• Text smaller
  • Text bigger

Because so many novice pilots stall, crash and burn while flying low and
slow — on takeoff and landing, mostly, with flaps and wheels down — FAA
examiners require pilots to demonstrate their ability to fly their aircraft
at minimum controllable airspeed, right on the edge of a stall.

Of course, not being complete idiots, FAA examiners do not allow the
pilot to demonstrate those abilities unless the aircraft is up several
thousand feet above the ground, so that if the pilot does stall and the
aircraft quits flying and begins to fall like a rock there is time for
someone in the aircraft to recover from the stall — get it flying again –
before it crashes and burns.

What the operators of Chernobyl Power Plant Unit 4 — who apparently
were complete idiots — were trying to do was to operate their nuclear
reactor right on the edge of a stall. But when their reactor stalled, there
was no time to recover.

In any nuclear power plant, a fraction (10-15 percent) of the
electricity generated is needed to operate the plant itself, whether at
full power or zero power. Since when operating at zero power no electricity
is being generated, the electricity needed to operate the plant itself at
zero power has to be imported. What the Unit 4 operators were attempting to
do was to run the plant at the bare minimum power level to keep the plant
idling.

Chernobyl-style nuclear plants — called RBMKs — are known to be
extremely difficult to control at such low power levels and operating them
at that level was something the operators had been specifically warned not
to do. No surprise that when the operators did it anyway, they lost
control, crashed and burned.

But the consequences of their reactor crashing and burning would not have
been so severe to anyone but themselves if their reactor had been of a
different type. The RBMKs were what is called a dual-purpose design. They
could be configured to produce Plutonium-239 for nukes or to generate
electricity. Although the RBMKs at Chernobyl were configured to produce
electricity, they still couldn’t have the containment vessel around the
reactor core that almost all other power reactors in the world have,
including more recent Soviet designs.

Most power reactors are run at full power for a year or so and then shut
down, whereupon the containment vessel is opened and a third of the fuel in
the reactor core is replaced. The average fuel element remains in the
reactor core for four or five years. When the fuel element goes in, it
typically contains 3 percent Uranium-235, which is the isotope of uranium
that “burns.” And when that spent fuel element is removed, it typically
still has 1 percent Uranium-235 unburned. But the spent fuel element now
also has about an equal amount of plutonium that has been produced in the
burning of the 2 percent Uranium-235. The plutonium produced, which can
also be burned in a power reactor, can then be recovered via chemical
separation and incorporated in new fuel elements. This is what they do with
spent fuel everywhere else in the world, but because of Jimmy Carter and
Greenpeace, we are prohibited from recovering the burnable plutonium from
our spent fuel elements.

Carter and Greenpeace to the contrary, the plutonium produced in an
ordinary power reactor is not nuke weapon useable. Because the fuel
elements are left in the reactor for four or five years, the plutonium
produced is not pure or even mostly pure Plutonium-239. Plutonium-240 and
Plutonium-241 isotopes are also produced, and the longer the fuel element
stays in the reactor core, the more unusable the plutonium recovered from
the spent fuel is to the nuke weapon designer. For producing pure or nearly
pure Plutonium-239 for the nuke designer, the fuel elements should only be
left in the reactor for a few months.

So the RBMKs cannot be operated for a year or so and shut down for
refueling. They are essentially never shut down and every day some of the
fuel elements in the core are replaced. Replaced by robots, of course,
because the reactor core is highly radioactive when operating, even at zero
power.

What this means is that — unlike most power reactors — the RBMKs cannot
be surrounded by a bulletproof, fire and explosion proof, containment
vessel. So when the Unit 4 power plant operators stalled their low and slow
reactor, it exploded and burned.

When the water-cooled, graphite-moderated reactor core became uncovered
– losing its coolant — the core overheated and melted, which a) caused
some of the remaining water in the reactor vessel to disassociate into
hydrogen and oxygen, which then exploded like the Hindenberg, blowing the
roof off the reactor building, and b) set the graphite moderator in the
core on fire. The contaminated and highly radioactive graphite burned
furiously, producing dense clouds of radioactive smoke which then went out
the hole in the roof.

Most of the people who died — and most of those who received very large
doses of radiation — at Chernobyl, died trying to put out that fire. If
there had been a containment vessel — which for reasons set forth above
there couldn’t have been — there still would probably have been an
explosion and fire in the core, but there would have been no hole in the
roof and the smoke from the fire could not have spread over Central and
Eastern Europe.

And, of course, if the operators hadn’t been attempting to fly their
re-actor low and slow, none of it would have happened.

  • Text smaller
  • Text bigger
Note: Read our discussion guidelines before commenting.