Relax, That Scary Fukushima Headline Was Fake News
I blame 1950s B-movies: sixty years later, it appears that most of what journalists know about radioactivity came from watching Godzilla.
On February 8, Adam Housley of Fox News reported a story with a terrifying headline: "Radiation at Japan's Fukushima Reactor Is Now at 'Unimaginable' Levels." Let's just pick up the most exciting paragraphs:
The radiation levels at Japan's crippled Fukushima nuclear power plant are now at "unimaginable" levels.
[Housley] said the radiation levels -- as high as 530 sieverts per hour -- are now the highest they've been since 2011 when a tsunami hit the coastal reactor.
"To put this in very simple terms. Four sieverts can kill a handful of people," he explained.
The degree to which this story is misleading is amazing, but to explain it, we need a little bit of a tutorial.
The Touhoku earthquake and tsunami on March 11, 2011, along with all the other damage they caused, knocked out the TEPCO Fukushima Daiichi ("plant #1") and Daini ("plant #2") reactors. Basically, the two reactors were hit with a 1000-year earthquake and a 1000-year tsunami, and the plants as built weren't able to handle it.
Both reactors failed, and after a sequence of unfortunate events, melted down. I wrote quite a lot about it at the time; bearing in mind this was early in the story, my article from then has a lot of useful information.
Let's dispose of the silliest error first: "Four sieverts can kill a handful of people."
Here's what he really means: an exposure to four sieverts total dose will kill about half the people exposed. If you were inside the reactor, after a little over two minutes of exposure the chance you'll die is 50/50.
Next, let's look at the terror headline itself, the "unimaginable" level of radiation.
Here is a schematic of a "boiling water reactor" which is what is at the Fukushima plant. The "1." and "2." I've added; they'll be important in a minute:
To get a little bit better information than the Fox story, let's go instead to the Science Alert website for their article on this:
The radiation levels inside Japan's damaged Fukushima Daiichi nuclear reactor No. 2 have soared in recent weeks, reaching a maximum of 530 sieverts per hour, a number experts have called "unimaginable."
Now, let's refer back to the image above. Most commercial nuclear reactors have what's called the "primary containment" around the reactor: a sealed steel or reinforced concrete shell around the actual reactor. Outside that is the "secondary containment," another sealed building surrounding the primary containment. The unexpectedly high radiation levels -- and 530 Sieverts is way high, no question -- were detected inside the containment, the area marked by "1."