"In 1989, Korea began construction on their first domestically developed OPR-1000 design... Twelve reactors of this standard design began construction between 1989 and 2008, and their costs declined in a stable manner... representing a 13% cost decline (1% annualized)." (Lovering 2016)

The problem is, even after reaping this cost decline, totaling 50%, nuclear power is still noncompetitive in South Korea. They were built for energy independence after oil shock, not for cheap electricity.