Economic, safety and environmental prospects of fusion reactors

Abstract

Controlled fusion energy is one of the long term, non-fossil energy sources available to mankind. It has the potential of significant advantages over fission nuclear power in that the consequences of severe accidents are predicted to be less and the radioactive waste burden is calculated to be smaller. Fusion can be an important ingredient in the future world energy mix and can be part of an 'insurance policy' energy strategy to develop new sources as a hedge against environmental, supply or political difficulties connected with the use of fossil fuel and present-day nuclear power. Progress in fusion reactor technology and design is described for both magnetic and inertial fusion energy systems. The projected economic prospects show that fusion will be capital intensive, and the historical trend is towards greater mass utilization efficiency and more competitive costs. Recent studies emphasizing safety and environmental advantages show that the competitive potential of fusion can be further enhanced by specific choices of materials and design. The safety and environmental prospects of fusion appear to exceed substantially those of advanced fission and coal. For example, the level of radioactivity in a low activation fusion reactor at 1 year and at 100 years after shutdown is calculated to be about one-millionth of the radioactivity in a fission reactor of the same power. Likewise, the maximum plausible dose predicted at the site boundary in the case of a low activation fusion reactor is estimated to be between 100 and 500 times smaller than that estimated for a fission power plant. Clearly, a significant and directed technology effort is necessary to achieve these advantages. Typical parameters have been established for magnetic fusion energy reactors, and a tokamak at moderately high magnetic field (about 7 T on axis) in the first regime of MHD stability (|8 s 3.5 I/aB) is closest to present experimental achievement. Further improvements of the economic and technological performance of the tokamak are possible through the following achievements: higher magnetic fields to lower the required plasma current and reactor size; higher values of the plasma beta, including reaching the second stable MHD regime, to lower the requirements on field and plasma current; and more efficient techniques to drive the plasma current. In addition, alternative, non-tokamak magnetic fusion approaches may offer substantive economic and operational benefits, although at present these concepts must be projected from a less developed physics base. For inertial fusion energy, reactor studies are at an earlier stage, but the essential requirements are a high efficiency ( ^ 10%) repetitively pulsed pellet driver capable of delivering up to 10 MJ of energy on target, targets capable of an energy gain (ratio of energy produced to energy on target) of about 100, reactor chambers capable of absorbing the energy released per shot at conditions consistent with power generation, and effective means of isolating the target chamber and driver system.

Energy for Future Centuries - Prospects for Fusion Power as a Future Energy Source

“…It is not yet clear if they will meet a number of technical specifications with regard to thermo-mechanical properties and the ability to withstand a high neutron flux and further research is necessary to clarify these points [48]. But even if existing structural materials like stainless steel are used, the induced radioactivity in a fusion reactor is still about 10 times less than in a fission reactor of comparable power [29,39].…”

“…The European fusion effort is concentrated on the latter (with tokamaks, stellarators and reversed field pinches) and hence we will briefly review only this method here. The interested reader can find a wealth of additional information in the references [34,38,39,40].…”

“…However, a fusion reactor will require radiation shielding since it has a radioactive inventory consisting of (i) tritium and waste contaminated by tritium and (ii) reactor materials activated by the neutrons of the fusion reaction. Studies [34,38,39] indicate, however, that an adequate choice of the latter can minimise the induced radioactivity such that recycling should become possible after some decades to a century. Thus, radioactivity does not have to be inherent to nuclear fusion, in contrast to nuclear fission where the fission reaction itself leads to dangerous long-lived radioactive products.…”

How might controlled fusion fit into the emerging low-carbon energy system of the mid-twenty-first century?

“…Fusion energy systems have a number of potential qualitative advantages over fission-based energy systems [1]. Among other things, it is these potential advantages that have elicited sustained support for fusion research over 60 years.…”

Key Aspects of the Safety Study of a Water-Cooled Fusion DEMO Reactor

“…(For more details on a historical overview of fusion reactor safety studies from the dawning to the end of 1980's, see Ref. [1].) A series of Safety and Environmental Assessment of Fusion Power (SEAFP) studies was conducted in Europe in 1990's [2,3].…”