铁素体/马氏体钢CLF-1氢氘的渗透行为

低活化铁素体/马氏体钢(RA FM钢)作为聚变堆结构材料中最有前景的候选材料,其氢同位素渗透行为备受关注.采用氢同位素气相驱动渗透的方法,对中国低活化铁素体/马氏体钢CLF-1的氢同位素渗透行为进行了研究,研究了温度、气体压强、样品表面状态等因素对其渗透行为的影响.结果表明:氢、氘在RAFM CLF-1钢中渗透扩散过程...     

氟盐冷却高温堆氚输运特性数值研究

氚的控制是限制氟盐冷却高温堆（FHR）发展的关键问题,欲实现氚的有效控制,首先需明确氚在熔盐堆一回路中的输运行为。本文阐明了氚在熔盐堆一回路中的输运特性,包括氚的产生及存在形态的分化、石墨对氚的吸附、氚在熔盐中的溶解与扩散以及氚在管壁材料中的渗透等。针对氚在熔盐堆一回路中的输运行为,建立了数学物理模型,基于FORTRAN语言开发了适用于FHR的氚输运特性分析程序TAPAS。通过将实验数据与程序计算结果对比,说明了TAPAS程序计算的合理性和准确性。利用TAPAS对模块化移动式氟盐冷却高温堆（TFHR）中氚的输运特性进行了分析。计算表明,TFHR的初始产氚率约为5.54×10^-8 mol/s,一回路中的氚主要以T₂形式存在,腐蚀反应主要发生在热管段入口处。反应堆运行25 EFPD（等效满功率天）后,石墨吸附氚达到限值。反应堆稳态运行时,T₂向管壁表面的渗透速率可视为常数,其值为8.35 μmol/EFPD。本研究可为FHR的研究设计和辐射防护提供参考。     

ITER氦冷固态实验包层模块第一壁氢同位素双向输运数值分析

氦冷固态实验包层模块(HCCB-TBM)安装于国际热核聚变实验堆(ITER)中,用以验证HCCB包层概念的氚增殖能力与热移出能力。HCCB-TBM第一壁用于承受堆芯等离子体粒子轰击和包容内部功能材料。外侧等离子体驱动氘、氚粒子渗透与内侧氢分压驱动渗透的同时存在,形成了第一壁的双向氢同位素输运。此双向输运可能对第一壁外表面再循环系数、包层增殖氚的纯化产生重要影响。基于商业软件COMSOL建立第一壁双向氢同位素输运模型,研究第一壁的氢同位素的输运特征。仿真结果表明：第一壁中的冷却剂流道具有强的氢同位素移出能力,使得双向输运解耦合;在ITER等离子体脉冲周期中,放电过程中已扩散到材料内部的氚在等离子体关停时扩散回流到真空室侧,关停时的回流将降低向冷却剂流道的氚渗透损失。     

CLAM钢中氕氘的渗透与去除

低活化铁素体/马氏体钢（RAFM钢）是聚变堆产氚包层的优选结构材料。氢同位素在结构材料中的扩散渗透特性关系到产氚回收率、燃料循环及运行安全。本工作对国内研发RAFM钢之一的CLAM钢进行了气体驱动的氘渗透实验,得到573～873 K温度范围内氘的宏观溶解度S（mol/(m³•Pa^0.5)）为0.264exp(-22 447/RT),扩散系数D（m²/s）为1.38×10^-7exp(-17 271/RT),渗透率Φ（mol/(m•s•Pa^0.5)）为3.64×10^-8exp(-39 718/RT)。还进行了氕氘气体混合物的渗透实验,确认了渗透同位素效应;探索了钢中溶解氘的真空热释放去除。     

Characteristic of Two-phase Slanting Flow in Rod Bundle

Palladium membrane has been studied for sepration and purification of hydrogen isotopes because of its large permeability. In order to consider permeation of mixture of hydrogen isotopes, solubilities of protium and deuterium in palladium were studied in the temperature range of room temperature to 500°C using breakthrough method. It was observed that solubilities were represented by Sieverts' law and that the separation factor of protium-deuterium binary system was different from the isotope effect ratio. The ideal adsorbed solution theory by Myers and Prausnitz can be applied to estimate the separation factor of protium-deuterium binary system in palladium using the isotope effect ratio observed when protium and deuterium are handled independently. The permeation behavior of multi component hydrogen isotopes through palladium membrane is discussed applying observation on solubilities of this work.     

