Who is Dr. Frank Shu? Noted Astrophysicist on Alternative Energies

Dr. Frank Shu is a celebrated astrophysicist and Shaw Prize winner now dedicated to making an impact on climate change. He has developed a process that converts biomass to carbon neutral (or negative) coal that can be enhanced by a molten salt nuclear reaction.


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1 Comment

  • Reply December 18, 2014

    Raw Science

    Oliver Tickwell and Mark Caldo: Dr. Shu’s response to your comments is below.

    Oliver Tickwell and Mark Caldo make valid points. However, power reactors of any kind are unsuitable of making nuclear weapons for a very fundamental reason. They produce a flood of neutrons that quickly produce contaminating isotopes – Pu-240 in the case of Pu-239 bombs or U-232 in the case of U-233 bombs – that render such efforts ineffectual. To produce nuclear bombs, there are only two proven paths: enrich natural uranium so that U-235 is more than 90% of the total uranium or special nuclear reactors that release neutrons so slowly that it is possible to remove Pu-239 from the reactor before it absorbs another neutron and becomes Pu-240. Neither path is available to power reactors. Linking nuclear power to nuclear weapons is a false association.

    Comparing electricity from non-dispatchable solar PV to electricity from dispatchable nuclear power plants is an also unproductive activity. They both have positive roles to play in de-carbonizing the primary energy supply chain. But solar PV is not cheap if one considers actual energy generated (nameplate power multiplied by the effective time that one gets to use that nameplate power over the course of a year) because the effective time is typically only 20% the number of hours in a year. At high latitudes like Germany, the capacity (or load) factor is only about 10%; while it is more than 90% for nuclear power plants in France where Germany imports much of its clean electricity when the Sun isn’t shining or the wind isn’t blowing. While it is true that solar panel prices have plummeted over the last decade, total costs per kWh have leveled off in recent years because the costs of installation and maintenance do not decrease with time. Nevertheless, the threats of looming climate change are so fearsome that it would be foolhardy to eliminate any effective weapon we have to combat it.

    It is misleading to claim that molten salt reactors do not have their technological challenges. Intense bombardment by fast neutrons does make metal brittle on time scales of 2 years or less (which explains why metal-alloy fuel rods in conventional light water reactors need to be replaced typically every 18 months); and they will also cause dimensional changes in nuclear-grade graphite on time scales as short as 4 years, unless one uses enough graphite to moderate most of the fission neutrons to slow speeds. There is also the matter of decay heat, which is not solved merely by having freeze plugs and dump tanks. Freeze plugs take too long to respond to emergency conditions. To deal with the decay heat problem in dump tanks in a completely safe way, one either has to build only very small reactors (to decrease the ratio of the volume where the decay heat is generated to the surface area where the decay heat can be carried away by passive systems), or one must possess the capability of on-line cleaning of fission products from the fuel salt. The latter capability is also crucial to breeding Th-232 into U-233, so well-designed thorium breeder molten-salt reactors can automatically be walk-away safe, whereas other designs cannot automatically make this claim unless they are built at very small sizes.

    Finally, the store of used fuel from light-water reactors is the only plausible nuclear material abundant enough in the world to start up the desired fleet of thorium molten-salt breeder-reactors. We should not wantonly burn up this resource for temporary use if we want sustainable nuclear power that can supply most of the primary energy needs of the 21st century and beyond.

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