MOSCOW — A Russian atomic scientist surrendered to police on Tuesday eight containers filled with arms-grade nuclear material he had kept in his garage for eight years, Russian media reported.

But an Atomic Ministry official denied the 400 grams (14 ounces) of plutonium-238 found by Leonid Grigorov in a heap of rubbish at his laboratory was weapons-grade.

Interfax news agency said the lab near Russia's border with Kazakhstan, looted after the Soviet collapse in 1991, was eventually closed and deserted.

Grigorov decided to hide the material, which could theoretically be used to make a "dirty bomb," in boxes and only handed them in to local police after a newspaper offered a reward to anyone who surrendered weapons.

"As an expert, I knew that I had to (hide it) to avoid tragic consequences," Grigorov was quoted as saying.

Itar-Tass news agency quoted Nikolai Shingarev, a representative of Russia's Atomic Ministry, as saying the material was not arms-grade.

"It is not weapons-grade material, but an isotope which is widely used in different devices," Shingarev said. "Any enterprise which has a license can freely obtain plutonium-238."

Russia, with its huge nuclear arsenal, is under pressure to prevent dangerous atomic material from falling into the hands of extremists after the Soviet collapse left many nuclear facilities under-protected.

There is also speculation that individual nuclear scientists, underpaid since the Soviet collapse, may be secretly selling sensitive technology to what Washington calls "rogue" states. Russia denies such activity is taking place.

In a separate incident, 44 kg (97 pounds) of radioactive scrap metal was discovered in Chelaybinsk, Tass reported on Tuesday.

The region is heavily polluted with radioactive material from its nuclear reactor and plants producing plutonium for atomic bombs.

The local Mayak nuclear complex dumped 76 million cubic meters (2.68 billion cubic feet) of highly radioactive waste into a river between 1949 and 1956 and an explosion there in 1957 showered radiation over the southern Urals mountains.

Tass said the discovery was the second such find in a week, although it did not say how big the earlier find was.

Experts said Grigorov's plutonium-238 is normally used to generate heat but, if mixed with other materials, could be used in a nuclear explosive device. It is much more radioactive than plutonium-239, a radio-isotope normally used in atomic bombs.

Security at hundreds of Russian nuclear sites became a big issue for the West after this year's discovery of a global nuclear black market run by Pakistani scientist Abdul Qadeer Khan that supplied technology to Iran, Libya, and North Korea.

Source: Reuters