“Super-GAU”: Die ultimative Katastrophe?

Gudrun Pausewang vs. Reality

Grafenrheinfeld Nuclear Power Station (operating up until 2015). In the novel “Fall-Out” by Gudrun Pausewang, an accident at this plant causes radiation doses in the multiple Gray regime at even over 100 km distance. This is physically impossible.

Even if the Grafenrheinfeld plant had been pulverized in some way while running at full capacity (which would only be possible through external attacks, e.g. with a bunker buster weapon): Humans in Fulda (over 100 km from the plant) being subjected to doses in the range of 2 — 3 Gray, with symptoms like loss of hair, immune deficiency and diarrhea, is completely unrealistic. For this to occur, the entire radioactive inventory of the reactor would have to be dumped on Fulda. The novel “Die Wolke” (Engl.: “Fall-Out”) by Gudrun Pausewang does not hold up to the reality of radiation biology.

Radiation can be harmful to humans, as two thieves in Goiânia, Brazil had to find out in the absence of any nuclear power stations when stealing a forgotten radiotherapy source from an abandoned hospital. But as is always the case with toxins: It is the dose that makes the poison. Sudden exposure to doses of several Grays causes acute radiation sickness, higher values may lead to death. The effects of lower exposures, spread out over longer timespans, are more difficult to determine. But there are data and studies.

We are constantly exposed to ionizing radiation: Energetic cosmic radiation reaches us from space, in rocks, water, food, even our own bodies nuclear decay processes take place. In some locations, natural radiation is extremely intense. At Guarapari Beach in Brazil, values of over 100 Millisieverts per year can be measured. If this was artificial radiation, the place would have to be evacuated: During the Fukushima crisis, 20 mSv/year were defined as the limit. Guarapari radioactivity is emitted by thorium-containing monazite sand. There was never any observation of increased cancer or mutation rates. Different effects from natural and artificial radiation can be ruled out: From quantum mechanics, it is known that both kinds of rays are indistinguishable (and thus do not even represent “two kinds”).

In earlier days, radiation biology was based around what is known as the LNT-Hypothesis: “Linear, no Threshold” — every kind of radiation exposure is harmful, less is always healthier, cancer risk rises linearly with dose rate (absorbed energy per time). But this hypothesis has become discredited and the Hormesis Model is preferred: Low dose rates are not harmful, but in fact trigger the cells’ self-repair mechanisms, thus reducing cancer risk. Only at values above 100 mSv/year one may have reasons for worry.

The evacuation in the vicinity of Fukushima Daiichi nuclear plant was, at least in its full extent, overblown and caused more harm than the radiation itself. Most areas are suitable for habitation again. Not a single Japanese person was killed by the reactor accident (while earthquake and tsunami claimed 18.000 victims). Similarly, Three Mile Island did not have any measurable effects on the health of Americans. Only the Chernobyl meltdown took 30 lifes and caused over 100 non-lethal cases of radiation sickness; a further 6000 cases of thyroid cancer were found in children and adolescents up until 2005 in Belarus, Russia and Ukraine with the reactor accident being the suspected cause in at least part of the cases.

30 dead people are 30 dead people too many! But we must keep our perspective: Nearly all other industries cause deadlier accidents with more victims, such as chemical explosions or collapsing dams. Also, not all nuclear reactors are equally accident-prone.

Chernobyl is not the World

Roofs of abandoned Pripyat. In the distance, the power plant can be made out.

Imagine a car, which accelerates, when the driver intends to brake: This is what Soviet RBMK reactors do, one of which failed catastrophically in 1986. This model has a positive temperature coefficient: Increasing temperature will raise the fission rate. Thus, active control is always necessary, and critical operating errors unsurprisingly led to a disaster. In western nations, such power reactors are not permitted. Modern pressurised or boiling water reactors have to have a negative temperature coefficient: When temperature rises, fuel density and neutron moderation in the expanding water decrease, lowering the fission rate. Destroying a modern nuclear plant through reactivity excursions or even causing it to explode is not even possible through intentional sabotage.

What is possible is reactor meltdown from decay heat caused by the fission products embedded in the fuel. This is what happened in Three Mile Island and Fukushima. TMI caused no damage whatever outside of the reactor building. Fukushima resulted in substantial release of radiotoxicity, as the containment buildings missed hydrogen recombinators which are obligatory in western plants. Even here, there were no radiation-related casualties, increase in cancer rates should be unmeasurably low.

Modern-day nuclear plants are at the top of the list of safe industries. But there is still room for improvement, which will not only lead to broader public acceptance, but also increase profitability: Without the need for layered safety, the plant can be build at a lower price.