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l**a
发帖数: 6415 | 1 删掉一些了。
链接如下
plainenglishnuclear.blogspot.com
.......
1. I live on the West Coast. Am I in danger?
No. Absolutely not.
You won’t even notice except that everyone will keep talking about it for
ages, and it’ll take us even longer to get off coal and oil and natural gas
because people will be afraid of nuclear power again. Go outside, get some
sunshine (or rain, depending), be grateful for the fact that your city isn
’t completely destroyed in an earthquake or a tsunami, hug your loved ones,
and then find a way to donate to the relief efforts.
You might get cancer years from now, but it won’t be from this. It’ll be
from smoking or sun damage or plastics or those horrible processed foods
with the carcinogens you keep eating.
2. But I saw a fallout map on the internet, labeled “Australian
Radiation Services” or “U.S. NRC”!
It’s a hoax. A really, really mean one. See http://www.blogotariat.com/node/211958 for one of the best summaries I’ve found.
3. Even if the reactor has a meltdown? The media keeps saying we’re
headed for a meltdown. Isn’t that a very very bad thing?
Not necessarily. “Meltdown” is a very broad term – it applies to a range
of conditions. “Meltdown” is basically any time that the fuel gets hot
enough that the cladding (the metal wrapper that holds the fuel in place)
gets holes in it. But “meltdown” could mean just one teeny spot on one
single fuel pin (the cladding starts to fail at about 2200 degrees F) all
the way up to the entire reactor core in a liquid pool on the bottom of the
pressure vessel (the fuel itself melts at about 5000 degrees F). The media
seems to think it’s that whole-core thing. But that isn’t going to happen.
So far they’ve had a partial failure of some of the fuel pins in two of the
reactor units, and that’s about where it’s expected to stay. It may turn
out that a third reactor unit also had a partial failure of fuel pins.
This is a sad situation – we try not to have fuel failures, because it’s a
giant hassle – but it’s not by itself a dangerous one. It’s very
important to remember that these fuel pins are sealed inside a giant steel
pressure vessel, which itself is sealed inside a giant concrete containment
structure (you may also hear this called the “drywell”). Even if the core
*did* melt all the way down, either one of those two things on its own
would keep the radiation from the melted fuel from getting to the public.
4. But Chernobyl released lots of radiation!
This isn’t like Chernobyl. You can read why here:
http://news.yahoo.com/s/livescience/20110312/sc_livescience/che
http://online.wsj.com/article/SB1000142405274870489360457619842
http://www.csmonitor.com/World/Global-News/2011/0313/Japan-s-nu
Short version:
- Chernobyl used a different kind of fuel, and its fuel caught on
fire and the ash went everywhere in a great cloud that lasted for months in
affected areas. That can’t happen here; for one the fuel can’t catch on
fire, so no ash, and for two, any radiation release would be in gaseous form
and the cloud would pass over affected areas in hours.
- Chernobyl didn’t have a containment structure. These reactors do.
This is more like Three Mile Island, if you insist on picking an accident
for comparison.
5. But Three Mile Island was terrible!
Three Mile Island a) didn’t kill anyone, b) didn’t injure anyone, and c)
only released a very small amount of radioactive material, mostly gases that
went harmlessly into the atmosphere. (Seriously! Read about it!) [1]
During Three Mile Island about half of the core (including fuel) melted and
fell to the bottom of the pressure vessel [1]. But it didn’t melt through
the steel pressure vessel – in fact it only melted about 5/8 of an inch
through the wall.[2] (A typical pressure vessel is ~6 inches thick.) And
even if it had, it would have had to get through like 6 feet of concrete
after that. (We design it that way.)
Right now our best evidence indicates that yes, a small portion of the cores
in Fukishima One Unit 1 and Unit 3 have failed (although we don’t think
the fuel has melted, just the cladding), and maybe Unit 2 also. But it’s
thought that the majority of the fuel didn’t melt, and that the cleanup
will probably be less difficult than Three Mile Island.
