Chapter4- Nuclear Processes.ppt
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_05.gif)
《Chapter4- Nuclear Processes.ppt》由会员分享,可在线阅读,更多相关《Chapter4- Nuclear Processes.ppt(24页珍藏版)》请在得力文库 - 分享文档赚钱的网站上搜索。
1、NUCLEAR ENERGYPROFESSIONAL(SPECIAL)ENGLISH COURSECHAPTER 4 Nuclear Processes(核过程核过程)1CHAPTER 4 Nuclear Processes(核过程)核过程)Nuclear reactions(核反应核反应)-those in which atomic nuclei participate(参与参与)-may take place spontaneously(自然地自然地),as in radioactivity,or may be induced(感应感应,诱发诱发)by bombardment(轰击轰击,撞
2、击撞击)with a particle or ray.Nuclear reactions are much more energetic(精力充沛的精力充沛的,高能的高能的)than chemical reactions,but they obey the same physical laws-conservation(守恒守恒)of momentum(动量动量),energy,number of particles,and charge.2The number of possible nuclear reactions is extremely large because there are
3、 about 2000 known isotopes and many particles that can either be projectiles(发射体发射体,入射粒子入射粒子)or products(产物产物)-photons,electrons,protons,neutrons,alpha particles,deuteron(氘核氘核),and heavy charged particles(重带电重带电粒子粒子).In this chapter we emphasize(强调强调,着重着重)induced reactions,especially those involving
4、 neutrons.34.1 TRANSMUTATION OF ELEMENTS(元素的嬗变元素的嬗变)The conversion of one element into another,a process called transmutation(变形变形,嬗变嬗变),was first achieved in 19l9 by Rutherford in England.He bombarded nitrogen(氮氮)atoms with alpha particles from a radioactive source to produce an oxygen isotope and
5、a proton.(Fig.4.1)It is difficult for the positively charged(带正电子带正电子的的)alpha particle to enter the nitrogen nucleus because of the electrical forces(电场力电场力)between nuclei.The alpha particle thus must have several MeV energy.4Nuclear transmutations can also be achieved by charged particles that are
6、electrically accelerated to high speeds.5Since the neutron is a neutral(中性的中性的)particle it does not experience electrostatic repulsion(静电静电排斥排斥)and can readily penetrate(穿透穿透)a target nucleus(靶核靶核).Neutrons are thus especially useful as projectiles to induce reactions.Several examples:The conversion
7、 of mercury(汞汞)into gold,the alchemist(炼金术士炼金术士)s dream,is described by6A shorthand(简化简化)notation(符号符号)is used to represent(描绘描绘)nuclear reactions.Let an incoming particle(入射入射粒子粒子)a strike a target nucleus X to produce a residual nucleus(余核余核)Y and an outgoing particle(出射粒子出射粒子)b,with equation a+X=
8、Y+b.The reaction may be abbreviated(缩写缩写)X(a,b)Y.7The interpretation(解释)of nuclear reactions often involves the concept of compound nucleus(复合核).This intermediate(中间的,中级的)stage is formed by the combination of a projectile and target nucleus.It has extra energy of excitation and breaks up into the ou
9、tgoing particle or ray and the residual nucleus.84.2 ENERGY AND MOMENTUM CONSERVATION(能量与动量守恒能量与动量守恒)The conservation of mass-energy is a firm(坚定的,严格的)requirement for any nuclear reaction.Recall from Chapter l that the total mass is the sum of the rest mass m0 and the kinetic energy(动能)Ek(in mass un
10、its).9The calculations just completed tell us the total kinetic energy of the product particles but do not reveal(显示显示)how much each has,or what the speeds are.To find this information we must apply the principle of conservation of momentum(动量守恒法则动量守恒法则).Recall that the linear momentum(线动量线动量)p of a
11、 material particle of mass m and speed v is p=mv.This relation is correct in both the classical(经典的经典的)and relativistic(相对论的相对论的)senses.The total momentum of the interacting particles before and after the collision is the same.104.3 REACTION RATES(反应率反应率)We can perform a set of imaginary experiments
12、 that will clarify(阐明)the idea of cross section(截面).Picture,as in Fig.4.2(a)a tube of end area(截面积)1 cm2 containing only one target particle.A single projectile is injected(注入)parallel to(平行于)the tube axis,but its exact location is not specified(详述,指定).It is clear that the chance of collision,labele
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Chapter4- Nuclear Processes Chapter4
![提示](https://www.deliwenku.com/images/bang_tan.gif)
限制150内