

Radiation leak reported at Japanese nuclear plant, 10km evacuation radius - anigbrowl
http://edition.cnn.com/2011/WORLD/asiapcf/03/11/japan.nuclear/

======
aperiodic
There's really not much information in this article, and consequently it reads
a tad sensationalist to me. Let me try to break this situation down as I
understand it.

IAANRO (I Am A Nuclear Reactor Operator. I work part-time at my college's
research reactor[1])

Nuclear power reactors are of two main varieties: Pressurized Water Reactors,
and Boiling Water Reactors[2]. The plant in question is a Boiling Water
Reactor (BWR). BWRs work by using the core's thermal energy to boil the
cooling water into steam, and then channelling the steam in order to turn a
steam turbine. After it exits the turbine, the steam is cooled in a condenser,
where it turns back to water, and then is sent back into the core. The
condenser requires cool water to be actively pumped through it, to keep the
pipes upon which the steam condenses from becoming too hot. The water/steam
that runs through the core and the turbine is referred to as the "primary
cooling system", and the water running through the condenser is the "secondary
cooling system." The primary is assumed to be contaminated (that is, it is
measurably radioactive), whereas the secondary system is not, since it is
isolated from the primary.

As far as I can tell, the chain of events for this particular plant went
something like this:

Shortly after the quake, the reactor successfully shut down in anticipation of
the tsunami. This means that no more fission is occurring in the core. Since a
core meltdown is a result of uncontrolled fission, this means that the reactor
is now incapable of melting down. This will not be another Chernobyl. However,
just because U-235 is no longer fissioning, doesn't mean that the core isn't
producing heat. The fission fragments (those isotopes produced as a result of
the U-235 fissioning) will continue to decay through alpha, beta, or gamma
emission, until stable elements at the bottom of the decay chain are reached.
The decay of these fission fragments and their decay products will cause the
core to continue to produce heat for some time after shutdown.

Presumably due to the fact that every reactor near the east coast of Japan was
being shutdown, offsite power for the secondary cooling system was
unavailable, so the power plant had to rely on onsite backup power, but the
onsite power only lasted for 8 hours. After that, the secondary cooling system
failed, which is what triggered the declaration of the Nuclear Emergency, and
evacuation of those living within 3Km of the plant.

Since the core is continuing to produce heat, and consequently steam, the
steam pressure inside the primary system is rising above normal levels. They
are hesitant to bleed off steam into the containment dome, since the dome was
probably damaged in the quake, but obviously bleeding off some steam is better
than having the primary system rupture. Thankfully, most of the really nasty
decay products have a relatively short half-life. In particular, Nitrogen-16,
which gives off pretty high energy betas when it decays, has a half-life of
7.2 seconds.

Therefore, releasing the steam is undesirable, but not catastrophic, and
probably not even particularly hazardous. The radioactive materials in the
cloud will be longer-lived decay products of hydrogen and oxygen in, and as
far as I'm aware none of those are particularly active. The cloud will be
dilute itself after release, which will lower the intensity of the radiation
field significantly. Therefore, the total radioactivity release will be many
orders of magnitude lower than that of Chernobyl or Three Mile Island. The
media is playing this up to be bigger than it is, because nuclear power still
carries a stigma.

[1]: Reed Research Reactor: <http://reactor.reed.edu/>

[2]: Wikipedia Article on Boiling Water Reactors:
<http://en.wikipedia.org/wiki/Boiling_water_reactor>

~~~
w1ntermute
> IAANRO (I Am A Nuclear Reactor Operator

WDYJUAULAAATIEIATDTPOTAESYKIWNBUA? - Why did you just use an unnecessarily
long abbreviatory acronym and then immediately expand it and thus defeat the
purpose of the abbreviation, especially since you know it will never be used
again?

~~~
hallmark
To juxtapose with the IANAL that is imprinted in all our minds (just behind
our reading eyeballs) to show that he _does_ have authority on this subject.

------
dmfdmf
Please be aware that there is a lot of scare-mongering and "worst-case"
scenarios being reported in the press. (Enviros don't want to waste a crisis
for their anti-science agenda).

