Plutonium in Trinitite
or: Hiding in Plain Sight
by George Dowell
The "Gadget" used about 6100 grams (6.1 kg) of Pu-239, of which only about 20% actually fissioned. So there is
something just short of 5000 grams Pu-239 spread throughout the bomb debris worldwide. Some of this was neutron
irradiated and transmuted to Am-241 and progeny, which we easily see in Trinitite by virtue of their 59.5 keV
photons.
Elemental Plutonium-239 is difficult to detect because it emits alpha particles, those being easily blocked by almost
anything; dust, overburden, even a few inches of air. Trinitite sand is mostly silicon oxides. Tests with single crystal
silicon wafers used as filters show at 0.62 mm thickness, about 2/3 of the U-L X-Rays are blocked. Therefore what we
detect is within the top 1 mm or so of the surface.
For the last week I have been testing Trinitite with an eye on the lower photon energies, utilizing a newly purposedesigned and built probe, the Scionix GEO-4mm. It has a 4 mm thick NaI(Tl) cleaved crystal behind a 0.3 mm beryllium
window, all mounted on a premium PMT, feeding an MCA.
Look at attached photos to see the resulting gamma/X-Ray scans of Trinitite using this probe.
On those scans and others done by others at different labs, the photon energy lines at 13-18 keV are labeled as U-L XRays (uranium L shell characteristic X-Rays), which is certainly what they are.
A fellow Trinitite enthusiast laid down a challenge to look at those lines, then look for similar lines from known
Uranium sources such as DU, FiestaWare, ore, etc. Also to compare the U-K (shell) X-Rays between Trinitite and
Uranium samples.
The fact is that the L (shell) X-Rays don't exist- at least they don't predominate in actual uranium gamma scans.
Instead the K (shell) lines at +/- 100 keV predominate in actual uranium. IC (Internal Conversion) of the K (shell) Th
daughter X-Ray (characteristic X-Ray caused by electronic transition). (note 1)
Beta decay facts:
B- Beta Minus decay converts a neutron to a proton, moving the daughter atom to the next highest number on the
periodic chart.
B+ Beta Plus (positron) decay converts a proton to a neutron, the daughter atom is the next lowest number on the
periodic chart.
Alpha decay facts:
Alpha decay ejects and alpha particle (two neutrons bound to two protons), moving the daughter TWO spaces lower
on the periodic chart.
In either decay scheme the daughter MAY or MAY NOT itself be radioactive.
Study was done and some facts in evidence became clear to me for the first time.
Simplifying all the research I did comes up with this rule of thumb:
If a radioisotope undergoes beta decay, the daughter atom will usually give off its extra energy directly as a Gamma
photon and a K (shell) X-Ray (of the daughter).
If a radioisotope undergoes alpha decay, the daughter will usually give off an L (shell) X-Ray, energized by IC (Internal
Conversion).
Some classic examples:
Cs-137 beta minus decays, daughter Ba-137m gives us those beautiful 661.5 keV photons and Ba K shell X-Rays at 32
keV.
Sr-90 beta minus decays to Y-90 which is radioactive, which decays by another beta minus.
Uranium 235 alpha decays to Thorium, which gives us those Thorium L (shell) X-Rays.
Am-241 alpha decays, we see Neptunium L (shell) X-Rays.
Np-237 alpha decays, we see Pa L (shell) X-Rays.
and finally:
Pu alpha decays, we see Uranium L (shell) X-Rays.
In Trinitite or any other sample, if there is old Uranium making the X-Rays, you will see K (shell) X-Rays. If it is newly
created Uranium, you won't see so much K (shell) but lots of L (shell) X-Rays.
Summary:
So I think I have this figured out. And I can reproduce it.
When we use XRF to identify Trinitite you are activating the elements that
are already there, by generating characteristic X-Rays. You would see
uranium that was present in the bomb. You would also see K shell X-Rays.
It makes no difference if the Trinitite is red or green, but the plutonium is noticed almost entirely in the top layer, not
at all in the bottom layer.
When you take a gamma spec and see characteristic X-Rays, you are seeing
those from the daughter product of a heavier element that has just alpha
decayed.
Plutonium alpha decays to Uranium. We are seeing the L X-Rays from that uranium That uranium was not in the
bomb. It was just
created.
You can duplicate it same way with Am-241, you don't see Am characteristic
X-Rays, you see L shell X-Rays from the daughter Neptunium as it
restabilizes.
Same reason is why the uranium in FiestaWare presents predominately U K
shell X-Ray from XRF and upon gamma spec presents 13 keV from daughter Thorium L shell.
Note 1- Ref:
http://www.icdd.com/resources/axa/vol52/v52_13.pdf
George Dowell
©2012