Lesson 4 Nuclear Materials

1、1Lesson 4 Nuclear Materials核材料核材料2Words 1Cadmium 5kAdmiEm, n, 镉镉cobalt kE5bC:lt, 5kEubC:lt, n. 钴钴mercury 5mE:kjuri, n. 水银水银nitrogen 5naitrEdVEn, n. 氮气氮气uranium juE5reiniEm, n. 铀铀plutonium plu:5tEuniEm, n. 钚钚zirconium zE:5kEuniEm, n. 锆锆beryllium bE5riljEm, n. 铍铍 boric acid, n. 硼酸硼酸boron 5bC:rEn, n. 硼

2、硼carbide 5kB:baid, n. 碳化物碳化物chromium 5krEumjEm, n. 铬铬dioxide dai5Cksaid, n. 二氧化物二氧化物eutectic ju:5tektik, a. 共晶的共晶的hafnium 5hAfniEm, n. 铪铪 (拼音拼音ha-1)hydrocarbon 5haidrEu5kB:bEn, n. 碳氢化碳氢化合物合物gadolinium 7AdE5liniEm, n.钆钆 (拼音拼音ga-2)inert i5nE:t, a. 惰性的惰性的3Words 2Magnesium mA5ni:zjEm, n. 镁镁Magnox 5mAnCk

3、s, n. 镁诺克斯合金镁诺克斯合金metallurgy me5tAlEdVi, n. 冶金冶金nickel 5nikl, n. 镍镍oxide 5Cksaid, n. a. 氧化物氧化物(的的)oxidize 5Cksi7daiz, v. 使氧化，生锈使氧化，生锈paraffin 5pArEfIn, n. 石蜡石蜡wax wAks, n. 石蜡石蜡pellet 5pelit, n. 燃料芯块，片燃料芯块，片phase feiz, n. 相相potassium pE5tAsjEm, n. 钾钾pyrolitic, a. 热解的热解的silicon 5silikEn, n. 硅硅sodium 5

4、sEudjEm, -diEm, n. 钠钠tin tin, n. 锡锡lead li:d, n. 铅铅zircaloy 5zE:kElCi, n. 锆合金锆合金 toxic 5tRksIk, a. 有毒性的有毒性的 4Words 3Allotropic 9AlEJ5trCpIk a. 同素异型的同素异型的anisotropic E7naisEu5trCpik, a.各向异性各向异性ceramic si5rAmik, a. 陶瓷的陶瓷的component kEm5pEJnEnt, , n. 元素，组成部分元素，组成部分conductivity 7kCndQk5tiviti, n. 传导率传导率c

5、orrosion kE5rEuVEn, n. 腐蚀腐蚀erosion i5rEuVEn, n.冲蚀冲蚀crack krAk, n. 开裂开裂stress corrosion cracking (SCC), n. 应力腐蚀开裂应力腐蚀开裂 criticality kriti5kAliti n. 临界临界(性，状态性，状态) crystalline 5kristElain, a. 晶体状的晶体状的diffuse di5fju:z, n. 扩散扩散dimensional di5menFEnEl, a. 尺寸的尺寸的distortion dis5tC:FEn, n. 变形变形dose dEus, n.

6、 剂量剂量trap trAp, n. 阱，收集器阱，收集器viscosity vis5kCsiti, n. 粘性粘性 5Words 4Enrich in5ritF, v. 富集，浓缩富集，浓缩exposure iks5pEuVE, n. 辐照辐照fabricate 5fAbrikeit, v. 制造，生产制造，生产fraction 5frAkFEn, n. 分数，部分分数，部分homogeneous 7hCmEu5dVi:njEs, n. 均匀的均匀的inhalation 7inhE5leiFEn, n. 吸入吸入integrity in5teriti, n. 完整性完整性liable 5la

7、iEbl, a. 易于易于的的moist mCist, a. 湿的湿的pre-eminent pri(:)5eminEnt, a. 优秀的优秀的retain ri5tein, v. 保持，保留保持，保留saturation 7sAtFE5reiFEn, n. 饱和饱和self-annealing self A5ni:liN, 自退火自退火sublime sE5blaim, v. 升华升华susceptible sE5septEbl, a.敏感的敏感的thermodynamic 5WE:mEudai5nAmik, a. 热力热力学的学的transition trAn5ziVEn, -5siFEn

