The Guardian's science correspondent reported on 9 March 2018 that the dream of nuclear fusion is on the brink of being realized according to a major new US initiative that says it will put fusion power on the grid within 15 years.1 Prof Maria Zuber, MIT's vice-president for research, said that the development could represent a major advance in tackling climate change. "At the heart of today's news is a big idea ‒ a credible, viable plan to achieve net positive energy for fusion," she said. "If we succeed, the world's energy systems will be transformed. We're extremely excited about this."
Sadly, it can be said with great confidence that the MIT is talking nonsense. Fusion faces huge ‒ possibly insurmountable ‒ obstacles that won't be solved with an over-excited MIT media release.
In Nuclear Monitor #8422 we summarized an important critique3 of fusion power concepts by retired fusion scientist Dr Daniel Jassby. He has written another article in the Bulletin of the Atomic Scientists, this one concentrating on the International Thermonuclear Experimental Reactor (ITER) under construction in Cadarache, France.4
Jassby notes that plasma physicists regard ITER as the first magnetic confinement device that can possibly demonstrate a "burning plasma," where heating by alpha particles generated in fusion reactions is the dominant means of maintaining the plasma temperature. However he sees four "possibly irremediable drawbacks": electricity consumption, tritium fuel losses, neutron activation, and cooling water demand.
Electricity consumption: The "massive energy investment" to half-build ITER "has been largely provided by fossil fuels, leaving an unfathomably large 'carbon footprint' for site preparation and construction of all the supporting facilities, as well as the reactor itself." ITER is a test reactor and will never generate electricity so that energy investment will never be repaid.
And when ITER is operating (assuming it reaches that stage), a large power input would be required. For a comparable power-producing reactor, a large power output would be necessary just to break even. Power inputs are required for a host of essential auxiliary systems which must be maintained even when the fusion plasma is dormant. In the case of ITER, that non-interruptible power drain varies between 75 and 110 MW(e). A second category of power drain revolves directly around the plasma itself ‒ for ITER, at least 300 MW(e) will be required for tens of seconds to heat the reacting plasma while during the 400-second operating phase, about 200 MW(e) will be needed to maintain the fusion burn and control the plasma's stability.
Jassby notes that ITER personnel have corrected misleading claims such as the assertion that "ITER will produce 500 megawatts of output power with an input power of 50 megawatts." The 500 megawatts of output refers to fusion power (embodied in neutrons and alphas), which has nothing to do with electric power. The input of 50 MW is the heating power injected into the plasma to help sustain its temperature and current, and is only a small fraction of the overall electric input power to the reactor (300‒400 MW(e)).
Tritium: "The most reactive fusion fuel is a 50-50 mixture of the hydrogen isotopes deuterium and tritium; this fuel (often written as "D-T") has a fusion neutron output 100 times that of deuterium alone and a spectacular increase in radiation consequences. ... While fusioneers blithely talk about fusing deuterium and tritium, they are in fact intensely afraid of using tritium for two reasons: First, it is somewhat radioactive, so there are safety concerns connected with its potential release to the environment. Second, there is unavoidable production of radioactive materials as D-T fusion neutrons bombard the reactor vessel, requiring enhanced shielding that greatly impedes access for maintenance and introducing radioactive waste disposal issues."
Tritium supply is likely to be problematic and expensive: "As ITER will demonstrate, the aggregate of unrecovered tritium may rival the amount burned and can be replaced only by the costly purchase of tritium produced in fission reactors."
Tritium could be produced in the reactor by absorbing the fusion neutrons in lithium completely surrounding the reacting plasma, but "even that fantasy totally ignores the tritium that's permanently lost in its globetrotting through reactor subsystems. "
Radioactive waste. "[W]hat fusion proponents are loathe to tell you is that this fusion power is not some benign solar-like radiation but consists primarily (80 percent) of streams of energetic neutrons whose only apparent function in ITER is to produce huge volumes of radioactive waste as they bombard the walls of the reactor vessel and its associated components. ... A long-recognized drawback of fusion energy is neutron radiation damage to exposed materials, causing swelling, embrittlement and fatigue. As it happens, the total operating time at high neutron production rates in ITER will be too small to cause even minor damage to structural integrity, but neutron interactions will still create dangerous radioactivity in all exposed reactor components, eventually producing a staggering 30,000 tons of radioactive waste."
Water consumption: "ITER will demonstrate that fusion reactors would be much greater consumers of water than any other type of power generator, because of the huge parasitic power drains that turn into additional heat that needs to be dissipated on site. ... In view of the decreasing availability of freshwater and even cold ocean water worldwide, the difficulty of supplying coolant water would by itself make the future wide deployment of fusion reactors impractical."
The pumps used to circulate cooling water will require a power supply of as much as 56 MW(e).
Conclusions: Jassby concludes with some critical comments on conventional, fusion and fast breeder reactors:
"Critics charge that international collaboration has greatly amplified the cost and timescale but the $20-to-30 billion cost of ITER is not out of line with the costs of other large nuclear enterprises, such as the power plants that have been approved in recent years for construction in the United States (Summer and Vogtle) and Western Europe (Hinkley and Flamanville), and the US MOX nuclear fuel project in Savannah River. All these projects have experienced a tripling of costs and construction timescales that ballooned from years to decades. The underlying problem is that all nuclear energy facilities ‒ whether fission or fusion ‒ are extraordinarily complex and exorbitantly expensive. ...
"ITER will be, manifestly, a havoc-wreaking neutron source fueled by tritium produced in fission reactors, powered by hundreds of megawatts of electricity from the regional electric grid, and demanding unprecedented cooling water resources. Neutron damage will be intensified while the other characteristics will endure in any subsequent fusion reactor that attempts to generate enough electricity to exceed all the energy sinks identified herein.
"When confronted by this reality, even the most starry-eyed energy planners may abandon fusion. Rather than heralding the dawn of a new energy era, it's likely instead that ITER will perform a role analogous to that of the fission fast breeder reactor, whose blatant drawbacks mortally wounded another professed source of "limitless energy" and enabled the continued dominance of light-water reactors in the nuclear arena."
References:
1. Hannah Devlin, 9 March 2018, 'Carbon-free fusion power could be 'on the grid in 15 years'', www.theguardian.com/environment/2018/mar/09/nuclear-fusion-on-brink-of-b...
2. 'Fusion scientist debunks fusion power', 26 April 2017, Nuclear Monitor #842, 26/04/2017, www.wiseinternational.org/nuclear-monitor/842/fusion-scientist-debunks-f...
3. Daniel Jassby, 19 April 2017, 'Fusion reactors: Not what they're cracked up to be', Bulletin of the Atomic Scientists, http://thebulletin.org/fusion-reactors-not-what-they%E2%80%99re-cracked-...
4. Daniel Jassby, 14 Feb 2018, 'ITER is a showcase ... for the drawbacks of fusion energy', https://thebulletin.org/iter-showcase-drawbacks-fusion-energy11512