原子核很小。但是,事实上,一个原子的单个微小原子核会产生大量的核能吗?这种电的来源是什么?如何获得?让我们仔细研究一下核技术及其与其他类型能源的区别。
什么是核能?
核能是储存在原子核内的能量,原子是构成宇宙中所有物质的小颗粒。原子的质量通常集中在原子核的中心。原子核由两个亚原子粒子组成:中子和质子。将原子结合在一起的键提供了大量的能量。
放射性
法国物理学家安东尼·亨利·贝克勒尔(Antonie Henri Becquerel)发现,铀会自发发射辐射。铀或热元素的自发辐射被称为放射性。显示放射性性质的物质或元素被称为放射性物质或放射性元素。
In 1897, Rutherford found that the radiation emitted by radioactive elements are of three types:
(i) Alpha particle: The alpha particle is a helium nucleus i.e. a helium atom that has lost its two orbital electrons.
(ii) Beta particle: The Beta particles are the streams of fast-moving electrons.
(iii) Gamma rays: The gamma rays are simply the radiation of small wavelengths.
当放射性物质发出辐射时,其质量降低。假设M是发射辐射之前的放射性物质的质量,并且M是发射辐射之后的物质的质量。因此,该物质的质量降低由下式得出:
△m =(M – M’)
质量的下降(△m)根据爱因斯坦的质能关系转换为能量E,
E =△mc 2
其中c在真空中的光速等于3×10 8 m / s,能量E被称为核能。
核能单位:核能以电子伏特(eV)表示。
因此,将1 eV定义为通过一伏电位差通过一次选举获得的能量。 1 eV的核能等于焦耳:
1电子伏特= 1.6×10 -19 C×1个V = 1.6×10 -19或CV 1.6×10 -19 J.
核能的另一个单位是兆电子伏特(MeV)。 1 MeV的核能定义为:
1 MeV = 10 6 eV = 10 6 ×1.6×10 -19 J = 1.6×10 -13 J。
核反应
原子核由于核反应而发生修饰,从而导致原子本身发生变化。核反应将一个方面变成了全新的事物。但是,核发生散射是因为一个核与其他粒子相互作用,然后分裂而没有改变其他核的性质。
There are two kinds of nuclear reactions that can produce nuclear energy:
(i) Nuclear Fission: Nuclear fission is the mechanism by which a radioactive atom’s heavy nucleus, such as plutonium or uranium, breaks into smaller nuclei when bombarded by low-energy neutrons.
(ii) Nuclear Fusion: The reaction which requires the fusion of two light elements to produce a heavier element and the release of energy is called the nuclear fusion.
核裂变
奥托·哈恩( Otto Hahn)和斯特拉斯曼(Strasssman)发现,被中子轰击的铀235分裂为两个相对较轻的原子核。这个过程被称为核裂变。用于铀核裂变的中子能量低,被称为热中子。在铀裂变过程中,除了裂变产物外,还会发射两个或三个中子,并释放大量能量。
因此,当用热中子轰击时,将重核分裂为两个相对较轻的核,并释放大量能量的过程称为核裂变。
下面给出了慢速中子(称为热中子)轰击时92 U 235的核裂变:
92 U 235 + 0 n 1 → 56 Ba 141 + 36 Kr 92 + 3 0 n 1 +能量
每次裂变释放的能量为92 U 235 (铀的同位素)约为200 MeV。下图显示了这种裂变:
注意:可能需要指出,裂变1千克铀235所产生的核能等于燃烧25,00,000所产生的能。
核裂变造成的污染
