System tests under way at Watts Bar 2

Wednesday, 13 August 2014

Pre-operational system tests have begun at unit 2 of Tennessee Valley Authority's (TVA's) Watts Bar nuclear power plant ahead of its scheduled start-up late next year.

In its latest quarterly update on construction of Watts Bar 2, TVA said that the unit is now more than 90% complete, remains on schedule and within budget.

The core barrel - 10 metres tall and weighing 128 tonnes - has been placed inside Watts Bar 2's reactor vessel (Image: TVA)

TVA senior vice president for Watts Bar operations and construction Mike Skaggs said, "Most of the major construction work is concluding. We are making systems structures and components like new and are making sure they operate according to TVA, industry and technical standards. We have a lot of complex and challenging work still to go."

Testing of individual and combined plant systems is under way. The first major system test - open vessel testing - was successfully completed on 1 July. This test involved pumping some 700,000 litres of water into the reactor vessel through systems used in operations including reactor shut-down.

Workers are now reassembling the reactor in preparation for a second major test, cold hydrostatic testing. A TVA spokesman told World Nuclear News that the core barrel for unit 2 was lowered into its reactor vessel on 9 August and that installation of other key components, including the head of the core barrel, will be installed over the next few days. The core barrel sits within the reactor vessel and houses the fuel. Toward the bottom of the core barrel, there is a lower core support plate on which the fuel assemblies sit.

The cold hydrostatic tests are expected to begin in September. These tests will verify that welds, joints, pipes and components of the reactor coolant system and associated high-pressure systems meet quality standards.

Skaggs noted, "These tests are critical as we move toward receiving approval from the US Nuclear Regulatory Commission to load fuel by our most likely date in June 2015, and to begin operation later that year."

Work on Watts Bar 2 was suspended in 1985 when the unit was about 55% completed, 12 years after construction began. TVA decided in 2007 to resume the project, initially estimating a cost of $2.5 billion and a completion date of 2012. TVA revised both the cost and the completion date in April 2012, with the cost now estimated at $4-4.5 billion.

Researched and written
by World Nuclear News