8、, n. 转变转变64.1 fuels 燃料燃料4.1.1 UraniumUranium in one form or another is by far the most common fuel material for nuclear reactors. 不同形式的铀是反应堆中最常用的一种燃料。不同形式的铀是反应堆中最常用的一种燃料。by far是加重语气，说明了是加重语气，说明了the most的程度。的程度。It can be used either as pure uranium, a metal, or as compound such as uranium dioxide UO2

9、 or uranium carbide UC. 它可以或者作为纯铀金它可以或者作为纯铀金属状态使用，或者以化合物的形式，例如二氧化铀或碳化铀，来使用。属状态使用，或者以化合物的形式，例如二氧化铀或碳化铀，来使用。Uranium is a rather soft and ductile metal which oxidizes readily in air and water at high temperature. 铀是一种很软而且延展性很好的金属，它铀是一种很软而且延展性很好的金属，它在高温时容易在空气和水中氧化。在高温时容易在空气和水中氧化。Its melting point is 113

10、3oC. It exists in one of three allotropic forms depending on its temperature. These different forms are called the alpha, beta or gamma phase, and changes from one phase to another due to temperature changes are accompanied by density changes. 其其熔化温度位熔化温度位1133oC，根据其温度，它以三种同素异形体之一的形态存在，根据其温度，它以三种同素异形

11、体之一的形态存在，这些形态为这些形态为a a，b b或者或者g g相，并且它们之间因温度变化而相互转化时会伴有密相，并且它们之间因温度变化而相互转化时会伴有密度变化。度变化。Alpha phase uranium has a density of 19g/cm3 and a thermal conductivity which varies from 25W/mK at 25oC to 42W/mK at 665oC.The transition from alpha to the beta phase takes place at 665oC and is accompanied by di

12、mensional changes in crystalline structure of the uranium, expansion along one axis and contraction along the others. 从从a到到b相的转变发生在相的转变发生在665oC，并伴随铀晶体结构尺寸变化，沿一个轴伸长，并伴随铀晶体结构尺寸变化，沿一个轴伸长，另一个轴缩短。另一个轴缩短。To avoid distortion due to these anisotropic dimensional changes 665oC is considered to be the maximum

13、 operating temperature of uranium. 为了防止由于各向异性尺寸变化所造成的变形，为了防止由于各向异性尺寸变化所造成的变形，665oC被认为是被认为是(金金属属)铀的最高工作温度。铀的最高工作温度。Metallic uranium is also very susceptible to radiation damage which produces dimensional changes and swelling above about 450oC. 金属铀金属铀也非常容易受到辐照损伤，在大约也非常容易受到辐照损伤，在大约450oC以上产生尺寸变化和肿胀。以上产生

14、尺寸变化和肿胀。Consequently high burnups of metallic uranium fuel are not possible. In the British gascooled Magnox Reactors, which are the principal users of this type fuel, the burnup is limited to about 3500MWd/t. 在主要在主要采用这种燃料的英国美诺克斯气冷堆中，其燃耗被局限在采用这种燃料的英国美诺克斯气冷堆中，其燃耗被局限在3500MWd/t.8Uranium Dioxide 二氧化铀二氧化

15、铀nUO2 is a black powder, melting point 2865oC, theoretical density 10.96g/cm3.qMuch higher burnups (燃耗燃耗) than pure uranium qBy far the most common nuclear fuel for PWR NPPsqNo reaction with water at high temperaturenRadiation damageqDimensional changes 尺寸变化尺寸变化qSwelling (肿胀肿胀), cracks and voids (空位

16、空位), structural changes 结构变化结构变化To summarize, the low operating temperature, susceptible to radiation damage and low permissible burnup of uranium are serious disadvantages to its choice as a reactor fuel, and account for (说明，解说明，解释释) its very limited use. (参见参见p76注释注释2)Uranium dioxide UO2 is a blac

17、k powder which can be fabricated by cold pressing (冷压冷压) and sintering (烧结烧结) at high temperature to produce small cylindrical (sI5lIndrIk(E)l, 圆柱体的圆柱体的) pellets, and in this form it is by far the most common material for the fuel of commercial reactors. In this ceramic form UO2 has good stability a

18、t high temperature and good resistance to radiation damage which enables it to be used to high burnups. The melting point (熔点熔点) is 2865oC and the theoretical density (理论密度理论密度) is 10.96g/cm3, although in practice (实际上实际上) the density of UO2 pellets produced as described above is about 10g/cm3. The

