It is necessary to enrich the fuel by increasing the percentage concentration of uranium-235.
必须提高铀235浓度的百分比，使燃料浓集。
There are different kinds, or isotopes, of uranium, and the type used in nuclear power plants is called uranium-235, because these atoms are easiest to split in two.
铀有许多不同的种类，或称同位素，而在核电站中所使用的是铀235这一类，因为这些的原子最容易一分为二。
It is made up of old fuel rods that have become sufficiently depleted of uranium-235, the isotope that drives a reactor’s main chain reaction, to be no longer useful.
乏燃料由完全耗尽铀-235的旧燃料棒组成，核反应堆的链式反应就是由铀-235激发的。
On the other hand, analyses of 85 Kr, a fission product of uranium-235 and plutonium-239, can serve as a means to help verify compliance with the Nuclear Non-Proliferation Treaty.
另一方面，氪-85是铀-235和钋-239的核裂变产物。 对氪-85的同位素含量测定可以用于监督国际核公约的执行情况。
When you split a uranium 235 atom you will create what we call fission fragments.
当你们将铀235原子分离的时候,你会创造出我们称为裂变碎片的。
Now first of all we're gonna talk about the fundamentals of the neutron capture and what happens in the neutron capture of a uranium 235 atom.
现在，首先我们要谈论，中子捕获的基本原理，在铀235原子的，中子捕获方面发生了什么。
You can have an elastic scattering collision where the neutron just essentially bounces off the uranium 235 atom and just continues on and it's possibly slowed down ever so slightly.
你可以得到一个弹性散射的碰撞，在那，原子就会反射，铀235原子，还会继续，那也可能会减慢一点。
Now if you wanna calculate how much, if you fission one gram of uranium 235, you can, if you convert it to electricity, make twenty four thousand kilowatt hours of electricity, which is a lot.
现在，如果你们要计算有多少，如果你们将一克的铀235裂变，你们能，如果你们将它转化成电，制造出2万4的，千瓦每小时的电，那很多了。
A neutron striking a uranium 235 atom, releasing some gammas and some neutrons, creating two fission fragments which themselves have a distribution of occurrence.
一个撞击铀235原子的中子，释放出一些γ，和一些中子，创造出2个裂变碎片,那它们自己会有出现的分布。
Fertile meaning the none fissionable uranium 235.
丰富的意思是裂变的铀。
To make fuel for electricity-generating reactors, uranium is enriched to less than 5 percent of the isotope U-235.
为将燃料做成电能反应堆，铀被浓缩至U-235同位素含量5%以下。
Uranium 235 — the fuel inside a nuclear reactor — undergoes nuclear fission.
铀235——反应堆中的燃料——经过核裂变。
Now when you look at this you see these people handling the uranium pellets. Now uranium 235 in this form is very low in activity because uranium235 has a very long half-life.
现在，当你们观察这个，你们能看到这些人,铀正在处理铀芯块，现在,在这个形式里，是活跃度是很低的，因为铀5,的半衰期很长。
So you put in more fuel, more uranium 235, a higher enrichment and you need to balance that excess reactivity in a number of ways.
所以你放入更多的燃料，更多的铀，一个能咖的浓缩度，你需要平衡，剩余反应性，用很多方法。
Nuclear fission can only occur in some types of heavy and unstable nuclei such as in the uranium -235 and plutonium -239.
核裂变只能在某种类型的重核及不稳定核素内发生，如铀- 235及钚- 239。
The prime example is the element uranium (U), which occurs naturally as two isotopes-the lighter, fissionable U-235 and the heavier, non-fissionable U-238.
铀（U）元素就是一个很好的例子。天然铀有两种同位素；较轻的负235可以裂变，较重的铀238则不会裂变。
In the mid 1940s the process to produce uranium - 235 was scaled up from lab to plant with a scale-up factor of 1061. Obviously this is a big risk, but so were the perceived returns.
40年代中期，生产u- 235的工艺从实验室规模到工厂规模的放大系数是1061显然这是个大冒险，不过也收到了大回报。
In the mid 1940s the process to produce uranium - 235 was scaled up from lab to plant with a scale-up factor of 1061. Obviously this is a big risk, but so were the perceived returns.
40年代中期，生产u- 235的工艺从实验室规模到工厂规模的放大系数是1061显然这是个大冒险，不过也收到了大回报。
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