Japan's Chubu Electric Power Co. completely shut down the Hamaoka nuclear plant Saturday following a request last week by Japanese Prime Minister Naoto Kan to suspend the plant in Shizuoka Prefecture for safety concern.

The utility, Japan's third biggest, finished work at 10:15 a.m. to stop atomic fission at its last active reactor, the No. 5 unit, of the plant in Omaezaki, about 180 kilometers southwest of Tokyo. The utility began putting control rods into the reactor's core earlier in the day.

The No. 4 reactor, the other unit which was operating, was suspended Friday. The Nos. 1 and 2 reactors have already been shut down for decommissioning, while its No. 3 reactor was suspended for regular checkups.

Japanese government predicted an 87 percent likelihood of a magnitude-8 earthquake or higher striking the area near the nuclear plant within 30 years, and deemed the nuclear power plant lacks medium-to-long-term measures for protection against disasters, such as embankments.

The government reached the conclusion to suspend Hamaoka plant after evaluating the country's 54 reactors for quake and tsunami vulnerability after the magnitude 9.0 earthquake and ensuing tsunami on March 11 devastated the Pacific coastal regions of northeastern Honshu.

Chubu Electric Power Co., based in Nagoya, said it hopes to resume the plant soon after taking measures to block quake- triggered tsunami waves but Shizuoka governor Heita Kawakatsu remains cautious about the idea. The government said the suspension will last for two to three years.

Chubu Electric will lose more than 10 percent of its power supply capacity with the shutdown of the 3.6 million-kilowatt Hamaoka plant, its only atomic plant. Concerns about electricity shortages in summer when demand peaks will purportedly be offset by increased output by non-nuclear power generation.

The Hamaoka plant in Shizuoka, populated by 3.75 million people, is known as "the most dangerous" nuclear power plant in Japan due to its aged reactors, proximity to a massive fault-line and coastal area and inability to sustain a sizable earthquake similar to the quake and tsunami that crippled Fukushima No.1 plant on March 11.