is increased. Eliminating the external recirculation piping also reduces occupational radiation exposure to personnel during maintenance. An operational feature in the ABWR design is electric fine motion control rod drives, first used in the BWRs of AEG (later Kraftwerk Union AG, now AREVA). Older BWRs use a hydraulic locking piston system to move the control rods in six-inch increments. The electric fine motion control rod design greatly enhances positive actual control rod position and similarly reduces the risk of a control rod drive accident to the point that no velocity limiter is required at the base of the cruciform control rod blades. Certifications and approvals Slightly different versions of the ABWR are offered by GE-Hitachi, Hitachi-GE, and Toshiba. In 1997 the GE-Hitachi U.S. ABWR design was certified as a final design in final form by the U.S. Nuclear Regulatory Commission, meaning that its performance, efficiency, output, and safety have already been verified, making it bureaucratically easier to build it rather than a non-certified design. In 2013, following its purchase of Horizon Nuclear Power, Hitachi began the process of generic design assessment of the Hitachi-GE ABWR with the UK Office for Nuclear Regulation. This was completed in December 2017. In July 2016 Toshiba withdrew the U.S. design certification renewal for the ABWR because "it has become increasingly clear that energy price declines in the US prevent Toshiba from expecting additional opportunities for ABWR construction projects". Locations The ABWR is licensed to operate in Japan, the United States and Taiwan, although most of the construction projects have been halted or shelved. Japan and Taiwan , four ABWRs were in operation in Japan: Kashiwazaki-Kariwa units 6 and 7, which opened in 1996 and 1997, Hamaoka unit 5, opened 2004 having started construction in 2000, and Shika 2 commenced commercial operations on March 15, 2006. Another two partially constructed reactors are in Lungmen in Taiwan, and one more (Shimane Nuclear Power Plant 3) in Japan. Work on Lungmen halted in 2014. Work on Shimane halted after the 2011 earthquake United States On June 19, 2006 NRG Energy filed a Letter Of Intent with the Nuclear Regulatory Commission to build two 1358 MWe ABWRs at the South Texas Project site. On September 25, 2007, NRG Energy and CPS Energy submitted a Construction and Operations License (COL) request for these plants with the NRC. NRG Energy is a merchant generator and CPS Energy is the nation's