On Fri, 03 Nov 2006 17:52:31 GMT, "JoeSpareBedroom"
<dishborealis@yahoo.com> wrote:
[color=blue]
>"Scott in Florida" <askifyouwant@mindspring.net> wrote in message
>news:a70nk2hk3si15sf48o1tkpm6d67ej7i2re@4ax.com...
>[color=green][color=darkred]
>>>> The United States Military under the orders from George W. Bush
>>>> invaded Iraq and took care of finding Saddam.
>>>>
>>>> Problem solved....
>>>> Scott in Florida
>>>>
>>>
>>>No. I don't recall when the HEU was removed. Be specific. No more stupid
>>>responses, if you can help it.
>>>
>>>When was the HEU removed?
>>>[/color]
>>
>> Ask Joe Wilson!!!!!![/color]
>
>When was the HEU removed?
>[/color]
IRAQ: HOW CLOSE TO A NUCLEAR WEAPON?
It has recently been revealed that Iraq had initiated a crash program
in August 1990 to build a nuclear weapon within eight months, by
recovering highly-enriched uranium (HEU) metal from its inventory of
French- and Russian-supplied research reactor fuel. Although the
research reactor fuel was under International Atomic Energy Agency
(IAEA) safeguards, it was only being inspected twice per year, leaving
open the possibility that the conversion of fuel could have been
completed in the interval between visits.
It remains an open question whether Iraq would indeed have been
successful in obtaining enough HEU in weapons-usable form for at least
one nuclear device prior to the IAEA inspection scheduled for April
1991, if the Gulf War had not intervened. This issue depends on three
interrelated factors: (1) the minimum amount of HEU required for a
weapon of a design compatible with the purpose intended for it, (2)
the rate of fuel processing that could be achieved and (3) the level
of progress made in other aspects of the weaponization program. In
addition to providing historical insight, an assessment of these
factors is relevant to the determination of how close Iraq may be to
possession of nuclear weapons today, with its existing level of
expertise and capability, should it be able to acquire the requisite
amount of fissile material.
The inventory of HEU in research reactor fuel possessed by the Iraqis
at the time of the Gulf War was as follows (not counting materials at
36% initial enrichment or below):
* fresh: 13.7 kg at 80% enrichment (corresponds to 11.0 kg 93%
equivalent);
* fresh: 0.4 kg at 93% enrichment;
* lightly irradiated: 11.9 kg at 93% enrichment;
* heavily irradiated: 15 kg at 80% initial enrichment.
* unknown level of irradiation: 4.4 kg at 80% initial enrichment.
1. HEU requirements
How much HEU would Iraq have needed for a weapon? One of the most
important weapon parameters is the nuclear yield that can be
guaranteed with high probability. This is determined by the efficiency
of the weapon (the fraction of material fissioned), which depends
strongly on the degree of supercriticality (the number of critical
masses present) at the time of the initiation of the chain reaction.
The desired overall weight of the device places a constraint on the
yield obtainable from a given quantity of fissile material.
A good example of a basic, largely declassified implosion design
accessible to Iraq is the weapon dropped on Nagasaki, with HEU
substituted for plutonium in the core. With a 10.2 centimeter-thick
reflector of natural uranium, a material which Iraq had in plentiful
supply, about 18.5 kg of HEU enriched to 93.5% U-235 (or its
equivalent) would be required.
Utilizing HEU in an implosion device would result in a greater yield
than the same amount of material in a gun-type device (such as the
weapon dropped on Hiroshima). According to Carson Mark, former head of
the theoretical division of Los Alamos National Laboratory an HEU
implosion device capable of attaining a two critical-mass assembly
could generate a yield of around 10 KT HE (high-explosive) equivalent,
on the order of the Hiroshima and Nagasaki weapons. This degree of
supercriticality can be attained with one critical mass of material at
normal density in a relatively unsophisticated implosion device which
would compress the core by a factor of 2 (1.41), which is considerably
less than the factor of two achieved in the Nagasaki device.
