The high-stakes shell game Iraq has played with its clandestine nuclear
program is coming to an end. While not all information has been gathered
by
a U.N. Special Commission responsible for finding and eliminating Iraq's
nuclear weapons capabilities, officials involved in the effort are confident
there will be no surprises as great as those of the last few
months-especially the revelation that Iraq may have been as close as a few
years from possession of nuclear weapons.
Six months ago, after the Pentagon ordered the destruction of Iraq' s
nuclear infrastructure, President George Bush said, "Our pinpoint attacks
have put
Saddam Hussein out of the nuclear bomb-building business for a long time
to
come." In an article published in the Bulletin last March, we questioned
whether bombing could accomplish that goal, since we believed that Iraq's
nuclear program had been hindered by export controls and by considerable
lack of expertise. We also surmised that it would take Iraq a year to build
a single nuclear weapon, and a number of years to produce--in a gas
centrifuge plant--the highly enriched uranium necessary to build a small
nuclear arsenal.
In spring, a defecting Iraqi expert revealed that Iraq, using a technology
discarded by the United States for weapons purposes in 1945, may have been
able to produce significant quantities of highly enriched uranium within
two
or three years.
But the new revelations were apparently not alarming enough for Washington's
purposes. In June and July, when the extent of Iraq's secret program became
apparent, U.S. officials-who had hyped up Iraq's nuclear program to justify
the allied offensive in January-again leaked inflated estimates of Iraqi
nuclear prowess to eager journalists, whose front-page stories tested the
waters for another effort to oust Iraqi dictator Saddam Hussein.
The admission
After a confrontation with U.N. inspectors in Iraq in late June and a
diplomatic showdown at the U.N. Security Council July 5, Iraq admitted that
it had been working on three clandestine, parallel programs to enrich
uranium. The 30-page document Iraq submitted to the Security Council July
7
contradicted denials top Iraqi officials had been making just days earlier.
Iraq insisted in the July 7 report that it had not violated the
Non-Proliferation Treaty (NPT), claiming that the programs were for civilian
purposes. But the report acknowledged that Iraq had secretly produced
uranium oxide and had enriched some uranium. NPT signatory states that do
not have nuclear weapons--Iraq is in this category--are required to report
such materials to the International Atomic Energy Agency (IAEA). The IAEA
Board of Governors voted July 18 to condemn Iraq for violating the NPT and
Iraq's safeguards agreement with the agency.
The July 7 report included vague descriptions of Iraq's nuclear activities
and lists of equipment and components. It was inaccurate and incomplete.
After the U.S. government asked for clarification, Baghdad officials
provided more information. Washington remained skeptical and expected more
disclosures before July 25, the deadline for Iraq to fully reveal its
nuclear program under U.N. Resolution 687 (after the deadline for this issue
of the Bulletin).
U.S. officials are now certain that Iraq concentrated its enrichment effort
on calutrons--an old, expensive, energy-intensive technology. The United
States developed calutrons, or electromagnetic isotope separators, during
World War II to make the highly enriched uranium for the atomic bomb that
destroyed Hiroshima. Iraq had also been developing gas centrifuge and
chemical enrichment technologies [see "Other Paths," page 211,
but these
efforts had been progressing more slowly than the calutron program, most
officials say now.
The defector
Ironically, the United States may have gotten its first hint that Iraq was
engaged in a calutron program after Western hostages were released last
December. According to one official, particles removed from hostages who
had been held near nuclear sites gave evidence of calutron activity. This
information was not considered conclusive, however, until more direct
information about the program became available.
The surprises began unfolding in the spring, with reports that an Iraqi
defector had revealed to U.S. authorities details of an extensive Iraqi
program to enrich uranium. The defector was a young electrical engineer
who
had been trained abroad but returned to Iraq in May 1990 to try to bring
his
family out of the country. Instead, he was pressed into service in the
secret nuclear program.
The defector told U.S. authorities for the first time about the calutron
program Iraq had mounted in the 1980s, unknown to U.S. intelligence. The
defector was not specifically trained in calutron technology, although he
was trained in some specialized areas applicable to a calutron program.
Much of his testimony is thought to be credible because he was, according
to
one official, familiar with "a lot" of the calutron sites.
According to what U.S. officials learned from the defector, Iraq devoted
significant resources to its calutron effort, perhaps most of the several
billion dollars U.S. experts now believe Iraq may have spent on its nuclear
program during the 1980s. The defector also reported, however, that Iraq's
calutron effort "lacked depth" in skilled personnel.
Iraq acknowledged in its July 7 report that it had eight operable calutrons
"set up for scientific and technical experiments, seventeen separators
being
set up, and five separators fabricated and being set up." One U.S.
official
said that Iraq intended to set up several hundred calutrons. But he said
that Iraq had not yet crossed the threshold from research and development
into large-scale production.
