Although I have been covering the nuclear industry, nuclear weapons and proliferation issues for about 20 years, I have not commented on Fukushima on this blog. I didn’t feel I had anything to add to what was being reported in the popular media.

But now, the information being released is beginning to appear inconsistent and contradictory. These are signs of a coverup in progress.

The nuclear event at Fukushima looked bad from its very beginning with the Tohoku 2011 earthquake. My initial concern was that it could get much worse from there. And it did.

I think my Australian colleague Mark Colvin summed it up best in his Twitter message: “Most worrying thing about Fukushima: every day something happens that was categorically ruled out the day before.”

A ghostly image from inside the control room at Fukushima, where emergency workers are trying to assess the situation with flashlights. Click to enlarge. Foto: TEPCO

It is rather typical for such incidents that the public is not told the entire truth at all times.

I  remember Chernobyl well. I was in Vienna at the time, when suddenly the Scandinavians began to wonder why they were suddenly measuring radioactivity in remote lakes, and soon thereafter, in the rain. The Soviet Union was still not admitting that their Chernobyl reactor No. 4 was literally on fire and out of control.

The Chernobyl event turned out to be the most massive nuclear debacle in history, forcing the evacuation and resettlement of hundreds of thousands of people, spewing radioactive pollution over areas thousands of miles away, and resulting in countless deaths. And yet, the seriousness was only gradually admitted — too late for many who ultimately paid with their lives.

Let’s jump back to Fukushima: there was a little noticed tidbit released by Japan’s Kyodo news agency. It reported that a neutron beam had been detected on 13 different occasions, over a period of several days, at a location 1.5 km  (about a mile) southwest of the plant. (Source: http://english.kyodonews.jp/news/2011/03/80539.html)

The beam was reportedly weak — but this distracts from the real issues: Why was it there in the first place? And why was it not made public until 10 days later?

When heavy atoms split in an event called “nuclear fission”, highly energetic particles called “neutrons” shoot out with high velocity. They are so fast that they will simply fly through most matter.

Although these free neutrons can damage living tissues through which they pass, they are too fast to split heavy atoms. Therefore, in a nuclear reactor, a “moderator” substance is employed to slow them down. At just the right speed (and therefore: the right energy level), these neutrons will split additional heavy atoms in the nuclear fuel. This results in the release of more neutrons, which split more fuel atoms, and so forth — the so-called self-sustaining “chain reaction”.

Normally, these free neutrons are contained within the reactor vessel. They certainly should not be measurable from a mile away. For the neutron beam to exist, some kind of nuclear fission reaction must have taken place without shielding. But how and why?

So the report of a neutron beam is very alarming for several reasons:

First, it could be an indication that a reactor containment vessel has split open. Or, at least that pipes have vented or spilled gas or liquid containing fissile materials from the inside of the reactor core.

Unfortunately, it is most likely that the point of origin would have been Fukushima Daiichi Unit 3. This is the only of the three destroyed units running on mixed-oxide fuel. This type of fuel contains a high percentage of plutonium, which could be the explanation for the observed neutron beam.

Depending on how bad the leak is or was, this might mean that the surrounding ecosystem could be poisoned for generations.

But what alarms me even more is that the neutron emissions were reportedly detected on March 13, but not admitted to the public until March 23. What exactly happened on March 13?

In hindsight, it now seems interesting that days ago, some sources at the IAEA were already speaking of suspicions that the primary reactor containment vessel had failed. But they did not clarify what evidence they had.

Has the IAEA been told of the neutron emissions much earlier, and has everyone conspired to keep this tell-tale sign from the public? Perhaps in order to allow an ordered evacuation?

During the subsequent days and until today, the official line of TEPCO has been that a primary vessel breach was “unlikely”, then “not certain”. Today, Japan’s prime minister reportedly voiced concerns that indeed, it may have occurred.

Short of a reactor containment vessel breach — could the neutrons have originated from spent fuel? Not unless there is something very seriously wrong. After fuel elements are used in the reactor, they are hot and highly radioactive. So they are stored outside of the primary reactor vessel, in a “spent fuel pool” of water. The water does two things: it cools the fuel, and it also absorbs some of the radiation it emits.

The fuel for the types of reactors used at Fukushima Daiichi comes in form of pellets, which are contained in long metal rods. We know that at Fukushima some (most? all?) of the water in the pool was lost. The fuel elements were partially or fully exposed to air. Without proper cooling, the casings holding the fuel may split, and gases containing fissile materials may escape.

Meanwhile, workers have been dousing the reactors inside the destroyed buildings, and the exposed spent fuel elements with salty sea water, which of course is corrosive and generally a material of last resort among firefighters.

Minerals from the water will undergo chemical reactions with the radioactive isotopes emitted from the reactors or leaking spent fuel elements. This results in thousands of different radioactive chemicals with different soluability, some of which will seep into the soil, ground water and the coastal waters. But right now, this is seen as the lesser evil.

Still, the flow of information is spotty and consists of pieces of a puzzle that does not seem to fit together. Something is very fishy here.

UPDATE, March 26, 2011:
TEPCO admitted today that water pools in the basement of at least one reactor building was “10 million times more radioactive” than what was to be expected of water from inside the reactor cores. This is another indication that (a) casings of fuel elements have broken and (b) a primary reactor vessel has been breached.

UPDATE, March 27, 2011:
In a stunning reversal comes now TEPCO’s announcement that it made a “mistake in the assessment of the measurement of iodine-134” and that the “the number is not credible”.

As Julie Makinen and Kenji Hall write in the Los Angeles Times today, “But now, more than two weeks into the disaster, the updates — via news conferences, press releases, website data charts and Twitter feeds, all laden with technical terms such as “bequerels,” “microsieverts,” “millisieverts” and “iodine-131″ — have become so frequent and so granular as to become essentially indecipherable and meaningless to the average person.”

Actually, I’d expand this to say the releases (both the radioactive and the information) are full of gaps, contradictory and inexplicable even to experts.

UPDATE, March 28, 2011:
According to TEPCO announcements today, traces of plutonium have been found in several soil samples taken from the site. This is almost irrefutable proof for a breach for a primary reactor containment vessel, fuel element casings, and a partial fuel meltdown.