Fukushima, the catastrophe caused by criminal negligence - BF

Fukushima, the catastrophe caused by criminal negligence (by Peter Ungerer and Dr. Bernd Fleischmann, 3/31/2022) A magnitude 9 earthquake off the coast of Japan and the subsequent tsunami triggered one of the largest nuclear power plant (NPP) accidents on March 11, 2011. This report describes the causes, sequence and consequences of the accident. At the outset, the operating crews of the six reactors at Fukushima Daiichi deserve our respect for their mastery of the disaster caused by management and corrupt institutions. There was not even an emergency manual for the simultaneous power failure in two or more reactors.

Simplified, the reactors at Fukushima are equivalent to a 21 m high pressure cooker with a diameter of 5.53 m, in the center of which sits a reactor with more than 400 fuel elements. Each decaying uranium atom exports 2 neutrons, which, if they hit other uranium 235 isotopes at the right speed, will split them. In the process, 2 neutrons are exported again. A chain reaction starts when the neutrons have the right speed. This requires a moderator that slows them down accordingly. The moderator at Fukushima is water. If the water evaporates in the event of a fault, there is no longer a chain reaction.

A nuclear reactor therefore cannot "explode", even if some opponents of nuclear power plants claim so, thereby disqualifying themselves.

Back to our cooking pot, where we want to regulate the amount of steam produced; this is done by control rods between the fuel elements, which absorb some of the neutrons.

The further they are inserted, the lower the power of the reactor becomes. After the control rods have been fully inserted, the fuel elements still generate power for a certain time because some elements decay naturally. This so-called residual heat is 2.5% of the nominal power after one minute, 1% after one hour and about 0.13% after one month. If you dump boron salt into the reactor, it has the same effect as completely inserting the control rods. This is the safe quick stop of the chain reaction in nuclear power plants.

The residual heat was the problem in Fukushima.

After the earthquake, which had a magnitude of 6 to 7 at the nuclear power plant site, the control rods were automatically fully inserted and the so-called "cold status" was initiated. The cold status is reached when the temperature in the "pressure cooker" has fallen below 100 °C. Then the water stops boiling and the pressure drops. Pumps supply cold water to the reactor vessel before the cold state and the steam is cooled down until it becomes water again. The pumps in Fukushima need electricity from outside. However, the earthquake caused the electricity poles to fall because they were not designed to be earthquake-proof.

First scandal: The electricity poles should have been built earthquake-proof.

Electricity to the NPPs was then supplied by two emergency diesel generators each and the cold-state procedure started successfully. Damage caused by the earthquake, which would have prevented the cold status, was not detected. However, most of the diesel generators were installed in the basements of the nuclear power plants due to gross

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negligence and were not water-protected. Forty minutes after the seaquake, the tsunami, which was more than 15 m high at this point, overtopped the Fukushima Daiichi coast and tsunami walls, which had a total height of 10 m (reactor units 1 to 4) to 13 m (units 5 and 6). The Meiji-Sanriku seaquake of 1896 resulted in a 25 m high tsunami. So one was warned and should have built higher tsunami protection walls.

Second scandal: construction without sufficient tsunami protection should never have been approved.

The diesel generators of reactor units 1 to 4 were flooded, rendering them unusable.

Units 5 and 6 were powered by an air-cooled diesel installed at a higher level and reached the safe cold phase. Elevated diesels should also have been provided for units 1 through 4.

Third scandal: The accident would not have happened if all diesel generators had been installed at a higher altitude.

Power plant units 1 to 4 in Fukushima Daiichi were therefore without power, the control center was flooded and there was no information about the status of the power plant units. It was not possible to open or close any valves. Three units had been running at full capacity prior to the earthquake. They had degraded perhaps 20 to 30 °C from the 250 °C operating temperature, and were still evaporating their cooling water. With high school physics one can calculate when the reactor core, still producing residual heat, will begin to melt without cooling water. What does our cooking pot do then? It ruins its seals and blows off the radioactive steam via emergency valves. That's still better than a pressure rupture in the big pot, which would contaminate the environment even more.

The "steam boiler" sits in a containment made of the best reinforced concrete as a second line of defense. Since the containment has a much larger volume, the pressure is reduced.