Transport of hydrogen and deuterium in the reduced activation martensitic steel ARAA

Advanced reduced activation alloy (ARAA) is a reduced activation ferritic/martensitic (RAFM) steel under development at the Korea Atomic Energy Research Institute. The transport of hydrogen and deuterium in ARAA was investigated in an elevated temperature range of 250–600 °C. A continuous-flow method, a time-dependent gas-phase technique, was used for the measurements. Complete sets of transport parameters (permeability, diffusivity, solubility, trap site density, and trapping energy) of hydrogen and deuterium in ARAA were successfully obtained. We show that appreciable trapping effects are observed only at low temperatures (250–350 °C) and that the isotope effect ratio for the diffusivity differs from the classical prediction. However, the measured values of permeability, effective diffusivity, and effective solubility of ARRA were within the range of results reported for other RAFM steels.     

Research on the effect of the heavy nuclei amount on the temperature reactivity coefficient in a small modular molten salt reactor

Small modular thorium-based graphite-moderated molten salt reactors(sm TMSRs), which combine the advantages of small modular reactors and molten salt reactors, are regarded as a wise development path to speed deployment time. In a sm TMSR, low enriched uranium and thorium fuels are used in once-through mode, which makes a marked difference in their neutronic properties compared with the case when a conventional molten salt breeder reactor is used. This study investigated the temperature reactivity coefficient(TRC) in a sm TMSR, which is mainly affected by the molten salt volume fraction(VF) and the heavy nuclei concentration in the fuel salt(HN). The fourfactor formula method and the reaction rate method were used to indicate the reasons for the TRC change, including the fuel density effect, the fuel Doppler effect, and the graphite thermal scattering effect. The results indicate that only the fuel density has a positive effect on the TRC in the undermoderated region. Thermal scattering from both salt and graphite has a significant negative influence on the TRC in the overmoderated region. The maximal effective multiplication factor, which shows the highest fuel utilization, is located at 10% VF and 12 mol% HN and is still located in the negative TRC region. In addition, on increasing the heavy nuclei amount from 2 mol% HN to12 mol% HN(VF = 10%), the total TRC undergoes an obvious change from-11 to-3 pcm/K, which implies that the change in the HN caused by the fuel feed online should be small to avoid potential trouble in the reactivity control scheme.     

Mechanism of hydrogen absorption during the exposure of alloy 600-like single-crystals to PWR primary simulated media

The main purpose of this study is to investigate the mechanism responsible for the hydrogen absorption in alloy 600 exposed to pressurized water reactors primary water in order to evaluate the possible role of hydrogen in the stress corrosion cracking (SCC) of this alloy exposed to these environmental conditions. Alloy 600-like single-crystals were exposed to a simulated PWR medium where the hydrogen atoms of water or of the pressuring hydrogen gas were isotopically substituted with deuterium, used as a tracer. SIMS profiling of deuterium was used to characterize the deuterium absorption and localization in the passivated alloy. The results show that the hydrogen absorption during the exposure of the alloy to PWR primary water is associated with the water molecules dissociation during the built up of the passive film.     

Investigation on Retention and Release Behaviors of Hydrogen and Helium in Vanadium Alloy

Vanadium alloy is proposed as an attractive candidate for first wall and blanket structural material of fusion reactors. The retention and release behaviors of hydrogen and helium in vanadium alloy may be an important issue. In the present work, 1.7 keV deuterium and 5 keV helium ions are respectively implanted into V-4Cr-4Ti and V-4Ti at room temperature. The retention and release of deuterium and helium are measured with thermal desorption spectroscopy (TDS). When the helium ion fluence is larger than 3 ×1017 He/cm2, the retained helium saturates with a value of approximately 2.5 ×1017 He/cm2. However, when the ion fluence is 1×1019 D/cm2, the hydrogen saturation in vanadium alloy does not take place. Experimental results indicates that hydrogen and helium retention in vanadium alloy may lead to serious problems and special attention should be paid when it is applied to fusion reactors.     

Radiation induced deuterium absorption for RB-SiC,HP-SiC,silicon and graphite loaded during electron irradiation

Absorption, diffusion, and desorption of hydrogen isotopes are expected to occur during operation in future fusion reactors and these processes will strongly depend on the irradiation conditions, neutron flux and purely ionizing radiation. The main aim of the work is to address the electron irradiation induced absorption of hydrogen isotopes in RB-SiC. Deuterium loading was carried out with both the sample and the surrounding deuterium gas exposed to 1.8 MeV electron irradiation in order to evaluate the radiation enhanced deuterium absorption. Thermo stimulated desorption (TSD) measurements were carried out for both electron irradiated and unirradiated samples in order to evaluate the possible radiation enhanced retention of the previously loaded deuterium. The materials subjected to the deuterium loading process were also studied by SIMS. Noticeable radiation enhanced deuterium absorption was observed. Most of the deuterium absorbed during irradiation was thermally released at about 600 °C.