The use of plutonium produced in a civil nuclear-power reactor to
fabricate nuclear weapons
In a civil nuclear reactor, generating electricity, plutonium is inevitably produced. Reactor-grade plutonium
(R-Pu) will generally consist of 60% of the isotope plutonium-239, 24% plutonium-240, 9% plutonium-241
and 1% plutonium-238. Plutonium produced in plutonium-production reactors - used to produce
plutonium specifically for nuclear weapons (W-Pu) - will generally consist of at least 93% of plutonium-239
and less than 7% plutonium-240.
Eminent and highly competent physicists, with extensive knowledge of the characteristics and production
of nuclear weapons such as Richard L. Garwin,41 Theodore Taylor, J. Carson Mark, Harold M. Agnew,
Wolfgang K. H. Panofsky and Michael M. May have stated that effective nuclear weapons can be
fabricated from reactor-grade plutonium.
Carson Mark, the head of the Theoretical Division at the Los Alamos National Laboratory for many years, stated:
“The difficulties of developing an effective design of the most straightforward type are not appreciably
greater with reactor-grade plutonium than those that have to be met for the use of weapons-grade plutonium”.42
The US Department of Energy has also warned about the weapon-usability of R-Pu,43 as did Hans Blix when
he was Director General of the International Atomic Energy Agency.44
In fact, as Matthew Bunn of Harvard University explained at an International Atomic Energy Agency
conference in Vienna in June 1997, it may actually be easier for a terrorist group or a small country to make
a nuclear weapon from R-Pu than from W-Pu because no neutron generator would be required to initiate
the explosion.45 A neutron from spontaneous fission of Plutonium-240 would initiate it instead.
A major difference between reactor-grade and weapon-grade plutonium is that the critical mass
(the minimum amount needed to sustain a fission chain reaction and produce a nuclear explosion) of a
bare sphere of R-Pu is thirteen kilograms compared with ten kilograms for W-Pu (both for alpha-phase metal
with a density of 19.6 grams per cubic centimetre). This means that about 30% more R-Pu is needed
than W-Pu to fabricate a nuclear weapon.
Iran’s experiments with plutonium
If plutonium is produced in the heavy water reactor planned at Arak and used to produce nuclear weapons,
it will be necessary to chemically separate the plutonium from the irradiated reactor fuel elements. Similarly,
if Iran decided to use plutonium produced in the Bushehr nuclear-power reactor in nuclear weapons, it would
need to separate the plutonium from the unused uranium and fission products in the fuel elements.
Therefore, the experiments performed by the Iranians in plutonium separation are significant.
The Iranian government acknowledged to the IAEA that it irradiated uranium dioxide targets with neutrons
in the Tehran Research Reactor and subsequently chemically separated the plutonium produced in the targets.
According to the Iranians, only a small amount of plutonium was separated.
Removing plutonium from spent reactor fuel elements (known as reprocessing) is straightforward chemistry.
The elements are very radioactive and adequate shielding against radiation is required. The PUREX (an acronym
standing for plutonium and uranium recovery by extraction) process is the standard chemical method for
reprocessing. Unused uranium, plutonium, and fission products are separated from each other and
from the fission products.
Bookmarks