I have often mentioned the longevity of nuclear waste. U-235, the isotope that provides power in many nuclear reactors has a half-life of about seven hundred million years. U-238 constitutes most of the naturally occurring uranium and it has a half-life of four billion years. The Pu-239, the isotope which is produced in nuclear reactors and used as fuel or in nuclear weapons, has a half life of over eighty thousand years. If we create nuclear waste repositories for the permanent disposal of spent nuclear fuel and nuclear waste from weapons production, they will have to be secure for thousands of years at the very least. There has been a great deal of discussion about what sort of symbolic warnings could survive beyond our current civilization.
I have been blogging lately about the Waste Isolation Pilot Plant near Carlsbad, New Mexico. The WIPP is the only permanent geological repository designed to take radioactive waste and irradiated clothing, tools and equipment from the production of U.S. nuclear weapons. A year ago a drum of waste exploded and nuclear particles of plutonium and americium were released into the environment around Carlsbad. When the damage is repaired and systemic problems addressed, it is hoped that the repository will resume accepting the stream of waste from nuclear warhead manufacture. Eventually, the WIPP will be sealed and the old salt mine that the repository is located in will collapse, further entombing the waste. It is estimated that the repository should safely contain the nuclear waste for hundreds of thousands of years.
Following the sealing of WIPP, as time passes, our culture will be replaced by other cultures and our language will vanish. As the centuries turn into millennium, our world will become ancient history and much will be forgotten. Around the time that the WIPP was being constructed in 1990, the U.S. government invited geologists, linguists, astrophysicists, architects, artists and writers to visit the WIPP. Their mission was to consider how best to design some sort of marker system to warn people away from the WIPP repository for at least ten thousand years. Although the wastes will be dangerously radioactive for hundreds of thousands of years, it was thought that projecting beyond ten thousand years would be impossible. Looking back ten thousand years, most of the human race was farming in small villages. It is not possible to know how different the world will be ten thousand years from now but it is certain that it will be very different.
Since language can change enormously over thousands of years, it was understood by the team that a warning could not be text in a current language. The conversation turned to symbols. What symbol could convey "Danger!" for thousands of years. Some suggested the "Mr. Yuck" cartoon face. Others suggested the famous skull and cross bones used by pirates. However, even this ghastly image has changed meaning through the centuries. The panel decided that a particular symbol was not the answer. Another suggestion was a series of illustrative panels like a comic strip that would show someone being exposed to the waste (symbolized as the standard trefoil design for "radiation") and getting sick. One problem with this approach was the fact that different cultures read from right to left or left to right, down the page or up the page so the original intention might be lost. An architect said that they could build a bunch of tall thorn like columns to make the are forbidding but such a place might wind up attracting attention instead of warning people away.
Ultimately, the team adopted an idea that had first been proposed in 1981 for the now cancelled Yucca Mountain Nuclear Repository in Nevada. The idea was that it might be possible to create a folk tradition that would be passed down through the ages. A species of domestic can could be bred that would change color in the presence of radiation. Legends and myths could be created about the cat and the danger associated with changing colors. This may sound clever but any message in a myth or legend can be distorted, removed, exploited, etc. The cats might become talisman of power or pets of royalty.
I don't think that any of these ideas has any real chance of warning people away for thousands of years. It would be better for us to either find a way to eliminate these radioactive isotopes or bury them miles down where they would never be dug up or leak into the environment.
Artist's concept of warning spikes at WIPP:
