Watts Bar 2 Nuclear Power Plant, Tennessee, United States of America

The much-delayed 1,200MW Watts Bar 2 nuclear power plant in Tennessee, US, will now begin to operate from 2012, one year ahead of schedule. It will be the seventh nuclear reactor operated by Tennessee Valley Authority (TVA).

The Watts Bar Unit 2 PWR (Pressurised Water Reactor) costs the TVA around $2.5bn. Siemens is making a $170m refurbishment and upgrade of the turbine island. It is supplying one new high-pressure (HP) turbine and three new low-pressure (LP) turbines.

However, TVA later approved completion of the plant to meet the growing energy needs of the region. Construction was resumed in October 2007 while construction permit was extended from 2010 to 2013 in 2008.

Watts Bar 2 is expected to serve 650,000 homes in the Tennessee Valley area.

Plant history

TVA began building nuclear power plants in the 1960s, in response to the growing prosperity of the Tennessee Valley and the rising demand for power.

Watts Bar is TVA's third nuclear power plant. The company started building Watts Bar 1 and 2, but in 1985 a large number of deficiencies in the plants were identified. This was shortly before the WBN Unit 1 license was to be issued by the Nuclear Regulatory Commission (NRC), and the NRC asked for TVA's plans to address the deficiencies. These were found in the operating and construction activities, as well as in the company's other nuclear facilities.

In response, TVA developed a Nuclear Performance Plan (NPP) to address a wide variety of material, design and programmatic deficiencies. Unit 2 construction was suspended at about that time, with major structures in place and equipment such as reactor coolant system piping installed.

Watts Bar Unit 1 was completed in 1996 and has a Westinghouse PWR that can generate 1,167MW. In September 2000 the unit set a record for continuous operation of similar TVA reactors. Unit 1 operated for 512 consecutive days, breaking the old mark of 468 days set at TVA's Sequoyah Unit 1 in February 2000. Watts Bar is also used for tritium production for nuclear weapons.

Technology

PWRs fission uranium fuel rods to heat the water in the primary coolant loop. At Watts Bar, the hot water in the secondary loop is pumped into a steam generator to produce steam at about 300ºC (580ºF) for the main turbine and generator. Steam from the turbine is cooled in a condenser and the water is pumped back to the reactor.

Plant details

The Watts Bar 2 generator will be a completely advanced reactor, including a RIGI-FLEX™ rewind of the stator and new retaining rings. The exciter rotor is being refurbished.

There will be six new moisture separator re-heaters and more than 40,000 individual replacement parts. The primary loop testing and hot functional testing is expected to begin in the second quarter of 2011 with fuel loading to begin in April 2012. Unit 2 is scheduled to begin full operation in October 2012. Unit 2 will be operationally the same as Unit 1. It will have the same systems, equipment, operating procedures and technical specifications. However, there will be some licensing and design differences between the units due to changes in regulatory requirements.

TVA was criticised by anti-nuclear groups for basing its Unit 2 estimates of costs and schedules on a $20m study done in part by Bechtel Power Corp. and other contractors that likely will work on the reactor's construction.

Nation's largest public power provider

TVA is now the nation's largest public power provider. In 2004, TVA nuclear plants generated a record 47,075,964MWh of electricity. In May 2005, TVAN developed an index of 20 performance indicators for improved plant reliability and performance. About 6.9GW (30%) of TVA's power supply comes from its three nuclear plants: Browns Ferry, near Athens, Alabama; Sequoyah, in Soddy-Daisy, Tennessee; and Watts Bar.

The existing construction permit for Watts Bar Unit 2 expires in 2010, but TVA must obtain an operating permit from the NRC (Nuclear Regulatory Commission) before bringing the reactor on line.