6. But the media says they released radiation, and there’s all these
numbers floating about radiation levels, and they evacuated everyone who
lives near the reactor. Can you put this in context?
There were several small, planned releases of slightly radioactive gases.
Each of these radioactivity releases to the environment at Fukushima so far
has produced about the level of one dental X-ray if you were standing right
over the release and breathing in really hard. If you weren’t standing
right over the release, the particular kind of radioactivity released would
have nearly all gone away before the vented gases reached you on the ground.
Even the people on the ship that sailed right into the plume only got a
maximum dose about equal to a month of background radiation [6] – that is,
the natural radiation you get from living on Earth.
The most recent explosion at Fukushima One Unit 2 and near-simultaneous fire
and Fukushima One Unit 4 (about 6 am and 9 am Japan time March 15) did
release a one-time gust of radioactive gases that was larger. Radiation
levels at the edge of the nuclear plant briefly spiked to 8217 microSieverts
per hour. [10] How bad is this? 8217 microSieverts is about six times the
allowable annual exposure for a member of the public in the U.S. It would
take standing in this kind of radiation for 24 hours before you would be
considered to have radiation sickness (with a total dose of 200 milliSievert
). [9] But 8217 microSieverts was the peak of the spike, the total spike
lasted less than three hours, and dose rates at the edge of the plant were
at 489.8 microSieverts/hr as of 4:30pm Japan time March 15. (This means you
would get your annual dose if you stood there for an hour. Perspective:
This is about the same as smoking 350 packs of cigarettes in a year [12], or
living in Denver for a year [15].)
They evacuated people because it was safer that way – just like we evacuate
people during tornado and hurricane warnings. No exposure to the public
was expected, but better safe than sorry!
7. But something exploded! Three times! And it knocked down buildings!
First: There is no way for a nuclear power reactor to explode like an atomic
bomb. You just can’t. Even if you tried. Explosions can happen at
nuclear plants, yes – but they are either mechanical explosions (like
pressure building up in a confined space until it pops) or chemical
explosions (like a fire setting off a diesel storage tank, or a bunch of
hydrogen ending up somewhere that there’s a bunch of oxygen and a spark
setting it off like the Hindenberg). The explosions at Fukushima were not
caused by radioactive material.
Now: let’s take a look at what we’ve got right now. Here’s a typical
media graphic (thank you, Daily Mail): http://i.dailymail.co.uk/i/pix/2011/03/15/article-1366341-0B2D7BFA00000578-51_964x678.jpg
Here’s what you need to know: The fuel is in a steel pressure vessel. The
pressure vessel is in a veeeeeeery thick concrete-and-rebar structure
called the containment. The containment is located in a reactor building,
which is another building made of concrete and rebar (though not quite as
thick). On *top* of the reactor building is an additional structure made of
steel frame with sheet steel walls. This structure houses a fuel transfer
crane used when they change the fuel in the reactor.
What you see in the picture above is the reactor buildings for Unit 1
through Unit 4 of Fukushima One. The explosions in Unit 1 and Unit 3 were
hydrogen explosions that each happened in the fuel transfer crane areas,
blowing the sheet steel off the walls. Since that structure isn’t designed
to withstand explosions, they look pretty rough. What you can’t see in
the photos: the pressure vessels are just fine and the containments are just
fine. (Those structures *are* designed to withstand explosions.) And the
reactor buildings under the steel frames look okay.
Unit 2 had a hydrogen explosion also – but this one was in a thing called a
suppression pool, outside the main containment structure but inside the
reactor building. Officials suspect that a small portion of the pressure
vessel may have gotten damaged, but this is still unconfirmed.
Unit 4 had a fire inside the reactor building but outside the containment
structure.
So contrary to the captions in the photo: no reactor has exploded and no
reactor has caught fire. (Grrrr, bad reporting, Daily Mail!)
