Building a Better Bomb

While condemning India for its nuclear testing, the U.S. government quietly funnels billions to research programs aimed at creating an ever-more-virulent nuclear arsenal

The warheads already in our arsenal have been tested extensively, and by all accounts they are quite good, and quite safe. If you assume that no new weapons are going to be built, that we must simply maintain the ones we have, how much additional research is needed?

Most anti-nuclear activists and several prominent physicists contend that maintaining the nuclear stockpile should be relatively no more complicated, or expensive, than maintaining that fleet of cars. There is no need for the billions of dollars in fancy equipment the government is purchasing, they argue. Just remanufacture new parts identical to the old parts.

"The weapons that we have in the current stockpile are conservatively designed. That really was a requirement for weapons that made it to the stockpile," Kidder says. "You should be able to maintain them by simply copying them and remanufacturing them when they deteriorate. You have to have a strong surveillance program, but we've always had that. If you combine enhanced surveillance with remanufacture, as far as I'm concerned you can maintain the stockpile forever, safely and reliably."

In 1987, Kidder studied the records of nuclear weapons dating back to the 1950s, attempting to determine how important actual testing was in keeping the arsenal safe and reliable. His report, published by Lawrence Livermore, concluded in part that "the performance of U.S. nuclear weapons ... is predictable and reliable to a truly remarkable degree."

Most of the problems with weapons in the past, Kidder found, occurred on designs that were rushed into the arsenal without proper testing, primarily in the late 1950s. Since then, weapons designs have been subjected to rigorous enough testing that there is little reason to suspect unknown problems are lurking in the stockpile, he found.

In other words, Kidder said, the bombs were fine, just keep making them the same way as before. "The nuclear test record, together with properties intrinsic to nuclear weapons themselves, clearly indicates that the nuclear weapons in the present U.S. stockpile are sufficiently robust to allow reliable replication," his report said.

In the 11 years since Kidder's report, the stockpile has become even safer, experts note, because the oldest, least vetted weapons have been retired.

"The prediction is that these [existing warheads] will probably go another quarter-century before there's a problem," says the Natural Resources Defense Council's Paine. "We do have pretty good data on stockpile aging up to about 25 years, and no warhead has ever been retired because of premature aging."

But other weapons scientists argue that keeping the stockpile up to snuff is not as simple as Kidder makes it sound. Many of the parts used in past bombs just aren't available anymore. Many of the plants where bomb parts were manufactured have been closed, in large part because they created environmental nightmares that will cost tens of billions of dollars to clean up.

"The country doesn't want us to make nuclear weapons the way we did before," says Livermore's Hogan.

Replacing parts on a nuclear bomb isn't comparable to going to an auto parts store for a new solenoid, they contend. "If you have an old car and they're not manufacturing parts for it anymore, you basically have to try to remake them yourself, and when you do that you never make them to exactly the same specifications," says Dearborn, who has himself made parts for an old Studebaker.

There are hundreds of parts on a nuclear weapon. But the vast majority of them are similar to parts found on any bomb, things like wiring, fuses, and metal casings. All of those are non-nuclear and can be tested at any time, just like conventional bombs. A test ban makes no difference.

"With the exception of the nuclear explosive part of the weapon, all of the other parts you can test as much as you want," says Kidder. "They don't have anything to do with nuclear testing, and they never have."

In fact last July, with little notice, scientists from the New Mexico labs began returning to the Nevada desert and conducting underground tests. Three times, they have blown up devices under the sand. All three tests involved high explosives and radioactive components like those in a nuclear bomb, but stopped short of full-blown nuclear reactions. More tests are planned, aimed at gathering additional information about the initial stages of a nuclear explosion.

Only two major components make up the actual nuclear "physics package" -- the guts of the bomb -- which cannot be tested under a treaty. These are the parts that lie at the heart of the argument over stewardship.

The "primary" is the part that explodes first. It is something like a peach. A layer of conventional high explosives -- like TNT -- surrounds a small "pit" made of either plutonium or enriched uranium. When the high explosives are set off, they compress the plutonium, causing a nuclear fission reaction. This is not the fireball. The fission reaction in the primary just kick-starts the big blast, which comes from the "secondary."

The secondary sits right next to the primary in the warhead, and holds thermonuclear fuel, usually tritium or deuterium. When the primary goes off, it subjects the secondary to intense pressure and heat, triggering an uncontrolled fusion reaction, and a mushroom cloud.

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