The slow and shocking meltdown of Japan’s quake-hit Fukushima nuclear power plant is raising fears of radiation poisoning in the country. Crikey asked Australia’s nuclear experts for clarification…
What sort of danger are the people of Japan in?
“It’s a difficult question to ask,” said Professor Aidan Byrne, an expert on nuclear physics and Dean of Science at the Australian National University. “There are two schools of thought at play here: one is that any amount of exposure to radiation is dangerous for humans; the second is that we live in an environment where we are exposed to radiation everyday, therefore humans have evolved to live with small amounts of exposure.
“Saying that, I don’t think the radiation-related health risks are of real danger to anyone other than the workers on site. And even then, the biggest danger they face is not from radioactive poisoning, but from the likelihood of fires and explosions.”
According to the World Nuclear News, Japanese authorities told the International Atomic Energy Agency (IAEA) that radiation levels at the plant “reached a peak of some 400 millisieverts per hour.” Yet while this is considered to be a high dose-level, the IAEA said it should be understood as “a local value at a single location and at a certain point in time.” Later readings suggested radiation was at 11.9 millisieverts per hour, followed six hours later by 0.6 millisieverts, which the IAEA said indicated the “level of radioactivity has been decreasing.”
Yet Professor Byrne said it was difficult to ascertain the exact levels of radiation (due to patchy information provided by the Japanese government), and therefore difficult to be conclusive on the possible radiation-related health risks. Byrne notes that it’s unclear whether the levels being reported are the stable levels or whether it’s simply the peaks: “Some radioactive chemicals will be in the steam vapour itself, but the lifetime of most of these radioactive materials is very short so that it decays away quickly.”
He says that to determine the health risks for individuals, the total dose per person needs to be assessed. Yet he doubted the dose would be high enough to severley affect people outside of the evacuation zone. (The Australian Media Science Centre held a briefing yesterday. It told journalists the materials being released into the atmosphere at present are not as dangerous as other chemicals released in mass quantities during Chernobyl.)
So the radiation disappears?
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“Yes,” said Professor Byrne, “the materials currently exposed are inert and short lived, they decay quickly and don’t pose a lot of danger to people who breathe them in.”
What happens to the materials, once inside the body?
“What is important is the total radiation per person and how long it stays in the body, but at the moment, unless you are on the site itself, radiation contained within the body would be minimal. The material exits the body via excrement, perspiration and can be exhaled.”
There’s been a lot of talk about “low-level” radiation in the media — what does this actually mean?
Gerald Laurence, Adjunct Associate Professor at the University of Adelaide and a radiation safety consultant to the University of Adelaide and Flinders University, told Crikey: “It’s the most terrible word! It’s bandied around by people who can’t be expected to [know] anything. It’s misleading and causes confusion as it doesn’t mean anything.”
What matters, says Professor Laurence, is how people absorb the radioactivity: “Older people and younger people absorb radioactive energy more easily. I assume however, in this case, ‘low-level’ means there will be no further immediate health effects. I would feel it is a reasonably low risk, because the radioactive contaminants form fuel rods have released relatively slowly.”
Does everyone within a 30km radius need to take potassium iodine tablets?
That depends on what happens next, says Professor Byrne: “If nothing major happens then no.”
Some are comparing this nuclear event to Chernobyl — is that fair?
“What we have here is nothing to do with the core of reactor, it is not a nuclear explosion,” said Professor Laurence. “The radiation is coming from spent fuel rods, that were stored in a pond, it protects against radiation and provides cooling. The water leaked after the earthquake so now they are generating heat and radioactivity.”
“Chernobyl was a reactor that burnt for days and days and spewed radioactive material high into the atmosphere; it wasn’t contained. This event, and if we get through today without further fire and explosions, it will remain contained and pose a relatively low health risk to those in surrounding areas,” said Professor Byrne.
The 1986 disaster was a Level 7 event on the International Nuclear Event Scale. The World Health Organisation (WHO) defines this as “an accident involving a major release of radioactive material with widespread (major accident) health and environmental effects”.
Considered the worst nuclear event in history, the cause was attributed to a fault in the design of the reactor. A disruption to power on April 26, 1986 lead to a rupture in the graphite reactor, which caught fire and caused a series of explosions. It remained on fire and contaminants spread as far as northern Europe.
Estimates on the number of deaths directly related to the incident are vague — most sources cite the toll at around 50, including workers and fisherman — while related deaths are even more contested, ranging from thousands to a million. Thyroid cancer is listed as the main health risk caused by the radioactivity, a result of humans ingesting the iodine-131 released into the atmosphere. Experts called the event a nuclear meltdown, with vast amounts of highly radioactive materials being released high into the atmosphere, affecting drinking water and food supplies. About 336,000 people were relocated because of the accident.
Experts say radiation is being released slowly, from water vapour emanating from spent fuel rods. The Fukushima event is not as bad because of the superiority of the structure of the power station itself — the really dangerous radioactive materials are being contained within the reactor.
As Steve Crossley, a radiation physicist based in Perth, said of the Fukushima plant: “[Materials are] contained within a thick steel pressure vessel which is inside a containment structure, these structures are specifically designed to prevent release of core materials even during accident situations. Also boiling water reactors (BWR — the kind at Fukushima) are cooled and moderated by water which, unlike the graphite core at Chernobyl, cannot burn.”
What about the Three Mile Island accident?
On March 28, 1979 reactor 2 at the Three Mile Island nuclear power plant suffered a partial meltdown. The cause of the accident was due to a failure of the reactor itself. There were no listed deaths or long-term health effects, although that’s still a contested issue.
It was categorised as a Level 4 event, which is defined by the WHO as an “accident without significant off-site risk.”
The latest Japan disaster at the Fukushima plant has been categorised as a “serious accident” Level 6 incident: “An accident involving a signiﬁcant release of radioactive material, and likely to (serious require full implementation of planned countermeasures, but less severe than a accident) major accident.”
Has the media reported the latest event fairly?
Professor Byrne believes the health risks from the disaster have been overstated. “No one in Tokyo should be worried unless conditions in the plant get worse,” he said. “Media beat-up isn’t helpful at a time like this, instead they should be focusing on the dangers of aftershocks.”