Japanese military helicopters helped ground crews Thursday in the effort to stabilize temperatures at the Fukushima Dai-ichi nuclear plant by dumping loads of water on a damaged reactor to avoid a massive radiation release.

A pair of CH-47 Chinook choppers, with lead plates slung underneath and flight crews in protective gear, dropped 7,500-litre loads of water on the Unit 3 reactor, passing over in missions 40 minutes each to limit radiation exposure.

Aside from trying to bring down the temperature, the helicopters were also trying to fill the Unit 3 cooling pool where spent fuel rods are stored. The plant’s operator, Tokyo Electric Power Company, said that pool was nearly empty, which could cause the rods to overheat and emit more radiation.

On the ground, police water cannons, usually used during riots, were also used to help fill the Unit 3 pool. Military vehicles used to extinguish plane crash fires were also put to use at the plant, Chief Cabinet Secretary Yukio Edano said. It’s not known yet if the enhanced effort worked. Officials plan to continue the spraying Friday.

And the possibility of plutonium being released into the environment was yet another concern that emerged at the Unit 3 reactor Thursday.

The United Nations Atomic Energy Agency said the situation remains “very serious” but noted there’s been no “significant worsening” in the last 24 hours.

American officials have also raised concern about the cooling pool in Unit 4. U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko said all the water in that pool is gone. Tokyo Electric Power Co. said it believes the fuel rods at that reactor are still covered, but an official with the Japanese nuclear safety agency appeared to be more on side with the American assessment of the situation Thursday.

Other crews are rushing to run a power line to the plant to restore its cooling systems — a move that could potentially ease the crisis.

Tokyo Electric Power Co. had a slightly more positive outlook on the dire circumstances Thursday, saying radiation levels had stabilized at low levels and that workers are making headway with the spraying and efforts to connect the power line.

A core group of emergency workers, dubbed “The Fukushima 50”, who’ve likely put their own health on the line to avert a meltdown, had to temporarily evacuate Wednesday when radiation levels surged due to a possible breach in the Unit 3 containment vessel.

Last week’s 9.0-magnitude earthquake and subsequent tsunami devastated northeastern Japan and knocked out power to the Dai-ichi plant and the backup diesel generators, crippling its cooling systems. Since then, there have been three hydrogen explosions and fires at four of the facility’s six reactors — Units 1 through 4. Over the past two days concern has been growing over rising temperatures at the Unit 5 and 6 reactors.

The death toll is now 5,700 but it’s believed the twin natural disasters killed more than 10,000 people and left thousands homeless.

The Japanese government has no plans to extend its 20-kilometre exclusion zone around the Dai-ichi plant. It’s also advising anyone within a 30-km radius of the plant to remain indoors.

The United States has stepped up screening of inbound passengers and cargo for radiation.

The Department of Homeland Security handles more than half a million radiation alarms a year, though most are related to medical procedures, The Associated Press reported.

More than 4,500 people passed through a voluntary screening gate at Taiwan’s Taoyuan airport Thursday and at least 26 passengers from Japan were found to have mild radiation contamination.

On Thursday, a Canadian government spokesperson told CityNews:

“The Government of Canada is not currently screening passengers or cargo arriving in Canada from Japan. However, we will continue to monitor the evolving situation related to the nuclear power plant in Japan.”

The U.S. has now joined countries like France and Australia by chartering planes to get its nationals out of Japan.

The Canadian government has no evacuation plan in place now, but is advising citizens to stay at least 80 km away from the affected power plant. It’s also advising Canadians to think about leaving Tokyo and areas hit by the quake and tsunami.

On Thursday the government said it chartered two buses to get Canadians out of the quake zone.

The Foreign Affairs Department says there are 185 registered Canadian citizens still in the affected area.

Canadians seeking information on loved ones in Japan should call Foreign Affairs at 1-800-606-5499.

With files from The Associated Press.