OPR-1000
The OPR-1000 is a South Korean designed two-loop 1000 MWe PWR Generation II nuclear reactor, developed by KHNP and KEPCO. The OPR-1000 was originally designated as the Korean Standard Nuclear Power Plant (KSNP), and was re-designated as the OPR-1000 in 2005 for foreign sales. It was developed based on the Combustion Engineering (C-E)'s system 80 design, through a technology transfer agreement. The reactor core design was derived from the C-E designed Arkansas Nuclear One Unit 2, the nuclear steam supply system (NSSS) was derived from the C-E designed units at Palo Verde Nuclear  Generating Station and auxiliary plant design was derived from the earlier Unit-1 and Unit-2 at the Yeonggwang (now Hanbit) Nuclear Power Plant. Based on the OPR-1000 design, KEPCO has developed a Generation III+ uprated plant, the APR-1400. Reactor fleet. The reference plants used to develop the OPR-1000 design using technology transfer are Yeonggwang (now Hanbit) Unit-3 and Unit-4, which came on-line in 1995 and 1996, respectively. The first plants designated as OPR-1000 plants are Ulchin (now Hanul) Unit-3 and Unit-4, which came on-line in 1998 and 1999, respectively. Korea Hydro & Nuclear Power (KHNP) states an improved OPR-1000 design  has been implemented at eight units: Including the reference Unit-3 and Unit-4 at Hanbit (formerly Yeonggwang), there are a total of twelve OPR-1000 plants, all inside South Korea. Notes. The first plants incorporating the APR-1400 design are still under construction. Ten units are planned: History. The first start of the OPR-1000 at Shin Kori Nuclear Power Plant Unit-1 was 28 February 2011. This OPR-1000's first malfunction was noted on 2 October 2012 at 8:10 a.m. Shin Kori-1 was shut down after a warning signal indicated a malfunction in the control rod, which is used to control the rate of  fission of nuclear materials, according to the Korea Hydro & Nuclear Power Co. It is the first time that reactor, located 450 kilometers southeast of Seoul, has been shut down due to a malfunction since it began commercial operation on 28 Feb. 2011. An investigation was undertaken to verify the exact cause of the problem. In 2012, a probe was opened regarding some fraudulently-certified parts installed in five OPR-1000 reactors over a ten-year period. Hanbit-5 and -6, which had a greater number of fraudulent parts, were shut down until the parts could be replaced, and Hanbit-3 and -4 and  Hanul-3 were allowed remain on-line pending parts replacement. Hanbit-5 and -6 were cleared for restart in early 2013, but in April 2013, following a tip, four additional units were shut down and not allowed to restart until fraudulently-certified safety-related control cabling was replaced: Shin Kori-1 and -2 and Shin Wolsong-1 and -2; although construction on Shin Wolsong-2 was complete, it had not yet achieved operational status, and it was not allowed to start up until cabling was replaced. The same cabling was used at the APR-1400 units then under construction at Shin Kori (Units 3 & 4), forcing  a year-long delay in their startup. After cabling was replaced, Shin Kori-1 and -2 and Shin Wolsong-1 were approved for restart in January 2014. Shin Wolsong-2 was connected to the grid in February 2015, with commercial operation commencing in July 2015.