Amid press reports that Great Britain is secretly developing a new generation of nuclear warheads, activists fear that could lead to renewed nuclear testing in Nevada — upwind from Utah.

The Times of London reported last week that Britain has been hiring the best and brightest young physicists it can find to develop a new warhead to replace the aging ones now aboard its Trident submarines.

The Times said that as part of such work, the British scientists conducted at the Nevada Test Site on Feb. 23 an underground "subcritical test," where no critical mass was formed and no nuclear reaction occurred.

That test examined the behavior of plutonium as it was "strongly shocked by forces produced by chemical high explosives," according to a Nevada Test Site press release. When combined with analysis by supercomputers, it helps predict how warheads will perform.

After the Times report, top British officials would neither confirm nor deny that they have a secret program to develop new warheads.

British Foreign Secretary Jack Straw told the BBC, "We are giving consideration to the development of a new system." When asked if a program is already under way to develop a successor to current Trident warheads, he said, "There is a discussion about whether we do."

The British and U.S. governments have not acknowledged that the test last month in Nevada was part of a program to develop new nuclear arms, as reported by the Times.

A Nevada Test Site press release said merely that the test, code-named "Krakatau," was to provide "crucial information to maintain the safety and reliability of each nation's nuclear weapons without having to conduct underground nuclear tests."

Also, Kevin Rohrer, spokesman for the National Nuclear Security Administration's Nevada Site, told the Deseret Morning News that nothing in the test was designed "to help develop a new weapon."

But Steve Erickson, director of the Citizens Education Project in Utah and a longtime opponent of nuclear testing in Nevada, believes the British press reports — and is worried by them, and about U.K.-U.S. mutual defense agreements that allow testing in Nevada.

"We have never fielded a brand-new design for a warhead without nuclear testing it first," Erickson said.

"They've crossed a crucial threshold with that last test," Erickson added. "With it, we charge that they have moved into weapon development as opposed to stockpile sustainment. . . . Why are we doing this to help the British?"

Erickson worries that underground nuclear tests could occur again, but not the open-air tests that led to cancer downwind in Utah. Congress later apologized for those tests and created a compensation fund for some downwind cancer victims.