[ RadSafe ] Article: Scientists Try to Resolve Nuclear Problem With an Old Technology Made New Again

[John Jacobus]

I apologize is this has been posted before.  From the
New York Times, at
http://www.nytimes.com/2005/12/27/science/27nuke.html?th&emc=th

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December 27, 2005

Scientists Try to Resolve Nuclear Problem With an Old
Technology Made New Again 
By MATTHEW L. WALD

WASHINGTON, Dec. 25 - Decades ago, scientists and
engineers thought it would be easy enough to deal with
the radioactive waste from nuclear power plants: sort
out and save the small portion that was reusable, and
put the rest in a hole in the ground. 

It did not work out that way. Reprocessing the waste
proved to be both expensive and risky: the main
material being scavenged, plutonium, is a nuclear bomb
fuel. 

And that hole in the ground - the proposed Yucca
Mountain repository in Nevada - is years behind
schedule, bogged down in politics and environmental
disputes. Even if it opens, it will be far too small
for the amount of waste that is being generated.

So last month, Congress voted $50 million for the
Energy Department to explore a new kind of
reprocessing, one that would reuse a much larger
fraction of the waste. 

The idea is extremely ambitious. It would require
perfecting not only a new method of reprocessing, but
also a new class of reactors to burn the salvaged
material. Still, proponents said it would have two
great advantages: It would mean that Yucca Mountain
would be big enough to accommodate the waste that
could not be recycled. And it would make Yucca easier
to open, because the material still to be buried would
generate less heat in the centuries to come. 

"Reprocessing, or processing spent fuel before it's
put in the repository, is a very good way to buy
time," said Roger W. Gale, a former Energy Department
official who is now an electricity consultant. "It's a
fail-safe in case we continue to have problems with
Yucca Mountain." 

Many experts are skeptical that the new strategy,
which would involve separating the components of spent
fuel and putting the salvaged material in reactors
using higher-energy neutrons, will work. 

Another former Energy Department official, Robert
Alvarez, noted that the idea of reprocessing had been
around for at least 40 years, each time with a
different rationale. 

"Once, it was part of breeder program," Mr. Alvarez
said, referring to a scheme to use reactors to make
more nuclear fuel than the reactor consumed. "Then it
became a proliferation thing," with supporters
reasoning that such a system would safely consume
materials that could be used for a bomb.

"And now it's a waste-management thing," he said. "But
the whole problem is they're pouring money into
something that's cutting-edge for the late 1960's."

Some scientists argue that recycling is essential. At
a recent Washington forum on nuclear waste and its
possible uses, Phillip J. Finck, deputy associate
director of the Argonne National Laboratory, an Energy
Department complex, said that by 2010, long before
Yucca Mountain can open (if, indeed, it ever does),
the United States would have more than the 70,000
metric tons of fuel that will fit there. 

Moreover, Mr. Finck argued, without recycled fuel, the
world will have to rely on finite reserves of uranium.


At the forum, sponsored by the Foundation for Nuclear
Studies of Washington, Ernest J. Moniz, a physics
professor at the Massachusetts Institute of Technology
and a former under secretary of energy, said that if
the world built enough reactors to provide energy
without contributing to global warming, a new Yucca
Mountain would be needed every three and a half years.


But Professor Moniz and others expressed caution about
reprocessing. Frank N. von Hippel, a physicist at
Princeton, said that a new generation of reactors
would cost tens of billions of dollars and that it
would be a long time before it was clear that
reprocessed fuel was needed. 

The fuel to be reprocessed would be too radioactive to
move very far; hence the idea was that the
reprocessing plant would be adjacent to the reactor.
Ivan Oelrich, vice president of the Federation of
American Scientists, said that building scores of new
reactors, with a reprocessing plant adjacent, was
unlikely, and that while opening Yucca would be hard,
switching to this kind of reprocessing was "trading
one difficult political problem for an impossible
problem." 

Still, concern over global warming and the increase in
natural gas prices have given hope to nuclear
advocates, who want new waste techniques as well as
new reactors. 

The reprocessing strategy is subtle - to extract more
use out of used fuel and to reduce the heat created by
waste that cannot be recycled and still has to be
buried. 

The heat is not a problem in the first few decades,
when a repository could be left open for ventilation.
The harder time is the next 1,500 years, when heat
would be given off by longer-lived radioactive
materials, mostly a category called actinides, and
also the isotopes that are created as those actinides
go through radioactive decay.

Heat, not volume or weight, determines the physical
capacity of Yucca or any other underground repository,
because designers want to keep the repository below
the boiling point of water. 

Above the boiling point, the resulting steam could
damage the containers and possibly the rock as well.

Reprocessing means chopping up nuclear fuel and
separating the ingredients, uranium that was not used
in the reactor and other elements that were created in
the reactor and could be used as fuel, including
plutonium and neptunium. 

Gulf Oil tried to do that in the early 60's in West
Valley, in upstate New York, but dropped it as
uneconomical, leaving the taxpayers with a cleanup
bill of more than $1 billion.

At that plant, and at plants still operated in Britain
and France, the plutonium is recovered by chemical
separation. The new plan is for "electrometallurgical"
reprocessing, in which giant electrodes are inserted
in a mix of waste components, somewhat like
electroplating.

The salvaged materials include uranium 235, the
isotope used in bombs, which splits easily, and
uranium 238, which makes up more than 99 percent of
uranium in nature but is harder to split.

One use of uranium 238 in a reactor is as a "fertile"
material that can absorb stray neutrons and become
plutonium 239, which can be used in reactors and
bombs. 

But existing reactors split the uranium using
"thermal" neutrons. The new ones would use "fast"
neutrons, which travel thousands of times as fast. 

The current generation of American power reactors uses
water to slow the neutrons to the speed optimal for
splitting uranium 235. 

The water also carries off the heat, which is used to
make electricity. Fast neutrons, in contrast, have
enough energy to split uranium 238. But to make use of
them, reactors would need a heat transfer fluid that
does not slow down the neutrons, probably molten
sodium. 

The water-based reactors are kept under high pressure
to keep the water from boiling. A sodium reactor could
run with the sodium at atmospheric pressure. At some
point, the sodium has to be run through a heat
exchanger, a cluster of thin-walled metal tubes, to
give off its energy to ordinary water, which turns to
steam and spins a turbine for electricity. And if
there is a leak and the sodium and water come into
contact, the sodium burns. 

There are other problems. Plutonium and neptunium are
potential bomb fuels; the risk that they might be
illicitly diverted, or that other countries might
follow the United States' example and build their own
reprocessing centers, led two presidents, Gerald R.
Ford and Jimmy Carter, to block General Electric from
opening a reprocessing center in Morris, Ill.

Further, the companies that run reactors are showing
no interest in new kinds of reactors and little
interest in plutonium. 

When the Energy Department decided to get rid of some
surplus weapons-type plutonium by turning it into
nuclear fuel, no utilities would take it, even at no
charge.

The Tennessee Valley Authority finally agreed to take
the fuel. It described the transaction as selling the
government "irradiation services."

Copyright 2005 The New York Times Company

+++++++++++++++++++
"Efforts and courage are not enough without purpose and direction."
"John F. Kennedy, U.S. President and former Naval Officer 

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com


		
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