Outsiders Get Glimpse of French Nuclear Tests : Secret Experiments Take Two Years to Prepare and Last Less Than One Second

The secret experiments take two years to prepare, are conducted in precisely 1/1,000th of a second and require two months of analysis to find out if they worked.

The slow-quick-slow rhythm is that of French nuclear tests, which have been taking place at regular intervals at Mururua atoll in the South Pacific for almost 20 years.

For obvious reasons, the process of refining the destructive power of France’s nuclear weaponry is the ultra-secret domain of a select band of atomic scientists and military commanders.

Journalists Invited

However, an unprecedented invitation to be present during a recent underground test gave a small group of journalists an intriguing glimpse of what goes on behind the protective screen of warships, airborne radar and marine commando guards.

Contrary to popular belief, the aim is not to see if experimental warheads explode--the French are sufficiently well advanced in this field to know that whatever they create is going to go off with a stupendous bang.

Rather, the goal is to find out how they explode, with a view to producing more compact and versatile weapons with the same massive power--in effect, to get more bang for the franc.

The civilian scientists of France’s Atomic Energy Commission--known by the French acronym CEA--use terms like “miniaturization” and “cost-effective,” as if discussing improvements to a domestic computer system.

But they are talking about a new generation of submarine-launched multiple-warhead missiles, high-radiation artillery shells and medium-range tactical nuclear missiles for fighter-bombers.

The nature of the devices being tested is never disclosed. However, French Prime Minister Laurent Fabius, who was present at the recent test, confirmed press reports that current research includes these three weapons.

Perhaps the most controversial is the neutron bomb, which is designed to kill enemy troops with intensified radiation while limiting blast damage.

Former Defense Minister Charles Hernu has said he watched a neutron test at Mururua four years ago. Last September the army general staff disclosed that an artillery system due to enter service in 1992 would be able to fire “reduced collateral effects weapons”--otherwise known as the neutron bomb.

The United States currently stockpiles its neutron weapons at home because of widespread concern that their deployment in Europe would increase the risk of a nuclear holocaust. France has not announced any political decision to produce the weapon so far.

Regardless of the device being tested, the process undertaken at Mururua follows a set pattern.

A drilling rig bores a deep pit six feet in diameter through the coral reef into the basaltic rock of a dormant volcano, which supports the atoll. The explosion chambers vary in depth from 2,000 to 4,000 feet.

For the biggest blasts, the shafts are sunk directly into the volcano from a floating platform on Mururua’s huge lagoon.

A cylinder containing the bomb and high-speed measuring instruments is then lowered into the pit and covered by successive layers of concrete.

‘Totally Irreversible’

This is the point of no return. According to Alain Bougat, the CEA assistant director of tests, once the device is in the explosion chamber the process is “totally irreversible.” In other words, there is no way of safely recovering it.

A six-man “firing squad,” turning two keys in separate control centers, initiates a final automatic countdown sequence, which can be interrupted manually up to the last second in an emergency.

The experiment lasts 1/1,000th of a second--the life span of the measuring instruments before they are atomized by the blast. By then, scientists hope they will have transmitted 200,000 separate items of data, including photographs, to equipment on the surface.

French officials say that more than 95% of the radioactive gases are absorbed within 1/10th of a second by thousands of tons of vitrified lava. The remainder, they assert, is trapped in the pit as the molten rock rapidly solidifies.

The final effect of shock waves is said to be 100 times less powerful than the energy yield of the bomb.

Within minutes, security teams wearing anti-radiation suits inspect the site to ensure that what Bougat calls “the unlikely” has not happened. “Theoretically, a leak caused by a bigger explosion than planned cannot be excluded.”

The scientists then move in to recover their registers and send the data to laboratories in France for analysis.

The direct cost of assembling and detonating a bomb, excluding the enormous infrastructure involved, is officially estimated at between $6 million and $12 million, depending on its size and complexity.

French authorities maintain that security at Mururua is more than adequate and cite a survey by Australia and New Zealand scientists two years ago, which concluded that the underground tests posed no apparent threat to the environment.

“We’re not kamikaze freaks here,” a senior scientist at the CEA command center said.

“The Draconian security measures are there for good reason. I’ve been here for 15 years now, and I’m not ready to take any risks,” he added.