Such a design would be compatible with the stated goal of the "crash
program," which was to produce weapons components from the research
reactor fuel by purifying 20 kg of 93%-enriched equivalent HEU metal
in six months. This design is also consistent with the the fact that
Iraq planned to use a composite reflector/tamper of natural uranium
and iron, materials which were readily available.
To meet the goal of the crash program, it would have been necessary to
process the 26 kg (23.3 kg of 93%-equivalent) fresh fuel and lightly
irradiated fuel, provided the overall losses in processing could be
kept to approximately 20% or below. Otherwise, some of the heavily
irradiated fuel might also have to have been used. The 3.5 kg of
93-equivalent HEU contained in fuel of unknown burnup may also have
been easily accessible.
Using another material as a reflector would have enabled Iraq to
reduce the amount of HEU necessary. With a beryllium reflector of
15-cm thickness, such a device would only require 12 kg of 93%
equivalent HEU. No evidence has been uncovered that Iraq had been
planning to use beryllium as a reflector, however. Furthermore, the
critical mass reduction achieved by using a beryllium reflector would
not alone result in increased efficiency, without simultaneous
improvements in other aspects of design, such as the achievable
compression. This is because the lower critical mass of the
HEU-beryllium system is a consequence of the increased moderation of
neutrons, which would tend to lower the efficiency of the weapon.
2. Processing time
The IAEA has argued that conversion of the reactor fuel would have
been so difficult that Iraq could not have completed the task in six
months and would have needed from 12-18 months instead. Therefore, the
IAEA asserts that the diversion would have been detected by the
routine bi-annual inspection. However, this conclusion, which is based
in part on information provided by the Iraqis themselves, appears to
be based on an overly pessimistic assessment of Iraq's technical
capabilities.
The extraction and purification of uranium metal from aluminum in the
fresh fuel would be "peanuts ... a good undergraduate chemistry lab
exercise," according to experts on research reactor fuel at the U.S.
Department of Energy. One series of straightforward (and widely known)
chemical steps which could be used are: dissolution in caustic-nitrate
solution, precipitation of uranium as ammonium diuranate, drying,
denitration, fluorination and bomb reduction with magnesium. Solvent
extraction would not be necessary. This applies to fuels based on
uranium aluminide (the French-supplied fuel), uranium-aluminum alloys
(the Russian-supplied fuel) or oxide dispersion fuel. Batch sizes
would have to be limited to less than 1 kg U for criticality reasons,
but that would have little impact on the time scale because so little
material was required in total. The most difficult step would probably
be the reduction of uranium tetrafluoride to metal, since it is an
energetic process requiring a sealed ceramic crucible. However, it is
known that Iraq already had produced hundreds of kilograms of natural
uranium metal using this process.
Furthermore, one pass would likely have been sufficient for the
purification of uranium from the unirradiated fuel. Processes for
Mo-99 extraction from irradiated isotope production fuel targets exist
in which uranium metal, sufficiently pure for refabrication into new
fuel, is separated from aluminum and fission products in one pass.
The chemical operations involved here are not associated with large
uranium losses. Descriptions of the process dating from the 1960s
indicate that losses can be kept below a few percent.
Because the specifics of its initial irradiation have not been
publicly disclosed, it is unclear whether the "lightly irradiated"
fuel would be substantially harder to reprocess than the fresh fuel.