19、thermal conductivity is low, being about 2.5W/mK in the temperature range from 1000 to 2000oC, however this low thermal conductivity (热导率热导率) is compensated for (补偿补偿) by the very high melting point which permits high maximum fuel temperatures. Uranium dioxide does not react with water at high tempe

20、rature, a very valuable characteristic as otherwise cladding failures in water cooled reactors would lead to serious reactions. 二氧化二氧化铀在高温下不与水发生反应，铀在高温下不与水发生反应，(这是这是)一个重要的特性，否则水冷堆的一个重要的特性，否则水冷堆的包壳破损将导致严重的反应。包壳破损将导致严重的反应。It can retain a large fraction of the gaseous fission products at temperatures b

21、elow 1000oC, but as the fuel temperature at the center of a pellet is likely to be greatly in excess of this value, provision (预防预防) must made for fission product gas release. 在在1000度以下，它可以保持裂变气体产物的一大部分，但是由于燃料度以下，它可以保持裂变气体产物的一大部分，但是由于燃料芯块中心的温度可能超过这个温度，必须采取预防措施防止气体释芯块中心的温度可能超过这个温度，必须采取预防措施防止气体释放。放。Th

22、is is usually done by having an empty space at the top of each fuel tube into which the gases can diffuse. 这通常是通过这通常是通过在燃料棒上部留出一个空间来使气体向其扩散的方式来实现。在燃料棒上部留出一个空间来使气体向其扩散的方式来实现。During operation in reactor UO2 pellets suffer structural changes, principally as a result of the high operating temperatures a

23、nd high temperature gradients, but also as a result of prolonged irradiation. 在反应堆运行过程中，二氧化铀芯在反应堆运行过程中，二氧化铀芯块会发生结构变化，主要是由高运行温度、大的温度梯度、以及长时块会发生结构变化，主要是由高运行温度、大的温度梯度、以及长时间的辐照造成的。间的辐照造成的。The effects may include swelling (肿胀肿胀), formation of cracks and voids in the pellet and changes in the grain struct

24、ure of the UO2. 辐照效应包括肿胀、芯块中形成裂纹和空位、以及二氧化铀的辐照效应包括肿胀、芯块中形成裂纹和空位、以及二氧化铀的晶粒结构变化。晶粒结构变化。This type of fuel is normally subjected to much higher burnups than pure uranium, and 5 per cent or more of the original uranium atoms in the fuel may undergo fission and be changed, each one to two intermediate mass

25、 fission product atoms (中等中等质量的产物原子质量的产物原子). 这种燃料通常比纯铀可以达到更高的燃耗，发生裂这种燃料通常比纯铀可以达到更高的燃耗，发生裂变的铀原子增加变的铀原子增加5，每个铀原子转变成为一到两个中等质量的裂变，每个铀原子转变成为一到两个中等质量的裂变产物原子。产物原子。 12UC - Uranium Carbide 碳化铀碳化铀nAdvantages over UO2qHigher thermal conductivity 高热导率高热导率qHigher densitynDisadvantagesqReact with water unsuitable

26、 for use in water cooled reactorsnCan be used in fast reactors (快堆快堆) and principally as the fuel for HTGR(高温气冷堆高温气冷堆)Uranium carbide, UC, is another ceramic fuel of possible interest, but it has not been developed or used to anything like the same extent as UO2. 碳化铀是另一种可能感兴趣的陶瓷性燃料，但却没有像碳化铀是另一种可能感兴趣

27、的陶瓷性燃料，但却没有像UOUO2 2那样得到那样得到开发使用。开发使用。It may have some advantages over UO2, principally its higher thermal conductivity and higher density which leads to more uranium atoms per unit volume of fuel, which is an advantage in a reactor. 它有一些优它有一些优于于UOUO2 2的特点，主要是它的高热导率和高密度，这可以使每单位体积的燃料的特点，主要是它的高热导率和高密度，

28、这可以使每单位体积的燃料中包含更多的铀原子，这对于反应堆来说是它的一个优点。中包含更多的铀原子，这对于反应堆来说是它的一个优点。Uranium carbide reacts with water, which makes it unsuitable for use in water cooled reactors, but it does not react with sodium (钠钠) below 500oC, so it might be used in fast reactors. 碳化铀与水发生反应，这使碳化铀与水发生反应，这使它不适合用于水冷堆，但是它不适合用于水冷堆，但是500

