- wio
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这是中文的一片文章,你可以整理一下看看,然后翻译成英文
核能的利用
核能俗称原子能,它是指原子核里的核子(中子或质子)重新分配和组合时释放出来的能量。核能分为两类,一类叫核裂变能,它是指重元素(铀或钚等)的原子核发生裂变时释放出来的能量。另一类叫聚变能,它是指轻元素(氘和氚)的原子核在发生聚变反应时释放出来的能量。
核能有巨大的威力,1公斤铀原子核全部裂变释放出的能量,约等于2700吨标准煤燃烧时所放出的化学能。一座100万千瓦的核电站,每年只需25~30吨低浓度铀核燃料,而相同功率的煤电站,每年则需要有300多万吨原煤,这些核燃料只需10辆卡车就能运到现场,而运输300多万吨煤炭,则需要1000列火车。核聚变反应释放的能量更可贵。有人作过生动的比喻:1公斤煤只能使一列火车开动8米,1公斤铀可使一列火车开动4万公里;而1公斤氚化锂和氘比锂的混合物,可使一列火车从地球开到月球,行程40万公里。地球上蕴藏着数量可观的铀、钍等核裂变资源,如果把它们的裂变能充分地利用起来,可满足人类上千年的能源需求。在汪洋大海里,蕴藏着二十万亿吨氘,它们的聚变能可顶几万亿亿吨煤,可满足人类百亿年的能源需求。
核能是人类最终解决能源问题的希望。核能技术的开发,对现代社会会产生深远的影响。
核裂变能
核能的成就虽然首先被应用于军事目的,但其后就实现了核能的和平利用,其中最重要也是最主要的是通过核电站来发电。
核电站已跻身电力工业行列,是利用原子核裂变反应放出的核能来发电的装置,通过核反应堆实现核能与热能的转换。核反应堆的种类,按引起裂变的中子能量分为热中子反应堆和快中子反应堆。由于热中子更容易引起铀235的裂变,因此热中子反应堆比较容易控制,大量运行的就是这种热中子反应堆。这种反应堆需用慢化剂,通过它的原子核与快中子弹性碰撞,将快中子慢化成热中子。早在本世纪50年代初,人类开始开发利用核能,诞生了核电站。经过30多年的发展,核电已是世界公认的经济实惠、安全可靠的能源。
截至1993年12月31日,全世界已有34个国家或地区的422座(堆)核电站正在运行,总装机容量为3.56235亿千瓦;正在建造的核电站有61座(堆),总装机容量为5586.6万千瓦。全世界1993年全年核发电总量为21817679GWh,核发电量占世界总发电量的17%以上。世界核电厂一览表见下表。
国家或地区 堆数 正在运行总功率(MW) 堆数 正在建造总功率(MW) 总计堆数 总计总功率(MW) 至1993年总发电量(GWh)
阿根廷 2 1015 1 745 3 1760 86924
比利时 7 5756 - - 7 5756 515760
巴西 1 657 2 2618 3 3275 15146
保加利亚 6 3760 2 2000 8 5760 -
中国 2 1250 1 950 3 2200 -
中国台湾省 6 5144 - - 6 5144 373600
德国 20 22529 - - 20 22529 1762961
芬兰 4 2400 - - 4 2400 258318
法国 56 60357 4 6064 60 66421 3395919
英国 29(35) 14090 1 1200 30(36) 15290 1305690
印度 9 2035 5 1175 14 3210 87892
伊朗 - - 2 2600 2 2600 -
日本 48 39641 6 5887 54 45528 2500910
加拿大 22 16713 - - 22 16713 1118343
哈萨克斯坦 1 150 - - 1 150 -
韩国 9 7616 5 4600 14 12216 432156
古巴 - - 2 880 2 880 -
立陶宛 2 3000 - - 2 3000 -
墨西哥 1 675 1 675 2 1350 15217
荷兰 2 538 - - 2 538 76967
巴基斯坦 1 137 - - 1 137 6992
罗马尼亚 - - 5 3500 5 3500 -
俄罗斯 29 21242 6 5600 35 26842 -
瑞典 12 10386 - - 12 10386 889258
瑞士 5 3141 - - 5 3141 351484
斯洛伐克 4 1760 4 1760 8 3520 -
斯洛尼亚 1 664 - - 1 664 50050
西班牙 9 7400 - - 9 7400 550212
南非 2 1930 - - 2 1930 85467
捷克 4 1782 2 1962 6 3744 -
乌克兰 15 13818 6 6000 21 19818 -
匈牙利 4 1840 - - 4 1840 -
美国 109 104809 6 7650 115 112459 7938413
总计 422(428) 356235 61 55866 483 421101 21817679
资料来源:德国《原子经济》,1994年3月。
