| KURCHATOV, Kazakhstan
KURCHATOV, Kazakhstan Khafiz Matayev dived for cover when he saw the mushroom cloud rise from the steppe. Sixty years have not dulled his memory of the sound that accompanied the blast.
"That day, we heard the voice of the earth itself," he says.
Matayev, 81, grew up next to the Soviet Union's main nuclear test site. He grew accustomed to the showers of incandescent dust that would fill the sky over his home village whenever an explosion took place.
The former school director ascribes his long life to the fact he eventually moved away. Both of his parents died of cancer. He watched his brother die of cancer too.
"This is my tragedy," he says.
The Soviet Union conducted 456 nuclear tests at the Semipalatinsk Polygon in eastern Kazakhstan from 1949 to 1989. On August 29, 1991, exactly 42 years after the first explosion, Kazakh leader Nursultan Nazarbayev signed a decree to close the test site.
Independence followed months later, setting Kazakhstan on a unique path to nuclear disarmament. The Central Asian country voluntarily surrendered the formidable nuclear arsenal inherited from the Soviet Union, the world's fourth-largest at the time, and has accepted international assistance in destroying it.
"Our country decided that the might of our new state would be determined not by our nuclear muscle, but by our total rejection of it," Nazarbayev, who remains president two decades later, said in a recent speech.
Kazakhstan, with uranium reserves second only to Australia's, is at the forefront of the global movement for a world free of nuclear weapons. Where test explosions once shook the earth, scientists are now researching peaceful applications for atomic energy.
Working with the United Nations nuclear watchdog and the U.S. government, the country has dismantled its nuclear weapons and delivered used fuel for safekeeping under the auspices of the U.N. International Atomic Energy Agency (IAEA).
U.S. Deputy Secretary of Energy Daniel Poneman told Reuters that Kazakhstan last month completed the blend-down of 33 kg (73 pounds) of highly enriched uranium for transfer to a research institute near the country's largest city, Almaty.
The country has also shipped used fuel across the country from a dismantled Soviet-era reactor in the Caspian port city of Aktau to a secure site within the Polygon area.
"That was 775 nuclear weapons' worth of material taken out of harm's way," Poneman said. "If the world can start to follow that lead, I think the world will be a safer place."
Kazakhstan's first-hand experience of nuclear testing was a big factor in its decision to abandon its arsenal. More than 1.5 million people suffered in some way from the tests.
"Radiation affected more than 300,000 square kilometers of land, equivalent to the size of a large European country like Germany," Nazarbayev said in a speech to a conference commemorating the 20-year anniversary of the Polygon's closure.
Matayev recalls being evacuated with other residents to live for three months in yurts, the tents of Kazakh nomads, when the test he saw took place in 1953.
"They warned us not to look at the blast," he says. "But a young man is curious."
At least he received a warning. Four years earlier, when the first test took place, the authorities had told his parents they had nothing to fear. "They said it wasn't dangerous," he says.
The 18,500 sq km (7,140 sq mile) site of the Polygon, the Russian word for military testing ground, was chosen by Lavrenty Beria, head of the Soviet secret police under Josef Stalin.
Supposedly, it was uninhabited. But there were in fact people living in the area, and it wasn't long before they began to fall ill.
Local doctors were not officially allowed to diagnose cases of cancer or leukemia. Nor did they reveal a fact disclosed only after Soviet records were opened up, that suicide rates in the region were up to twice the republic's average.
"Everybody knew it was harmful, but where could we go?" said another local resident, 74-year-old Maksut Koshzhanov. He blames the tests for the cancer that killed both of his sisters.
Radiation is still above safe levels in some areas of the Polygon today. Near the epicentre of 'First Lightning', the inaugural test, guards in military fatigues and face masks record radiation levels on hand-held Geiger counters.
Less than a kilometer from where they patrol, red flags mark the danger zones among the abandoned concrete observation towers that housed cameras, thermometers and other equipment to monitor the blasts.
The results of the tests were studied at Polygon headquarters 50 km (30 miles) away in the town of Kurchatov, named after the bearded Soviet physicist Igor Kurchatov, who was in charge of testing at the site from its inception until 1955.
A museum in the building houses the control panel used to detonate the test explosions, as well as slabs of granite reduced to pumice-like rock from the underground testing and the twisted tailpieces of missiles found years later.
But Kurchatov, a town of derelict apartment blocks where the population has dropped to 13,000 from around 50,000 in Soviet times, has been re-invented as the center of a drive to find innovative applications for atomic energy.
MUSHROOM CLOUDS TO MEDICINE
Directly opposite the old test headquarters, a modern industrial park houses an industrial electron accelerator used for the production of polyethylene foam, waterproof roofing material, heating panels and medicines.
"We are working toward the peaceful application of atomic energy," says Kairat Kadyrzhanov, the Moscow-educated doctor of physics and mathematics who heads the National Nuclear Center.
Kadyrzhanov says his center is also assessing safe areas for animal husbandry and mining within the former test site.
"There was a time in the 1990s when large amounts of scrap metal and copper cable were being collected on the site and sold, mainly to China," he says.
Work is still being done to determine the extent to which radiation from underground testing has found its way into the water table. One underground blast blew a 100-meter deep crater into the steppe, which filled with floodwater to form a landmark now known as the Atomic Lake.
Tests have revealed radiation levels at coal, copper and fluorite mines to be within permissible levels. Agriculture in contaminated areas is forbidden, although the National Nuclear Center acknowledges unlicensed animal grazing is prevalent.
It says studies have revealed elevated levels of tritium, a radioactive isotope of hydrogen, in milk samples from grazing sites close to the region's main waterway, the Shagan River.
The National Nuclear Center says some areas within the test site cannot be used for commercial activity in the foreseeable future, but through further research it plans eventually to return up to 80 percent of land to commercial use.
Poneman, the U.S. energy official, calls the closure of the test site "a terrific model."
The number of nuclear tests worldwide has fallen dramatically in the last decade, during which only North Korea has broken a de facto worldwide moratorium. This compares with around 500 tests in the preceding 10 years.
For Kazakhstan, this is now part of a history it has no desire to repeat. "More than anything, it was the joy of triumph over evil," Nazarbayev said.
(Additional reporting by Raushan Nurshayeva in Astana; Editing by Sonya Hepinstall)