Wednesday, August 02, 2023

Boom Town

In 1969, a forty-kiloton nuclear bomb was detonated underground in Colorado, near the town of Parachute, between Glenwood Springs and Grand Junction, west of Denver and a little south of what is now Interstate 70. The test shaft was over 8,400 feet deep. It was a test to see if small nuclear devices could free up natural gas deep underground, part of Project Plowshare. Edward Teller, one of the developers of the H-bomb, was there during the test.

In 1973, three thirty-kiloton nuclear bombs were detonated underground in Colorado, in Rio Blanco County, in the northwestern part of the state. It was another Project Plowshare effort to find peaceful uses for nuclear bombs.

These efforts to extract natural gas were a partial success. Partial because the gas was so radioactive it could not be sold, so was instead burned off.

As a result, Colorado passed an amendment to its state constitution such that approval for the detonation of a nuclear device in the state has to pass a state-wide popular vote. It is the only state in the U.S. with such a requirement.

This all happened before the Spousal Unit and I moved to the Denver area in 1989. But that's not the only adventure with radioactivity you may find in Colorado.

Given the depth of the H-bomb detonation near Parachute, the site is probably not nearly as radioactive as the site of the old Rocky Flats Nuclear Weapons Plant, between Denver and Boulder Colorado, just a few minutes drive from my home, and which I drove right past when I commuted to Boulder every day to work in the early 1990s. Rocky Flats - somewhat euphemistically - manufactured triggers for nuclear bombs; the trigger for a nuclear (fusion) bomb is an atomic (fission) bomb. Rocky Flats was an EPA superfund site for a long long time after it closed in 1992, following an FBI raid.

Radioactivity is a natural phenomena here in Colorado, thanks to decaying uranium ore underground that creates radioactive radon gas. Like a lot of folks in our neighborhood, we have radon mitigation in our home: a fan that runs 24x7 that pulls air (and presumably radon) out of our crawl space and exhausts it above the house.

Huge piles of mine tailings around Colorado mountain towns contain a lot of uranium ore, which was just a waste product when it was originally dug out during the gold and silver mining era. No one at the time had any idea they were creating an environmental hazard that would last, for all practical purposes, forever.

For reasons unrelated to any of this, my tiny little company owns a couple of geiger counters. One day, the Spousal Unit asked me if my watch with a tritium dial gave off enough radiation to be detectable. Good question. Tritium is a radioactive isotope of hydrogen. Its radioactive decay produces helium, an electron (a.k.a. beta particle), and an electron anti-neutrino. Tritium watch dials have hour and hand markers that are tiny vials containing tritium gas and a phosphorescent compound. The beta particles from the decaying tritium excite the phosphor, making it glow. No external light source is needed, although in time all the tritium will have decayed and the vial will stop glowing. Gun sights for use at night may use this mechanism too.

I swept one of my geiger counters close over the watch, and got a reading of normal background radiation. Beta particles from tritium decay are so feeble energetically that they typically can't penetrate more than about a quarter inch of air, much less human skin. Most probably can't make it past the wall of the vial.

Then, I happened to sweep the geiger counter across one of my other watches, where it went completely nuts. It turns out an old mechanical French Army surplus watch from the 1960s that I own has a radium dial. I had no idea; that wasn't in the original description when I purchased it. Radium is a decay product of naturally occurring uranium, and radon gas is in turn a decay product of radium. As it decays, radium produces ionizing radiation in the form of helium nuclei (a.k.a. alpha particles) and gamma radiation.

That watch dial was hot. The watch now resides in a lead-lined envelope on a shelf in the basement, along with some samples of uranium ore.

In these parts, it's no accident that we all have a healthy glow.


Westword, "The Boom Years", 2023-07-30

Wikipedia, "Rocky Flats Plant", 2023-06-19