TOKYO — The operator of a coastal nuclear power plant agreed Monday to the Japanese government’s request to shutter three reactors there until it builds a seawall and other tsunami protections.

Chubu Electric Power Co. acted at a special board meeting after Prime Minister Naoto Kan requested the temporary shutdown at the Hamaoka plant amid concerns a earthquake magnitude 8.0 or higher could strike the region within 30 years.

The government acted after evaluating Japan’s 54 reactors for quake and tsunami vulnerability after the March 11 disasters that crippled the Fukushima Dai-ichi nuclear plant in northeast Japan.

“We understand that the prime minister’s request is based on increased concerns over nuclear power in the wake of the Fukushima Dai-ichi nuclear power plant accident,” Chubu Electric President Akihisa Mizuno said at a news conference.

About 79,800 people live within a 6-mile (10-kilometer) radius of the Hamaoka plant about 125 miles (200 kilometers) west of Tokyo.

Nuclear energy provides more than one-third of Japan’s electricity, and shutting the Hamaoka plant is likely to exacerbate power shortages expected this summer.

The three reactors account for more than 10 percent of Chubu’s power supply. The Hamaoka plant is a key power provider to central Japan, including nearby Aichi, home of Toyota Motor Corp.

Since the March 11 disasters, Chubu Electric drew safety measures that include building a 40-foot-high (12-meter) seawall nearly a mile (1.5 kilometers) long over the next two to three years, company officials said. Chubu also promised to install more emergency backup generators and other equipment and improve the water tightness of the reactor buildings.

The Hamaoka plant lacks a concrete sea barrier now. Sand hills between the ocean and the plant are up to 50 feet (15 meters) high, deemed enough to defend against a tsunami around 26 feet (8 meters) high, officials said.

The government earlier estimated the improvements to the Hamaoka plant could take two years.