Media reports have alleged that the defector said that Iraq had secretly
produced 40 kilograms of highly enriched uranium using calutrons [see "Bomb
Hype II," below]. But U.S. officials familiar with the testimony of
the
defector question the credibility of these statements. According to one
official, the defector had "no first-hand knowledge" of the amount
of
enriched uranium Iraq's calutrons could have produced. He likened the
defector to an auto assembly-line worker who installs one component but
he
the car can go 150 miles per hour.
In mid-July, U.N. inspectors arrived at a "best estimate" of how
much highly
enriched uranium Iraq could have produced: at most 3 kilograms.
According to one U.S. official, an earlier intelligence estimate-leaked
to
the New York Times and the Washington Post-that Iraq's calutrons had
produced about 12 kilograms of weapon-grade uranium was a "severe worst-case
scenario" derived from assumptions for which there was no supporting
evidence. One assumption was that Iraq had begun producing highly enriched
uranium very soon after it began work on calutrons in the 1980s. Another
was that the calutrons in Iraq were far more capable than technical experts
at U.S. national laboratories believe they could have been, based on what
they know about calutrons and the Iraqi program.
The inspectors
But other parts of the defector's supposed testimony have been easier to
confirm-that pilot work was carried out at the Tuwaitha nuclear research
center, south of Baghdad, and that Tarmiya, 60 kilometers north of Baghdad,
was intended as a large-scale production site. These sites were inspected
in May and again in June.
Inspectors at Tuwaitha, which had been heavily bombed, found the remains
of
Iraq's safeguarded, known nuclear program, but they also found that all
the
equipment and plant records had been removed from two nearby buildings.
One
of the buildings had been completely razed and the other largely dismantled.
In June they found calutron equipment and reported to the Security Council
in a July 11 confidential memo that they believed Iraq had facilities to
operate as many as 5-10 calutrons at the site. According to a confidential
U.N. inspection report, "Iraqi declared evidence" shows that Tuwaitha
also
hosted research and development of ion sources, magnets, and special
insulators for high-voltage equipment. [See "Making and Running Calutrons,
"
pages 18-19.]
Their estimate that Iraq might have produced as much as three kilograms
of
enriched uranium was based on a supposition that calutrons at Tuwaitha had
operated continuously, at a very high rate of output, for at least two years
before the Gulf War.
At Tarmiya, inspectors found that electrical and ventilation equipment had
been ripped out of buildings, and building materials had been moved about
by
bulldozers. They found "clear indications" that the facility was
to be
dedicated to uranium enrichment. Inspectors noted a mix of buildings with
unusually large electrical power supplies, one over 100 megawatts and a
similar building with about 40 megawatts. Nearby were large chemical
processing buildings. They found cranes for disassembling calutrons, large
cooling systems, and building layouts appropriate for calutrons.The larger
calutron building was believed to have been designed to hold up to 100
calutrons, intended for an initial uranium enrichment stage. A smaller
building would have had 20 calutrons for completing the enrichment.
According to one U.S. official, Tarmiya, when fully operational, might have
produced as much as 20 kilograms of highly enriched uranium a year.
The inspectors estimated in their confidential report that the facilities
had been about 6-18 months from being operational before the bombing. They
have been "rendered non-operational and may be adequately monitored
by
periodic inspections," according to this report. Inspectors later said
that
about 30 calutrons had been located at Tarmiya, and had been test operated.
According to senior IAEA officials, Iraq acknowledged having produced
one-half kilogram of 4 percent enriched uranium at Tarmiya in these
calutrons. U.S. officials believe the numbers may be higher.
On July 15, inspectors found another calutron production facility, nearly
identical to the Tarmiya complex, at Al Sharqat, located about 200
kilometers north of Baghdad, between Tikrit and Mosul. One U.S. official
doubted that Iraq had other calutron production sites. But other
calutron-related sites existed, such as a facility near Mosul, which a U.S.
official said was to produce uranium tetrachloride feed material. The
inspectors also visited two suspected calutron equipment-manufacturing
facilities at Zaafarniyah, 300 kilometers southeast of Baghdad.
Rumors about nuclear activities in northern Iraq abounded long before the
Gulf War. Late last year speculation ranged from gas centrifuge enrichment
plants in the region, to uranium hexafluoride conversion plants, uranium
mines, and-after the war began-an underground reactor to produce plutonium.
None of these have been confirmed.
Before and after the allied bombing campaign, Iraq moved some of its key
calutron equipment to secret storage sites. After the war, tipped off by
U.S. intelligence, U.N. inspectors paid a visit on June 23 to the Abu
Gharaib military barracks north of Baghdad. For three days the Iraqis
denied the inspectors access to the site-while they moved calutron
equipment, believed to have been taken from Tarmiya, away from the site.
