Separation of Isotopes by Laser Excitation

kaos

Is this for real???

http://www.smh.com.au/news/national/...524888448.html

pallidin

Seems like it. Look here: http://www.silex.com.au/

Morbius

kaos,

Actually this technology was developed in the early '70s at Lawrence Livermore
National Laboratory:

http://www.llnl.gov/50th_anniv/decades/1970s.htm

[Scroll down to the entry for the year 1973 ]

The process is called AVLIS - Atomic Vapor Laser Isotope Separation.

Here's how it works. The equations of Quantum Mechanics that describe how
electrons "orbit" atoms contains in one of its terms the mass of the electron.
However, since the electron orbits a nucleus of finite mass; this is a "two-body"
problem - and one has to use the so-called "reduced mass" of the electron -
m = m*M / (m + M) where "m" is the electron mass, and "M" is the mass of the
nucleus.

Therefore, the mass of the nucleus "M" enters into the equations that define the
orbits of the electrons. When you do the calculations, you will find that the
"ionization potential" - that is the amount of energy you have to add to the outermost
electron to kick it free and form a charged ion - is very slightly less for U-235 than it
is for U-238.

You then need a VERY precise tunable laser. LLNL developed a tunable dye laser
pumped by copper vapor lasers. You tune the laser to a frequency so that the laser
photons have enough energy to ionize U-235; but not enough energy to ionize U-238.

You send this laser zig-zagging through a chamber of UF6 gas or vaporized U and
the laser will ionize the U-235, but not the U-238. The U-235 can then be deflected
electrostatically by a charged plate into a separate stream from the U-238.

To learn more about AVLIS, tunable laser applications, and a spin-off from this
work called the "laser guide star" - a powerful new tool for astronomers first deployed
on the 3m Shane telescope at Lick Observatory - but now in use at largest telescopes
in the world - the Keck telescopes on Mauna Kea in Hawaii; see:

www.llnl.gov/str/pdfs/05_00.2.pdf

Dr. Gregory Greenman
Physicist

theCandyman

I have a figure in one of my texts that shows that light of a lower wavelength is used for U-235. Does this not correspond to a higher energy for ionization for U-235 than for U-238?

Morbius

Candyman,

You may be correct. I forget whether U-235 absorbs at a lower frequency - in which
case it has a lower ionization potential; or at a lower wavelength [ higher frequency ],
in which case it has a higher ionization potential.

Dr. Gregory Greenman
Physicist

Astronuc

The 'shorter' wavelength corresponds to a slightly higher ionization energy, but not by much.

According to Wikipedia - The absorption lines of ²³⁵U and ²³⁸U differ slightly; for example, the 238[/sup]U absorption peak shifts from 5027.4 Angstroms to 5027.3 Angstroms in ²³⁵U.

According to the UWisc NE notes, the wavelength used to ionized U-235 is 5915 Å, so I'll have to find other references to clarify.

Some discussion here - http://fti.neep.wisc.edu/neep423/FALL99/lecture8.pdf

Contrary to what other sources say, USEC took over ALVIS from LLNL then abandoned it.

ref: http://www.llnl.gov/str/News1097.html

Just the Facts: The USEC Business

Other interesting data - Table of Ionization Energies (eV) of Atoms and Ions -
http://www.astro.lsa.umich.edu/~cowley/ionen.htm