From: John Marlow (johnmarrek@yahoo.com)
Date: Sat Jan 06 2001 - 23:17:29 MST
Herewith, a report of an accidental NUCLEAR
criticality and consequent radiation release. Note
that Japan is non-Communist. Note also the level of
blinding stupidity. As Edward Teller once remarked,
Nothing is foolproof. Fools are so ingenious...
john marlow
--
Japan’s Nuclear Criticality Accident
Steven Dolley
Research Director
Nuclear Control Institute
October 4, 1999
When and where did the accident take place?
An inadvertent nuclear chain reaction, or
so-called “criticality accident,” began at 10:35 AM
local time on Thursday, September 30 at the JCO Co.
Ltd. Conversion Test Building at Tokai-mura, Japan,
about 75 miles northeast of Tokyo. The chain
reaction, which gave off intense heat and radiation,
could not be stopped until 18 hours later.
The accident began when workers were converting
enriched uranium into oxide powder for use in
preparing fuel for the Joyo experimental fast breeder
reactor. This reactor is part of Japan’s
plutonium-production program. The uranium was
enriched to 18.8% U-235, far higher than the 3 to 5%
enriched uranium used as fuel in Japan’s conventional
nuclear power reactors. Breeder fuel, whether
enriched uranium or plutonium, is far more susceptible
to criticality accidents than power-reactor fuel.
What happened?
It appears that workers deliberately circumvented
safety measures to save time. A solution of uranyl
nitrate was transferred into a large-volume
precipitation tank, rather than the smaller,
cylindrical container required by regulations.
According to JCO Inc. official Yutaka Tatsuta, one of
the injured workers reported that some 16 kilograms of
uranium solution had been poured into the
precipitation tank, nearly eight times more than its
criticality safety limit of 2.4 kilograms.
Workers reported seeing a blue flash and then started
to feel ill. According to one report, “the area was
wrapped in a haze of blue smoke.” Workers told plant
staff that “they saw a blue flame rising from the
fuel.” Kenji Sumida, a member of Japanese
government’s Nuclear Safety Commission, concluded, “I
know this is difficult to believe, but I think that we
have no choice but to recognize this accident as
having been critical.” The criticality continued for
about 18 hours until the water that was moderating the
flow of neutrons and allowing the chain reaction to
continue was drained and the tank was flooded with
boron, a neutron absorber.
How much radiation was released?
At one point, radiation levels near the plant were
15,000 times above normal background. A total of at
least 49 people were contaminated with radiation,
including 39 JCO staff, seven residents, and three
firefighters who transported the injured workers. Two
of the workers received such high doses of radiation
that they are not expected to survive.
---
Michael M. Butler wrote:
--One historical quibble on your otherwise quite
worthwhile post: The way
I heard it, the "going critical" of the radwaste was a
_chemical_
criticality, not a nuclear one. You didn't specify,
but I like to get
that information out.
For those who don't know:
At least as I heard it, there was something like a
mineshaft full of
contaminated stuff that was largely ammonium nitrate.
That substance is
one which in crystalline form can achieve a chemical
"critical mass"
("critical configuration" is probably a better
term)--if you pile up
enough, the physical pressure on the bottom crystals
causes detonation.
I'm not sure how far the detonation wave spreads. I
believe they
delivered the waste as liquid or sludge, and it didn't
stay liquid.
Oopski.
And yes, the end result was a large nuclear waste
contaminated area. So
it doesn't blunt John's point, necessarily.
John Marlow wrote:
> As to Mikle Lorrey's comment on "failing" to prove a
> catastrophe resulting from nuclear mishaps--anyone
> recall a certain Russian radwaste storage facility
> going critical and devastating the surrounding
> countryside?
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