South Africa's Pebble Bed Modular Reactor (PBMR) Company has shipped enriched pebble fuel to Russia for irradiation tests to demonstrate the fuel's integrity under reactor conditions.

The PBMR Company, in collaboration with the South African Nuclear Energy Corporation (Necsa), manufactured high temperature reactor fuel spheres, or ‘pebbles', containing 9,6% enriched uranium.

In December, PBMR and Necsa manufactured enriched uranium-coated particles, 14 000 of which were contained in a pebble.

"The manufacturing of the fuel spheres is the culmination of many years of intensive development work at PBMR's Fuel Development Laboratories on the Necsa site at Pelindaba near Tshwane. The irradiation tests are the final step in the development of the fuel for the PBMR demonstration unit and we are keenly anticipating the results," said PBMR CEO Jaco Kriek.

The tests would be conducted by the Institute of Nuclear Materials (INM) in Zarechny, near Ekaterinburg in Russia, where similar tests have been carried out previously.

PBMR chief technology officer Dr Johan Slabber said that INM is also able to provide independent verification of PBMR's fuel manufacturing capability.

He said that the test pebbles were similar to the fuel that would be used in a PBMR reactor in future. The irradiation tests would determine whether the fission product retention capability of PBMR fuel spheres was comparable with that of the German HTR fuel on which the PBMR technology was based.

Four of the sixteen fuel spheres shipped to Russia would be irradiated as part of the tests, which would begin in January 2010 and take about two years to complete.

The remaining fuel spheres would be loaded into a Cold Finger Apparatus, or ‘KUFA', furnace and subjected to heating tests.

During irradiation, the release of gaseous fission products would be measured. This would give a measure of any defective particles in the fuel. After the tests, the fuel spheres would be subjected to further examinations.

Earlier this year, PBMR sent coated particles to the US for irradiation testing, due to start in early 2010 at the Idaho National Laboratory.

Kriek said the intention was to, in the long run, develop the capability to test and irradiate nuclear fuel in South Africa.