核裂变比化石燃料引起更严重的污染问题。在核裂变期间,会发射核辐射,即α粒子(u粒子),β粒子(B粒子)和伽马射线(y射线)。这种辐射对生物体非常有害。生命有机体长期持续暴露在这些辐射下会导致人体中许多疾病或病症,例如:
- 核辐射可以改变或破坏人体细胞的结构
- 它们会导致癌症,白血病和失明等疾病。
- 它们会导致人体遗传疾病。
- 它们导致年轻一代的不育。
核裂变的利弊
使用核裂变能的优点是:
- 少量核燃料(U-235)通过核裂变过程提供大量能量,而产生大量热量则需要大量化石燃料。例如,1千克铀235释放的能量等于燃烧25,00,000千克煤所释放的能量。
- 在核电厂中,一次插入核燃料可在很长一段时间内获取能量。另一方面,在火力发电厂中,要不断供应化石燃料以获取能量。
使用核裂变能的缺点是:
- 核裂变比燃烧化石燃料引起更严重的污染问题。在核裂变期间,会放射出非常有害的辐射。它们会导致危险的疾病,例如癌症,白血病和不育症。
- 使用核裂变能的最大问题是核废料的安全处置。核废料继续散发有害的核辐射。它们不可能完全消除核废料,而化石燃料废料则可以完全消除。例如,如果我们燃烧煤炭,将产生灰烬,可将其扔到田间。
核聚变
原子核的融合并不像看起来那样容易。实际上,原子核带正电,因此它们在彼此靠近时会互相排斥。如果这些核以很高的速度运动以克服它们之间的排斥力,则可以将它们融合在一起。如果温度很高(大约10 K),则会发生这种情况。在此温度下,氢原子的电子完全脱离,因此我们得到一个裸核(即裸核)和一个自由电子。
裸核以非常快的速度和自由电子运动的集合称为等离子体。由于裸核(带正电)的数量等于电子(带负电的数量),因此等离子体上的净电荷为零。氢的这些裸核以非常高的速度移动(因为速度与温度成正比),因此融合在一起形成氦核。在氢核聚变期间,释放出大量能量。
因此,可以说,两个或多个轻核融合在一起(或结合在一起)以形成重核并释放能量的过程称为核融合。根据汉斯·贝特(Hans Bethe)的说法,太阳和其他恒星的能量来源是热核或核聚变反应。
当Tri( 1 H 3 )与氘( 1 H 2 )融合时,会形成以下产物:
1 H 3 + 1 H 2→2赫4 + 0 N 1 + 17.6兆电子伏
下图显示了这种融合:
核聚变的利弊
使用核聚变的优点是:
- 核聚变释放的能量远远大于核裂变反应释放的能量。
- 在核聚变中,氢核融合在一起形成稳定的氦核。氦核不发出任何类型的有害辐射。因此,我们可以轻松处理它。另一方面,核裂变反应的副产物会散发有害的辐射。因此,该产品的处置是一个大问题。
使用核聚变的缺点是,在实验阶段要控制核聚变发电。发现的主要问题是在难以做到的极高温度下包含核聚变的成分。
印度原子能发电厂和研究中心
- Bhabha Atomic Research Centre at Trombay near Mumbai, this center has been established to carry out research work to use nuclear energy for peaceful purposes.
- Tarapur Atomic Power Station (Maharashtra), was the first atomic power station established in India.
- Rajasthan Atomic Power Station at Rana Pratap Sagar near Kota.
- Narora Atomic Power Station at Narora in Uttar Pradesh.
- Madras Atomic Power Station (now known as Indira Gandhi Centre for Atomic Research) at Kalpakkam in Tamil Nadu.
India gets most of the Uranium from the Jaduguda mines in Bihar. The uranium obtained from these mines is taken to Nuclear Fuel complex situated at Hyderabad for processing. At this complex, after enriching the uranium the fuel elements are formed. These fuel elements are then sent to different Nuclear power plants.
