AVLIS
Encyclopedia
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
ic vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
isotope separation
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
and is a method by which specially tuned lasers
Tunable laser
A tunable laser is a laser whose wavelength of operation can be altered in a controlled manner. While all laser gain media allow small shifts in output wavelength, only a few types of lasers allow continuous tuning over a significant wavelength range....
are used to separate isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
using selective ionization of hyperfine transitions.
In the largest technology transfer
Technology transfer
Technology Transfer, also called Transfer of Technology and Technology Commercialisation, is the process of skill transferring, knowledge, technologies, methods of manufacturing, samples of manufacturing and facilities among governments or universities and other institutions to ensure that...
in U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
government history, in 1994 the AVLIS process was transferred to the United States Enrichment Corporation
United States Enrichment Corporation
The United States Enrichment Corporation, a subsidiary of USEC Inc. , is a corporation that contracts with the United States Department of Energy to produce enriched uranium for use in nuclear power plants.-History:...
for commercialization. However, on June 9, 1999 after a $100 million investment, USEC cancelled its AVLIS program.
The AVLIS process provides high energy efficiency comparable with gas centrifuge
Gas centrifuge
A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centripetal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container.A prominent use of gas...
s, high separation factor, and low volume of radioactive waste
Radioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
.
AVLIS continues to be developed by some countries and it presents some specific challenges to international monitoring. Iran is now known to have had a secret AVLIS program. However, since it was uncovered in 2003, Iran has claimed to have dismantled it.
A similar technology, using molecules instead of atoms, is molecular laser isotope separation
Molecular laser isotope separation
Molecular laser isotope separation is a method of isotope separation, where specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions of uranium hexafluoride molecules. It is similar to AVLIS...
(MLIS).
Principle
The absorption lines of 235 and 238U differ slightly due to hyperfine structureHyperfine structure
The term hyperfine structure refers to a collection of different effects leading to small shifts and splittings in the energy levels of atoms, molecules and ions. The name is a reference to the fine structure which results from the interaction between the magnetic moments associated with electron...
; for example, the 238U absorption peak shifts from 502.74 nanometer
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
s to 502.73 nm in 235U. AVLIS uses tunable
Tunable laser
A tunable laser is a laser whose wavelength of operation can be altered in a controlled manner. While all laser gain media allow small shifts in output wavelength, only a few types of lasers allow continuous tuning over a significant wavelength range....
dye laser
Dye laser
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...
s, which can be precisely tuned, so that only 235U absorbs the photons and selectively undergoes excitation and then photoionization. The ions are then electrostatically deflected to a collector, while the neutral unwanted uranium-238 passes through.
The AVLIS system consists of a vaporizer and a collector, forming the separation system, and the laser system. The vaporizer produces a stream of pure gaseous uranium.
The laser commonly used is a two-stage tunable pulsed dye laser
Dye laser
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...
usually pumped
Laser pumping
Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited...
by a copper vapor laser
Copper vapor laser
Copper vapor laser uses vapors of copper as the lasing medium in a 3-level laser. It produces green laser light at 510.6 nm and yellow laser light at 578.2 nm. The pulse width is typically from 5 to 60 ns, and peak power from 50 to 5000 kW. Its pulse repetition frequencies can be 2 to 100 kHz...
; the master oscillator is low-power but highly precise, and its power is increased by a dye laser amplifier acting as optical amplifier
Optical amplifier
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed...
. Three frequencies ("colors") of lasers are used for full ionization of uranium-235.
See also
- Nuclear powerNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
- Nuclear fuel cycleNuclear fuel cycleThe nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in...
- Gaseous diffusionGaseous diffusionGaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride through semi-permeable membranes. This produces a slight separation between the molecules containing uranium-235 and uranium-238 . By use of a large cascade of many stages, high separations...
- Gas centrifugeGas centrifugeA gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centripetal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container.A prominent use of gas...
- CalutronCalutronA calutron is a mass spectrometer used for separating the isotopes of uranium. It was developed by Ernest O. Lawrence during the Manhattan Project and was similar to the cyclotron invented by Lawrence. Its name is a concatenation of Cal. U.-tron, in tribute to the University of California,...
- Molecular laser isotope separationMolecular laser isotope separationMolecular laser isotope separation is a method of isotope separation, where specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions of uranium hexafluoride molecules. It is similar to AVLIS...
- Chemical reaction by isotope selective laser (CRISLA)
External links
- USEC News Release Cancelling AVLIS
- Report on Iranian AVLIS program
- Oxford Research Group report on Iran's nuclear activities.
- Laser isotope separation uranium enrichment
- Overview of Uranium Atomic Vapor Laser Isotope Separation R.M. Feinburg and R.S. Hargrove. UCRL-ID-114671 August 1993.
- Laser Isotope Separation page at LLNL