If one manages to pump water into the reactor building and sprinkle the containment from the outside, one has a good chance to cope with above scenario without contaminating the environment. But this could not be done in Fukushima until days after the accident, because there were fire trucks, but no freshwater ponds! These ponds were mandatory, but for 30 years they were not enforced to be built. Modern nuclear plants have a large water tank above the reactor vessel that provides adequate cooling for three days without pumps (by gravity alone). During this time, power lines or diesel generators can be repaired.

Fourth scandal: there was no fresh water reservoir, although it was mandatory.

If only one of the four scandalous mistakes had not been made, the disaster would not have happened.

In NPPs, there is a risk of hydrogen being released. That's why there are catalysts in which hydrogen reacts with oxygen to form water. In Fukushima, these were not

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installed for cost reasons; instead, cheaper electricity reactors were used, which of course could not function without electricity. In addition, the pipe shafts between the power plant units were not sealed and the hydrogen spread between the units. Because of this, there were explosions of oxyhydrogen gas in two of the buildings, which blew away the walls of the nuclear power plants. Because of the parts of the buildings lying around, access to the reactors and their cooling was further impeded.

Fifth scandal: There were no catalytic converters that would have prevented the oxyhydrogen explosions.

Courageous workers cut holes in the roofs of units 5 and 6, where the hydrogen could escape and there was no oxyhydrogen explosion. This was against the law, but the threatened prosecution did not happen. The two units continued to run until 2014 because the high altitude diesels allowed for a clean shutdown after the earthquake.

The second-generation reactors have too small containments and can survive a shutdown for only 4 to 8 hours without outside power and water. This was known to the designers. If electricity and water are available, then the Fukushima accident will not be repeated even with these old designs. Third-generation reactors have much larger containments and survive a shutdown for at least 3 days, current NPPs even 7 days. The residual heat is then less than half a percent of the rated power and does not cause any further damage. The reactor vessel is located below the feedwater tank, both are inside the containment. In de-energized emergency mode, the water circulates without pumping due to the thermosiphon effect: the water in the reactor heats up until it starts to evaporate, and the steam condenses on the inside walls of the containment, which is air-cooled from the outside. Water from a tank above the containment supports the cooling. It would only have to be refilled after 3 to 7 days. The power of a fire truck would be sufficient for this. In heat exchangers inside the containment, the heat from the reactor is passed on; the radioactive steam cannot escape to the outside. In the old generation of reactors at Fukushima, on the other hand, radioactive steam drives the turbines outside the containment. But even these old reactor types continue to operate, with improved power and water supplies. Third-generation nuclear plants are at least a factor of 10 safer than second-generation plants without the mistakes made in Japan.

Strictly speaking, Fukushima proved that preventing such an accident costs some money but the contamination of the environment is easily avoidable. But it has to be planned, documented and implemented. At the time the Fukushima power plants were built, the cost for nuclear power was 2 US-$ cents per kWh. The NPP operator TEPCO and the Japanese government did not enforce essential regulations for cost reasons and simply "forgot" about them. The statement of German chancellor Angela Merkel: "If Japan does not manage the risks of nuclear energy, who will?" was therefore unfounded!

Today, nuclear energy is well manageable if the planning and supervision of NPPs is competent and not corrupt. After the Three-Mile-Island-problem, the US created a national safety authority and took competences away from the states. Experts from the

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authority reside at the NPPs. They have access to all information in the NPP and the authority can completely take over control of the NPP in an emergency. We should adopt the system for the EU. US companies have to insure their employees against industrial accidents. For years, NPP operators have paid the lowest insurance premiums, which proves the confidence of insurance companies in the NPPs. Germany has put a lot of money and engineering effort into the peaceful use of nuclear energy. Together with France, we were on the way to becoming the world's leader in nuclear power. Now Germany has the highest electricity costs in the world - twice as high as in France or the US - with constantly declining security of supply.

The most consequential scandal: Angela Merkel accelerated the "Energiewende” with the nuclear phase-out in order to save the elections in March 2011 in Baden-Württemberg for her party, the CDU. This populist maneuver did not help, but the energy policy and financial damage will burden Germany for decades to come!

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