When they finally admitted the inspectors on June 26, no calutron equipment
was to be seen.
On June 28 the inspectors paid another unannounced visit, this time to
Fallujah, near Baghdad, before any equipment could be moved. Once again
they were denied access. Inspectors climbed atop a 30-meter water tower
outside the facility and filmed a convoy of 60-80 trucks slowly leaving
the
site. Inspectors pursued the convoy in a jeep, approached it, and filmed
calutron equipment visible in the trucks. The Iraqis then fired warning
shots over the heads of the inspectors, who got the message and backed off.
Calutrons
Iraq's calutron program is alarming to U.N. and U.S. officials not only
because it was so well hidden but also because calutron technology is so
accessible. A great deal of information about this technology,
electromagnetic isotope separation, was declassified after World War II.
The United States concluded that calutrons were a dead end, and there was
little reason to keep the technology under wraps.
Not only is information freely available, but calutrons are also easier
to
build than equipment for other, more advanced enrichment technologies such
as those based on gaseous diffusion or gas centrifuges. The U.S. government
never controlled export of specific calutron components, as it did for other
enrichment technologies.
At the same time, however, electromagnetic isotope separation technology
presents several major challenges that are not easily overcome. An early
problem with calutrons, for example, was that ion source components such
as
iron, nickel, chromium, and copper could partially vaporize and create
unwanted beams that literally cut the operating equipment to pieces.
Ernest 0. Lawrence invented the calutron electromagnetic isotope separator
at the University of California in the early 1940s. It was based on the
cyclotron; the name is a shortening of "California University cyclotron.
"
The calutron separates the rare, fissile 235 isotope of uranium from the
more plentiful, non-fissile uranium 238 by injecting an ionized beam of
high-energy uranium atoms into a large magnetic field (see illustration).
Because the two isotopes have different masses, they follow slightly
different trajectories, and a collector in the right position will
theoretically admit only uranium 235. But the beams are imperfect, so some
uranium 238 becomes mixed with the uranium 235.
Little uranium 235 ends up in the uranium 238 collector, however, which
means that the extremely "depleted" uranium from this collector
can be a
telltale signature of calutron activity. U.N. inspectors have collected
many samples of soil and material near the suspected Iraqi calutron sites,
looking for this evidence, which would lend proof that Iraq has enriched
uranium. U.S. officials would not say whether the particles they removed
from Western hostages in December revealed this signature.
During World War II, the Manhattan Project spent the equivalent of about
$5
billion in 1990 dollars to build a calutron production installation at the
Y-12 plant at Oak Ridge, Tennessee. In 1944, the plant began producing the
highly enriched uranium used in the bomb dropped on Hiroshima. At its peak
in 1945, the program employed nearly 25,000 people and had over 1, 100
separating units in nine buildings. Eight electrical substations at Oak
Ridge used more electricity than Canada produced during World War II.
The plant had two types of calutrons. The larger "alpha" units
enriched
natural uranium to 10-30 percent uranium 235; the smaller "beta"
calutrons
enriched this product further, up to about 90 percent, for use in weapons.
The calutrons were connected into "racetracks" of about 100 units
to use the
magnets and power supplies more efficiently.
A small number of these calutrons were used after the war to purify stable
isotopes for medical purposes and scientific research, but the technology
was abandoned for making weapons material because it was extremely slow
and
costly and required enormous quantities of electrical energy. Still, U.S.
government scientists worried that the technology might spread. A report
issued by Los Alamos National Laboratory in 1982 suggested that a country
with lots of cash, excess electrical energy, and a large labor pool might
find the technology attractive. The report listed 20 countries that had
researched calutrons, mostly small-scale work for civilian purposes. The
list did not include Iraq.
According to an enrichment expert, there have been "no major breakthroughs"
on calutrons since the Manhattan Project. Technology has improved
incrementally, but not enough to dramatically increase the output of
production-scale calutrons.
A successful calutron program would require considerable expertise.
According to an enrichment expert, a "fair amount of art" has
not been made
public about building and operating calutrons, and this would have to be
learned by experience if the machines were to work properly.
Today, a typical calutron costing over $1 million might produce several
hundred milligrams of uranium 235 a day, although this amount could vary
greatly depending on its design and its power source or whether enriched
uranium is used as "feed" into the calutron. An enrichment expert
said that
5-10 calutrons might be enough for a pilot operation which would be followed
by a plant using 50-100 units. A plant designed to produce 50 kilograms
a
year of uranium enriched to 80-90 percent uranium 235, with two to six ion
sources in each calutron producing a usable beam current of 150-600
milliamperes at the collectors, might need 225-900 units. If a large supply
of low-enriched uranium is available from other sources, output of highly
enriched uranium can be increased fourfold or more. The output of Iraqi
production calutrons was not known at press time, although an enrichment
expert believes Iraq would have a "tough time" operating calutrons
at the
upper end of the current range.