29、500o oC C以下它不与钠发生反应，所以它可能被用以下它不与钠发生反应，所以它可能被用于快堆。于快堆。Its melting point, 2380oC, is rather lower than that of UO2, but this is compensated for by its higher thermal conductivity. 其熔点为其熔点为23802380o oC C比比二氧化铀要低，但这一缺点被其高热导率所补偿。二氧化铀要低，但这一缺点被其高热导率所补偿。 The development of uranium carbide so far has been pr

30、incipally as the fuel for high temperature gas-cooled reactors. 迄今为止，碳化铀主迄今为止，碳化铀主要被用作高温气冷堆的燃料。要被用作高温气冷堆的燃料。 144.1.2 Plutonium 钚钚nPure plutonium is not suitable as a reactor fuelqLarge number of crystalline phases up to melting point 640oCqLow thermal conductivity, 4.2W/mK at RTqHighly reactive in m

31、oist airqVery dangerous: radioactive, toxic (毒性的毒性的), serious health hazard.nNuclear weapon materialnPuO2 is used as a reactor fuel.qMelting point 2400oCq20-25% Mixed with UO2 to form Mixed Oxide Fuel (MOX 混合燃料混合燃料), with properties similar to those of UO2 alone.Pure plutonium metal is not suitable

32、as reactor fuel due to the large number of crystalline phases which exist up to its melting point of 640oC. 纯钚由于其在熔点纯钚由于其在熔点640640o oC C以下有多种晶相，不适合于作反应堆燃料。以下有多种晶相，不适合于作反应堆燃料。The thermal conductivity is also very low, about 4.2W/mK at room temperature. Plutonium metal is highly reactive in moist air,

33、 but it can be stored in dry air at low temperature. It is a very dangerous material, being radioactive, toxic and an essential component of nuclear weapons(宾补宾补), and is potentially a serious health hazard, particularly if it exists as dust in the atmosphere and is taken into the lungs by inhalatio

34、n(条件状语从句条件状语从句). As a reactor fuel plutonium is used as the oxide PuO2. Its melting point is 2400oC. Plutonium dioxide is mixed with uranium dioxide to form mixed oxide fuel (MOX) which for fast reactors typically contains 20 to 25 per cent of PuO2. 二氧化钚与二氧化铀混合形成混合二氧化物燃料，通常快堆二氧化钚与二氧化铀混合形成混合二氧化物燃料，通常

35、快堆MOXMOX燃料含有燃料含有20202525的二氧化钚。的二氧化钚。The properties of this mixed oxide fuel are similar to those of UO2 alone. 164.1.3 Thorium 钍钍nHas not been used to great extent except as HTGR fuel.nFertile (可增殖的可增殖的) isotope to produce U-232.nPure metal is not used as fuel, instead, ThO2 and ThC2.nThO2 is simila

36、r to UO2 in many respects.nThC2 is used as coated particle fuel (包覆颗粒燃料包覆颗粒燃料) in HTGR.qParticles are dispersed in graphite to form a homogeneous mixture of fuel and moderator. 碳化钍燃料颗粒均匀分布在石墨中，碳化钍燃料颗粒均匀分布在石墨中，形成了燃料和慢化剂混合物形成了燃料和慢化剂混合物qVery high operating temperature and good resistance to radiation d

37、amage.Thorium has not been used as a reactor fuel to any great extent yet except in a few high temperature gas-cooled reactors. 除了在几个高温除了在几个高温气冷堆中，钍没有被广泛用作反应堆燃料。气冷堆中，钍没有被广泛用作反应堆燃料。Thorium 232 is the fertile isotope from which uranium 233 is produced, and it is theoretically possible to obtain high b

38、reeding ratios in thermal as well as fast reactors using this combination. 钍钍232232是一种用于生成钍是一种用于生成钍233233的的( (可增殖的可增殖的) )有生同位素，从理论上讲它不管在热堆还是在块堆中都可以有生同位素，从理论上讲它不管在热堆还是在块堆中都可以得到比较高的增殖比。得到比较高的增殖比。Pure metallic thorium has a melting point of about 1700oC. It is superior to uranium due to its better stab

39、ility, but it is not used as a fuel in its pure form. Instead it is used either as thorium dioxide ThO2 or (as 被省略掉了被省略掉了) thorium carbide ThC2. To date these compounds have only been used to a very small extent in a few high temperature gas-cooled reactors. Thorium dioxide is similar in many respec