It would not be unusual for there to be radiation released during an emergency
reactor shutdown (scram) with equipment damage due to the earthquake. It does
not necessarily imply core damage or melt down. The primary coolant system of
a BWR is radioactive due to neutron activation but that type of radioactivity
is short lived, emergency release during over pressure may have been necessary
to maintain the integrity of the cooling system. If the reactors are shutdown
the situation is fairly stable and the operators have numerous options (and
time) to deal with the equipment failure and insure the core is adequately
cooled of residual heat. I am waiting for more info as not enough details are
getting out at this point...

N.B. I used to design BWR feedwater control systems. AMA

~~~
marshray
The operator is saying they've "lost control of the ability to control
pressure in some of the reactors". The cooling systems of three reactors at
another plant are "malfunctioning".

How do we read that?

~~~
patio11
I would read that in knowledge that a Japanese company producing _cell phone
camera gaskets_ where any two in a batch of 1,000 were defective would report
"the manufacturing process is out of control" and the $10 an hour operator
would have scrammed production until the engineers investigated and fixed the
machinery.

If you knew _nothing_ of Japanese engineering culture, would today's
unceasing, relentless drumbeat of lack-of-catastrophe worry you?

~~~
marshray
When a government minister reports that the cooling system is offline and the
pressure is 2.1x design norms, I don't think that's a cultural thing
comparable to a 2-in-1000 bad gasket production shutdown. But maybe it is.

These guys seem pretty matter-of-fact: [http://www.tepco.co.jp/en/press/corp-
com/release/index-e.htm...](http://www.tepco.co.jp/en/press/corp-
com/release/index-e.html)

For example: "Reactor Core Isolation Cooling System was used to inject water
into the reactor to cool it. Today at 4:50AM, water injection by Make-up Water
Condensate System begun. Subsequently, at 5:32AM, the temperature of the
suppression chamber exceeded 100 degrees. As the reactor pressure suppression
function was lost, at 5:32AM, it was determined that a specific incident
stipulated in article 15, clause 1 has occurred."

This sounds like a mechanical regulatory reporting issue.

Other text like:

"We have decided to implement measures to reduce the pressure of the reactor
containment vessel for those units that cannot confirm certain level of water
injection by the Reactor Core Isolation Cooling System, in order to fully
secure safety."

I'm just wondering how to interpret this. For example, when they say "reactor
containment vessel" do they mean the "reactor vessel" or the "containment
building" in en.wikipedia.org terminology?

Why couldn't they "confirm certain level of water injection" in some units? Is
it that the plant design didn't include the necessary sensors, or that they
were damaged?

------
jarin
This is why we should be investing in thorium reactors:

[http://en.wikipedia.org/wiki/Thorium#Thorium_as_a_nuclear_fu...](http://en.wikipedia.org/wiki/Thorium#Thorium_as_a_nuclear_fuel)

They apparently self-regulate in the event of a power loss, plus they can be
used to "burn up" spent fuel from traditional reactors.

~~~
pjscott
That doesn't really apply here. Any decent nuclear reactor will shut itself
down when things get hairy. The reactors in question all shut down, very nice
and orderly. The remaining issue here is dealing with the decay heat from the
fission products in the fuel. _That_ is what's overtaxing the cooling system
right now.

------
anigbrowl
'150 micro sievert per hour in control room' - not so bad as I feared, as long
as it's not rising.

[http://www.yomiuri.co.jp/national/news/20110312-OYT1T00153.h...](http://www.yomiuri.co.jp/national/news/20110312-OYT1T00153.htm?from=top)
via google translate.

------
anigbrowl
Correction: 3km evacuation radius (TEPCO bulletin [1]), 10km radius residents
urged to remain indoors (NHK).

