John DEveau explains how a nuclear reactor works. (Hawaii 24/7 photo by Baron Sekiya)

Karin Stanton | Hawaii 24/7 Editor

Hawaii residents are not in any danger from radiation that has escaped the Fukushima Daiishi nuclear plant in Japan.

John Deveau, a Navy veteran who worked more than three decades in the nuclear energy industry, reassured about 40 people during a presentation Friday evening at NELHA in Kona.

Deveau said he doesn’t have all the answers, but he is confident that potentially dangerous levels of radiation are not currently threatening the Hawaiian Islands.

“I’m not trying to un-scare anyone. There are risks,” he said. “But these are very low levels.”

Deveau said the highest recorded level of radiation at the Fukushima site was 155.7 millirems, which was reduced to 4.4 millirems after the units were dosed with sea water.

The dose limit for the public is 100 millirems per year.

Deveau said radiation can be absorbed through the skin or ingested, but cautioned that the dose limits are based on consistent exposure for an entire year. People won’t be harmed by a single serving of Japanese spinach, he said.

John Deveau talks about the nuclear reactor in Fukushima, Japan. (Hawaii 24/7 photo by Baron Sekiya)

He also cautioned against taking potassium-iodide. Iodine radiation settles in the thyroid, he said, as does potassium-iodide. If you dose up on potassium-iodide, the iodine has no place to go and flushes out in the body’s regular elimination process.

The situation in Hawaii is being closely monitored, Deveau said, with air sample stations in Hilo and Oahu constantly checking airborne radiation levels.

“Have we killed anyone from radiation? No. But does it scare you silly? Yes. Because you can’t see it,” he said. “I haven’t heard of a single person being contaminated (from the Fukushima crisis).”

Deveau said the Fukushima Daiishi power plant was not damaged by the 9.0 magnitude earthquake, but was knocked offline about an hour later when a 20-30 foot tsunami washed through the complex.

“Things continued on in normal fashion,” he said, as the plant began its automatic shutdown process.

The Fukushima Daiishi complex includes six reactors built between 1971 and 1979. Three were online at the time of the earthquake and tsunami. However, all six house spent fuel pools – large vats of radioactive water covering the fuel rods removed from the reactor.

Each reactor is housed in a building about 70 feet tall and about 30 feet wide. The core of the reactor is where uranium atoms are split, which superheats water that turns to steam and is funneled to huge turbines.

The 14-foot fuel rods are immersed in 50 feet of water, which is used to cool reactors that operate at a temperature of about 3,000 degrees Fahrenheit.

Although the mainline power and back up diesel generators were knocked out, the plant had about eight hours of emergency battery power.

“That’s a station blackout,” Deveau said, and the water began to boil off in the reactors.

Left uncooled, reactors can eventually will melt down, or begin a corrosion process that will eat through the 15 feet of concrete and leach radiation into the air and ground.

“That’s scary point No. 1,” Deveau said.

Deveau said plant operators must strike a balance between pressure and temperature. Once the pressure started building up, he said, plant operators had to make an ‘ugly decision’ to vent some of the radioactive steam instead of risking an explosion of the containment vessel.

It was the build up of hydrogen gas that blew the roofs off the Fukushima buildings, he said. At that point, crews began pumping sea water into the shattered buildings and making every effort to cool the cores and fuel pools.

“We saw those roofs blow off and that’s bad,” he said. “I don’t know how they’ve done it for two weeks. In the dark and without any instruments.”

Although nuclear plant crews make public health and safety the No. 1 priority, Deveau said, sometimes venting the containment vessels of heat and pressure is the best choice.

“Radioactivity is bad. A lot of radioactivity is really bad,” he said. “All that stuff will come up into the atmosphere and gets distributed real easily.”

However, Deveau said, he has no intention of leaving Hawaii and would not hesitate to visit Japan right now.

Deveau also answered questions from the audience. Here are some highlights:

Is the worst part over for the Fukushima Daiishi power plant?

“No. I don’t know. I’d love to say ‘yes,’ but I really don’t know. They need to get the power back on, get water in to cool it and figure out what is operable first.”

What does the immediate future hold for Fukushima Daiishi power plant?

“Nobody knows. We don’t know the status of what’s going on in there and probably won’t for some time.”

What really happened inside the six reactors?

“It might be years before we find out.”

Earlier this week, Japanese authorities said the plant would be permanently closed once the crisis is over.

John Deveau talks about the nuclear reactor in Fukushima, Japan. (Hawaii 24/7 photo by Baron Sekiya)