Tokyo Electric Power Co., the operator of the troubled Fukushima Daiichi nuclear power plant, has begun steps to suspend operations at its last running nuclear reactor in order to carry out checks.
The No. 6 unit at the company's Kashiwazaki-Kariwa plant is expected to be shut down early on Monday, leaving all of the 17 reactors idle, including three units which have suffered a meltdown at the Fukushima Daiichi.
The No. 6 unit is scheduled to undergo checks for about two and a half months.
As a result, only one of Japan's 54 commercial nuclear reactors will remain online. It is a unit at Hokkaido Electric Power Co.'s plant on Hokkaido, northern Japan.
But that reactor is also due to be shut down in early May for scheduled maintenance work.
"We are expected to secure a stable supply of electric power for the time being," Tokyo Electric president Toshio Nishizawa said in a statement.
"But we call on the customers to continue cooperating in saving electricity within a reasonable range."
A 9.0-magnitude earthquake and ensuing massive tsunami ravaged Japan's northeast coast in March last year, leaving 19,000 dead and sparking meltdowns at the Fukushima plant, some 220 kilometres (140 miles) northeast of Tokyo.
Due to safety worries following the worst nuclear accident in 25 years many power utilities cannot restart reactors even after undergoing regular checks.
Despite the government's declaration in December that the crippled Fukushima plant had been brought to a stable "cold shutdown" state, 92 percent are worried about it, a survey has said.