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核反应堆与核武器是一回事吗?

Nuclear Reactors vs. Nuclear Weapons

核反应堆与核武器的关系
A nuclear reactor and a nuclear weapon are
就像仓鼠与短吻鳄的关系一样
about as similar as a hamster and an alligator.
它们成分相同
They’re both made of cells,
但明显一者更危险
but one is clearly more dangerous than the other.
因此
So, the thing in common
核武器与核反应堆共同点是
between nuclear weapons and nuclear reactors
它们都由同位素裂变产生能量
is they’re both powered by fissile isotopes,
比如 铀235或者钚239
like uranium 235 or plutonium 239.
裂变同位素是特殊元素
Fissile isotopes are special elements
受中子轰击时会裂变
that break apart when neutrons hit them.
裂变后 就会产生更多中子
When this happens, they release more neutrons,
和称为裂变产物的小原子
and little atoms we call fission products,
随之产生大量能量
which carry off a lot of energy.
核反应堆中
In nuclear reactors,
裂变能量经过较长时间缓慢释放
this energy’s released over a long period of time,
核武器中 则是瞬间完成
whereas in weapons, it’s released all at once, instantaneously.
因此 在核反应堆和核武器中
So, fissile isotopes are the key ingredients
裂变同位素都是最关键的元素
in both nuclear reactors and nuclear weapons,
但二者的相似点仅此而已
but that’s where the similarity stops.
许多差异中最明显的就是
The difference, one of the many differences,
核武器几乎是纯裂变材料
is that a nuclear weapon is almost pure fissile material,
裂变同位素浓度达百分之九十
it’s about 90 percent of the fissile isotopes,
不论是铀235还是钚239
either uranium 235 or plutonium 239,
反应堆中核燃料浓度仅有百分之五
whereas reactor fuel’s only about five percent.
然而 仅仅把一堆铀或钚弄在一起
And, just getting a bunch of uranium and plutonium together
并不能造出核武器
doesn’t make a weapon.
如果你点燃一块铀235
If you lit a block of uranium 235 on fire,
也只是化学上的燃烧
it would burn chemically,
产生的火焰
there’d be a fire
与其他可燃物燃烧的火焰并无不同
just like if you lit any other flammable material on fire,
但是不会产生核爆炸
but it would not be a nuclear explosion.
事实上 你必须极度压缩它
You actually have to compress it so much
使得原子的密度
that you get the atoms to slam together
比通常情况下大的多
much denser than they’d normally be.
因此 核武器中
So, a nuclear weapon,
通常由某材料组成内核
there’s usually some sort of a core
一般是铀或者钚的核碎片
of uranium or plutonium in pieces,
裂变材料周围是一圈炸药
and around that is a bunch of explosive
爆炸后压缩裂变材料
that smashes them into each other,
更外面则是一层外壳
and around that is some sort of a shell
把爆炸限制在内 直到压力足够大
that contains the explosion until it gets big enough.
这些条件很难实现
These are exceedingly difficult to make.
如果拿来上百万根炸药棒
If you took millions of sticks of dynamite
放在一个铀构成的球体周围
and put them around a sphere of uranium
然后同时引爆所有炸药
and blew them all up at the exact same time,
爆炸的威力不足以大到
the force would not be large enough to
能把铀压缩到武器级浓度
compact the uranium to make a weapon.
如果炸药选的对
If you got the right kind of explosive
然后把球状铀包围起来
and surrounded this sphere of uranium with the explosive,
并且同时引爆所有炸药
and got’em all to go off at the same time,
这仍造不出核武器
it still wouldn’t make a weapon.
如果拿来一大堆铀材料块
If you took a whole bunch of bricks of uranium
堆在一起
and put them all together,
再开来一辆装满汽油的罐车
and then drove a tanker full of gas next to it,
在周围引爆烈性炸药
and has a whole bunch of high explosive blowing up all around it,
并有足够的铀达到裂变临界点
if you had enough uranium to go super critical,
那么在极短极短的时间内
it would, very very briefly.
会产生一束中子脉冲
You would get a quick pulse of neutrons,
一切都迅速升温 爆炸开来
at which point everythingwould heat up and blow apart,
一旦铀炸成了碎片并相隔一段距离
and once all the uranium’s in different pieces too far away,
反应就终止了
the reaction stops.
没有恰当的物理结构和精心设计
Without the proper physics and design,
我们国家花了很长时间才做到这点
which has take countries like ours years to do,
否则 最多也就是麦克湾式的大爆炸
the best you could do is a Michael Bay style explosion,
还远达不到核爆炸的标准
but you couldn’t actually get a nuclear explosion.
我刚刚说的事 在曼哈顿工程中
I’ve just described what took the Manhattan Project
花了五年才做到
about five years to do,
那可有上万名优秀的工程师参与
and tens of thousands of absolutely brilliant scientists,
其中一些甚至是诺贝尔奖得主
some of whom won the Nobel Prize.
想用麻省理工反应堆核燃料造出核武器
In order to use the MIT reactor fuel to make a weapon,
会是件很难的事情
yeah, that would be difficult,
这就是所谓的 说到比做到简单
that’s the definition of easier said than done.
你不仅要想出
Not only would you have to figure out
怎样把武器部件凑齐
how to put the weapon together,
还要想办法接触到反应堆核燃料
but you’d have to physically get to the reactor’s fuel,
而这基本上没可能
and that’s basically impossible.
反应堆建筑牢不可破
The building is about four feet thick
由四英尺厚强化钢筋混凝土构成
of rebar enforced concrete.
经受过模拟满载飞机撞击
That’s actually been simulated to take a loaded plane crash,
因为 这是国家规定的
cause that’s one of the safety criteria
核反应堆安全标准之一
