Plutonium

The more element-savvy among you may have clicked this link thinking to yourselves “How does this guy have plutonium? Nobody’s allowed to have plutonium?” The answer is that, in fact, I do not have any plutonium. However, I, like many other element collectors, have devised a way to represent element 94 despite its highly regulated nature.

While there are some elements in my collection that are represented only through the radioactive decay of another more easily acquirable element, plutonium is the only element for which I use a sample that contains none of the element it represents. Instead, I have a sample that is tied to plutonium in that it was indirectly created by plutonium… by way of a nuclear bomb detonation.

On July 16, 1945, “the gadget”, the first ever nuclear bomb, was detonated at New Mexico’s Alamogordo Bombing and Gunnery Range. The resulting explosion was claimed to be heard up to 200 miles from the test site, and dug a 10′ deep, 1100′ wide crater in the desert floor. This massive crater was lined with a green, glassy layer of sand that had been melted by the incredible heat generated by the explosion. Having been created by the Trinity test, this substance came to be known as “trinitite”.

A mounted sample of trinitite.

My first sample of trinitite, mounted by the seller on a photo of the trinity test.

From a historical perspective, my trinitite samples are probably the most interesting specimens in my element collection. On that day in 1945, the world changed (it is up to the  individual to decide the magnitude of that change).

A small sample of trinitite.

A close-up detail shot of one of my smaller pieces of trinitite.

As I stated earlier, trinitite contains no actual plutonium. It does, however, contain a slew of other elements, as shown by the results of a gamma spectroscopy analysis of a sample of trinitite.

Gamma spectroscopy results for trinitite.

The results showing the relative concentrations of the major radioactive isotopes present in trinitite approximately sixty years after the trinity test. I did not create this image. It was uploaded to the Wikimedia Commons by the wikipedian “Cadmium”, who then released it into the public domain.

In gamma spectroscopy, the  emissions of gamma radiation from a sample are analyzed by a device called a “scintillator”. Unlike a Geiger counter, which can only measure the number of decay events detected by the probe, a scintillator can measure the energy levels of radiation. Each gamma-emitting radioisotope emits gamma radiation of a certain energy level. The scintillator measures these energy levels, allowing the number of decays of each energy level to be tallied up, and the relative amounts of each isotope in the sample calculated.

Looking at the graph above, it is apparent that trinitite displays some classic isotopic examples of nuclear fallout, such as cobalt-60, cesium-137, and potassium-40.

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