This is an expanded and corrected version of the prior post in this
thread.
I think the primary danger from Fukushima 1 lies in the fact it uses
MOX fuel (mixed oxide fuel, the oxides being of uranium and
plutonium). Also, there is a vast amount of stored fuel outside all
the reactor containment vessels. There is at this point no telling
what the condition of the stored fuel rods is. In addition,
plutonium produces a lot of neutrons, which increases the chances for
spontaneous chain reactions if the fuel melts into a blob. These
would be small explosions or thermal excursions, but still very
dangerous, and possibly repetitive if the material is located in a
confined space, like a hole bored into the ground.
See:
http://www.washingtonpost.com/business/economy/nuclear-crisis-deepens-
as-third-reactor-loses-cooling-capacity/2011/03/14/ABk6rQV_story.html
http://tinyurl.com/67tp62y
"A commercial satellite photo of the complex showed piles of debris
on top of units 1 and 3, which raised new fears about the condition
of the pools where spent fuel is stored, especially at unit 1, where
a design by General Electric placed the pool on top of the reactor
but below the outer structure that was destroyed. The ability of
workers to assess the damage was hindered by fears that another
explosion might occur."
"In March 2010, 1,760 tons of spent fuel was stored in the six pools
— 84 percent of capacity, according to Tokyo Electric."
That is over 250,000 kg of uranium (plus possibly some plutonium in
the case of MOX) per storage pool on average. What is that going to
do if it melts into a blob and starts boring a hole into the earth?
That's a rhetorical question. For many answers google(China syndrome).
That 250,000 kg contains many times the fissionable material in an
atom bomb. This is a big problem even given it is almost all U238.
MOX fuel, used in unit 3, is a *huge* problem. Plutonium is one of
the most radiologically poisonous materials on earth. Pu242 has a
half-life of 376,000 years. The atomic bomb Little Boy, dropped on
Hiroshima, had 64 kg of uranium. Fat Man, dropped on Nagasaki,
contained 6.2 kg of plutonium. For background information on Fat Man
and Little Boy see wikipedia.
Material that melts down inside the reactor steel containment has a
chance of cooling down, due to the presence of control rod material,
which should end up in the mess along with the fuel glob. However,
spent fuel storage does not include control rods. It amounts to a
water pool with storage racks. If the pool leaks the fuel rods can
be exposed.
Lesson learned too late: don't store fuel rods near reactors that
have to be cooled and might explode. Second lesson: MOX fuels are a
very bad idea in commercial power reactors.
"Also notable, according to information on the website of Tokyo
Electric Power Co., which operates the Fukushima facility, more than
200 tons of spent fuel is stored [away from the reactors] in casks."
See:
http://www.propublica.org/article/status-of-spent-nuclear-fuel-in-
question-at-crippled-japanese-power-plant
http://tinyurl.com/4taefqa
The above web site has a good satellite photo taken before Fukushima
No 2 blew. There are many amateur model airplane and drone builders
that could get much closer much higher resolution photos. What is
really needed are little robots to explore inside. The US Navy
should be able to provide some help along those lines.
The Fukushima reactors typically are loaded with 56 to 91 tons of
fuel. See table on page 1 (called page 70) of:
http://www.tepco.co.jp/en/challenge/energy/pdf-1/nuclear-e.pdf
If the fuel loaded into reactor 3 is 0.5% plutonium, then that is
about 280 kg of plutonium, about 45 times that in the Fat Man bomb.
If a China SYndrome develops, then huge amounts of soil material can
become neutron activated, made radioactive, so many additinal tons of
radiologically toxic material could end up in the environment.
What has happened and is happening in Japan is deeply saddening. The
photos of the tsunami damage are heart wrenching. I hope for a quick
resolution to the nuclear problems and for a minimal release of
material. More pain in this situation is just unthinkable. However,
it appears the dangers are great and not fully appreciated by the
public, and there may be a need to calmly but rapidly prepare for the
worst.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
