The Fusion Future By William Lama, Ph.D
It’s not an exaggeration to say that nuclear fusion is the fundamental life force. The Sun generates this life-giving energy in a process that involves both implosion and explosion. The inward gravity force produced by the its immense mass compresses the Sun’s core, producing temperatures of 15 million degrees Celsius and pressures more than 300 billion times the atmospheric pressure at the Earth’s surface. These extreme conditions cause hydrogen nuclei (protons) to fuse into helium nuclei giving off millions of electron volts (MeV) of explosive energy. This fusion energy balances the gravitational force and shines vitalizing light and heat on the Earth.
Here on Earth, nuclear fusion can induce an uncontrolled reaction (a bomb) or a much more difficult controlled reaction in a nuclear power plant. The so-called “hydrogen bomb” came first.
Just like in the Sun, a hydrogen bomb involves both implosion and explosion. On the left: An atomic (fission) bomb implodes the core producing temperatures and pressures that cause the hydrogen nuclei in the core to fuse. On the right: The uncontrolled fusion causes an immense explosion. Hydrogen bomb | PNGWing
We are interested in the controlled fusion of hydrogen isotopes. Deuterium and Tritium contain a proton plus a neutron (D) or a proton plus two neutrons (T). The fusion reaction D + T → He + n requires a temperature of 39 million degrees Celsius. The fusion creates a helium nucleus and a fast neutron.
Ignition
In my last article I mentioned that “nuclear fusion is suddenly all the rage” since “ignition” had finally been achieved after decades of work and $billions spent. Power Up By William Lama, Ph.D — Palos Verdes Pulse On Dec. 5, 2022 the 192 lasers at the U.S. National Ignition Facility irradiated a gold cylinder about the size of a pencil eraser that contained a frozen bit of hydrogen encased in diamond. In less than a billionth of a second, two megajoules (MJ) of energy heated the cylinder to millions of degrees, producing x-rays that vaporized the diamond shell of the fuel capsule. The X-rays then compressed and heated the BB-size fuel pellet of deuterium and tritium. The resulting fusion produced energetic neutrons which carried away about three MJ of energy. This 50% energy gain (3MJ/2MJ) achieved “ignition” - where the fusion energy exceeded the energy from the lasers.
Progress
The National Ignition Facility achieved the “holy grail” of producing more fusion energy than was in the laser pulse. However, the 92 lasers required 300 MJ of electrical energy to produce the 2 MJ of beam energy and 3 MJ of fusion energy. Thus, the overall system efficiency was only about 1% (3/300).
In a fusion reactor, the energetic neutrons are absorbed by the surrounding vessel, where their kinetic energy is transferred to the walls as heat. The heat is captured by water circulating in the walls producing steam and - by way of turbines and electrical alternators - electricity.
Commercializing this fusion reactor will not be easy. It would need to generate 100 times more energy per laser pulse. It would have to vaporize 10 capsules a second, every second, for long periods of time. The fuel capsules are extremely expensive, and they rely on tritium, the short-lived radioactive isotope of hydrogen that future reactors would have to make on-site.
The tiny diamond sphere that could unlock clean power - BBC News
But fusion researchers see the technology as an incredible tool for humankind whenever it is ready—whether that is 20, 50, or 100 years from now.
In the meantime, it behooves us to embrace nuclear fission as the best source of electrical energy. Leading the way is France with 56 nuclear reactors at plants across the country generating 70% of its electrical energy, and plans to build six more.
Even United Nations researchers, not enthusiastic in the past, now say plans to keep the Earth’s temperature rise under 1.5 °C will rely on a substantial jump in nuclear energy. We need to build more nuclear plants, especially in California.
Dr. William Lama has a PhD in physics from the University of Rochester. Taught physics in college and worked at Xerox as a principle scientist and engineering manager. Upon retiring, joined the PVIC docents; served on the board of the RPV Council of Home Owners Associations; served as a PV Library trustee for eight years; served on the PV school district Measure M oversight committee; was president of the Malaga Cove Homeowner's Association. Writes about science, technology and politics, mostly for his friends. email: wlama2605@gmail.com