By contrast, here’s a picture of an oil refinery in Japan: http://cdn.theatlantic.com/static/infocus/jpq03111/j16_RTR2JQR2.jpg (It’s still on fire, as far as I know.)
8. What’s the worst thing that could happen? What about the most
likely?
My short-version prediction: The fuel in Units 1 and 3 of Fukushima One have
been damaged, and the status of the fuel in Unit 2 is unknown. Fuel in all
three of these units could melt further, but the radioactivity will remain
contained by the containment structures. Small amounts of radioactive steam
and gases have already been released, and more small releases could occur.
Right now I think 150 people are being monitored for radiation exposure and
23 have been sent for decontamination – but that includes workers. (Can’
t remember a source; would appreciate one.) Worker injuries (there have
already been 15 injuries) will be due to explosions, not radiation. No harm
will come to members of the public. No harm will come to the environment,
except for any little algae and bacteria critters caught up in the seawater
they are using for emergency cooling.
The worst thing that could happen is getting a hole in one of the
containment structures. That has possibly happened in Fukushima One Unit 2,
due to the hydrogen explosion there. But radiation levels near this unit
fell after an initial spike – which is what you would expect to happen if
the suppression pool exploded but the containment held – so their guess is
that if there is a hole, it’s actually in the pressure vessel and not the
containment structure. (It’s also expected to be a small hole.) If there
were a hole in the containment structure, radioactivity carried in liquid
coolant could leak out of the hole and into the surrounding reactor building
. Radioactive gases could leak out of the hole and up into the atmosphere.
It’s important to emphasize that the only members of the public who would
be at risk in this situation would a) be downwind, and b) probably not get a
dose that would kill them or cause cancer - probably a dose closer to 2 or
3 CT scans put together. I’m not a health physicist, though, so I could be
wrong.
There is one complicating factor, though. If radiation levels from a unit
with a hole in the containment structure are too high, it could mean workers
trying to make sure the other units at Fukushima One stay shut down would
have to evacuate or risk radiation poisoning by staying to operate the
reactors. Probably if this happened they would rotate the workers in on
short shifts to minimize exposure. If workers were completely evacuated,
Units 1 and 3 would probably melt down. Again, as long as the main
containment didn’t get compromised, there wouldn’t be a major release of
radioactivity.
9. That sounds pretty bad, still.
It is. It’s never good when people get hurt. And I bet some investors are
going to be mad. And it’s going to take some work to clean everything up
and repair it. But listen: this is not the thing that needs your fear and
attention right now.
Here’s some perspective: There are over 10,000 missing and presumed dead
from the quake and tsunami. [13] Over 3600 people are confirmed as having
died in this quake, so far – more than 9/11. Property damage is estimated
to be as much as $100 billion, according to some reports. [14] And
aftershocks keep happening.
Quit freaking out about the reactors; freak out about the dead and the
wounded. Freak out about the towns wiped off the coastline. Get out there
and do what you can: donate money, donate time, let Japan know we support
them. And spread good information, not fear.
10. Okay, I’m gonna quit reading now. That was already too long.
Sure, no problem. But forward this link to all your non-sciency friends:
http://online.wsj.com/article/SB1000142405274870489360457619842
And forward this to your sciency friends:
http://enochthered.wordpress.com/2011/03/13/all-right-its-time-
If you want more details, though…
11. Well, okay. First, I can’t keep all the plants and stuff straight.
Where is the problem?
There are two nuclear plants that we’re primarily concerned with right now:
Fukushima Dai-ichi (Fukushima One) and Fukushima Dai-ni (Fukushima Two).
We’ll use the Americanization of these names here because it’ll be a bit
easier for English-speakers to keep straight. Along with a third plant
called Onagawa, these two plants were the closest to the epicenter, and are
also near the coast.
Fukushima One has six separate nuclear reactors (we call them “units”).
