"Dear Arjun"

Dear Arjun:

-Vittorio Vitalin, Vadalia, VT

The term "vitrification" comes from the Latin vita, meaning "life," and the Old English ryfe, meaning "widespread" or "common." In ancient translations of Genesis, God instructs Adam and Eve to "Be fruitful and vitrify," and this populating of the earth was known as "vitrification." Modern translations dropped the term, however, after powerful lobby groups from Florida insisted that God told Adam and Eve to "Be fruitful and citrify." Distressed at the commercialism of the translation, biblical scholars changed the term to "multiply," and in so doing, warmed the hearts of mathematicians everywhere.

In the nuclear arena, vitrification refers to the process of mixing radioactive waste, mixed waste, or materials such as plutonium with molten glass and forming them into glass marbles, blocks, logs, or frit (fragments). The first pilot vitrification plant was built in Marcoule, France in 1967 to vitrify highly radioactive waste. Since that time, vitrification on a commercial scale has been successfully carried out in Russia, the United States, France, and several other countries.

Vitrification plants are typically designed to process high level waste, but plutonium can be vitrified as well. Vitrification is being considered as one option for putting surplus weapons plutonium in a non-weapons usable form (the option IEER recommends ( see editorial). In this process, plutonium, in concentrations in the range of a fraction of one percent to several percent, would be mixed with a large quantity of molten glass and poured into metal containers to form glass logs, which can then be stored. Plutonium vitrification has only been tested on a very small scale, but large quantities of materials far more radioactive than plutonium (namely, high-level wastes from reprocessing) have been vitrified. Plutonium vitrification could be done in a number of ways, depending on the desired result and on the nature and form of the plutonium being vitrified. (See table in Centerfold for discussion of options.)

Since it is possible to re-extract plutonium from glass, provisions need to be made to prevent theft. One vitrification method is to mix the plutonium with highly radioactive fission products such as cesium-137. This would deliver a lethal radiation dose to anyone trying to steal the plutonium and would make re-extraction more difficult and costly.

Another method is to put the plutonium-laden glass log in a highly radioactive container that would be resistant to theft. Re-extraction could be further inhibited by mixing the plutonium with actinides ( elements that are chemically similar to plutonium. Actinides such as thorium-232 are difficult to separate chemically from plutonium, as are non-radioactive "rare earths" that have properties similar to actinides. An advantage of this option is that the vitrification plant would not have to handle high gamma-emitting materials, allowing vitrification to begin and be completed sooner.

Surplus weapons plutonium is currently in several forms: plutonium pits removed from warheads, and scrap and residues such as ash, sludge, and contaminated materials. In principle, each of these forms can be vitrified, but further research is needed to determine which vitrification technologies are most appropriate, and to develop them to handle the various forms of plutonium safely. Oak Ridge National Laboratory has experimented with direct vitrification which could be used for scrap and residues, but this technology has not yet been demonstrated at the pilot plant level.

Currently in the United States, high level waste is being vitrified at the Defense Waste Processing Facility at the Savannah River Site in South Carolina, and at the West Valley Demonstration Project in West Valley, New York. Simulation experiments are also being done to study "can-in-canister" vitrification, where high concentrations of plutonium in small glass logs would be placed inside high-level waste glass logs for storage or disposition.

The US could draw on the expertise of other countries with more experience in vitrification technology. France has three decades of experience with high level waste vitrification, and Russia has operated a high-level waste vitrification plant at Chelyabinsk-65 for five years. In addition, Russia is constructing a new vitrification plant, which is nearly complete.

Plutonium vitrification is different from high-level waste vitrification in some important aspects. Problems specific to plutonium vitrification include accidental criticality risks both during processing and after vitrification, and the difficulty of achieving uniformity of the plutonium in glass. In order to sort out existing technical problems and fully address plutonium safety issues, the US should build several pilot plants to compare and study vitrification technologies. Two of these plants could be pursued jointly with Russia, with one pilot plant being constructed in the US and one in Russia. A cooperative effort could facilitate technological exchanges as well as progress on immobilization of surplus military plutonium.

For more information about plutonium vitrification, see IEER's report, Fissile Materials in a Glass, Darkly. The report is currently out of print, but photocopies are available for $5. See publications page.

Ghost-written by: Pat Ortmeyer