

Japan Does Not Face Another Chernobyl - dicemoose
http://online.wsj.com/article/SB10001424052748704893604576198421680697248.html

======
dicemoose
Really appreciated the following especially as I try to balance local (JP)
coverage and international news. "With all the death, devastation and disease
now threatening tens of thousands in Japan, it is trivializing and almost
obscene to spend so much time worrying about damage to a nuclear reactor."

~~~
marshray
_"it is trivializing and almost obscene to spend so much time worrying about
damage to a nuclear reactor."_

* The nuclear situation is changing by the hour and people are making decisions and actively managing it.

* Having 3 to 5 nuclear reactors under various stages of meltdown is a big story in its own right. The existence of massive loss of life nearby does not diminish its importance.

* The earthquake+tsunami event is unlikely to get worse and there little people are able to do to prevent it anyway.

* Conflicting information keeps coming out about possible worst case scenarios (and their relative likelihoods) with the nuclear reactors.

* Some of these scenarios are, in fact, much worse than even the current unimaginably bad scenario. Just because things are bad doesn't mean they couldn't get worse.

* This has definite implications this for US and global energy policy. In my view, it's probably best to hold off that debate until these incidents are concluded and informs our hindsight, but the discussion is inevitable.

* The nuclear incidents are affecting rescue and cleanup. Rescue is hard enough without a 20km evacuation going on at the same time. For example there are reports that the US Navy had some ships which needed to relocate due to detected radiation.

* Tokyo, one of the largest cities in the world, faces a power shortage. Commuter trains are not running. It is unclear how long this will persist. This is a huge economic impact in its own right.

~~~
mpyne
> Conflicting information keeps coming out about possible worst case scenarios
> (and their relative likelihoods) with the nuclear reactors.

There is only one worst-case scenario, so although I very much agree that the
information coming out of Tokyo Electric Power Co. and the Japanese national
government is inconsistent, that doesn't mean new "worst-case" scenarios
become possible.

IMHO the worst-case scenario is fuel melting through the reactor pressure
vessel, through the thick steel containment which was not damaged in the
hydrogen explosion, and through the bottom of the concrete containment (the
top of which was damaged), and then from there into the environment.

The worst-case plausible scenario from what I can tell (which again, has been
true from the moment they lost cooling systems for decay heat removal) is fuel
melting to the bottom of the reactor vessel, possibly breaching the primary
boundary but getting trapped by the steel containment, with possible further
release of gaseous radioactivity.

I say this because cooling the fuel if it is outside the primary but inside
the steel containment is much easier than cooling the fuel inside the primary:
you must merely submerge the steel containment in seawater (which would boil
away as it heats up), but this time you don't have to worry about pumping to
high pressures. The fuel was transfer its heat across the steel containment to
the seawater.

As long as the steel containment is intact (as was true last I heard, but
refer to my earlier point about TEPCO) then there would be no additional
release of radioactive contamination from this. If there are air leaks in the
containment that would be worse, but a portable radiation monitoring device
would quickly identify such areas so they can be quickly patched or covered to
at least keep contamination from spreading.

So, I also disagree with "unimaginably bad". Unimaginably bad might be
something like coal slurry breaking through its retention walls and killing
all aquatic life in a nearby river for hundreds of miles (as actually happened
in Kentucky in 2000 IIRC). At my last check all three reactors that had been
operating at Fukushima-Daiichi have probably had fuel damage, which means that
any steam they vent from the plant will contain radioactive contamination. So,
definitely bad.

Unfortunately I can't seem to find to many numbers for activity concentration
(how frequently the radionuclides are actually decaying) or for dose rate (a
measure of biological damage per unit time). A Guardian article mentions 680
microsievert per hour to the northwest of the site, which would be 68
millirem/hour, which is a value that is actually fairly high, but far below
levels that would lead to immediate health risk.

For a point of comparison, there are (inhabited ;) spots in the world (Ramsar,
Iran) where you would receive 70 millirem/day, every day, which is far above
what a trained radiation worker would be permitted to receive and yet still
appears to have little (if any) effect on the local population.

Of course any unnecessary exposure is unacceptable! But I also wouldn't come
close to calling it "unimaginably bad", except in regards to the economic cost
to TEPCO and the substantial loss of generating capacity (which as you
mention, can have a substantial economic impact).

~~~
marshray
By "unimaginably bad" I meant the earthquake+tsunami disaster scenario. This
is now the unfortunate baseline against which the nuclear issues are, perhaps,
the most significant remaining unknowns. Reading again what I wrote I see it
was ambiguous.

 _There is only one worst-case scenario, so although I very much agree that
the information coming out of Tokyo Electric Power Co. and the Japanese
national government is inconsistent, that doesn't mean new "worst-case"
scenarios become possible._

This is an interesting question.

Repeatedly we've seen commentators and outside observers saying "this can be
no Chernobyl because...". But the situation at Fukushima-Daiichi is still very
dynamic and many questions remain. These cores still have a lot of energy left
to dissipate and thus each still seems to have a life of its own.

As much as we would like to know the current state of the reactor cores and
all the possible paths they could take, the picture emerges that those
officials in charge of the mitigation efforts don't have a perfect picture
either.

Whether there are multiple worst case scenarios, or there is only one that we
can't see clearly yet seems to be a philosophical question about a highly
physical phenomenon.

~~~
mpyne
> Repeatedly we've seen commentators and outside observers saying "this can be
> no Chernobyl because...".

Yes, because this can't be a Chernobyl. I do understand that you don't exactly
have time to train yourself on the ins and outs of nuclear energy. But if
you're really interested in the topic, Wikipedia actually has good articles on
Chernobyl and the Chernobyl disaster, including a lot of information on the
_design flaws_ that were present in the Chernobyl design, flaws which are not
inherent to either nuclear plant design in general, or the Fukushima boiling
water reactors in particular.

> But the situation at Fukushima-Daiichi is still very dynamic and many
> questions remain.

I agree. But that does _not_ mean that any disaster conceivable is in the set
of possible outcomes of the casualty. Although I know it may not seem like it,
especially with all the confusing and contradictory information being put out,
but what has occurred up to this point has occurred almost like clockwork from
the initial conditions leading up to the casualty and the actions taken (and
unable to be taken) thereafter.

A full nuclear fuel meltdown has been the final disaster since the start. The
bad things that have happened since then have taken TEPCO progressively closer
to that stage but as I said before, it's not like there's a multitude of
different paths for the casualty to go down.

> These cores still have a lot of energy left to dissipate and thus each still
> seems to have a life of its own.

Yes, but the response is _completely predictable_. Everything that has gone
and is currently going on (as far as the nuclear core response goes) is due
just to the laws of nature. Decay heat is a well-understood concept (it is,
after all, why so many redundant systems were part of the design in the first
place), and the decay heat itself depends fully on things which can be figured
out before shutdown, such as average power level, operating time, etc. It's
not like some nuclear fuels have randomly different heat generation profiles
and the Fukushima plant happened to pick up the super-reactive uranium.

The only variable so far has been how much cooling could they provide? So far
it hasn't been enough, but that hasn't changed the underlying phenomena, and
the worst case is completely predictable (i.e. no cooling could be provided
whatsoever under any circumstances).

This is not like the weather where the phenomenon interact in such a chaotic
way that it's effectively unpredictable: Decay heat production is easy to
predict (to at least a general approximation) and even the decay of that
residual decay heat over time is predictable. Even the hydrogen production
from steam-zirconium reaction is a well-known and predictable effect, even
during the time of Three Mile Island. The hydrogen explosions _themselves_
were unpredictable, but even they were unsurprising.