核能是能源的重要发展方向,特别在世界能源结构从石油为主向非油能源过渡的时期,核能、煤炭和节能被认为是解决能源危机的主要希望。为此,各国都在大力发展核电。然而特别令人担心的是,根据目前探明的有经济开采价值的铀矿储量,如果继续按现有速度建造眼下的热中子堆核电站,由于它只能利用铀资源的1%~2%,则要不了50年,经济可采的铀矿也会耗尽。如果到那时,还不能脱离核裂变能利用的初级阶段,人类将可能面临新的能源危机。
在能源新挑战面前,核科学家早已在寻找应战的武器,这就是已经过40多年研究开发的快中子增殖堆(简称快堆)核电站。有了它,相当于把铀资源的利用率提高了50~60倍,那样能源的供应将出现新的奇迹,在今后上千年内,人类完全可以靠快堆发电,保证有富足的能源可用。
快堆的最显著的特点是直接靠核裂变产生的快速飞行的中子来维持链式裂变反应。它以钚-239作燃料,“炉膛”里不设慢化剂,只有冷却剂(钠或氦)。在快堆中,每“烧掉”一个钚-239原子,能够使铀-238吸收中子后新生产出1.4个钚-239原子,这样在快堆中就出现了神话般的奇迹——核燃料越“烧”越多。这就是所谓的核燃料的增殖过程。
快堆开动起来之后,会不断地有铀-238吸收中子变成钚-239,经过一段时间后(例如15~20年),人们可以队“烧”过的核燃料“灰烬”中,提取出足以装备与自身功率一样大的新堆所需要的钚燃料,在此期间,快堆电站只要继续添加热堆中不能作燃料的铀-238贫料,而所得的电能却比热堆核电站还要多。人们把快堆誉为能发电的“核燃料生产厂”。
快堆实际上是核电站家族中资格最老的成员。早在1951年8月,美国建成了世界上第一座实验快堆,而且成功地作了发电试验。虽然当时它的电功率只有200千瓦。可它却是世界上最先问世的快堆核电站。
30多年来,一些工业发达的国家(如美、英、法、前苏联、日本和德国),投入大量人力、物力,耗资几十亿美元来发展快堆。目前,全世界总共有21座快堆。其中在运行的有13座,正在建造的有4座,计划建造的有7座。原型快堆已经成功地运行了十年多,已经证明快堆在技术上是可以实现的,增殖核燃料也是可能的(凤凰快堆的增殖比为1:15)。现在电功率为120万千瓦的大型商业验证快堆正在法国运行。快堆技术已经走出了实验室的大门,正走向工业化应用的康庄大道。
各国普遍认为,快堆是发电堆的最终归宿,特别是在受控核聚变难以在今后相当长时期内工业推广的情况下,快堆发电更是重要。但需要指出的是,快堆技术至今尚未成熟,重要原因是快堆技术本身要比热堆复杂得多,尚有不少技术关键问题需要攻克。此外,快堆的建造费用要比热堆大得多,现在快堆的造价要比同规模的热堆贵2~3倍。有人估计,当快堆的单堆功率超过200万千瓦时,经济上可能与热堆媲美。预计到下世纪初,人们一定能建造出这样的大型快堆,那时快堆电站将会在全世界推广应用。发展快堆进展最快的法国,计划从下世纪初开始,推广快堆电站工业,因此天然铀的需要量将逐步下降,从而减轻了进口能源所造成的压力。快堆必将是从热堆核电站向核聚变电站过渡的桥梁。
核聚变能
人类将最终解决能源需求的希望,寄托在受控核聚变的实现和推广上。核聚变能是利用轻原子核(如氘-氘或氘-氚)在极高温度(几千万度或上亿度)下聚合成较重的原子核(如氦)过程中释放出来的巨大的能量。核聚变的主要燃料是氘,可以比较容易地从海水中提取到。据推算,每升海水中所含的氘若完全“燃烧”,可产生相当于300升汽油的能量。海水中至少含有35万亿吨氘,可以供全世界享用百亿年以上。更为可贵的是核聚变反应中几乎不存在放射性污染,而且核聚变反应堆在任何时刻都只有一丁点的氘在聚变,所以不存在失控所带来的危险。聚变能是名符其实的理想、干净的能源。但是,要使核聚变能顺从地在人为控制下为人类服务却是一件十分困难的事。为了驯服核聚变能,从50年代初开始,科学家们就热心地进行受控核聚变的研究。
全世界已有40多个国家在进行受控核聚变的研究,它们投入了大量人力和物力,建造了几百个实验装置,从事研究的科学人员约有12000多人。目前,全世界每年用于核聚变研究的费用已超过20亿美元。
经过几十年的艰苦努力,受控核聚变为什么进展如此缓慢呢?主要是因为实现受控核聚变的条件非常苛刻。首先,我们无法同时造成太阳中心那样高的等离子体密度和极高的温度,只有追求比太阳中心更高的温度来解决问题。理论研究表明,氘核的聚变点火温度达四亿摄氏度,氘氚混合气体的热核反应也要在五千万摄氏度才能进行。要创造这样的环境在技术上是困难重重的。随着新技术的开发利用,人们试用电流、激光等方法来加热气体。其次,还要使这样高的温度保持一段时间,等离子体温度越低,数量越少,密度越小,超高温保持时间就越要长。还有,超高温的等离子体,有强烈地向外扩张的特性,必须有极强的磁场来约束住它们,绝对不让它们与四周容器壁接触,否则任何材料也挡不住如此高的温度,顷刻气化,变为乌有。要解决这些重重困难,有待于激光技术、超导技术、新材料技术等崭新技术的飞跃发展。
