Letter to the Editor

In the January Newsletter, Parmentola and Kessel (hereinafter called P&K) replied to my article [1] that pointed out seven shared drawbacks of fission and fusion reactors with a manifesto on the need for nuclear energy to save civilization [2]. Nevertheless, they concede that both classes of nuclear reactors do share the problems of radiation damage, radioactive waste disposal, remote handling and tritium release, but purport to show that these drawbacks can be mitigated or eliminated.

On the other hand, P&K deny that the additional drawbacks of nuclear proliferation, water demands and overwhelming operational costs will apply to fusion reactors. The following observations emphatically re-affirm the relevance of these problems for fusion systems.

Nuclear Proliferation. It’s a relatively simple matter to produce fissile material (Pu-239 or U-233) in a fusion device, while extraordinarily difficult to generate net electricity. In fact Pu-239 could be produced even today, albeit in tiny amounts, in the JET assembly at Culham operating in deuterium simply by placing natural or depleted uranium oxide at any location inside the bore of the magnet coils or between the coils. Slower neutrons will be those most readily soaked up by U-238.

P&K’s Ref. 9 and related publications emphasize the high weapons quality of the Pu-239 that can be produced in fusion reactors, and call for elaborate safeguards. Implementing safeguards to prevent plutonium production (or tritium diversion) may be feasible, but that is surely a drawback shared with fission reactors.

Coolant Demands. Constraints on water usage will increasingly curtail the deployment of any large thermoelectric power plant. ITER is likely to be the only fusion facility even remotely resembling a reactor for the next thirty years, and ITER will use only water as the primary coolant. If successful, water will probably be the primary coolant in subsequent fusion facilities as well as the fluid for the secondary coolant loop, just as water has been used almost exclusively in commercial fission reactors for the last sixty years.

Despite the endless succession of "Advanced Fission Reactor Initiatives" (P&K’s headline) that incorporate alternative coolants, all commercial fission reactors under construction worldwide continue to be cooled by water. This sobering circumstance indicates that water cooling of fusion reactors cannot be readily replaced by gas or liquid metal or molten salt.

Outsized Operating Costs. At least 1,000 mostly skilled personnel (over four shifts) will comprise much of the operating cost. Another significant expense as exemplified by the 100 MWe to be consumed continuously on the ITER site [3] is the background power drain by essential auxiliary systems — helium cryostats, water pumping, vacuum pumping, tritium processing, building HVAC, etc. This non-interruptible power consumption has nothing to do with the reactor’s recirculating power during operation, the subject addressed by P&K, and must be purchased from the regional electric grid during planned and unplanned outages.

For inertial confinement systems, the manufacture of millions of target fuel capsules every year will be a huge ongoing expense. And all types of nuclear plants must fund the periodic disposal of radioactive wastes as well as end-of-life decommissioning.

It is inconceivable that the total operating cost of a fusion reactor will be less than that of a fission reactor, and therefore the capital cost of a viable fusion reactor must be close to zero (or heavily subsidized) in localities where the operating costs alone of fission reactors result in a non-competitive cost of electricity.

[1] D. L. Jassby, APS Physics & Society, Vol. 45, No. 4 (Oct. 2016), pp 5-6.

[2] J. A. Parmentola and C. E. Kessel, APS Physics & Society, Vol. 46, No. 1 (Jan. 2017), pp 9-12.

[3] J. C. Gascon, et al., "Design and Key Features for the ITER Electrical Power Distribution," Fusion Science & Tech. Vol. 61, Jan. 2012, p. 47-51.

Daniel L. Jassby
PPPL (retired)
dljenterp@aol.com

These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the view of APS.