Experts say one of the technology's biggest disadvantages is the large
amount of energy it requires to power the beams and the magnets. A
distinguishing feature of a calutron building is the large power requirement
per square foot of floor space. For example, a plant designed to produce
50
kilograms of highly enriched uranium a year would require well over 50
megawatts of electrical power. Since most of this energy turns into heat,
calutrons require extensive cooling. The large amounts of heat they
discharge to their surroundings may provide a way to detect clandestine
facilities through infrared detection devices. This may also suggest a
reason intelligence failed to detect Iraq's program before the Gulf War
started: large-scale production had not begun.
Calutrons are not very efficient; about 90 percent of the uranium introduced
into the unit does not enter the collectors but ends up on the inside of
the
machine. This uranium must be recovered, particularly in a calutron that
starts with valuable partially enriched uranium, entailing a very messy
process. A typical operating cycle might be 40 days of continuous
operation, followed by a week of maintenance. During this period, the
vacuum chamber, which typically can weigh about 10 tons, would be removed
with a crane, taken apart, and scrubbed with nitric acid. Collectors and
special liners would be sent to a chemical processing area to recover the
uranium.
Putting it together
According to the inspection report, there is "documented evidence"
that Iraq
could manufacture all key components for calutrons, although scientists
at
U.S. national laboratories are skeptical that Iraq could have supplied all
components for the calutron program on its own.
In any case, mastering calutron technology becomes easier if a country has
access to high voltage, regulated, direct-current power supplies; modern
ion
sources; special insulators; and machining technologies and equipment to
produce the uranium collectors. The United States does not explicitly
control exports of these items.
Iraq may have exploited this loophole when it purchased sophisticated power
supplies from Hipotronics of Brewster, New York. In 1990, Iraq received
four 45-kilovolt direct-current power supplies rated at 5 amps which might
have accelerated several ion beams in a single calutron. Power supplies
are
large devices that convert alternating-current power to direct current,
and
increase the voltage as well.
U.S. Customs approved the export of the items without any review. Because
the power supplies used vacuum tubes, not modern electronic components,
they
would have been relatively easy to duplicate, assuming Iraq could have
imported or made vacuum tubes and other electronic equipment. Hipotronics
officials pointed out, however, that the voltage regulators on the equipment
they exported to Iraq would not have been precise enough for calutrons;
Iraq
would need to get better regulators from another source.
Iraq also tried to buy 27 large-throat vacuum diffusion pumps from CVC
Products, Inc. in Rochester, New York, in 1989, but U.S. Customs became
suspicious about the pumps' ultimate use and seized the shipment. Experts
speculated at the time that the pumps might have been for an enrichment
program, but it now seems likely that they were explicitly for calutrons.
U.S. export officials are now considering establishing more controls on
the
equipment used in calutrons. Sophisticated high-energy power supplies,
insulators, and large vacuum pumps are likely candidates for control.
What else is new
The new information about Iraq's plans to make enriched uranium is by far
the most significant development since our article in the March 1991
Bulletin went to press. But certain other facts have come to light as well
that may relate to Iraq's capability to make nuclear weapons.
Recent revelations have focused attention on the enrichment programs. As
of
mid-July, no new public information about Iraqs capability to actually make
a deliverable nuclear weapon using highly enriched uranium had been
revealed, although the U.N. inspectors were just beginning to look for
indications of such an effort. Everyone agrees that the amount of fissile
material Iraq possesses under internal safeguards would be enough for an
experienced nuclear weapons state to make into more than one nuclear device
with an explosive yield of many kilotons. But how quickly Iraq could do
so
remains a matter of conjecture. The following summarizes what we have
learned in recent months:
More safeguarded highly enriched uranium, but some less usable. Until
the Gulf crisis came to a head late last year, U.S. officials studying
Iraq's nuclear program said Iraq had 12.3 kilograms of uranium enriched
to
93 percent uranium 235. This material, presumably usable in weapons, had
been obtained from France for use in the Osirak research reactor, which
Israel bombed in 1981.
In addition, Iraq possessed a small but publicly unknown quantity of
material enriched to 80 percent uranium 235, supplied by the Soviet Union
and under IAEA safeguards. Before the Gulf War, several U.S. and IAEA
officials said they believed that this material totaled about 10 kilograms,
and that much of it had been irradiated (burned as fuel) in a small,
Soviet-supplied research reactor at Tuwaitha. This would present a problem
for Iraq: the greater the irradiation of the fuel, the less uranium 235
it
would contain, and the more difficult it would be to chemically extract
the
remaining highly enriched uranium. Of course, it would in any case take
more 80 percent-enriched material than 93 percent material to make a bomb.
