Melted nuclear fuel eroded reactor container by up to 65 cm: TEPCO

This is no news to many. Enhanced erosion of metal in reactors has been a problem since the Manhattan Project days, when Bradford Shank and others worked on the problem at Los Alamos. Tepco’s use of seawater was an attempt to cover up and present self sufficiency when US experts were aghast.

The intermittent ongoing criticality of the molten cores and the resultant neutron flux in the presence of water simply accelerates the process. The longer it goes on, the greater the chance of reactor vessel damage of far greater magnitude than has occurred already.

The Mainichi Daily explains:

Melted nuclear fuel eroded reactor container by up to 65 cm: TEPCO
In this image released Saturday, April 16, 2011, by Tokyo Electric Power Co., top of the container of the nuclear reactor, painted in yellow, of Unit 4 at the Fukushima Dai-ichi Nuclear Plant is observed from its side with a T-Hawk drone Friday, April 15, 2011 in Okuma, Fukushima Prefecture, northeastern Japan. (AP Photo/Tokyo Electric Power Co.)
In this image released Saturday, April 16, 2011, by Tokyo Electric Power Co., top of the container of the nuclear reactor, painted in yellow, of Unit 4 at the Fukushima Dai-ichi Nuclear Plant is observed from its side with a T-Hawk drone Friday, April 15, 2011 in Okuma, Fukushima Prefecture, northeastern Japan. (AP Photo/Tokyo Electric Power Co.)

TOKYO (Kyodo) — The operator of the crippled Fukushima Daiichi nuclear power plant said Wednesday that the concrete base of the No. 1 reactor container had been eroded by up to 65 centimeters when the fuel inside melted, although the steel container itself was left intact.

According to Tokyo Electric Power Co.’s analysis, all of the fuel inside the No. 1 reactor melted after cooling functions failed in the wake of the March 11 earthquake and tsunami, with a substantial amount of the fuel melting through the base of the reactor pressure vessel and dropping into the outer primary container.
In this March 12, 2011 image made from video from NTV Japan via APTN, smoke rises from Unit 1 of the Fukushima No. 1 Nuclear Power Plant in Okuma, Fukushima Prefecture. (AP Photo/NTV Japan via APTN)
In this March 12, 2011 image made from video from NTV Japan via APTN, smoke rises from Unit 1 of the Fukushima No. 1 Nuclear Power Plant in Okuma, Fukushima Prefecture. (AP Photo/NTV Japan via APTN)

If the erosion had expanded another 37 cm, the damage would have reached the steel wall, according to the utility known as TEPCO.

As for the Nos. 2 and 3 reactors, which also experienced meltdowns, the amount of fuel that dropped to the bottom of the pressure vessel is estimated to be around 60 percent.
Fukushima No. 1 nuclear plant’s No. 1 reactor building, with its nearly-completed cover, is seen on Oct. 8 in this photo provided by Tokyo Electric Power Co.
Fukushima No. 1 nuclear plant’s No. 1 reactor building, with its nearly-completed cover, is seen on Oct. 8 in this photo provided by Tokyo Electric Power Co.

The bottom of the two reactors’ pressure vessels is unlikely to have been damaged on a large scale. But if the fuel had melted through the vessels, the primary container of the No. 2 reactor could have been eroded by 12 cm and that of the No. 3 reactor by 20 cm, TEPCO said.

Currently, the melted fuel inside the Nos. 1 to 3 reactors is believed to be cooled by water injection and no further erosion is occurring, it said.

(Mainichi Japan) November 30, 2011 http://mdn.mainichi.jp/mdnnews/news/20111130p2g00m0dm147000c.html

I disagree with the idea that “no further erosion is occurring”. That’s got to be crap. Water plus neutrons and gamma = Hydrogen peroxide. Some coolant. Fill your car up with that and see how long the metal in your engine lasts.

See also http://jcwren.chem.uwo.ca/research.html

http://jcwren.chem.uwo.ca/research.html#steel

Another point in this article is the contining “Tepco don’t know” situation eg “IF the fuel had melted through the vessels, the primary container of the No. 2 reactor could have been eroded by 12 cm and that of the No. 3 reactor by 20 cm, TEPCO said.”

For 60 years the nuclear industry reckoned it knew it all. That ordinary were ignorant. Reverse is true. It seems to me. If this was 1954, I’d be called a Communist by General Electric and if American, the State Department would take my passport away, like they did to Linus Pauling.

These days, well, I’m just a fanatic according to them. Na, I’m just a Mac geek who likes writing the truth because it gives an excuse to crank up the Macbook.

It’s all Steve Jobs fault.

Think Different. Think truth. Anyway, on with the show.

From Clara Wren’s research site at http://jcwren.chem.uwo.ca/research.html#steel

One important topic is the effect of gamma radiation during nuclear plant operation,
as it pertains to corrosion of steels. We look at many materials, but here are a few
interesting results from carbon steel at pH 10.6.

The effect of the gamma radiation is to drive the steel to a more oxidizing potential as
this experiment shows, regardless how the initial steel is treated. When we ramp up
the temperature, we can make thick films, and we see differences between radiation
and no radiation cases. In both cases, notice how the oxide is very uniform.

Sure enough, the oxide film is a little thicker after a few hours when radiation is
applied. HOWEVER, the outer layers are slightly different, as no radiation leaves a
slightly amorphous film. Does this lead to less or more corrosion over time? We’ll let
you know…

Now about those uniform films… This is thanks to the pH we have picked (10.6,
similar to room temperature CANDU coolant). This pH finds a nice low solubility for
iron cations, particularly enhanced for Fe(II) – containing species. Take a look at our
solubility diagram, and the comparative pH 7 films, which are rough/patchy.

At pH 7, the higher corrosion potential will likely cause more corrosion, since Fe(II)
species will dissolve away. The film structure would agree with this, as a very rough
surface is formed, consistent with dissolution/precipitation.

Radiation Related Aqueous and Colloid Chemistry
Most of the time, water is relegated to a couple of roles in corrosion processes:
Hydrogen evolution to support corrosion of active species and transportation/solvation
of species necessary for corrosion.
Within an environment subject to ionizing radiation, water can play a more active role
in corrosion. When high energy radiation interacts with water, a host of species is
formed, including solvated electrons, hydrogen peroxide, superoxide and hydrogen
and oxygen gases. These species change the chemistry of the water, and alter the
corrosion behaviour of associated steels. The process is outlined below:

end quote.

Finally, the more water TEPCO dumps in the reactors, the greater the chance of water moderated fission occurring in the still molten cores. That the cores remain molten is confirmed by the Mainichi article above, which quotes TEPCO. TEPCO does not know precisely where the corium are. Much has been made of the fact that the reactor temperatures have dropped below 100 degrees. Not surprising seeing as the molten fuel has done an Elvis. Its left the building.

The limitations of reactors in this situation are not TEPCO’s fault. Except that they bought and operate them. GE salesmen must have been pretty good at what they did.

These uncertainties regarding the state of the Fukushima reactors, which continue to vent fission and fuel particles, make a full evacuation of the wider Fukushima area crucial if safety of people, rather than the limiting of costs to TEPCO, are to be the main priority.


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