40、ts to uranium dioxide. 二氧二氧化钍在很多方面与二氧化铀是相似的。化钍在很多方面与二氧化铀是相似的。It is produced by the same methods of powder metallurgy (粉末冶金粉末冶金), and it is chemically inert (化学惰性化学惰性), and has a good resistance to radiation damage. Thorium carbide has been used in the form of coated particle fuel (涂涂层颗粒燃料层颗粒燃料) in H

41、TGRs. Very small spherical particles less than 1 mm diameter of mixed ThC2 and UC2 (highly enriched in 235U) are coated with thin layers of pyrolytic carbon (热解碳热解碳) and silicon carbide (碳化硅碳化硅) to retain fission products. 直径小于直径小于1mm的的ThC2和和UC2球形小颗粒被用薄层的热解碳和碳化球形小颗粒被用薄层的热解碳和碳化硅包覆以保持裂变产物。硅包覆以保持裂变产物。

42、These particles are dispersed in graphite to form a homogeneous mixture of fuel and moderator which has a very high operating temperature and good resistance to radiation damage. 这些颗粒被均匀这些颗粒被均匀分散在石墨中形成燃料和慢化剂的混合物，这种混合燃料具有很高的工作温分散在石墨中形成燃料和慢化剂的混合物，这种混合燃料具有很高的工作温度和良好的抗辐照损伤能力。度和良好的抗辐照损伤能力。194.2 Moderator

43、s 慢化剂慢化剂nRequirementsqLow mass number 低质量数低质量数qVery low neutron capture cross-section 极低吸收截面极低吸收截面qHigh scattering cross-section 高散射截面高散射截面nCandidate materials 候选材料候选材料qHydrogen and its isotopes deuteriumnWater, heavy water, paraffin waxqCarbonngraphiteqBerylliumnBeing toxic, presently not suitable

44、for application in any form.The requirements of the moderator for a thermal reactor, namely (即，即，也就是也就是) low mass number, very low neutron capture cross-section and high scattering cross-section, limit the choice to only a few materials. Hydrogen and its isotope deuterium, carbon and beryllium are t

45、he only elements that are suitable. Hydrogen and deuterium, being gases, are not sufficiently dense and must be used in the form of compounds, water and heavy water being the obvious choices (表示结果表示结果). 氢和氘是气体，密度不高，必须以化合物氢和氘是气体，密度不高，必须以化合物的形式使用，所以水和重水是明确的选择。的形式使用，所以水和重水是明确的选择。The use of hydrocarbon

46、(烃，碳氢化合物烃，碳氢化合物) has been tried, but has not been successful and such materials are not used as moderators. It is interesting to recall, however, that Fermi used paraffin wax in his early experiments in the 1930s to slow down neutrons and study their interactions with the elements, so he was one of

47、the first scientists to be aware of the effects of neutron moderation. 但是，回顾历史，十九世但是，回顾历史，十九世纪三十年代费米在早期的实验中曾经利用固体石蜡来慢化中子，从而研究中纪三十年代费米在早期的实验中曾经利用固体石蜡来慢化中子，从而研究中子与元素的交互作用，所以，他是最早意识到中子慢化效应的科学家之一。子与元素的交互作用，所以，他是最早意识到中子慢化效应的科学家之一。Beryllium has a very low neutron capture cross-section (0.009barns), high m

48、elting point (about 1300oC) and good strength, and at one time it seemed possible that it would find an application either as the moderator or the fuel cladding in thermal reactors. 铍有极低的中子俘获铍有极低的中子俘获截面、高熔点和良好的强度，曾一度好像可能成为热堆慢化剂或者燃料包壳。截面、高熔点和良好的强度，曾一度好像可能成为热堆慢化剂或者燃料包壳。However, it and its compounds ar

49、e toxic, and beryllium itself has low ductility (延展性延展性) and poor corrosion resistance (抗腐蚀性抗腐蚀性). 但是，其化但是，其化合物具有毒性，并且铍本身的延展性比较低，抗腐蚀性也比较差。合物具有毒性，并且铍本身的延展性比较低，抗腐蚀性也比较差。Beryllium oxide BeO also has undesirable properties. As a result of this neither beryllium nor its oxide have found any use in power