Documents that Baghdad submitted to the United Nations in late April
confirmed that Iraq had 12.3 kilograms of 93 percent enriched fuel. Less
than half a kilogram of it, however, was "fresh"; the rest had
been slightly
irradiated, making it more difficult for Iraq to use in a weapon. Iraq was
believed capable of extracting and purifying uranium from fresh reactor
fuel, but until recently, not from "spent" (fully irradiated)
fuel. During
a May inspection at Tuwaitha, IAEA officials were surprised to find that
Iraq had separated two grams of plutonium from irradiated materials. This
indicates that Iraq may have been able to retrieve usable bomb material
from
irradiated fuel.
But the documents also stated that Iraq had over three times as much 80
percent enriched fuel as our earlier sources indicated--33 kilograms- -and
13.7 kilograms of this fuel was fresh. The rest had been irradiated: 4.4
kilograms remained in the reactor core, partially irradiated; 14.9 kilograms
was "spent fuel," that is, fully irradiated.
Iraq also indicated that it possessed 4.5 kilograms of 36 percent enriched
fuel-one kilogram spent, the rest fresh. This is also classified as highly
enriched, but it is much less useful for a weapon. All the material that
Iraq declared was located at Tuwaitha. U.N. inspectors confirmed that the
material was there, although some of it, including that in the
Soviet-supplied reactor, was buried under rubble.
In mid-July the highly enriched uranium was expected to be removed from
Iraq
shortly. Britain and France have agreed to take it.
In all, only about 14 kilograms of the 80 and 93 percent enriched uranium
were unirradiated and could quickly have been made into a weapon, if Iraq
was ready to do that. In addition, the nearly 12 kilograms of slightly
irradiated 93 percent material and the partially irradiated 4.4 kilograms
in
the reactor might also have been recoverable.
Ignoring the fully irradiated material, Iraq had 25-30 kilograms of highly
enriched uranium, putting the country somewhat closer to a nuclear weapon
than it would have been with only 15-20 kilograms. But U.S. laboratory
experts who during the crisis puzzled over whether Iraq would make a grab
for the material and shape it into bomb components do not believe the
additional quantity would have made much difference. According to one, "The
extra material would allow Iraq more latitude in material economies during
manufacture, but would provide no breakthroughs which would dramatically
reduce reflector requirements or provide greater confidence about the
probability of success."
More ways to make a weapon. In our earlier article we concluded that
with such a small quantity of fissile material, only an implosion
(Nagasaki-type) device was possible. But Carson Mark, former head of the
Theoretical Division at the Los Alamos National Laboratory in New Mexico,
has expanded on the theoretical possibilities of making nuclear explosive
devices with small amounts of highly enriched uranium.
In a paper written for the Nuclear Control Institute, Mark theorized that
with the 12.3 kilograms of 93 percent enriched uranium, Iraq might have
been
able to make a device weighing about a ton with a yield of about 10
kilotons-provided it made "commendably effective use of the implosion
method." The device would also require a very thick beryllium metal
reflector around the core; if another type of reflector were used, the
device would weigh "several times more." Such devices might be
too bulky to
be deliverable by Iraqi attack aircraft.
In addition, if the 93 percent material were blended with about 10 kilograms
of the 80 percent enriched uranium, Mark believed that it might just be
possible to make a gun-type (Hiroshima bomb) device with a yield of one
or
two kilotons-also if a thick beryllium reflector were used. Mark said a
gun-type device is easier to build than an implosion device but has many
demanding mechanical requirements.
Mark said that these calculations did not take into account numerous
problems Iraq would have to solve in order to build a successful device.
He
estimated that "for a new project to have a device in hand a fairly
large
and competent staff, with diverse experience and capabilities, with all
necessary bureaucratic support (but free of bureaucratic supervision) would
have to work intensively for at least a year."
Iraq probably lacks beryllium. In designing a weapon with a small
amount of fissile material, beryllium is essential, as Mark has pointed
out,
to reduce the weight and size of the device. But the Israeli Defense Forces
concluded, in an assessment of Iraq's nuclear weapons capability compiled
in
February, that Iraq probably has no beryllium. The assessment also
estimated that Iraq would need up to two years to produce a primitive weapon
that would poison large areas with radioactive fallout, without a
full-fledged nuclear blast, and five years to produce a 5-kiloton device
of
the type that destroyed Hiroshima.
Little warhead proficiency. According to W Seth Carus, an expert at
the Washington Institute for Near East Policy, assertions that Iraq could
put a nuclear warhead on a 1960s-vintage ballistic missile any time soon
are
"far-fetched." Information available about Iraq's chemical warheads
suggests
that they are "fairly crude" and fused to explode on impact, he
said in an
interview. Iraq may have desired to make a nuclear warhead for a ballistic
missile, "but that is a long-term concern-five years away or more-
not an
immediate one," Carus concluded.