科学技术的进步,不断地给受控核聚变的研究带来福音,经过了漫长的接力赛跑之后,受控核聚变的研究已经到了关键的时刻。1982年12月24日,美国建成了一座有三层楼高的“托卡马克型”核聚变实验反应堆(TFTR),从设计到建成这座核聚变实验堆总共花了七年时间,耗资3亿多美元。设计这座反应堆的目的是为了实现输出能量等于输入能量,以便证明实现受控核聚变的可能性。
我国进行可控核聚变的研究也已多年,并取得一定的进展。我国建有近十个小型托卡马克受控核聚变试验装置,其中最大的是“中国环流器一号”,已于1984年9月建成,并顺利启动。经过一年多的调试,已于1985年11月16日通过国家验收,它为我国核聚变能的研究和等离子体技术的发展,提供了有效的手段。
现在,美、英、俄等国正在共同建设一座博采众长的国际核聚变反应堆,这种国际核聚变堆将采纳30年来全世界核聚变研究的成果。它的设计输出热功率为62万千瓦,真空室半径为520厘米,等离子体磁约束环形半径为130厘米,比美国新建的核聚变实验堆规模要大一倍。各国科学家寄希望于这座核聚变堆在受控核聚变攻关中实现质的飞跃。最重要的是,要求在聚变反应中得到的能量超过输入能量,从而证明实现受控核聚变发电在技术上和工程上是可行的。
当然,人类要真正用上廉价的聚变能,尚需经过艰苦的奋斗,经受时间的考验。有人估计,到2020年可以建成实证堆,然后,经过工程技术和经济上的验证,才能逐步地推向商用。总之,在能源革命中占有重要地位的核聚变能开发和利用的曙光已在前头。
- CarieVinne
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Why We Should Use Nuclear Energy
The growth of nuclear energy in the United States suffered a double whammy in 1979 with the almost simultaneous occurrence of the Three Mile Island accident and the release of the movie The China Syndrome.
The Three Mile Island accident, which is most significant accident in the nuclear power industry in the United States, in retrospect was a very minor incident that resulted in zero deaths or injuries. However, it was used by anti nuclear activists to basically kill off any new nuclear plants in this country.
Jane Fonda, the star of The China Syndrome, used the incident to campaign against nuclear power and promote her movie. Most of the opposition to nuclear power comes from irrational fear, a fear that is fed by those opposed to nuclear power.
Many people who formerly were opposed to nuclear power are now strong supporters of it. Among these people are:
Patrick Moore, a co founder of Greenpeace, who stated in a September 2006 appearance before the U.S. House of Representatives, Subcommittee on Energy and Water Development:
In the early 1970s, I believed that nuclear energy was synonymous with nuclear holocaust, as did most of my Greenpeace compatriots.
That"s the conviction that inspired Greenpeace"s first voyage across the North Pacific coast to protest the testing of U.S. hydrogen bombs in Alaska"s Aleutian Islands.
But a lot has changed in the 35 years since then, and my views have changed along with these new circumstances.