They are numbered: Unit 1 through Unit 6. Fukushima Two has four units (
predictably, Unit 1 through Unit 4).
At the time of the earthquake, Fukushima One Units 1, 2, and 3 were
operating. Fukushima One Units 4, 5, and 6 were shut down for routine
maintenance and were not operating. Fukushima Two Units 1 through 4 were
all operating.
As of the last update I saw ([4], 7 pm Japan time March 15):
* Fukushima One Unit 1 through Unit 3 are pretty bad off and not
completely out of the woods. These reactors will not be usable again when
this is all over, but we don’t expect more than partial melting of the
cores and limited releases of radioactive gases (like in Three Mile Island).
* Fukushima One Unit 4 had a hydrogen explosion and subsequent fire in
the spent fuel pool and a fire in the reactor building, but the reactor is
just fine and was never in danger. Also, the reactor currently has no fuel
in it.
* Fukushima One Units 5 and 6 are just fine and were never in danger.
* Radiation levels at the border of Fukushima One were at 489.8
microSieverts/hr as of 4:30pm Japan time March 15. As stated above, this
would give you your annual dose as a member of the public in one hour, and
is about equivalent to smoking 350 packs of cigarettes in a year.
* As for the four units at Fukushima Two: they are all safely shut down.
Unit 3 was never damaged and had a normal shutdown. Units 1, 2, and 4 are
not damaged; originally there were problems with the emergency cooling
system, but these problems were fixed quite quickly, and the units are shut
down and there is no further danger. Even though these plants did not have
to release any radiation, radiation levels were slightly higher than normal
at the border of Fukushima Two (13.7 microSieverts/hr as of 12:00pm Japan
time March 15) – perhaps because Fukushima One is nearby?
12. Can you explain – briefly and in plain English, please – how this
kind of reactor works?
There are a lot of people who have done this for me. See the following
links:
http://www.boingboing.net/2011/03/12/nuclear-energy-insid.html
http://en.wikipedia.org/wiki/Boiling_Water_Reactor_Safety_Syste
http://enochthered.wordpress.com/2011/03/13/all-right-its-time-
My own simplified recap:
For this reactor, the fuel is uranium oxide, which is a ceramic form (one
report I saw indicates that one unit might have MOX fuel, which also
contains plutonium oxide, but I can’t confirm that). It’s shaped into
mostly-cylindrical pellets that are about as big as the first knuckle on
your pinky finger.
The fuel is contained inside cladding. Cladding is a metal tube, made of
zirconium in this kind of reactor, that surrounds a stack of fuel pellets.
It’s capped at both ends so the pellets are completely sealed inside, and
it’s about as big around as your pinky finger but ~13 feet long. Fuel
pellets inside one piece of cladding = one fuel pin.
Fuel pins are held in a fuel assembly, which is a metal rack about 6 inches
square by 13 feet long that keeps them in the right position. Fuel
assemblies are put into the reactor in another, bigger, rack to form the
reactor core.
The reactor core sits down inside a big metal container called a pressure
vessel. It’s made of steel that’s ~6 inches thick. The pressure vessel
has pipes going in at the bottom where coolant comes in, and pipes going out
at the top where steam goes out. It’s also got some vents that only open
when engineers tell them to (more on that later).
The coolant is regular water that moves past and through the reactor core (
using the spaces in between fuel pins). Yep! Regular water. It’s very,
very pure to try to remove any minerals or anything that’s not H2O. The
water never touches the fuel – remember the fuel is sealed inside cladding
– so there are no radioactive materials “leaking” into the coolant unless
the cladding is damaged. The water does get exposed to radiation, yes.
But that doesn’t make the water radioactive. In order for a thing to
become radioactive when it’s exposed to radiation, it has to “activate”,
and only specific materials can activate. H2O can’t activate[*], so the
H2O going out of the reactor is just plain H2O. Now, there’s always trace
amounts of stuff in the water that *can* activate (like boron), so the
coolant is very very slightly radioactive.
[*] Note that this is a simplification. Oxygen-16 can activate into
nitrogen-16, which has a halflife of 7 seconds. So basically: if you take a
cup of water out of a BWR and then sing “Twinkle Twinkle Little Star” it
’s pretty much not radioactive anymore.
The reactor works because the reactor core gets hot, and the heat boils the
coolant (water), and the steam goes out the top and into the turbine
building where it turns a turbine, and the moving turbine runs a generator,
and yay electricity! When the steam goes out the back end of the turbine,
it gets condensed back into water and pumped back into the bottom of the
reactor to be boiled again in a closed loop. If you’ve ever seen a tea
kettle with the little whirligig on the spout, that’s exactly what happens,
only you it’s like you reroute the steam back into the bottom of the
kettle.
So we have the reactor core and the coolant inside the steel pressure vessel
. The pressure vessel sits inside a giant thing called the containment
structure, made of concrete and lots of steel rebar. It’s usually 4-8 feet
thick. (That’s a lot, y’all.) The containment structure is completely
sealed up; nothing (not even air) goes in or out unless they intentionally
open a hatch. (The coolant goes in and out through pipes that snake through
the containment structure; they are big and huge pipes.)
Now, what makes the fuel hot? Short answer: Uranium and plutonium in the
fuel can fission (break apart), and when they fission, they produce moving
particles (neutrons and fission fragments), and the moving particles hit
other things, and the hitting-things produces heat. There are two things
that make uranium and plutonium fission: they do it spontaneously at a low
level (because they are naturally radioactive [**]), and they do it when
neutrons hit them in just the right way. A fission chain reaction works
like this: since fissions create neutrons, and neutrons can create more
fissions, if you set everything up just right, you can get a reaction that’
s self-sustaining. That’s what makes a reactor run. To stop that reaction
, you do something that makes the neutrons not hit the fuel as much – in
this case, you put control rods in the reactor and the control rods sort of
soak up the neutrons that are whizzing around and the whole thing slows down.
[**] Although note! Not all radioactive elements fission; fission is just
one way to be radioactive.
Let’s recap for just a second at this point: There are three physical
things standing between the radioactive fuel and someone at the main gate of
the plant. The first is the fuel cladding on each of the fuel pins, made
of zirconium. The second is the pressure vessel, an 6-inch thick steel
container. The third the containment structure, a 4- to 8-foot thick
construction made of concrete and rebar. All of these are air-tight and
radioactivity-tight. There is also the reactor building, also made of
concrete, but this one isn’t air-tight.
13. So what happened in the accident?
This description is (generally) of Fukushima One Units 1 through 3.
Fukushima Two Units 1 through 4 started out the same, but they were able to
restore cooling much earlier. (I don’t think they lost their backup diesel
generators at all.)
First, the control rods automatically dropped into the core of the operating
units in what’s called a scram. The control rods went all the way in, and
brought the fission reaction in the reactor screeching to a low level. [
Safety system #1 (control rods): worked as designed.] At this point the
reactors were in “hot shutdown” – the reactor was producing somewhere
around 4-7% of full power, and the temperature of the coolant was still at
normal operating levels (about 550 F). The power level in the reactor will
normally coast down from there over the next couple days until the power
level is around 0.5% of full power. (You can’t get it to go lower than
that without pulling all the fuel out, remember, because the fuel does do
some spontaneous fissions.) This point is called “cold shutdown” – when
the temperature of the coolant is less than boiling (212 F). When you’re
in cold shutdown, you almost don’t need to run the cooling system anymore.
During either kind of shutdown, the fuel is still producing heat. You have
to keep the cooling system going the whole time to keep pulling heat away
from the fuel so that the fuel doesn’t overheat and damage itself. BUT you
just shut down your reactor that produces electricity, so how are you
running your pumps? Answer: Pumps are usually run using power from the
offsite power grid, not your onsite reactor.