The tradeoff between weight and range is great in Iraq's modified Scud-B
missiles. A nuclear weapon on such a missile, launched at an Israeli
target, Carus said, "would have to weigh less than 200 kilograms."
Mark's
designs would weigh over a ton.
The components of a nuclear warhead require great protection from forces
of
gravity and other stresses during flight. The fact that some of the Scuds
used in the Gulf War broke up in flight suggests that Iraq "could not
build
a rugged device which could withstand normal stresses required, let alone
handle the requirements of nuclear warheads," Carus said.
Experts confirm Iraq lacks metallurgical skills. It takes more nuclear
material to make a bomb than the final components contain, because the
components must be machined into precise form. The smoother and more
precise the shape must be, the more scrap is created in trimming and
smoothing. The scrap can be recovered and used in other components if more
than one device is produced, but precision machining, with minimal loss,
is
especially important if only one or two devices are being made from a small
amount of material.
With extensive experience, scrap can be kept to 10 percent for a solid,
simple shape. But U.S. and European officials have surmised that Iraq does
not have the expertise in metallurgy and metal machining to keep losses
so
low. They point out that lack of expertise in precision diemaking held up
Iraqs effort to manufacture centrifuges. They also note that when Iraq
bought a quantity of maraging steel (possibly for missiles) from a German
firm in 1990, German experts had to perform the purity tests because Iraqis
could not have done the tests reliably.
Neutron initiators a major problem. Iraq would probably need steady
access to a supply of polonium 210, which is used with a small amount of
beryllium as a neutron initiator for either an implosion or a gun system.
The amount of beryllium is small and easily obtained, but that is not the
case for polonium 210. The isotope has a radioactive half-life of only 138
days and is extremely hazardous to handle. It can be obtained by extraction
from radium or from large quantities of uranium, or by irradiating bismuth
in a reactor. Some external neutron generators are commercially available,
but they might not be usable in an implosion system, which requires
microsecond timing to initiate the chain reaction.
Still no uranium mine. U.N. officials said they asked the United
States to reevaluate the possibility that uranium was being mined in the
Gara Mountains in northern Iraq, near the Turkish border, as media
accounts--notably CBS's Sixty Minutes--suggested in late 1990. Diplomatic
sources say that U.S. intelligence investigated the suspected site but found
no evidence of a uranium mine there.
Conclusions
A final assessment of Iraq's nuclear program must await analysis of all
information obtained in the field by U.N. inspectors. We remain convinced
that Iraq would have needed about a year to build a crude explosive device,
but we now believe that Iraq might have developed a usable nuclear arsenal
in as little as two or three years.
Since the end of the war, U.S. officials said, no new evidence has surfaced
about Iraq's ability to make a nuclear bomb. Because Iraq now appears to
have needed a few years to produce significant quantities of highly enriched
uranium, Iraq might have had sufficient time to design a nuclear bomb and
develop confidence in the design.
The revelation that Iraq had spent as much as $8 billion on its calutron
program implies that Iraq sought to develop a large and renewable weapons
material stockpile. It might also imply that Iraq did not intend to divert
a small quantity of safeguarded nuclear material, as many observers had
feared before the war. If Iraq had tried to make one or two weapons in a
hurry, the prospect of success would have been far from certain and might
in
any ease have provoked nuclear retaliation.
While the calutron revelations are alarming, a nuclear weapons program
requires more than equipment to produce fissile materials. Iraq lacked the
hands-on experience required to nudge its fledgling gas centrifuge program
out of the laboratory and into the large-scale production phase. No
information to date suggests that Iraq would have escaped serious
difficulties as it moved from a calutron pilot stage to large-scale
production of highly enriched uranium.
The revelations have raised hard questions about the quality of
reconnaissance information on Iraq's nuclear effort. But the heat
fingerprints left by a large calutron production plant would become visible
only after the facility was producing enriched uranium. One U.S.
intelligence official said, "Either we really screwed up and missed
it, or
they just didn't get that far."
U.N. and U.S. State Department officials have expressed exasperation with
the inaccurate and highly speculative assertions being circulated by some
members of the U.S. administration, in an apparent effort to intimidate
Iraq
and oust Saddam Hussein. U.N. officials have accused the Pentagon of using
worst-case scenarios to discredit the multilateral inspection effort in
Iraq.
While the U.S. leaks drew ire at the IAEA, by mid-July, ironically, the
Pentagon seemed to be coming around to the view that bombing Iraq' s nuclear
facilities would not eliminate Iraq's nuclear capabilities. One Pentagon
official said, "We can bomb all we want, but we'll never get all Iraq'
s
material and equipment by bombing. We can use bombing as a technique to
punish Saddam or scare him. But when the dust has settled, you still could
have some material left plus the nuclear experts."
