POLYGON NUCLEAR TEST SITE, Kazakstan (AP) - An international team of scientists destroyed the last of Kazakstan's nuclear test facilities Saturday, scratching the Central Asian nation from the list of nuclear-capable countries.
Kazakstan, a former Soviet republic, has worked with the United States since 1995 to destroy silo launchers for intercontinental missiles and other nuclear weapons at the vast nuclear testing grounds in the rocky steppes of northern Kazakstan.
The controlled detonation of 100 tons of explosives in the final remaining tunnel of the Polygon test site effectively ends Kazakstan's status as a nation capable of testing and launching nuclear weapons.
As officials watched from a hillside several miles away, a ball of flame leapt from the tunnel entrance, followed by a shock wave and blast of wind. The explosion was used to calibrate equipment at seismic stations around the world to help them monitor future underground explosions.
"The event we witnessed today was significant for all of us," said Vladimir Shkolnik, Kazakstan's minister of energy, trade and industry. "Two issues were resolved, one to do with threat reduction and the second to do with our ability to monitor future secret tests."
Susan Koch, U.S. deputy assistant secretary of defense for threat reduction, said it was "a truly landmark event, one the world has never seen before: the elimination of a country's entire infrastructure for nuclear weapons. We hope this will be an example to other nations."
Between 1949 and 1989, the Soviet Union set off 470 nuclear explosions at the testing grounds. More than 100 of the tests took place above ground.
The local population was not warned about possible ill effects of radiation. The area is sparsely populated, but people living downwind as far as the city of Semipalatinsk, 125 miles to the east of the Polygon test site, suffered aftereffects of nuclear radiation, including high incidences of birth defects and cancer.
Dubbed Omega 3, Saturday's explosion concluded a five-year cooperative program between the Kazak and U.S. governments.
The joint effort, organized under the international Comprehensive Nuclear Test Ban Treaty, closed 118 tunnels and 13 boreholes at the test site.
The test site, once the world's largest nuclear testing ground covering 32,800 square miles, was ordered shut down in 1991 by President Nursultan Nazarbayev.