If this is all surprising to you because it's the first you've been exposed to
nuclear theory then don't feel bad, but that doesn't make what's happening at
the Fukushima-Daiichi plants at all unpredictable or chaotic, or for that
matter, philosophical.

~~~
marshray
I've actually read a good bit about it. E.g.: <http://www.nrc.gov/reading-
rm/basic-ref/teachers/03.pdf>

I know it's not voodoo and obviously the laws of physics are well understood,
but it also seems like there hasn't been enough experience with actual
meltdowns that these things are entirely predictable.

I understand that the Chernobyl design contained a large quantity of graphite
and little containment beyond the vessel itself.

But I still have questions:

* If the engineering is well-understood, then why did the buildings blow up due to accumulated hydrogen?

* Do these reactor designs (GE Mk I and II) include a "core catcher"? Some analysts act like it's obvious that they do, but I find no mention of it in the NRC docs. Mainly it's counted as a feature of more advanced designs.

* What does it mean for the suppression pool to be damaged? Was that optional equipment? It's being described as the "last line of defense" by a smart-looking fellow from Tokyo U.

* Can the control rods fall out? They don't drop in from above, they're pushed up from the bottom hydraulically.

* Do the materials of the fuel and the control rods melt at different rates? It seems like this could result in the materials separating as they melt and a partial core re-igniting as a lump at the bottom of the vessel. Or was this possibility considered and designed against in this '60s-era reactor?

* What is the real implication of the plutonium in the MOX fuel in Fukushima Daiichi reactor No.2? They were mostly exposed for 2+ hours.

And so on...press conference on NHK world right now (available on ustream.tv
nhk-world-tv).

~~~
mpyne
Now these are better questions. :)

As far as hydrogen goes, the building itself was not designed to be the
containment (instead there's a hefty steel containment around the reactor and
primary piping from what I understand), so I don't think they bothered trying
to make the building resistant to explosion from the inside (since they didn't
have to). It would still be better to have the building in place, but I think
the answer is as simple as it wasn't necessary for the meltdown casualty
analysis.

I'm not sure if the Mk I and II containments contain a core catcher or not.
Modern designs do from what I understand, but I would imagine the Mk I does
not. Perhaps the Mk II does.

The Three Mile Island core suffered much greater fuel melting and still didn't
make it past the reactor vessel, but a lot of that depends on core geometry as
melting progresses, and the TMI reactor vessel was much stronger than the
Fukushima plants since TMI was a pressurized-water reactor. On the other hand,
the Fukushima designs have the steel containment that would catch any core
leakage out of the primary initially and as long as they have seawater
available they can keep the steel containment intact, and without having to
send that seawater into a high-pressure system.

I'm not sure what they mean by damage to the suppression pool. The suppression
pool is a torus of water that steam from the primary system is ducted to when
pressure relief valves lift, which acts to condense the steam and help with
filtering some of the radioactive contamination to keep it from going
airborne. Doing this heats up the suppression pool, which will itself boil
eventually.

I assume this is what they meant when they talked about venting the
containment (as opposed to the reactor or primary). Anyways, if the
suppression pool is damaged I assume that means there is a leak of the water
inside of it, which would leak to the bottom of the steel containment. Without
water in the suppression pool any venting of the reactor would not be
immediately condensed, and would cause higher levels of airborne radioactivity
inside the containment building for Unit 2 (intact AFAIK). This would not
affect the ability of venting the reactor to lower pressure though, which is
important for allowing water to be forced into the coolant system.

Anyways, some of my IRC buddies have clued me more into a blast at Unit 2's
suppression pool? I'll try to read up on that. Until then:

According to [http://rushi-langaliya.blogspot.com/2011/01/boiling-water-
re...](http://rushi-langaliya.blogspot.com/2011/01/boiling-water-reactor-bwr-
advantages.html) control rods are inserted into the core from the bottom. I'm
not certain of BWR design but obviously if all the metal is melted then the
control rod could fall out (this was actually a concern with Chernobyl which
used metals with very low melting points to hold up control rods). I will say
the plant I was on had about 5 different ways to keep control rods in position
whether there was power or not so I'd be very surprised if the control rods
weren't latched in place now at the very least. But I don't know for sure,
don't want to tell you otherwise.

* I don't know what their control rods are made out of, but the good assuming is that control rods melt after fuel does. That actually means the fuel would melt _down_ away from the control rods before lumping up. If there is coolant there, the fuel shouldn't melt further. If there is no coolant, the nuclear chain reaction can't go critical again since the fuel is not enriched enough (the coolant actually also helps aid the neutron chain reaction). I can't speak to reactor protection analysis for BWR to that level of detail, but again I'd be very surprised if that's something that wasn't considered _at some point_ between the 1960's and the last couple of years.

If they had considered it and concluded there was a risk of re-criticality
they would have taken measures to preclude it. That might be why they're
already using boric acid for instance.

