ROBERT SIEGEL, host: This week we’ve heard plenty about policy, about who has all of this plutonium and highly enriched uranium and about the risk of a kilo falling into the wrong hands. But we’ve heard far less about the practical side of the nuclear conversation. How is this material actually stored and moved, and what can be done to make it safe besides simply locking it up?

Well, for answers, we turn to Robert Alvarez, a senior scholar at the Institute for Policy Studies in Washington. He served as a senior policy adviser to the secretary of energy during the Clinton administration. And I asked Alvarez about the materials that Ukraine has agreed to hand over. First, the more than 100 kilograms of highly enriched uranium.

Mr. ROBERT ALVAREZ (Institute for Policy Studies): How do you store that and move it is – if it has not been put in a reactor, it is still radioactive but mildly radioactive and you can, if you’re a bad guy and want to steal it, this is the kind of stuff you can put in a satchel or a duffle bag and it won’t necessarily get picked up by remote sensing equipment.

The spent fuel, on the other hand, that has been in a reactor and especially if it’s been removed very recently, is very radioactive and has to be put into a shielded container and then transported to a storage site where it’s usually placed in water basins to shield it and keep it cool.

SIEGEL: Transported by rail, by truck?

Mr. ALVAREZ: By rail, by truck, by aircraft.

SIEGEL: And if it were plutonium that were being moved around, similar situation or not?

Mr. ALVAREZ: Separated plutonium is also radioactive, but if it’s in a relatively pure form, it’s again, you can’t necessarily pick it up with remote sensing equipment. The thing about plutonium and highly enriched uranium is that you can’t have too much of it in one place at one time because it will undergo spontaneous fissioning or criticality.

SIEGEL: There will be a critical mass (unintelligible).

Mr. ALVAREZ: There will be a critical mass and that will usually lead to severe radiation exposures. And then in the extreme situation, by design if you are able to do it, it could lead to a nuclear explosion.

SIEGEL: Once these materials have been stored, must they simply be stored forever or is there something that can be done with them, some useful purpose that we can make (unintelligible).

Mr. ALVAREZ: Well, with the highly enriched uranium, we have been retrieving this material from research reactors around the world for many years. And we now have about 20 metric tons of it stored mostly at a federal nuclear site in South Carolina, the Savannah River plant. And so the current plan is to process that material so we could extract the highly enriched uranium and mix it with natural uranium and then use it in nuclear power plant fuel and then that will be that.

SIEGEL: What we’re talking about here, what we heard Secretary of State Clinton talk about, when she talked about all of the material that the U.S. and Russia have recovered, this is the fruit of the arms race from decades past.

Mr. ALVAREZ: Well, it’s both the aftermath of the arms race, especially with respect to excess plutonium, the agreement that the United States and Russia have just struck to – actually renewed this is a renewal of an agreement struck in the year 2000, to ultimately dispose of each dispose of 34 metric tons of plutonium from dismantled warheads.

SIEGEL: It would seem that any country that created a nuclear arsenal, which would be us and the former Soviet Union, Russia and a few other countries in the world, has people who’ve been in the business of guarding these materials when they were in weapons or about to become part of weapons. Are the weapon supplies, by that reasoning, inherently more secure than fuel for reactors?

Mr. ALVAREZ: Well, I think that they have become more secure, especially in Russia, where during the Cold War they had a different system of protection and safeguarding these materials, which was largely based on what we call gates, guards and guns. And not necessarily on material accountancy principles or keeping track of every gram and doing mass balances of what came in and what’s there and where is it going. That has greatly improved largely because of financial assistance by the United States under the Nunn-Lugar program for the last 15 or so years.

SIEGEL: Robert Alvarez, thank you very much for talking to us.

Mr. ALVAREZ: Thank you for having me here.

SIEGEL: Mr. Alvarez is a senior scholar at the Institute for Policy Studies.