It’s expected in earthquakes (and other accidents) that the power grid
might get damaged, and that offsite power being supplied to the power
station will stop. So there are backup diesel generators to run everything
you need to run onsite: pumps, valves, control panels, etc. It appears that
after the earthquake, the connection to the Japanese power grid dropped (as
expected) when the tsunami washed away the power lines. And the backup
diesel generators kicked in. [Safety system #2 (backup diesel generators for
cooling recirculation): worked as designed.]
But then after about an hour the diesel generators at Fukushima One failed,
reportedly due to damage to the fuel supply from the tsunami. [Safety
system #2 (backup diesel generators for cooling recirculation): temporary
problems due to MASSIVE TSUNAMI.] This meant there was nothing to run the
cooling system at Fukushima One Units 1, 2, and 3. Heat began to build up
in the reactors, and the heat boiled the coolant, and the coolant turned to
steam, and the pressure began to build up in the pressure vessels. Why is
this a problem? Two reasons: one, the increase in pressure could
eventually cause your pressure vessel and associated piping to give way (
like a popping balloon), and two, fuel that’s not actually underwater gets
hotter much faster and could get hot enough that it fails (gets holes in the
cladding). The more coolant that boils into steam, the more the coolant
level drops (like boiling a pot of spaghetti), and eventually the reactor
would boil dry if you didn’t stop it. (And then you would melt your
spaghetti, I mean fuel.)
This sort of event is also planned for: first, you have some time before
things get really iffy (pressure too high or water level too low) during
which you can restart cooling, and second, there are a bunch of other things
you can do in the meantime.
One of them is you have things that can act as a heat sink – basically
large pools of water. However, they’re sort of one-time use; once you heat
them up, you have to cool them down before you can use them again. These
were used and they worked. [Safety system #3 (automatic depressurization
system and isolation condensers): worked as designed.]
One of them is you can add more (cold) coolant while the system is at full
pressure. The pumps to do this run off of steam from the reactor (neat,
right? The fact that the reactor is getting hotter automatically powers the
thing you need to make it colder). This ran just fine, and more coolant was
put in. [Safety system #4 (high pressure coolant injection system): worked
as designed.] There’s also a second (less powerful) system that puts more
coolant in, that runs off of batteries. They ran that too. [Safety system
#5 (reactor core isolation cooling system): worked as designed.] However,
the control valves that this new coolant runs through work off of batteries.
After eight hours, the control valves lost power because the batteries ran
out. [Safety system #6 (battery-operated control valves for RCIC line):
worked as designed to the end of design lifetime.] Solution: replace the
batteries! But they ran through all the batteries they had, and were having
problems getting more because of all the earthquake damage in surrounding
regions. Hours passed, during which the core kept heating up and coolant
kept turning to steam. Then they got a delivery of portable diesel
generators and were able to start a different backup pumping system to top
up the coolant in the core.
One of them is you can vent coolant into the space between the pressure
vessel and the containment structure. You open a hatch, and steam goes out,
and yay! Pressure reduced back to safe operating levels. At this point
the steam is still mostly just steam (only very slightly radioactive),
because your fuel cladding is still intact. It’s also trapped in the
containment structure and hasn’t been released to the environment yet. So
they vented steam to the containment structure. [Safety system #7 (pressure
vessel venting): worked as designed.]
So there’s lots of stuff that was being done, to buy time to get the
cooling recirculation working. But the longer your reactor sits without
cooling, the more you risk the water level dropping to uncover the fuel rods
, and the more you risk those fuel rods overheating. When your fuel rods
get uncovered, two things can happen. One, the cladding can fail – usually
because it gets so hot that it can’t take the strain, and it splits open.
Two, even if the cladding doesn’t fail, the high temperatures and the
steam can cause it to oxidize – basically, to rust – at an accelerated
rate. This is important because the oxidizing reaction takes H2O and turns
it into oxygen (bound up in the zirconium oxide) and hydrogen.
