Forget about IR changes, says Doug, if anything needs a good whitewash, it's nukes. Take it from me, we have a whole room full of spin doctors (sorry, corporate communications consultants) working flat out to squelch public panic on uranium, well before it's out of the ground. The message is so monotonously tame and reassuring, Doug nods off just thinking abou...... .

Hugh White, though, (The concern is no longer if, but when) is nothing but a scare-monger. If there's no good reason for Israel to have do-gooders snooping into its secrets, it follows that the Saudis, Pakistanis and Iranians can do what they like (Where terror and the bomb could meet). It's called globalisation. It's not as if Saudi Arabia is unstable (Jihad knocks on House of Saud's door),the Saudis have been doing business with the US for decades, so they must be OK. Doug's texters are pushing out this little ditty - "Trade b4 Aid". Coming to your mobile soon.

For a good, light read on the plane, Janette recommends this primer on US nuke knowhow. It's full of tasty tips on how to convert millions of the lesser breeds into vapour and lumps of fused gunk. It's reproduced in full, below, in case the link suffers a mysterious failure.

With the world's largest laser in the political crosshairs, federal weapons officials and executives at Lawrence Livermore nuclear weapons lab are playing their most powerful card: suggesting that without all 192 beams of the National Ignition Facility, U.S. nuclear bombs and warheads might well stop working.

Faith in U.S. weapons would decline, former weapons designer George Miller, associate director at large for Livermore Lab, told the Los Angeles Times. Without the laser, the United States may have to return to explosive nuclear testing, freeing the rest of the world to advance the state of weapons know-how.

"There are very serious implications to canceling this project," said Miller.

But bomb designers disagree strongly on what relationship, if any, the National Ignition Facility has to keeping the U.S. nuclear arsenal in working order.

Livermore's most prolific weapons designer, retired physicist Seymour Sack calls NIF "worse than useless" because it draws money and attention from the less glamorous examination of weapons for signs of degradation and replacement of the parts that break down.

"There's a lot of nonsense" in claims that without NIF, the nation won't have confidence in its weapons, Sack said. "It's not a purely useless boondoggle but in terms of any critical element of understanding of the stockpile, my answer is no."

Retired Sandia weapons manager Bob Peurifoy said the big laser makes "an interesting scientific playpen." Its beams will create 100 million-degree temperatures, crushing pressures and an incredible density of energy, taking scientists on a tour inside a miniature sun. "I understand that some scientists just wet their pants to use this thing. NIF is fun science," Peurifoy said. But "NIF has little if anything to do with the present and future health of the enduring stockpile."

So far the nation has kept a stockpile of nuclear bombs and warheads without having a $4 billion laser. In addition to inventing new ones, scientists cut open weapons every year, watching for problems and replacing bad parts. "We did it for 40 years," Peurifoy said.

Sen. Pete V. Domenici, chairman of the Senate Energy and Water Appropriations subcommittee, killed construction funds for the big laser for 2006, saying the "single-minded" pursuit of NIF was choking off other valuable research programs, not least in his home state of New Mexico. The Senate passed a bill Friday with no construction money for the laser.

Weaponeers broke into pro- and anti-NIF camps in the mid-1990s, when Congress approved building the laser for $1.2 billion. The divide deepened as the price tag soared to more than $4 billion, and the government cut other projects to keep NIF alive.

For years, Livermore executives barely could get more than a tepid endorsement of their laser from top scientists at the other two weapons labs.

To an extent, the debate turns on different philosophies about maintaining 20- to 40-year-old bombs and warheads.

Some scientists favor careful watching over the weapons as they age and remanufacturing the parts that degrade. But since the mid-1990s, two presidents have opted instead for a more expansive and costly program called "stockpile stewardship."

Scientists are rebuilding the weapons with new parts, and they are relying on supercomputers and giant experimental machines such as NIF to verify those changes.

Do the changes affect the detonation? Do they impair energy flow from one part of the bomb to another?

So far, scientists say stockpile stewardship answers those questions reasonably well. But officials of the weapons labs recently warned that the weapons are changing enough away from the original, proven designs to lessen confidence in their reliability.

As these warheads continue to age and are refurbished, an accumulation of small changes could lead to increased risk or increased uncertainty in warhead certification, four weaponeers wrote in a paper endorsed by the labs' weapons chiefs.

They argued for designing new bombs and warheads, replacing everything in the arsenal with simpler weapons that would be easier to make. With a moratorium on nuclear testing in place since 1992, weapons scientists would verify the new designs work with software that simulates a nuclear weapon in detonation.

The software is full of physicists' best estimates and formulas for things that are difficult to measure, such as the roiling hot gases and radiation inside a star or a detonating nuclear weapon. Fusion shots on NIF would explore those processes in greater detail than possible before, albeit at very small scale. Physicists would try to translate these small fusion observations into more accurate physics for the computer simulations.

Livermore weapons chief Bruce Goodwin argues that scientists have to understand precisely what happens in the several millionths of a second when the primary and the secondary are subject to millions of pounds of pressure, unimaginable amounts of energy and millions of degrees of temperature.

Once all 192 beams start firing in 2010, the National Ignition Facility is expected to be the only way of creating those conditions, short of an underground nuclear test, for a decade or more.

"There ain't no place else we're going to do fusion burn on the Earth in my lifetime," Goodwin said.

But many weaponeers see NIF as adding little to weapons questions already answered by nuclear testing and concerning bomb components no more delicate than a bowling ball.

U.S. thermonuclear weapons are like two eggs nestled in foam inside a can. One egg supplies most of the fusion energy and is a heavy, layered sphere usually of uranium and lithium salts. It is called a secondary, and it is more or less a fuel tank.

There's more action in the other egg, called a primary — a softball-size hollow shell of plutonium, wrapped in high explosives and detonators. A pressurized gas canister with explosive valves is poised to inject hydrogen into the egg's hollow core at the right moment to deliver a small boost of fusion but a big boost in explosive energy.

Physicists who design primaries tend to think not much else matters.

"When you're all through, damned secondaries seem to work. They have worked repeatedly, and that's thanks to a lot of really smart physicists, chemists and materials scientists," Peurifoy said.

The A-bomb creates such a torrent of energy that igniting fusion in the spherical secondary is pretty much a given, they say, like unleashing a flame thrower on a gas tank.

"I used to think like that," said Livermore's Goodwin, himself a primary designer. "The issue isn't quite so simple."

Scientists need to understand fusion burn in both the primary and secondary, as well as the energy flow between them, he said.

"Then you can say why this weapon that's 35 years old and has had 52 significant findings (of possible problems) and has had many parts replaced, still is worthy of confidence," Goodwin said.

Where scientists across the debate agree is that National Ignition Facility will be a training ground for bomb design. The laser's targets closely mimic H-bombs, with a sphere of fuel inside a can full of radiation. The physics of implosion, hot and turbulent radiation and thermonuclear burn are roughly the same.

"At some point, say in eight or 10 years, there could be an erosion of confidence, not in the (weapons) stockpile, but in the intellectual understanding of what's going on. It's exactly that area that NIF is supposed to address," said Berkeley planetary scientist Raymond Jeanloz, who advises the University of California on research at two weapons labs.

The question for NIF's critics is whether at $4 billion and counting, the big laser offers better bomb tutelage than anything else.

It's good to keep up with the latest trends in full spectrum dominance. How about the John and Janette Ignition Facility for Oz, in Adelaide.?