Tracking down and eliminating Iraq's nuclear weapons capabilities under
the
terms of Resolution 687, and a continued embargo to halt imports of relevant
technologies and equipment, will be the most effective way to prevent Iraq's
nuclear program from resurfacing.
By DAVID ALBRIGHT and MARK HIBBS
David Albright is a senior scientist at Friends of the Earth in Washington,
D. C. Mark Hibbs European editor of Nuclear Fuel and Nucleonics Week, in
Bonn, Germany.
BOMB HYPE II
As pressure mounted to "complete the job" done by Operation Desert
Storm and
topple Saddam Hussein, U.S. officials once again hyped Iraq's nuclear threat
through leaks to the media-and the media eagerly cooperated, just as it
had
(lone when the United States was preparing to go to war. Administration
officials, quoted in one of the first calutron stories (Washington Times,
June 11), said that Saddam Hussein had managed to secretly produce and hide
40 kilograms of highly enriched uranium and planned to build an atomic bomb
this year. The 40-kilogram estimate has not survived the scrutiny of U.S.
officials; however, it resurfaced in media accounts throughout June and
July.
In July, just before the Pentagon announced it had targeted 20
command-and-control sites in Iraq for further bombing strikes, Washington
officials leaked information to reporters from the New York Times and the
Washington Post. Both papers then published accounts that Iraq might
already have produced a bomb's worth of highly enriched uranium. The
reports did not say that the estimate was a worst-case scenario, or that
there was no evidence for the scenario.
As President Bush was talking up the military option with leaders in London
and Paris, Reuters News Agency reported that a secret U.N. study indicated
that "Saddam Hussein could produce 2040 nuclear weapons."
A State Department official said that the "grandiose" press reports,
which
appeared when the U.S. administration was renewing pressure on Saddam
Hussein to cooperate with the United Nations, exaggerated Iraq's nuclear
capabilities.
MAKING AND RUNNING CALUTRONS
A calutron consists essentially of an intense source of uranium ions, a
way
to accelerate the ions to high energy within a vacuum system, and a way
to
collect the uranium 235 and uranium 238 ions after they have moved in
sepal-ate ares between the poles of a very large electromagnet. The
components at the heart of the system are ion sources, collectors, and
high-voltage, regulated direct-current power supplies.
An ion source unit is basically a box, one foot by two feet by ten
inches, with a slit in it and a hot filament inside. Electrons "boiled"
off
the filament ionize uranium vapor that is admitted into the ionization
chamber. Accelerating electrodes extract the ionized uranium vapor through
the slit and create a beam by increasing the particles' energy to about
30-35 thousand electron-volts. Production calutrons at Oak Ridge in the
mid
1940s had one to four ion sources in each machine. Experts say Iraq' s
machines could have had two to six ion sources; however, it is difficult
to
use more than four.
The efficiency of a calutron is limited by the difficulty of ionizing the
uranium. Most of the uranium is deposited on the inside of the ion source
and in the vacuum chamber, not in the collectors; it must be recovered later
by scrubbing and chemical processing.
There are other problems. The uranium tetrachloride used in calutrons is
not as corrosive as the uranium hexafluoride used in most other enrichment
technologies. But during ionization, chlorine is released and it reacts
with materials in the ion source. And during the Manhattan Project,
insulators on the accelerating electrode within the vacuum chamber often
cracked from heat. The affected calutron would have to be shut down and
the
broken insulator replaced.
In its July 7 report, Iraq said it could produce 70 kilograms a day of
uranium tetrachloride, enough to supply several hundred ion sources.
The ion sources and accelerating system require high-voltage, regulated
direct-current power supplies in order to produce uranium beam currents
of
up to a few hundred milliamperes with a precisely defined energy. (Precision
is necessary to keep the beams on target.) The power sources must also be
protected with special circuitry against frequent sparking in the ion
source. The power sources Iraq obtained from Hipotronics [page 20] could
have been modified to accelerate several ion beams in a single calutron.
The collectors for the uranium vapor beams are usually located 180
degrees from the ion source. They are typically made out of graphite, with
precisely machined slits to admit the beams. Graphite is relatively easy
to
machine, and because it can be burned it simplifies the chemical recovery
of
uranium. The collectors are essentially disposable.
One of the more delicate tasks in operating a calutron is focusing and
maintaining stable beams inside the vacuum chamber. Because the beam
particles have the same electric charge, electrostatic repulsion causes
the
beam to spread. The rate of repulsion can be reduced by having positive
beam particles collide with gas molecules in the vacuum chamber, creating
electrons that tend to neutralize the repulsion. Reducing vacuum in the
beam region will increase neutralization, although it will also increase
loss of uranium in the beam. Once good beam conditions are established and
the beams, are going into the collector, only occasional adjustments are
necessary. In a calutron with several ion sources, however, the failure
of
one beam can cause all the beams to fail. Other techniques are available
to
improve the focus and stability of the beams.
