U-238
Let's walk through Uranium Radioactive Decay Schemes, one U isotope at a time to clarify the?
reason we see certain peaks on spectroscopy scans.
We use the convention in this science that:
X-Rays are generated in the electron shells of atoms.
Gamma Rays are generated in the nucleus of atoms.
Regardless of their energies.
U-238 is the most abundant isotope of uranium on earth. It's total decay scheme ends in Pb
but we can break the whole down into smaller groups of decay chains that may or may not be
included in the samples we study. An easy example is the Radium decay chain. Radium has been separated from raw Uranium ore for a long time now.
Even longer, the U-238/U-235 decay chain has been separated from rocks by mankind, the most obvious practical use being for making pretty colored pottery glaze (not just red either- different oxide states can make ivory and black). This kind of separation is chemical and the processes can easily differentiate Uranium from Lead daughters for example. Simple separation cannot tell U-234, U-235 and U-238 from one another, so in all chemical types of processes the preexisting mixture of isotopes remain in the same ratio.
In the study of Trinitite we know a few things about the Uranium that was used in the Gadget, for example the tamper was made of natural uranium metal, so it had a normal complement of U-235. Some scientists calculate that 30% of the total yield came from U-235 fission, so we can expect the natural radio to be altered. in the remains.
If we had a perfect sample of depleted uranium to test, it would have started with pure U-238 and the decay chain would be simple:
As illustrated, the U-238 is present in the greatest numbers in the sample, but daughter products immediately begin to build up.
First U-238 decays to Thorium-234 by Alpha Decay. Let's examine this first decay in detail.
A particular atom of U-238 decays by expelling an Alpha Particle at great speed. The nucleus of that? atom has instantly lost 2 positive particles and 2 neutral particles. At that instant the Alpha Particle takes off in some direction, and because it is going so fast, the remaining nucleus goes off in the other direction, the speed of which travel if in a vacuum would be a simple ratio of the mass of the two components (4 and 234). Sometimes this motion is probably fast enough to expel some outer electrons from the remaining atom, which at this time is already a Thorium-234 atom.
Now lets discussed this newly created Th-234 atom. It's pretty much the same as all the other Th-234 atoms but not identical because it must rearrange it's nucleus and electron shell before it can be a proper daughter. While doing this, it spits out unneeded energy to stabilize the nucleus (we call some of that energy Gamma Rays) which must of course interact with the electron shell area as it exits the atom and tries to find it's way to our Geiger Counters. Of these interaction with the electron shells, a certain number of them will generate a displaced electron, which of course must be replaced, leading to what we know as and XRF X-Ray, which we also want to find our sensor array for identification purposes.
Many other interactions happen during this process but we don't need to consider them in this discussion.
The take-away is the a U-238 DECAY makes a specific X-Ray come about from it's daughter. The XRF energy is NOT of a Uranium atom, but it's Daughter atom. Contrast this to the actual Uranium XRF X-Ray that is elicited by external excitement of? U, which is the actual Uranium XRF- these are two different and very distinct energies.
So it's clear to look for U-238 we have to look for Th-234 and Pa-234 Gamma Rays and especially XRF X-Rays.
There is one more Uranium atom to come out of this U-238 decay in fairly short order, the U-234. Notice the extremely long half-life T/2 of U-234. It is actually the head of a distinct decay chain but for that chain to reach equilibrium again, it will require centuries to go by. What's important to realize is that this is the ONLY Uranium being created in this Decay Chain, therefore the ONLY place a true Uranium XRF photon can be generated.
On the other hand, Many Plutonium isotopes decay into Uranium! The one of most interest in Trinitite is Pu-239 which decays into U-235.
My hypothesis is if we can PROVE U-XRF and can't prove any other logical reason (Th and Pa XRF) for it to be so predominant in every Trinitite sample, it might well be an indication of the presence of, and by analysis the quantity of Plutonium atoms.
Discussion welcome.
Geo?
