Author: Jan Mühlstein, Energy&Management
As of January 2015
What happens when a meltdown occurs in a reactor? Dr. Klaus Hassmann, spokesman for the Energy Technology Cluster, has summarized findings of risk studies from the 1970s and 1980s on the occasion ofthe accident at the Fukushima nuclear power plant in 2011 . In the approximately 40-page article "Der Supergau - Kernschmelzen und was man darüber wissen sollte" reminds Klaus Hassmann of the findings that have been available for more than 25 years about the physical and chemical phenomena and processes in nuclear meltdowns.
"I would not have thought it possible that the disaster in Japan would affect me so much," said Klaus Hassmann. The mechanical engineer, who earned his doctorate in 1977 at the Institute of Nuclear Energetics at the University of Stuttgart, thus describes his sympathy for the affected people, but also his lack of understanding for the chaotic countermeasures of the operator of the damaged power plant and its incomplete information policy. But Hassmann was also upset by the reporting in the German media: "Preconceived notions have long been repeated, but the physical processes in a nuclear power plant were only explained in a very rudimentary way, if at all." Above all, he criticized the absence in the public discussion of any reference to the "knowledge that has been available for more than 25 years about the physical and chemical phenomena and processes involved in nuclear meltdowns." By this he means the German Risk Study on Nuclear Power Plants, published in 1979 and revised again in the mid-1980s.
Research Program on Core Meltdowns
Hassmann is not one of those who leave it at that to get angry. He therefore sat down and summarized the results of the core meltdown research program conducted as part of the risk study, in which he was involved as a scientist. Or more precisely, he summarized the results again, because he had already done so with the book "Fission Product Release in Core Meltdowns, Methodical Determination Experimental Validation" published in 1987. Thus, he describes in detail what happens when a core meltdown occurs in a pressurized water reactor as a result of a "design-basis accident", which interaction processes take place, how the partially melted fuel elements can still be cooled. He does not conceal the danger posed by the released hydrogen. He reports how long the individual barriers - of which the reactor pressure vessel and the containment are the most important - can prevent the release of the radioactive fission products. He lays out the degradation mechanisms that operate when fission products can be kept inside for days.
No final certainty for core meltdown scenarios
Hassmann also knows the limits, however. Asked what makes him certain that all accidents would proceed only according to the scenarios studied, he answers succinctly, "Nothing." But the probability of that, he says, is high. In addition, the operating crews can still control the processes within certain limits, provided they have the necessary knowledge and are trained accordingly.
Would he be able to convince nuclear energy skeptics with this? "I don't want to do that at all," Hassmann answers. "I wrote for the curious who want to know more. The reader will not find an assessment of whether nuclear energy is justifiable or not in my text. This decision she or he, whether technically educated or not, must make himself."
He himself would have no problem settling next to a modern pressurized water reactor. Hassmann, however, does not see himself as a nuclear energy fetishist. After all, in his more than 20 years at Siemens, he has been involved not only with reactor technology, but with conventional power plants, coal gasification, hydropower, solar hydrogen, fuel cells and research into renewable energies. And even after his retirement in 2003, he continues to freelance and consult on energy issues, including as spokesman for the Cluster Energietechnik Bayern. "I didn't like certain things that happened with nuclear energy either," Hassmann adds. "What happened in Asse or in Krümmel has already made me very thoughtful."
The approximately 40-page pdf document "Der Supergau - Kernschmelzen und was man darüber wissen sollte" has been published by the trade journal Energie & Management at www.energiemarkt-medien.de/fileadmin/ftp/2011-04-kernschmelzen-hassmann.pdf.