Other components present fewer technical challenges:
The large vacuum chamber is situated between the pole faces of the
electromagnet. "Forepumps" are used to begin pressure reduction;
vacuum is
maintained primarily by one or two high-capacity diffusion pumps with
pipe-throat diameters of 15-20 inches. Iraq attempted to buy 27 such pumps
from CVC Products., Inc., in Rochester, New York, in 1989, but the shipment
was seized by U.S. Customs.
Special disposable stainless steel, water-cooled liners are often used in
the vacuum chamber to simplify recovery of the large amounts of uranium
that
end up on the chamber surfaces.
A calutron electromagnet has two circular poles, separated by a gap
30-60 centimeters wide in which the vacuum chamber is inserted. The magnet
is typically about one to two meters in diameter, weighs about 10- 20 tons,
and contains about a quarter-mile of thick copper wire. These extremely
powerful magnets use one-third to one-half of the energy consumed by
calutrons, and require cooling.
The power supply for the magnets requires a direct-current capacity of
about 1,000 amps at 300-800 volts-similar to that used to power elevators.
But the ones for calutron magnets must also be regulated precisely to
produce a stable magnetic field.
Calutrons are combined into production units called racetracks. The beta
calutrons at Oak Ridge were positioned in two rectangular tracks, each
containing 36 calutrons in two 30 meter-long parallel arrays and joined
across their ends by 10-meter iron yokes to make a closed magnetic circuit.
The associated chemical processing area is usually one of the largest parts
of the plant. In this area the collectors are burned and the uranium is
recovered from the ashes. In addition, the waste uranium must be recovered
from the other calutron components, by scrubbing with nitric acid, soaking
in acid baths, or burning or dissolving away disposable components.
The power supplies, magnets, and other components require extensive cooling
with oil or purified water. Iraq built plants to purify and chill water
at
Tuwaitha and Tarmiya.
Sources: L.O. Love, "Electromagnetic Separation of Isotopes at Oak
Ridge,"
Science (Oct. 26, 1973), pp. 343-52; H. London, Separation of Isotopes
(London: George Newnes Ltd., 1961); U.S. Department of Energy, Nuclear
Proliferation and Civilian Nuclear Power; Vol. II.: Proliferation
Resistance(1980);interviews with experts.
OTHER PATHS
Iraq's July 7 report to the United Nations revealed that Iraq had been
pursuing three paths to enriching uranium: calutrons, chemical processes,
and centrifuges. Although the calutron effort was the predominant one, the
report shed a little light on the other programs:
Chemical enrichment. Iraq began work in mid-1989 on two methods of
chemical enrichment, of which the report gave few details. An unofficial
translation says the two methods are "liquefaction and ion
[unintelligible]." This may refer to solvent extraction, a method the
French
are developing commercially, and an ion-exchange method the Japanese are
developing. Iraq asserts that it had a "good comprehension of the chemistry
of the processes" but had not completed the "laboratory technical
systems"
before they were destroyed by bombs.
Chemical enrichment depends on a slight tendency of uranium 235 and uranium
238 to concentrate in different molecules when uranium compounds are
continuously brought into contact. The French method involves combining
two
immiscible uraniumbearing liquids in a column-an effect similar to shaking
a
bottle of oil and water. The Japanese process involves an aqueous liquid
and a finely powdered resin through which the liquid slowly filters. Both
processes depend on catalysts to speed up the chemical exchange.
One enrichment expert believes that Iraq could not have got very far in
these technologies. Although Iraqi scientists might well have understood
the principles, it would have been difficult to develop the catalysts and
the processes to recycle the uranium compounds back into the separation
columns.
Gas centrifuges. The report confirmed what was widely known before the
Gulf War-that Iraq was working on gas centrifuges to enrich uranium. The
most important statement in the report was Iraqs admission that it had a
model centrifuge in which a small amount of separation had been achieved.
The centrifuge had been damaged by the bombing. A U.S. official familiar
with intelligence information said this was the first indication he had
seen
that Iraq had introduced uranium hexafluoride (the gaseous feed compound)
into a centrifuge. Iraq said in the report that it had produced about half
a kilogram of uranium hexafluoride.
The statement implies, however, that Iraq was working only on an archaic
trouble-plagued centrifuge design developed before centrifuge technology
was
classified in the 1960s. This contradicts information we published in our
March article, and which we still believe to be true: that Iraq obtained
the
design of an early Urenco centrifuge, which is a considerably more capable
machine than the Beams-type machine referred to in the report. Iraq
attempted to acquire centrifuge equipment matching Urenco design
specifications from the Swiss firms Scheublin, SA, and Schmiedemeccanica,
SA. According to a German enrichment expert who visited Iraq, this program
was in an early development stage.
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