And this is in fact what had happened, while they were sitting there with no
power waiting on the delivery of new diesel generators – the cladding in
some of the fuel rods failed, exposing the fuel, and the cladding started to
oxidize, creating hydrogen. [Safety system #8 (cladding): functioned as
designed for a very long time and then conditions changed causing it to
partially fail.] Now the steam in the reactor was slightly more radioactive
, because bits of the fuel were touching the steam, and particles could be
picked up and carried with the steam. But this wasn’t very much
radioactivity (way below guidelines for exposures to the public), pressure
in the pressure vessel was still rising, and the containment structure was
still intact and airtight. So they made the decision to continue to vent
radioactive steam to the containment structure. [Safety system #9 (
containment structure): worked as designed.]
If you keep doing this, eventually pressure will also rise in the
containment structure. So you can vent the containment structure, too.
Many plants have a design where the containment structure can be vented into
the reactor building that surrounds the containment, so that you are
sequestering any radioactivity. The reactor building isn’t airtight, but
it’ll keep the vast majority of radioactive release from getting out to the
environment. So they vented radioactive steam to the reactor building. [
Safety system #10 (reactor building): worked as designed.]
But remember, the cladding rusting made hydrogen. Hydrogen, you might
recall, is flammable. So the hydrogen went along with the steam, from the
pressure vessel (which had no oxygen gas in it), to the containment
structure (which had no oxygen gas in it), to the reactor building (which
had normal air in it, and normal air contains oxygen gas). And if a bunch
of hydrogen ends up somewhere that there’s a bunch of oxygen, then it can
go off like the Hindenberg (only smaller).
So the next thing that happened was there was a hydrogen explosion in the
top of the reactor building for Units 1 and 3 – or rather, in the metal
shed at the top of the reactor building, since the reactor building isn’t
airtight and all the hydrogen rose. The shed collapsed, releasing the small
amounts of radioactive steam that had been vented there (and more
impressively, explosion and loud noises and ooh fire and smoke!). Important
to note at this point: the pressure vessel and containment structure are
still intact – there is no direct line from the fuel to the environment.
The only radioactivity that was released was the slightly radioactive steam
that they previously chose to vent from the pressure vessel and containment.
At this point they chose to go with another option they had had all along.
This option, however, was sort of the last-choice option: adding seawater
to the pressure vessel, and if needed even filling the containment building
structure with it. This option was designed into the plant as yet another
safety system, in case they ever had a situation where they needed mass
amounts of coolant in a short time. And it sure is working: Units 1 and 3
have stable pressure as of this writing, and water levels appear to be about
halfway up the fuel rods and rising; Unit 2 is slightly behind but also
improving. [Safety system #11 (emergency seawater injection system): worked
as designed.] So why didn’t they do this from the start, or at least as
soon as they got electricity back to run the pumps? Because putting nasty,
gummy seawater, with minerals and algae and who knows what else, into your
nice clean shiny reactor is about like putting sugar in a car’s gas tank.
It’ll stop the car, alright – and then you’ll have a massive repair bill.
Units 1, 2, and 3 at Fukushima One will not run again unless most of the
components of the reactor are replaced.
14. So why did I overhear you say to that person that this was actually a
success for nuclear power?
First, at magnitude 9.0, this was one of the top ten strongest earthquakes
in recorded history. (Wow!) The subsequent tsunamis, combined with the
earthquake, make this one of the worst natural disasters EVER. (Also Japan
is apparently having a minor problem with a volcano, now. Guys can’t catch
a break.)
