Volunteers are being asked to grow sunflowers this year, then send the seeds to the stricken area where they will be planted next year to help get rid of radioactive contaminants in the plant's fallout zone.

The campaign, launched by young entrepreneurs and civil servants in Fukushima prefecture last month, aims to cover large areas in yellow blossoms as a symbol of hope and reconstruction and to lure back tourists.

"We will give the seeds sent back by people for free to farmers, the public sector and other groups next year," said project leader Shinji Handa. The goal is a landscape so yellow that "it will surprise NASA", he said.

The massive earthquake and tsunami left more than 23,000 people dead or missing on Japan's northeast coast and crippled the Fukushima nuclear power plant that has leaked radiation into the environment since.

Almost 10,000 packets of sunflower seeds at 500 yen ($6) each have so far been sold to some 30,000 people, including to the city of Yokohama near Tokyo, which is growing sunflowers in 200 parks, Handa said.

Handa -- who hails from Hiroshima, hit by an atomic bomb at the end of World War II -- said the sunflower project was a way for people across the nation to lend their support to the disaster region.

"This is different from donations because people will grow the flowers, and a mother can tell her children that it is like an act of prayer for the reconstruction of the northeast," Handa said.

"I also hope the project will give momentum to attract tourists back to Fukushima with sunflower seeds in their hands. I would like to make a maze using sunflowers so that children can play in it."

The low-interest $1.24 billion crisis response loan will be provided later this month through the Development Bank of Japan, government minister Banri Kaieda told a news conference on Friday.

Chubu Electric faces costs for shifting to other sources of power generation after Prime Minister Naoto Kan ordered the suspension of the Hamaoka nuclear plant due to its location in a high-risk earthquake zone southwest of Tokyo.

The March 11 earthquake and tsunami devastated Japan's northeast coastline, leaving 23,000 people dead or missing and crippling cooling systems at Tokyo Electric Power's Fukushima Daiichi nuclear plant, triggering reactor meltdowns.

More than three months on and tens of thousands of people remain evacuated from homes, farms and businesses in a 20-kilometre (12-mile) zone around the radiation-spewing plant, with evacuation pockets also further afield.

Utilities not directly affected by the earthquake and tsunami that battered the Fukushima Daiichi plant have not restarted reactors that were undergoing maintenance at the time, due to objections from local governments.

As a result, fewer than 20 of Japan's 54 reactors now are operating, raising the potential for power shortages across wider areas of the nation.

An effort to cut electricity usage by 15 percent in Tokyo and the surrounding region as well as the Tohoku region will begin on July 1 in a bid to avoid blackouts during the peak summer months.

Kansai Electric Power Co, which is based in western Japan, has said it will also ask businesses and households to voluntarily reduce their power usage this summer by 15 percent.

Japan, the world's number three economy, endures 20 percent of all major earthquakes and generates about 30 percent of its power from nuclear plants.