What are Fissile Materials?
According to the Institute of Energy and Environmental Research (IEER), fissile materials are composed of atoms that can be split by neutrons in a self-sustaining chain-reaction to release enormous amounts of energy.
Fissile Materials Needed for Both: Plutonium-239 and Uranium-235 (The numbers after the element represents a particular isotope.)
Uranium-235 occurs in nature, Plutonium-239 does not. (Thank goodness.)
Here is the difference between fissile materials for nuclear reactors and nuclear weapons:
Reactors- the fission process is controlled and the energy is harnessed to produce electricity.
Weapons- the fission energy is released all at once to produce a violent explosion.
If Plutonium is not natural, how is it made?
There are two steps to this process- First, in a nuclear reactor, uranium-238 absorbs a neutron. This leads to nuclear reactions which convert it to plutonium. The plutonium ends up in the spent nuclear fuel along with unused uranium and highly radioactive fission products. In the spent fuel pool, the plutonium is not usable for nuclear energy or weapons.
So the second step is to get plutonium into a usable form- through a reprocessing plant. This chemically separates out the plutonium from the other materials in spent fuel. This second part is known as reprocessing.
Reprocessing is generally regarded as one of the key links between civilian nuclear power capability and nuclear weapons production capability.
What is the Plutonium used for?
According to the IEER, once plutonium is separated, it can be processed and fashioned into the fission core of a nuclear weapon, called a “pit”. Nuclear weapons typically require three to five kilograms of plutonium. Plutonium can also be converted into an oxide and mixed with uranium dioxide to form mixed-oxide (MOX) fuel for nuclear reactors.
As of 1995, there were approximately 270 metric tons of separated plutonium in military inventories and roughly 180 metric tons of separated plutonium in civilian inventories worldwide. (IEER)
Where does this happen?
- Britain- Supplies plutonium to countries in Western Europe
- France- Supplies plutonium to countries in Western Europe
- Israel (Military Use Only)
- China (Military Use Only)
- North Korea has also operated a reprocessing plant
What about the United States?
On the IEER website it states, “In the U.S., reprocessing for nuclear weapons occurred at the Hanford Reservation, Washington and the Savannah River Site, South Carolina. Some civilian and military reprocessing also occurred between 1966 and 1972 at West Valley, New York. U.S. plutonium production reactors were shut down in 1988, and halting reprocessing for military purposes was codified into formal policy in July 1992. The United States does not support reprocessing because of its proliferation dangers, but in practice the U.S. has been selective in opposing reprocessing in other countries.”
Another Fissile Material: Highly Enriched Uranium
Highly enriched uranium (HEU) is usually defined as uranium whose proportion of uranium-235, the fissile isotope of uranium, has been increased to over 90%. The natural uranium mined from the earth consists of about 0.7% uranium-235 (U-235), and about 99.3% uranium-238 (U-238), and enrichment is the process of increasing the ratio of U-235 to U-238.
It is important to note that most nuclear reactors run on low-enriched uranium (LEU), which is usually 3%-5% uranium-235. LEU cannot be used in nuclear weapons.
*Many argue that if there are capabilities to enrich the uranium for reactors, weapons grade enrichment is a strong possibility.
How is HEU made?
There are now numerous ways to enrich uranium. Since uranium occurs naturally, it first mined from the ground. This natural uranium is processed and then enriched through either gaseous-diffusion, centrifuges or electromagnetic separation. All of these processes are very costly and require a large budget.
What is HEU used for?
HEU can be used both in nuclear weapons technology and in nuclear reactors. It was first developed for use in nuclear weapons.
Weapons- It can be combined with plutonium to form the “pit”, or core of a nuclear weapon, or it can be used alone as the nuclear explosive. The bomb dropped on Hiroshima used only HEU. About 15-20 kgs of HEU are sufficient to make a bomb without plutonium.
Reactors- It is used as a fuel in research reactors and the nuclear reactors that power some naval vessels.
According to the Physicians for Social Responsibility, about 2300 metric tons of HEU have been produced for military purposes worldwide — primarily by the United States and the Soviet Union. About 20 metric tons of HEU have been used in research reactors worldwide.
Where is this produced?
The International Atomic Energy Agency, a United Nations agency, is charged with ensuring that uranium from civilian nuclear programs is not diverted to weapons-purposes only in non-nuclear weapon states who are signatories to the Non-Proliferation Treaty (see resources for links to NPT).
United States- HEU was produced in the United States at Oak Ridge, Tennessee and Portsmouth, Ohio.
Institute for Energy and Environmental Research: http://ieer.org/resource/fissile-materials/fissile-material-basics/