He also said the government will seek to shut down the country's second-oldest nuclear reactor, the Wolsong No.1, as soon as possible depending on the country's power supply conditions.
The speech was Moon's followup on his presidential campaigns to cut coal and nuclear power. "So far, the country's energy policy focused on low prices and efficiency".
South Korea's oldest nuclear reactor, the 40-year-old Kori No. 1, was planned to halt operations at midnight on Sunday, becoming the country's first nuclear plant to close permanently amid plans for a shift towards natural gas and renewables. But it's time for a change.
"We will abolish our nuclear-centered energy policy and move toward a nuclear-free era".
Two new nuclear reactors now under construction would be subject to a public consultation and may be scrapped.
The Kori 1 was South Korea's first reactor, built in 1977, reports Yonhap News Agency. Former President Lee Myung-bak promoted nuclear energy as part of the country's clean energy strategy and helped local companies win billions of dollars worth of deals to build nuclear reactors overseas.
An official at the city government expected that the deal, if made, will be instrumental in making Busan an industrial hub in the sector of nuclear reactor decommissioning.
Moon said he will soon reach a consensus on the Shin Kori No 5 and Shin Kori No 6 reactors after fully considering their construction costs, safety and the potential costs of paying compensation.
Moon stressed that the operational lifespan of aged nuclear power plants will not be extended.
Moon hailed the reactor's shutdown as of Monday, calling it the "start" of a journey to becoming a nuclear-free nation. Its nuclear electricity production was the fifth-largest in the world, according to the World Nuclear Association.
But South Koreans' enthusiasm for nuclear energy quickly waned following the 2011 Fukushima meltdowns in neighboring Japan.
President Moon has said he wants to increase the portion of renewable energy to 20% by 2030 and increase LNG imports, possibly through a Russian pipeline passing through North Korean territory.
Numerous reactors are located near residential areas along the country's southeast coast.
The conservative administrations of former presidents Lee Myung-bak and Park Geun-hye both pushed for nuclear reactors.