However, the French have said that the fuel was loaded into the Tammuz
reactor and brought to power "until it became radioactive." U.S.
experts believe the irradiation time was less than one day and also
that the reactor was not operating at full power at the time, since it
usually takes several days to bring a reactor to full power; they
believe that the fuel was irradiated at no greater than 1/10 of full
power; according to this information, the average burnup of the fuel
would have been about 4 kWD/kgU. Thus the initial radioactivity level
of the fuel was quite low, and would have decreased significantly
after a couple of years of cooling. Actually, there would have been
approximately 0.01 Ci of Cs-137 per kilogram of fuel, a quantity which
could be handled in a glovebox with local shielding without causing
acute radiation sickness. It is therefore likely that the "slightly
irradiated" fuel could be processed without the use of a hot cell, and
therefore would not have been appreciably more difficult to handle
than the fresh fuel. One solvent extraction cycle, which can reduce
residual fission product concentrations by a factor of 100 or greater,
would probably have been sufficient. It is known that Iraq was capable
of performing PUREX-based solvent extraction, since it previously had
separated a small quantity of plutonium from irradiated reactor fuel.
Therefore, 23.3 kg of 93% equivalent HEU would be available with
relatively simple chemical processing, meaning that overall process
losses of up to 15% could be tolerated to meet the 20 kg goal
quantity, and greater losses could be compensated for by increasing
the thickness of the reflector in the weapon. U.S. experts have
estimated, on the basis of process flowsheets, that at least 1 kg of
HEU could be obtained per week based on a single shift (40 hrs/week),
which means that the job could be completed in under six months.
Increasing the number of shifts and process lines would lead to
corresponding reductions in the conversion time.
Even the "heavily irradiated" fuel would not have been inaccessible in
the time available. Iraq had some experience with the PUREX process
and the separation of HEU from this fuel could have taken place
concurrently with the processing of the other material, since that did
not require use of a hot cell.
The IAEA has also said that the Iraqis planned to build a
50-centrifuge cascade to increase the enrichment of the 80%-enriched
material to 93%. Since Iraq did not have a single centrifuge assembled
yet for this purpose, this undertaking would have taken "at least one
year...," according to the IAEA. Thus even if the Iraqis could have
converted the research reactor fuel relatively quickly, this
enrichment step would have clearly caused a substantial delay.
However, this enrichment plan would appear to be completely illogical
in the context of a crash program seeking a single weapon, since the
Iraqis already had more than enough material for a weapon of the type
described above. For a given core-reflector combination, the critical
mass of 93%-enriched HEU is only 20% less than that for 80%-enriched
material. The IAEA claims that the Iraqis were so concerned about
process losses that they could not afford to neglect this potential
reduction in critical mass.
It strains credulity to believe that the Iraqi nuclear establishment
would have been so foolish as to embark on this strategy.
Re-enrichment of all the 80%-enriched material in the fresh fuel would
increase the amount of 93%-equivalent HEU by 0.78 kg (7%),
unrealistically assuming one-hundred percent recovery (0.8/0.93 x 13.7
kg - 11.0 kg). such optimal conditions would have increased the amount
of 93%-equivalent HEU from the fresh and lightly irradiated fuel by a
mere 3%. The losses associated with the several additional processing
steps necessary for enrichment would in all likelihood have erased or
even overwhelmed this gain.
3. Status of weaponization program
The ability of Iraq to use the limited amount of HEU available to it
from the research reactor fuel depended on its successful development
of the implosion package to the specifications outlined above. A
recent report states that their implosion program had made "remarkable
progress" in HE testing, "but no evidence has come forth indicating
that compression levels reaching approaching a factor of two" had been
reached. However, this report does not clarify whether the Iraqis had
aquired the capability for a compression of 1.4, which some experts
assert is not a particularly challenging achievement. Furthermore, an
HE testing program would be relatively asy to conceal, even today. In
light of the considerable amount of information which Iraq has
withheld in the past, it is far from obvious that the full extent of
its nuclear weapons program has even now been revealed.
Given the fact that no nuclear-weapon components from Iraq's original
program have ever been recovered, and that Iraq maintains the same
nuclear expertise that it had before the Gulf War, Iraq today might
lack only the fissile material needed to rapidly assemble nuclear
weapons.
Dr. Edwin S. Lyman
Scientific Director
November 30, 1995
--
Scott in Florida
Linear Mode