The reactors were designed 40 years ago, and in 2008 were certified for
ground motion corresponding to about a magnitude 6.7 earthquake right under
the plant.[11] The reason this ground motion was selected was that Japan’s
regulatory agency expected (rightly so!) that a ground motion stronger than
that had a chance of happening only once in 10,000 years. We lost the
statistical gamble on that one. But here’s the amazing thing: the
reactors did exactly what they were designed to do: and so did the other
nuclear units all over Japan. Only 7 of the 55 units in Japan [7] had any
trouble shutting down, and they were the ones closest to the epicenter. And
the trouble wasn’t even in the reactor, or the containment structure, or
the piping – all of these things performed exactly as designed! The
trouble was the tsunami that took out the fuel supply for the backup diesel
generators. Let’s recap with a statement from Steve at Neutron Economy: “
What this proves is that in the very worst scenario - a once-in-a-lifetime
earthquake beyond the design basis - that the systems can safely contain the
integrity of the reactor, particularly with well-trained personnel”. [5]
Second, these plants are 40 years old. They don’t incorporate all of the
safety advances we’ve made since then. As a matter of fact, I read that
these particular plants were already planned to be replaced with newer
designs – designs that have passive cooling and wouldn’t have required any
electricity to cool the core at all. (Can’t find the reference right now,
sadly.) The fact that a 40-yearold design survived as well as it did –
with no health impact to the public expected – is pretty awesome.
Third, as Rod Adams points out [2], let’s keep this in context with regards
to the damage to, and impacts of, the other energy sources in Japan.
Damage from the earthquake and tsunami includes a fire at an oil refinery
that is still burning; breaks in a hydroelectric dam, explosions in natural
gas systems, and tons and tons of battery and gasoline spills. There is
damage to the environment and danger to people from every form of energy
that we use today.
So nuclear’s looking pretty good, right now. Fear aside, I think we’re
going to end up with the least damage to life, health, and the environment
out of all the energy sources in use in Japan. (Except solar.)
15. Where can I get more information?
My best recommended sources for updates right now:
* http://www.tepco.co.jp/en/press/corp-com/release/index-e.html – TEPCO owns the reactors in question. This is their side for press releases.
* JAIF is posting regular updates: http://www.jaif.or.jp/english/
* http://ansnuclearcafe.org/ – the American Nuclear Society is collecting media updates on the situation as it unfolds. They also have a lot of links to other sources that are updating.
* You can also see NEI http://nei.cachefly.net/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/ and World Nuclear News http://www.world-nuclear-news.org/default.aspx.
* The Wikipedia timeline gets updated a little more slowly, but has a
lot of things in one place: http://en.wikipedia.org/wiki/Timeline_of_the_Fukushima_nuclear_accidents
16. Show your work! | S*******w
发帖数: 24236 | 2 太长了 总结下就是：
对生活影响不大
people
【在 l**a 的大作中提到】
: 删掉一些了。
: 链接如下
: plainenglishnuclear.blogspot.com
: .......
: 1. I live on the West Coast. Am I in danger?
: No. Absolutely not.
: You won’t even notice except that everyone will keep talking about it for
: ages, and it’ll take us even longer to get off coal and oil and natural gas
: because people will be afraid of nuclear power again. Go outside, get some
: sunshine (or rain, depending), be grateful for the fact that your city isn
| l*******r
发帖数: 39279 | 3 我同意
people
【在 l**a 的大作中提到】
: 删掉一些了。
: 链接如下
: plainenglishnuclear.blogspot.com
: .......
: 1. I live on the West Coast. Am I in danger?
: No. Absolutely not.
: You won’t even notice except that everyone will keep talking about it for
: ages, and it’ll take us even longer to get off coal and oil and natural gas
: because people will be afraid of nuclear power again. Go outside, get some
: sunshine (or rain, depending), be grateful for the fact that your city isn
| l*******r
发帖数: 39279 | 4 yes
it is too long
did you finish?
【在 S*******w 的大作中提到】
: 太长了 总结下就是：
: 对生活影响不大
:
: people
| S*******w
发帖数: 24236 | 5 看不下去 看到Q6.
【在 l*******r 的大作中提到】
: yes
: it is too long
: did you finish?
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