Fukushima: Fuel Rod Fragments at Bottom of Reactor Vessels
April 16th, 2011Flashback: Arnie Gundersen: How Fukushima’s Fuel Rods Melted and Shattered
And now…
Via: Japan Times:
Melted fuel rod fragments have sunk to the bottoms of three reactors at the Fukushima No. 1 power plant and could theoretically burn through the pressure vessels if emergency water-pumping operations are seriously disrupted, the Atomic Energy Society of Japan said Friday.
If too many of the melted fuel fragments puddle at the bottom, they can generate enough concentrated heat to bore a hole in the pressure vessel, which would result in a massive radioactive release to the environment..
“It will take at least two or three months … until the situation of fuel rods is stabilized” said Takashi Sawada, vice chairman of the nuclear body.
The fuel rods are being cooled by tons of water that is being manually injected into the reactors and their spent-fuel pools by truck. But if those operations are interrupted for two or three days by an aftershock or other unforeseen event, the reactors’ cores will again be at risk of melting down further, he said.
The nuclear safety committee, consisting of nuclear engineers and academics, compiled the analysis based on the data disclosed by Tokyo Electric Power Co. and the Nuclear and Industrial Safety Agency, the government’s nuclear watchdog. Earlier reports quoting experts giving the same explanation have been circulating in western media for a week.
The fuel rods in reactors 1, 2 and 3 are heavily damaged. Pieces of the rods melted into fragments about 1 cm wide or smaller and drifted to the bottom of the pressure vessels, the committee said.
So here’s something to consider. China Syndrome.
For those that don’t know, the term was coined in 1971 by nuclear physicist Ralph Lapp, and a movie on the subject came out in 1979. Basically, in the amazingly unlikely event that a reactors coolant system and redundant systems were to fail, the fuel rods shattered, and the control rods were no longer in proximity to the fuel, an uncontrolled fission reaction would occur.
Oh.
That’s exactly what’s happening now.
Now lets consider something else. The proximity of Japan to the Pacific Ring of Fire. (Kevin, I’m sure you know it well). If the uncontrolled event were to continue downwards until it reached a point where the ground temperature reached the melting point of the material (I’m pretty sure magma meets this requirement). That would leave a nicely formed vertical lava tube, no resistant pressure other than maybe anything we’ve been tossing down the hole
Would they have just accidentally made the first man-made volcano? It saves all those pesky problems of miles-deep drilling and molten drill heads.
Excuse me while I go cancel my Japanese vacation plans for next December. It may not be quite as safe as I’d hope.
“The fuel rods in reactors 1, 2 and 3 are heavily damaged. Pieces of the rods melted into fragments about 1 cm wide or smaller and drifted to the bottom of the pressure vessels, the committee said.”
I’m not a nuclear engineer and I never took physics, but correct me if I’m wrong in my thinking and questions:
How are they going to get the unspecified amount (tons?) of 1 cm and smaller material into the “temporary” fuel storage casks? Those casks are built for UNDAMAGED fuel rods at specified spacing to prevent them from heating back up from friction of nuclear interaction.
With all of those particles lumped together in the bottom of the reactors and pools, they are going to generate LOTS of heat- there’s no control rods to dampen the nuclear reaction, so it just keeps getting hot enough to boil off the water. From what I understand, that’s why there have been reports of neutron flashes and radiation spikes without any new damage or leaks.
Based on the reading I’ve done about the mess in the tanks at Hanford, Washington, I think the folks at Fukushima are going to have to figure out a way to put the damaged rods and particles into a large circulating water bath (enclosed steel tank) with heat exchangers, for a few decades and hope to God that the power doesn’t ever go out on the circulation pumps, or they will have recriticality AGAIN and it could even explode or melt through the bottom of the tanks.
The logistics of this appear to be FAR greater in scope than Chernobyl, which was a graphite reactor. The graphite burned up and it was overwith in a sense. In Japan, there’s going to be a need for a seemingly endless supply of cooling water that is going to be contaminated with lethal levels of toxins and radioactive particles. That begs the question: Where are they going to store all of that lethal water and the particulates for all of eternity?
It’s no secret that I’m no fan of managers anywhere. Generally, their promotions have vastly exceeded the “Peter Principle” limits that were assumed since the 1960’s- i.e., most of them are blithering idiots. But is anyone in Japan even thinking about arranging a fleet of dump trucks, mountains of sand and oceans of concrete and miles of 1″ diameter rebar? Is there any discussion about how to entomb what they can and how to safely store the rest? Does anyone there have a clue or are they just a bunch of nuclear numb-nut amateurs? Is there a Nuclear “Red” Adair anywhere on the planet? If so, someone better get out the check book and pay him to kick ass, take names and string up the a-holes that get in his way before half of Japan is uninhabitable.
God help them- they need it and so do we.
Fukushima-Diachi logistics- photo series #8 from Cryptome: http://cryptome.org/eyeball/daiichi-npp8/daiichi-photos8.htm
Keep in mind that reactor #3 had MOX fuel in it, and some of the fuel rods in pool #4 are MOX and there’s something like 2 million pounds of fuel onsite.
As the melted fuel assemblies are constantly changing in geometry as well as being affected by neutron absorbing and neutron reflecting contamination, they are likely dropping in and out of criticality. If this molten mass gets to the point where it stays critical, such as in a concentrated mass at the bottom of what is left of the reactor, the amount of heat produced will increase without bound. Temperatures of the magnitude which can actually vaporize rock will be reached. This can continue for months until the remaining amount of un-fissioned material is reduced to the point where criticality is no longer possible. What we have here, my friends, is a real mess.
Depending upon the geometry and configuration of the molten fuel now melting (or having already melted) through the bottom of the reactor(s), the neutron flux may have reached levels never imagined in the design of the reactor(s). That enormous neutron flux will create various new radioactive isotopes through a process known as neutron activation. If there are fissures in the bedrock below the reactor(s), this contamination may reach groundwater aquifers, making natural underground water sources in this part of Japan unusable. Forever.
Just called up my dad, 40 yr veteran of heat exchange unit engineering (retired), multiple reactor applications. He said you bury it and kiss your ass goodbye.