As far as plutonium, it has a fairly long half-life, which means it's not very
radioactive. With that said it is an alpha-emitter so it is very important
that it is not inhaled. As long as it's not inhaled it's not a large concern
from there radiologically. As with any other heavy metal though, it is highly
dangerous chemically.

Hopefully better information gets put out at the press conference.

~~~
mpyne
Man, wtf happened at Unit 2? I keep repeating the NHK broadcast and I'm not
sure whether the suppression pool itself suffered damage and not the reactor
vessel, or both, or what.

They mentioned radiation going up right after the explosion, which could
indicate a reactor vessel or other primary piping rupture, but could also just
be from trapped radioactive contamination in the suppression pool being thrown
out by the explosion.

Either way it's important to make sure they don't allow the concrete building
shell to get damaged at Unit 2 if they want to avoid further airborne release.

~~~
marshray
It's almost as if they're speaking in code. They don't want to spread panic,
but they also can't hide the reality too much from those who understand
engineering.

My theory is that the vessel pressure vented into the suppression pool which
caused the drop in pressure. That could have made a loud noise, perhaps one
they had never heard in testing. Since the pool is a metal torus containing
water held up by concrete and tightly coupled to the other parts it's a rigid,
massful, structure. It may have been damaged by the quake.

If the radiation is explained by the spent fuel fire at unit 4, the question
remains whether or not the containment on unit 2 is still effective.

------
vilhelm_s
I certainly agree with his main point: the nuclear reactor accidents are a
comparatively small part of the earthquake catastrophe. But the rest of the
article reads like pure propaganda-- like he started out writing the article
with the goal of downplaying rather than assessing the risks involved.

I can spot at least one inaccuracy. He claims that TMI showed that there is no
risk of nuclear fuel melting through the steel containment structure. But at
TMI, the core was actively cooled through the entire incident, and the
temperatures were not even high enough to melt the fuel itself. So this does
not given any information about what would happen in the absence of cooling.

~~~
webXL
I wouldn't call it propaganda if your merely trying to get people to put facts
of an entire tragedy into the proper context. Yesterday morning I turned on
the ABC and saw this: <http://yfrog.com/h7r6rmcj> CNN has been treating the
nuclear accidents with equal importance, just because they know it freaks
people out, _publishing_ numerous errors on their website, according to one
MIT scientist (Dr Josef Oehmen):
[https://morgsatlarge.wordpress.com/2011/03/13/why-i-am-
not-w...](https://morgsatlarge.wordpress.com/2011/03/13/why-i-am-not-worried-
about-japans-nuclear-reactors/)

Don't get me wrong, there is definitely propaganda on both sides, but the
anti-nuclear crowd pouncing on this before we have all the facts, and while
there's a race against the clock to find survivors and prevent more loss of
life, is counter-productive.

~~~
hcurtiss
Thank you for the Oehmen link. Supremely useful.

~~~
Lazlo_Nibble
I've seen a lot of people latch on to this writeup as authoritative, and I'm
not sure why. Oehmen may indeed be a "research scientist" at MIT but his
specialty is _supply-chain risk management,_ not reactor design
(<http://web.mit.edu/oehmen/www/>). Is there any reason to believe that he's
anything more than an interested amateur on this topic?

~~~
knshaum
The post has been moved, and updated by members of MIT's Nuclear Science and
Engineering community: [http://mitnse.com/2011/03/13/why-i-am-not-worried-
about-japa...](http://mitnse.com/2011/03/13/why-i-am-not-worried-about-japans-
nuclear-reactors/)

~~~
Lazlo_Nibble
Possibly relevant: [http://geniusnow.com/2011/03/15/the-strange-case-of-josef-
oe...](http://geniusnow.com/2011/03/15/the-strange-case-of-josef-oehmen/)

------
neutronicus
That article makes it sound like the decision to use graphite is stupid and
will never be made again. This isn't true, a lot of the gen-4 designs are
graphite-moderated.

~~~
api
But I am sure they take into account the properties of graphite, and I'm sure
making sure that Chernobyl thing doesn't happen is high on the list.

~~~
neutronicus
Right, just pointing out that graphite is not in and on itself a stupid
choice.

------
face
I think it's relevant to point out that this is not a news article written by
a reporter; it is an opinion piece written by someone who has a very specific
viewpoint.

This is not ad hominem, I am not claiming anything about the correctness of
his claims. However, I think it is important to distinguish this from the
other numerous WSJ pieces on the situation of nuclear plants in Japan right
now.