核裂变与核聚变之间的区别
Nuclear Fission |
Nuclear Fusion |
---|---|
1. In nuclear fission, a heavy nucleus splits up into lighter nuclei. |
1. In a nuclear fusion, light nuclei combine together to form a heavy nucleus. |
2 In nuclear fission, harmful nuclear radiation is emitted. |
2. In a nuclear fusion, no harmful radiation ae emitted |
3. A nuclear fission starts when a slow neutron |
3. A nuclear fusion starts when light nuclei are heated at an extremely high temperature, bombards the heavy nucleus (like Uranium-235). |
4. Nuclear fission is a chain reaction i.e. it multiplies very fast |
4. Nuclear fusion is not a chain reaction |
5. Nuclear fission reactions can be controlled to produce electricity. |
5. Nuclear fusion reactions are still uncontrolled and cannot be used to produce electricity. |
6. Nuclear fission reactions produce a large amount of energy |
6. Nuclear fusion reactions produce nuclear fission much more energy. |
7. Temperature plays no role to start a nuclear fission reaction |
7. Temperature of the order of 10 K is required to start a nuclear fusion reaction. |
8. By-products of nuclear fission are radioactive and emit harmful radiation. |
8. By-products of nuclear fusion are not radioactive and hence do not emit harmful radiation. |
9. Nuclear fission causes more pollution |
9. Nuclear fusion causes no pollution. |
10. In nuclear fission, the disposal of nuclear waste is a big problem. |
10. In a nuclear fusion, no such problem is there. |
样本问题
问题1:使用哪个设备来控制连锁反应?
解决方案:
Nuclear reactor is a device used to carry out the controlled chain reaction.
问题2:三个元素A,B和C的质量数分别为2,180和235。其中哪一个适合制造氢弹?
解决方案:
As it is known that a hydrogen bomb is based on nuclear fusion reaction.
So element A is suitable for making hydrogen bomb.
问题3:印度核电站的发电量是多少?
解决方案:
About 3% of total energy is produced from nuclear power plants in India.
问题4:如果在92 U 235的单个原子核的裂变中释放了200 MeV能量,则每秒必须发生多少裂变才能产生1 kW的功率?
解决方案:
Given that,
The energy released per fission is 200 MeV or 200 × 1.6 × 10-13 J i.e. 3.2 × 10-11 J.
The energy required per second is 1 kW or 1000 W or 1000 Js-1 i.e. 103 Js-1
Therefore,
The number of fission per second is given as:
⇒ Energy required per second / Energy released per fission =103 Js-1 / 3.2 × 10-11 J
= 3.125 × 1013 s-1
问题5:详细区分核裂变与核聚变。
解决方案:
The detailed differentiation between the two types of nuclear reactions are as follows:
Nuclear Fission |
Nuclear Fusion |
|
1. | In a nuclear fission, a heavy nucleus splits up into lighter nuclei. | In a nuclear fusion, light nuclei combine together to form a heavy nucleus. |
2. | Harmful nuclear radiation are emitted. | No harmful radiation ae emitted. |
3. | A nuclear fission starts with a slow neutron. | A nuclear fusion starts when light nuclei are heated at a extremely high temperature, bombards the heavy nucleus (like Uranium-235). |
4. | Nuclear fission is a chain reaction i.e. it multiplies very fast. | Nuclear fusion is not a chain reaction. |
5. | Nuclear fission reactions can be controlled to produce electricity. | Nuclear fusion reactions are still uncontrolled and cannot be used to produce electricity. |
6. | Nuclear fission reactions produce a large amount of energy. | Nuclear fusion reactions produce than the nuclear fission much more energy. |
7. | Temperature plays no role to start nuclear fission reaction. | Temperature of the order of 10 K is required to start nuclear fusion reaction. |
8. | By products of nuclear fission are radioactive and emit harmful radiation. | By-products of nuclear fusion are not radioactive and hence do not emit harmful radiation. |
9. | Nuclear fission causes more pollution. | Nuclear fusion causes no pollution. |
10. | In a nuclear fission, the disposal of nuclear waste is a big problem. | In a nuclear fusion, no such problem is there. |