50、reactor, and it is unlikely that they will be used in the future. 结果，铍及其氧化物都无法在动力堆中使用，而且将来也不会派上用场。结果，铍及其氧化物都无法在动力堆中使用，而且将来也不会派上用场。The choice of moderators for thermal reactors is thus limited to three materials-water, heavy water and carbon in the form of graphite. 热堆热堆的慢化剂的选择范围被局限在三种材料水、重水和石墨状态的碳。的

51、慢化剂的选择范围被局限在三种材料水、重水和石墨状态的碳。 224.2.1 WaternAdvantages qThe right choice for the moderator of thermal reactor, and it can also serve as the coolant.qExcellent neutron slowing down properties.qAbundant, cheap and easily obtainable with high purity.ndisadvantagesqCapture cross-section is rather high, 0

52、.66 barns, reactor requires enriched uranium for criticality.qUnfavorable thermodynamic characteristics. 不理想的热力学不理想的热力学特性特性nHigh pressure is needed to prevent boiling at high temperature.nPressure of 150 to 160 bar are typical of PWRs.nCautionqIt is important to maintain water purity 保持水的纯度很重要保持水的纯度

53、很重要nTo minimize corrosion 减轻腐蚀减轻腐蚀nTo prevent radioactive transformation 防止放射性转变防止放射性转变Water is an obvious choice for the moderator of a thermal reactor, and it can also serve as the coolant. 水是热堆慢化剂很明显的选择，并且它也水是热堆慢化剂很明显的选择，并且它也可以用于作冷却剂。可以用于作冷却剂。 It has excellent neutron slowing down properties whic

54、h enable water moderated reactors to have much more compact cores than are possible in other types of thermal reactors. 它具有优异的中子慢化性能，它具有优异的中子慢化性能，这使水慢化的反应堆比其它类型的热堆堆芯更紧凑。这使水慢化的反应堆比其它类型的热堆堆芯更紧凑。 The capture cross-section of water is rather high (0.66 barns per molecule) so that water moderated and coo

55、led reactors require enriched uranium for criticality. 水的俘获截面比较高，所以水慢化冷却的水的俘获截面比较高，所以水慢化冷却的反应堆需要浓缩的铀以达到临界。反应堆需要浓缩的铀以达到临界。 It is, of cause, abundant, cheap and easily obtainable with high purity. (please translate into Chinese) The main problem associated with the use of water as the moderator and co

56、olant in a power reactor concerns its rather unfavorable thermodynamic characteristics. 水作为动力堆慢化剂和冷却剂的主要问题水作为动力堆慢化剂和冷却剂的主要问题是比较差的热力学性质。是比较差的热力学性质。 The saturation pressure and temperature relationship is such that high pressure are required to prevent boiling at high temperatures, e.g. a pressure of

57、150 bar is required to allow water to reach a temperature of 340oC without boiling. 饱和压力与温度之间的关系要求需要一个高压才能防饱和压力与温度之间的关系要求需要一个高压才能防止高温下的沸腾，例如，保持水在止高温下的沸腾，例如，保持水在340340o oC C不沸腾需要不沸腾需要150150巴的压力。巴的压力。Pressure of 150 to 160 bar are typical of pressurized water reactors, in which the temperature is limi

58、ted to about 325oC.It is important to maintain water purity in a water cooled and moderated reactor, firstly to minimize corrosion and secondly to prevent the water from becoming radioactive due to (n,g g) reactions with the impurities as the water flows through the reactor core. (不定式作状不定式作状语语) 在水冷却

59、和慢化的反应堆中保持水的纯度是非常重要的，这样第一可以减在水冷却和慢化的反应堆中保持水的纯度是非常重要的，这样第一可以减少腐蚀，第二防止当水流经堆芯时因杂质的少腐蚀，第二防止当水流经堆芯时因杂质的(n,g g)反应而被活化，反应而被活化，Radiation levels in the water can influence the radiation dose levels to which power station operating and maintenance staff are exposed, and the maintenance of high water purity as

60、sists in reducing operator exposures. 水的辐射水平会影响电站操作和维护人员的辐照剂量，保持水的水的辐射水平会影响电站操作和维护人员的辐照剂量，保持水的高纯度有助于降低操作人员的辐照剂量。高纯度有助于降低操作人员的辐照剂量。 25Heavy Water 重水重水nSimilar to ordinary water in most of its physical and thermodynamic properties.nAdvantages qDifference is that deuterium has a much lower capture cros