~~~
VladRussian
>it is an opinion piece written by someone who has a very specific viewpoint.

whether a core melts through the containment vessel or not depends on specific
temperature that pool of melted uranium on the floor will develop. That in
itself depends on the geometrical shape of the pool, uranium enrichment degree
and presence of the neutron moderator material in the pool. That in itself
depends on a bunch of other things ...

Nowhere it depends on the opinion or a viewpoint.

------
btmorex
This is a bad article.

1.) He argues that the three mile island accident means that the containment
vessel will hold now. Even if they were the exact same reactor design, that
doesn't logically follow, but they aren't the same design which gives even
less credence to this argument.

2.) He says that once the reactor is flooded with water they won't have to do
any more pressure releases. Again, I don't see how that follows. As long as
there is enough residual heat to boil water, there's certainly a possibility
that they will have to do more pressure releases.

~~~
ars
1.) Reactors aren't magic. They have very well defined properties. It's pretty
easy to calculate if a containment vessel will hold. This type of engineering
happens every day in every building you go in and every car you ride.

2.) The containment structure is quite large, and the residual heat is
relatively low. There is a lot of water there, presumably too much for the
residual heat to boil. (The water normally flows only in the much smaller
reactor vessel.)

~~~
adsr
Three reactors are affected, and two plants, Fukushima and Onagawa. I would
say that an earth quake and tsunami is outside the well defined.

~~~
rdtsc
> I would say that an earth quake and tsunami is outside the well defined.

But at the same time they are not completely independent events. Quite the
opposite. It is likely that an earthquake will be followed by a tsunami.

If they engineered it so that 2 events: quake and flood are independent, then
they made a mistake. Possibly there is nothing they could do but I doubt that.

This is somewhat similar to the birds and airplane engines. It is assumed that
once in a while a bird will hit an engine and possibly take it out. No big
deal, there are 1,2 or 3 more engines. But the problem is that birds fly in
flocks. So chances are that the plane will fly into a flock of birds and all
engines will go out. Which is what happened a year or two ago. Now there is
probably not much they could do but hopefully at least they didn't assume that
invidual engine failure due to bird hits would be completely independent
failure events.

~~~
adsr
Completely agree with this. On the other hand, all their safety mechanisms so
far have failed. Electric, diesel based and the automatic steam based. Which
is why they now manually try to pump in sea water (according to what I have
understood from the news). I'm not against science, but still, it seems that
the situation is surrounded by a fair amount of uncertainty. So, to my way of
thinking the most wise is to treat it as an uncertainty, until we know more
from official sources.

~~~
mistermann
>On the other hand, all their safety mechanisms so far have failed. Electric,
diesel based and the automatic steam based.

Wrong and wrong. Some backup cooling mechanisms have failed, not all safety
mechanisms.

The electric backup worked as designed. The diesel backup did not, as I
understand it, because it was affected by the tsunami (which is inexcusable in
my opinion). And the backup diesel generators brought in from off-site, _from
what I've read_ , could not be attached due to incompatible connectors (which
if true, is also inexcusable).

~~~
adsr
>The electric backup worked as designed.

No, that is the reason they where suppose to fall back on diesel based pumps.
The electrical outage after the quake made the electric pumps fail. The diesel
based pumps also failed as we agree upon. After that there was a mechanism
simply based on preasure which supposed to push out hot steam, cool it off and
feed it back as water. However this mechanism led a decreased level of water
(from what I have heard). Which is why they now resort to pumping it in
manually. I think it's safe to say that two major explosions at the plant
(even though it wasn't the reactor it self apparently) is a sign of failed
safety mechanisms.

~~~
krschultz
There are batteries, they ran the pumps for almost 8 hours. That was one of
the backups.

~~~
adsr
Yeah you are right, but that wasn't sufficient enough to solve this on the
other hand.

~~~
mpyne
Well the batteries are exactly the "electric backup" that was mentioned,
although you're also right in that it was never designed to solve the entire
casualty, only to last long enough to get other sources of power online.

------
tea3
If there is no risk of the second containment level being breached why do
newer reactors have a third level containment (which is missing from these
older reactors)? I'm just curious.