for reactors in this country,
即使受到飞机撞击
you have to be able to fly a plane into it,
反应堆也不会解体
and it shouldn’t break apart.
这还没算上建筑内的安保力量
That doesn’t even count the security inside the building,
更别说还有特警队随时集结待命
let alone the SWAT teams that would swarm the place
以防万一有人试图闯入
if anyone even tried to break in,
假设恐怖分子破解了所有安保措施
but lets say the terrorists got passed all of that,
想要接触到核燃料
then they still have to get to the fuel itself
还要穿过重重防护设施
which is normally kept behind a lot of shielding to keep it safe,
才能达到目的
so we can work with it.
如果 防护设施中
So, if they took away the lead,
导线 混凝土和钢铁被移走
the concrete, and the steel shielding,
恐怖分子就要面对核燃料
they’d be faced with the fuel itself,
一接触 其极强的放射性就将杀死他们
which is so radioactive that it would kill them on contact.
即使有人偷到了
Even if somebody were to steal
足够制造核武器的材料
enough material to make a weapon,
仅拼凑材料也造不出核武器
you can’t just put it together and have a weapon,
那根本做不成
it doesn’t work.
核燃料里别的杂质太多
There’s so much other stuff in the fuel.
我国大部分轻水核燃料
Most light water reactor fuels in this country
都由二氧化铀制成
are made of uranium dioxide.
你在铀原子中放了氧原子
You put oxygen in the way of those uranium atoms,
已经不再有用
it doesn’t work anymore.
这可造出核燃料 造不出核武器
It works as fuel, but not as a weapon.
反应堆核燃料铀235浓度仅为百分之五
Reactor fuel is only about five percent uranium 235,
还有其他结构材料
and there’s other structural materials,
有起支撑作用的钢铁
there’s steel holding the thing up,
有水围着反应堆
there’s water surrounding it,
还有支撑燃料棒和插脚的锆合金
there’s zirconium alloys holding pins and fuel rods in,
还有很多其他东西须进行化学分离
there’s all this other stuff that would have to be chemically separated.
反应堆和核武器的另一个区别就是
Another difference between reactors and weapons
链式反应的控制方式不同
is the way the chain reaction is controlled.
反应堆是一种严格控制的带有负反馈的链式反应
A reactor is a tightly controlled chain reaction with negative feedback,
一旦稍有不对 核反应就停下
so if anything goes wrong, the reaction stops.
核弹则设计成不受控制的链式反应
A nuclear bomb is an uncontrolled chain reaction
可极速达到最高热度
designed to get as hot as possible, as fast as possible.
当听到链式反应一词时
So, when you hear the word chain reaction,
你可能自然联想到不受控制的事物
you might automatically think of something that’s out of control,
但要保持反应堆运转相当困难
but it’s actually really hard to keep a reactor going.
设想一下
So, let’s say,
你有一定数量的铀235原子
you had a certain number of uranium 235 atoms.
每次这些铀原子分裂
Every time one of those uranium atoms splits apart,
都释放出二至三个中子
it gives off two or three neutrons,
中子轰击 又导致另一个铀原子裂变
which could cause another uranium atom to split apart,
但不是每次轰击都能成功
but not every one does.
有些中子泄露到反应堆外
Some of them leak out of the reactor,
而后被保护壳吸收
and get absorbed by the shielding,
另一些被反应堆其他材料吸收
some of them get absorbed by other materials in the reactor,
甚至铀235都吸收了一部分
and some of them can get even captured by uranium 235
而未引发裂变
without inducing fission.
随着裂变反应进行
As the fission reaction proceeds,
越来越多其他物质不断生成
more and more other stuff builds up,
这些物质称为裂变产物
and that other stuff, which we call the fission products,
裂变产物也吸收一部分中子
absorb some of those neutrons away,
使得链式反应无法进行
and makes them unavailable to keep the chain reaction going.
同样 裂变反应释放出热量
Also, when a fission reaction heats up,
导致初始聚集的原子离散
it causes the atoms to spread out,
让中子轰击原子成功的概率大减
making it harder for some of those neutrons to hit other fuel atoms,
反应也就更难进行
and keep the reaction going.
除此以外 还有控制棒
In addition to that, there’s control rods.
有的材料极易吸收中子
There are materials that are really, really good at absorbing neutrons,
比如 硼 铪和钆
like boron, hafnium, or gadolinium.
仅仅让这些东西附在反应堆上
And you can simply stick those down into the reactor
就能吸收中子 使链式反应停止
to absorb away the neutrons and shut down the chain reaction.
同样的吸收中子情况
The same sorts of reactions are happening
也发生在核电站和核弹中
in a nuclear power plant and a nuclear bomb,
但是 在核弹中
but in a nuclear bomb,
反应的速度快了无数倍
they’re happening quintillions of times faster,
在一刹那就已完成
and it’s all over in a split second.
核武器中的链式反应
The whole nuclear part of the explosion
用时不到一秒
takes less than a second,
核电站中的链式反应
and in a nuclear power plant,
释放同样能量需要几年甚至几十年
you’re releasing that same energy over years or decades
当然 反应方式必须要可控
in a controlled way that we can harness.

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视频概述

核反应堆和核武器的具体区别

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收集自网络

翻译译者

dumass

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审核员SY

视频来源

https://www.youtube.com/watch?v=pf5Vk6t2yMI

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