 _Evacuation has been instructed by the national government to the local
residents within 3 km radius of Fukushima Daiichi Nuclear Power Station_

 _Measurement of radioactive material (Iodine, etc.) by monitoring car
indicates increasing value compared to normal level. One of the monitoring
posts is also indicating higher than normal level. We will continue monitoring
discharge of radioactive material from exhaust stack and discharge canal,
etc._

 _We have decided to implement measures to reduce the pressure of the reactor
containment vessel for those units that cannot confirm certain level of water
injection by the Reactor Core Isolation Cooling System, in order to fully
secure safety._

[http://www.tepco.co.jp/en/press/corp-
com/release/11031210-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031210-e.html)

~~~
anigbrowl
Updated: NHK now says evacuation zone expanded to 10km after all.
<http://www3.nhk.or.jp/daily/english/12_25.html>

Your guess is as good as mine.

------
anigbrowl
Situation is somewhat ambiguous, understandable given the confusion and
circumstances. Commentator in Japan expressed '90% confidence', however.

<http://yokosonews.com/live> English audio live, mainly translation of...

<http://www.ustream.tv/channel/tbstv> live japanese tv

Ustream pages have annoying 30 second advert on load.

<http://www3.nhk.or.jp/nhkworld/index.html> English, but slow to update

[http://www.tepco.co.jp/en/press/corp-
com/release/index-e.htm...](http://www.tepco.co.jp/en/press/corp-
com/release/index-e.html) Power company hourly bulletins

<http://www.bbc.co.uk/news/world-asia-pacific-12720219> some live material,
updates a bit erratic at the moment.

~~~
jarek
> Situation is somewhat ambiguous, understandable given the confusion and
> circumstances.

In fact, I am amazed how well-understood the situation is considering the
circumstances. We're less than 24 hours after one of the five strongest
earthquakes on human record, half a world, a language, and a culture away -
that we know as much as we do about the situation is a marvel in itself.

------
tsotha
>Three of the Fukushima Daiichi reactor's six units shut down because of the
earthquake, while operations at the other two were out due to "regular
inspection," the Tokyo Electric Power Co. said in a news release Saturday.

I always wondered what happened to the sixth replicant.

------
ggordan
Both reactors at the plant have been damaged, and officials say they have
"lost control" of the pressure, according to Reuters.[1]

[1] [http://www.businessinsider.com/fukushima-nuclear-
plant-2011-...](http://www.businessinsider.com/fukushima-nuclear-
plant-2011-3#ixzz1GJKHx9hB)

EDIT: this is the latest update from business insider

------
anigbrowl
Updated, but no new information - just a compliance statement.

[http://www.tepco.co.jp/en/press/corp-
com/release/11031213-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031213-e.html)

[http://www.tepco.co.jp/en/press/corp-
com/release/11031212-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031212-e.html)

<http://www.nsc.go.jp/NSCenglish/documents/laws/8.pdf>

------
guscost
Well, it's certainly reassuring to see that people here don't fall for these
scare tactics easily. Can't say the same for most other web communities.

------
anigbrowl
New TEPCO bulletin just confirms expansion of evacuation zone to 10km around
Daiichii and Daini plants (ie #1 and #2). No other news, which is the closest
thing to good news.

[http://www.tepco.co.jp/en/press/corp-
com/release/11031211-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031211-e.html)

------
kgtm
This saddens me deeply. Two reactors damaged, the officials stating they have
lost control of the pressure. I hope the Japanese people find a way to secure
the site, but I'm afraid the world must be getting ready for another
Chernobyl.

~~~
jedsmith
Multiple nuclear engineers on Hacker News have written that the situation is,
effectively, far less dire than Three Mile Island. All of them have said there
are still options and time before core damage is even on the radar. You're
scaring a lot of people for no reason.

I trust Bob the self-proclaimed nuclear engineer on HN more than CNN, anyway,
even though I have no idea Bob is who he says he is.

~~~
kgtm
My post was before the nuclear engineer appeared on this thread and my sources
were the publicly available ones, which portrayed things rather grim.

Maybe i was not very subtle, but you must understand that i too am scared,
having experienced the Chernobyl events and the aftermath (European here). But
most of the downvoters don't even know what that feels like. Did i over
exaggerate my worries? Perhaps. I'm not known to be an overly optimistic
person.

Thanks for giving me the chance to reply.

~~~
lukeschlather
Chernobyl was a result of Soviet disregard for safety and human lives, not
nuclear power.

~~~
jarek
Chernobyl was the result of a systemic failure too complex to sum up in one
sentence.