~~~
_delirium
One reason is "the last level of containment held" doesn't give engineers the
safety margin they want, or the public-reassuring PR they'd want. Much better
to be able to say that the last level of containment is never even relied on,
but is purely insurance.

~~~
tea3
Thank you. If the fission reaction has indeed stopped, I wonder if whatever
heat is still being generated (especially if the fuel rods are exposed and
enough heat exists to melt the cladding) would still pose some danger to the
pressure vessel?

------
orblivion
"These produce radiation at about the level of one dental X-ray in the
immediate vicinity and quickly dissipate."

How do you compare nuclear radiation/poisoning (apples) to electro-magnetic
radiation (oranges)?

~~~
gallamine
It's all electro magnetic. It's an issue of energy. See:
<http://en.wikipedia.org/wiki/Ionizing_radiation>

~~~
kahirsch
No, it's not all electromagnetic. Alpha, beta, and neutron radiation are not
electromagnetic radiation.

There's also a very big difference between radiation and radioactive isotopes,
which can be inhaled or ingested.

------
fxj
do the math:
[http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.nav...](http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.navy.radiation/)
says the USS Ronald Reagan has been 100 miles away when "airborne
radioactivity" was detected, and
[http://www.dailymail.co.uk/news/article-1366055/Japan-
earthq...](http://www.dailymail.co.uk/news/article-1366055/Japan-earthquake-
tsunami-Navy-crew-months-radiation-1-HOUR.html) says that U.S. Navy crew in
relief effort get a month's radiation in just one hour. From wikipedia: The
worldwide average background dose for a human being is about 2.4 millisievert
(mSv) per year, which is 0.2 mSv per month. i.e. 100 miles away they measured
0.2 mSv/h which, if we assume a r-squared dependency, 2 Sv/h within one mile
at the reactor. Let's be conservative and assume linear dependence, then we
still have 0.02 Sv/h which is a rather significant dose per hour. A dose
greater than 0.5 sievert (Sv) is considered to be a high dose of radiation.
With absorbed doses of 1 to 2 Sv and above, mortality is expected to be about
20%, according to radiation medicine specialists. Above a dose of 7 Sv the
survival rate is zero.

~~~
bhousel
The pilots picked up the radiation while flying around the plant as it was
venting steam. They didn't pick up that radiation at the aircraft carrier 100
miles away, so your assumptions about crazy high levels of radiation at the
facility don't add up at all.

~~~
fxj
the ship personnel got the dose!

[http://abcnews.go.com/International/uss-carrier-ronald-
reaga...](http://abcnews.go.com/International/uss-carrier-ronald-reagan-moved-
detecting-radioactive-plume/story?id=13129409)

"The maximum potential radiation dose received by any ship's force personnel
aboard the ship when it passed through the area was less than the radiation
exposure received from about one month of exposure to natural background
radiation from sources such as rocks, soil, and the sun," Davis said.

According to 7th Fleet Commander and Spokesman Jeff Davis, the ships were
moved away from the downwind direction of the plant as a precautionary measure
on Sunday.

------
VladRussian
in Chernobyl it was burning graphite, in this case we have water being
separated into hydrogen and oxygen and later explosively recombining back -
the 2 reactors have exploded so far.

The differences:

\- burning graphite was adding energy, in the current water case - the energy
is provided only by the core.

\- containment structure.

So, while there is obvious similarity to Chernobyl, there is very significant
quantitative difference as to the intensity of the process. As long as the
core temperature going down, it should be fine. Is it going down?

------
moblivu
With everything the Japanese are passing through at least they have some good
news! I hope there will be a good ending to this !

~~~
zeigotaro
Not sure I would describe the permanent loss of a critical power plant as
"good news," but the aversion of a large radiation leakage is certainly less
bad.

~~~
moblivu
Well with what their living knowing that a nuclear reactor won't blow up is
still good news. I really hope it doesn't get worst...

------
bluedanieru
I keep hearing that this is the second-worst nuclear disaster after Chernobyl.
Folks, this isn't even the second-worst nuclear disaster _on Japanese soil_.

~~~
bluedanieru
Gee, thanks for the downvote. Why don't you come on over to Tokyo and we can
have a chat about it.

