Testing of the leak-tight enclosure system at Iran's new Bushehr nuclear power plant has been completed, the reactor's Russian builder AtomStroyExport has announced.

The strength and tightness of the enclosure system were tested as the reactor is prepared for hot testing on its way towards start up. The leak-tight enclosure system (LES) is a confining system that would prevent the release of radiation into the environment in the event of any failure in the primary circuit, as well as protecting primary equipment from external impacts.

Erecting and testing the LES at Bushehr was a first for the Russian company. Unlike Russian nuclear power plants, which use a reinforced concrete structure lined with steel sheets to provide the LES, Bushehr's LES comprises a protective shell made of a steel sphere 56 metres in diameter. This difference between Russian VVERs and Bushehr is part of the legacy of the Iranian reactor's inception as a German-designed plant on which work started in the 1970s. Russian contractors undertook to complete the first unit at the plant as a VVER-1000 reactor in 1994, some 15 years after work on the original Siemens KWU plant had been abandoned, integrating the Russian reactor design with existing infrastructure.

Hydraulic testing of the secondary circuit at Bushehr reactor was completed in January. According to AtomStroyExport, the plant's primary circuit has already been hydraulically tested up to 250 kg/cm2, 40% above normal operating pressure. The testing has confirmed that main and auxiliary equipment in the two circuits are functioning efficiently within plant design parameters.

The Bushehr VVER was originally scheduled to begin operation in late 2006 but the project has been beset with delays. Iranian plans now call for the plant to be operational by the end of March 2010. The Bushehr nuclear power plant will be operated by a Russian-Iranian joint venture during its first year of operation.

The Bushehr project stands outside the ongoing international concerns over Iran's uranium enrichment program. The reactor has been constructed and will operate under full International Atomic Energy Agency (IAEA) safeguards, using Russian-supplied nuclear fuel that will be returned to Russia after use.

World Nuclear News