As a co-chair of the Clean and Safe Energy Coalition along with Gov. Christy Todd Whitman, I make it known often that I strongly believe the rest of the environmental movement needs to update its views, too, because now—more than ever before—nuclear energy is the electricity source that can save our planet from another possible disaster: potentially harmful climate change.
James Lovelock, known for proposing the Gaia hypothesis, in which he postulates that the Earth functions as a kind of superorganism. Lovelock states:
“The important and overriding consideration is time; we have nuclear power now, and new nuclear building should be started immediately. All of the alternatives, including fusion energy, require decades of development before they can be employed on a scale that would significantly reduce emissions. In the next few years, renewables will add an increment of emission-free energy, mainly from wind, but it is quite small when compared with the nuclear potential.”
Stewart Brand, founder, publisher, and editor of The Whole Earth Catalog. Brand states:
“Now we come to the most profound environmental problem of all … global climate change. Its effect on natural systems and on civilization will be a universal permanent disaster. … So everything must be done to increase energy efficiency and decarbonize energy production. Kyoto accords, radical conservation in energy transmission and use, wind energy, solar energy, passive solar, hydroelectric energy, biomass, the whole gamut. But add them all up and it"s still only a fraction of enough. … The only technology ready to fill the gap and stop the carbon dioxide loading of the atmosphere is nuclear power. … It also has advantages besides the overwhelming one of being atmospherically clean. The industry is mature, with a half-century of experience and ever improved engineering behind it. … Nuclear power plants are very high yield, with low-cost fuel. Finally, they offer the best avenue to a ‘hydrogen economy," combining high energy and high heat in one place for optimal hydrogen generation.”
Much is always made about the issue of nuclear waste and what to do with it.
The United States only generates about 20% of its electricity from nuclear. Here is a sample of the percentage of electricity generated by nuclear power in other countries:
Country Percent
France 76.8
Lithuania 64.4
Slovakia 54.3
Belgium 54.0
Ukraine 48.1
Sweden 46.1
Armenia 43.5
Slovenia 41.6
Switzerland 40.0
So why don"t these countries have a problem of nuclear waste storage larger than the US? It is because they recycle their nuclear waste. Something that was banned in the US during the Carter Administration. The ban has since been lifted, but US policy still opposes recycling.
About 95% of nuclear waste can be recycled and reused. Using recycling, France estimates that all the nuclear waste generated to provide electricity for a family of four, for 20 years, can be stored harmlessly in a glass cylinder the size of a cigarette lighter.
Here are some more facts about nuclear energy from the Clean and Safe Energy Coalition:
Nuclear energy is:
Clean
Nuclear energy is an environmentally clean option to produce electricity choice – it produces no harmful greenhouse gases suspected to cause global warming and no gases that could cause ground-level ozone formation, smog or acid rain.
Nuclear already accounts for 73 percent of the nation"s emission-free electricity generation and needs be used in compliment with other renewables. Alternative renewable energy sources are important, but can only take us so far – wind and solar can be unreliable and geothermal power isn"t well-suited for all applications. The other major sources of emission-free electricity are hydroelectric plants, which provide 6.6 percent of our nation"s electricity; wind energy, 0.4 percent; and solar energy, 0.01 percent.
Safe and Secure
Nuclear energy is a safe choice. For example, you would have to live near a nuclear power plant for more than 2,000 years to get the same amount of radiation exposure that you receive from a single diagnostic medical x-ray.
Nuclear energy is secure. A two-day national security simulation in Washington, D.C., in 2002 conducted by the Center for Strategic and International Studies (CSIS) concluded nuclear plants “are probably our best defended targets,” with the industry spending $1.2 billion in security since September 11, 2001.
Affordable and Reliable
With rising energy costs a concern for every American, nuclear energy is an affordable and reliable economic choice for electricity. Nuclear power has the lowest production cost of the major sources of electricity. Nuclear plants are the most efficient on the electricity grid and their costs are more predictable than many other energy sources.
Economically Beneficial
Nuclear energy brings economic benefits. From new jobs around new plants to adding $500 million a year to the economy for each new plant brought on line, nuclear plants bring significant economic benefits. Additionally, employees at the plant earn an average of 36 percent more than average earnings in the surrounding communities, so the jobs are high-paying. Perhaps that is why an opinion survey, conducted by Bisconti Research Inc., found that 76 percent of Americans living in close proximity to nuclear power plants are willing to see a new reactor built near them.
Nuclear power is a technology that exists now. Nuclear energy can fulfill all of our electrical needs now and into the future. The fuel is readily available in the United States. It is safe and clean. It is recyclable. It is very affordable. In short there is no good reason not to use nuclear power