It is becoming increasingly difficult to open up the problems of science and its technological potentials to the general public. And yet it is essential that they are part of the democratic dialogue in an open society. However, they show such rapid and complex dynamics that their characteristics are not only removed from the intellectual, but increasingly also from the ethical radar of most people. It is therefore not surprising that important scientific discoveries and technological developments fly all too often underneath the radar screen of public attention.
One particular debate on science and technology policy, which is already more than 50 years old, is the debate on nuclear energy. One could call it the “grandmother of all technology-political discussions”. It is a master example of its own kind, both in a negative and positive sense. Its intensity and breadth would be desirable for other fields of technology, while the obvious commercial and political interests of many of its participants could be bound within narrow limits.
Recently, some science and television journalists gave a surprisingly strong pledge in favor of nuclear energy. However, most of today’s arguments of pro-nuclear power advocates are based on the promise of future technology rather than on the features of current reactors. Even the appeasing assurances of the nuclear industry have never been able to completely conceal the residual risks of today’s nuclear energy and to convince those voices which refuse to accept mathematically quantified model calculations for probabilities as the basis for social discourse on nuclear energy (if one multiplies very low numbers, i.e. low risk, with a very large number, i.e. a high, possibly civilization-harming damage after an event, the assessment of the result reaches its mathematical limits).
Particularly one concept stands out when it comes to the (not always) new promises of future super-safe and super-clean nuclear power technologies: the “Liquid-Fluoride-Thorium-Liquid Salt Reactor (LFTR)”. One might say (in an appropriate exaggeration) it represents the very future promises of the atomic industry. The LTFR is a nuclear reactor, in which the nuclear fuel is dissolved in molten salt (usually fluorides) which at the same time serves as a heat transfer agent. Such a reactor could also function as a breeder reactor. Once set in motion with a small amount of fission material, such as uranium-235 or plutonium-239, it could then be fed exclusively with non-fissionable nuclides, for example thorium-232. LFTRs differ in a variety of ways from conventional reactors, which brings many advantages (for example, no possibility of the core meltdown, since the fuel is already liquid and even in an emergency the pressure in the reactor does not increase, furthermore higher temperatures operation, which increases the thermodynamic efficiency), but also some severe challenges. Although breeding reactors had already been advocated by the nuclear industry as the new security and technology paradigm for nuclear reactors in the 1980s and already back then their security issues were hotly debated and after the 1986 reactor accident at Chernobyl subject to numerous political protests, their proponents seem to not be bothered to propagate an old message anew and provide this “potential omnipotent future technology” with four essential attributes that could “convince even hard-core nuclear opponents”: inherent security, 10’000 times less nuclear waste, lower risk of proliferation, lower costs. Too good to be true, one might think.
Well, indeed that is what it is: too good to be true. For it is already apparent that in reality neither of these attributes apply anywhere close to how their advocates present it to the public.
Concerning safe operation: The idea of LFTRs had already been implemented in the 1960s at the American Oak Ridge National Lab (albeit without using thorium). It is therefore neither new nor technically untested (the physicist Eugene Wigner was already thinking about the idea of salt-molten reactors in the course of the US atomic bomb “Manhattan Project” during World War II). The final report of this project in the 1970s concluded that “there are major problems with the concept which are inherently difficult to solve”. The fact that even the one or the other conspiracy theory came up, which declared this report as politically or even militarily motivated (the current uranium/plutonium technology is well suited for the production of nuclear weapons), can be interpreted as an attempt to sweep the open problems of the LFTR under the rug. For example, the problems of chemically separating the numerous fission products in the reactor are still very little understood. It is also not yet known how deal with the approximately 50 times higher amount of the produced radioactive tritium, which at the prevailing high temperatures of the LFTR diffuses quite easily through the walls of the reactor vessel. And as early as the 1970s, the physicists fought with severe corrosion effects in the containment and support materials caused by the fluorides. And in general, breeder reactors do not automatically have a negative steam bubble coefficient (as required by most international nuclear safety regulations), which, particularly in large reactors, requires additional safety devices compared to conventional systems (which in the case of a thorium reactor, however, are automatically provided by a tricky melt fuse, as its advocates claim). To date, there is no modern official safety assessment for LFTRs.
On reduced waste: The problem of treating and disposing weak to medium radioactive machine and plant components is probably similar to that of conventional uranium reactors (even if the decay time of the waste products is lower). Moreover, it is particularly difficult that some fission products of the LFTR have to be considered as not suitable for disposal, since solved in fluoride salts they are water soluble, and thus have to be processed into a form suitable for final disposal.
On the lower risk of proliferation: The breeding cycle in a LFTR produces uranium-233 (via protactinium 233), which has a similarly low critical mass as plutonium-239 which is ideal for nuclear weapons, plus it displays a much smaller spontaneous decay rate than plutonium. This makes it ideal for nuclear weapons. In addition, there is the formation of Neptunium-237 in a LFTR, whose neutron cross-section also makes it potential nuclear weapon material (even though no one has constructed a corresponding bomb yet; its critical mass is 60 kg).
And last but not least, on costs: Like every new nuclear technology, the initial investment sum required for an LFTR is enormous, which lets even operators of nuclear power plants react ambivalently on this new technology. In particular, doubts are voiced on the economic benefits of the considered small “modular units” of LFTRs. The manufacturers would have to contract thousands of them before production in order to justify the immense a priori investment costs – an economic adventure of its own kind! Furthermore also the running costs would not be automatically lower as claimed: On the one hand, the costs indeed decrease with the low pressure employed and with savings on less expensive containment. On the other hand, however, additional costs may arise as a result of the more expensive materials necessary to deal with the higher operating temperatures, and also due to more sophisticated systems for gas treatment or for the collection of tritium.
With all of these problems, it will take another 40 to 70 years to complete a commercially available LFTR, which even remotely lives up to what its proponents promise. Thus we recognize precisely the very argumentative structure of the nuclear industry, which has taken us politically hostage since its beginnings in the 1950s: Today, we are building on a technology that is associated with considerable uncertainties, risks, and unknown costs, but for the future we promise a golden age of unlimited energy availability, once we solve all problems (which, of course, requires billions of additional public funding!).
However, the old problems of nuclear power also arise in the new technologies. There is a saying in the investment world: “Do not throw good money after bad money “. We should also consider this in our energy policies, instead of embarking on the ever-same promises of an over-subsidized, uncertain, and both physically as well as politically questionably arguing industry. For as it is stated in Matthew 9:17: “Neither do people pour new wine into old wineskins. If they do, the skins will burst; the wine will run out and the wineskins will be ruined.”