The technical difficulties the US Senate cited to justify its rejection of the Comprehensive Nuclear Test Ban Treaty in 1999 are in fact manageable, says a new US report.
The treaty bans all tests of nuclear explosives. Opponents claimed it would impair US efforts to maintain its nuclear stockpile, that compliance by others could not be verified and that cheating would endanger US security.
But the US National Academy of Sciences study, released on Wednesday, refutes all three objections. It concludes that the US would be safer with the treaty than without.
Tackling the issue of detecting covert explosions, the panel said that any explosions small enough to slip under the detection threshold would be of little help to a country that did not already have nuclear weapons.
"We judge that an underground nuclear explosion cannot be confidently hidden if its yield is larger than one or two kilotons," the panel concluded - the crude fission bomb that destroyed Nagasaki yielded 20 kilotons. Concealing even two kiloton explosions would require conducting the test in an insulating cavity, or detonating large conventional explosions nearby at the same time.
Tests in water, air, space or solid rock would be easier to spot. Countries like Russia and China might be able to conceal smaller tests, but states lacking nuclear expertise would have trouble designing low-yield tests or learning much from them.
Worries that US weapons will decay without continued testing also are unjustified, believes the panel, headed by Harvard professor John Holdren. "The US has the technical capabilities to maintain confidence in the safety and reliability of its existing nuclear weapon stockpile" without further nuclear tests, says the report.
Most of the hundreds of US nuclear tests were part of weapon development, or were to verify newly produced models. Only two have been of stockpiled older weapons.
But the report, commissioned by the Democrat Clinton Administration in 2000, is unlikely to make a big political impact. The treaty was rejected by a Republican Senate and since then the Republican George Bush has become president, though the Senate is now Democrat controlled. The Bush Administration has said it will not submit the treaty to the Senate for ratification, but has announced no plans to resume testing.
Some observers warn that could change, with reports that pressure is growing to develop new "bunker-busting" nuclear warheads to attack hardened targets. Nuclear tests would probably be needed to verify the designs.
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