Power Up By William Lama, Ph.D
We need to get serious about the renewable energy revolution—by including nuclear power
Nuclear fusion is suddenly all the rage. There’s the technical triumph.
“The pursuit of fusion ignition is one of the most significant scientific challenges ever tackled by humanity, and achieving it is a triumph of science, engineering, and most of all, people.” -- Lawrence Livermore Lab director Kim Budil
And the promise of driving the new green economy.
“This astonishing scientific advance puts us on the precipice of a future no longer reliant on fossil fuels, instead powered by new clean fusion energy.” -- U.S. Senator Charles Schumer
Nuclear Fusion Breakthrough: The Future of Clean, Limitless Energy (forbes.com)
But is “ignition” the breakeven threshold? How severe are the remaining technical problems? Is nuclear fusion really ready to fuel the green economy?
Fission and Fusion
Energy is produced by nuclear fission and nuclear fusion, and both can be used to generate electricity. Fission is the splitting of a heavy, unstable nucleus into two lighter nuclei while fusion is the combination of two light nuclei. Both natural processes release energy.
Nuclear fission has been generating electricity and supplying it to the grid since 1951. Fission powerplants supply about 10% of the world's electricity, and 20% of the U.S. electricity. China plans to construct 150 new reactors in the next 15 years ― more than the entire world built in the last 35.
3 Reasons Why Nuclear is Clean and Sustainable | Department of Energy
By contrast, nuclear fusion power generation is a popular, long term research project. In this essay I’ll discuss the current state and future prospects for nuclear fission. Next month we’ll look at the fusion future.
Nuclear Fission
The world's first nuclear reactors “operated” naturally in a uranium deposit about two billion years ago. These reactions were in rich uranium orebodies moderated by percolating rainwater. Neutrons are at the heart of nuclear fission.
When radioactive radon is mixed with beryllium, neutrons are emitted. Enrico Fermi used the radon-beryllium mixture as a source of neutrons in his study of induced radioactivity and fission. When a neutron is absorbed by a U-235 nucleus it becomes U-236. This decays into Barium plus Krypton plus 3 more neutrons, which can sustain a chain reaction. Other decay products, such as [(Xe-140) + (Sr-94) +2n], also occur.
Fission Reactors
Nuclear fission reactors use Uranium-235 processed into small ceramic pellets. One Uranium pellet, slightly larger than a pencil eraser, contains the same energy as a ton of coal, 3 barrels of oil, or 17,000 cubic feet of natural gas.
The pellets are stacked together into sealed metal tubes called fuel rods. Typically, more than 200 of these rods are bundled together to form a fuel assembly. A reactor core contains a couple hundred fuel assemblies.
Here is a simplified diagram of a nuclear fission power plant.
Nuclear Power Plant Diagram: A Complete Guide 2022 | Linquip
Inside the reactor vessel, the fuel rods are immersed in water which acts as both a coolant and moderator. The water and control rods slow down the neutrons produced by fission to sustain a controlled chain reaction. The heat produced by fission turns the water into steam. The steam spins a turbine which turns the shaft of a generator to produce electricity.
Progress or Regress
There are 438 operating power reactors in the world, capable of producing 394 GW, which is 11% of the world electricity production. In the US there are 92 reactors. France is second with 56 and China has 54. On the other hand, in California there is only one nuclear plant with two reactors at Diablo Canyon. They are scheduled to close, with drastic consequences for the CA electrical supply and its green transition.
Why California Wants to Rescue Its Last Nuclear Power Plant (governing.com)
Today, reactors derived from designs originally developed for propelling submarines and large naval ships generate most of the world's nuclear electricity. Next generation nuclear fission reactors promise to be cleaner, safer and more cost-effective.
Advanced Fission Reactors
Generation I reactors were developed in the 1950-60s and the last one shut down at the end of 2015. They mostly used natural uranium fuel and graphite as moderator. Generation II reactors are typified by the present U.S. fleet and most in operation elsewhere. They typically use enriched uranium fuel and are mostly cooled and moderated by water. Generation III reactors have enhanced safety. The first few are in operation in Japan, China and Russia.
Many advanced reactor designs are for small units, under 300 MW. These small modular reactors may be chained together to produce a large power plant. NuScale Power, based in Portland, Oregon, has a 60 MW design that’s close to being deployed.
Generation IV designs, still on the drawing board, Top of Will use alternative coolants.
Pebble-bed reactors are graphite-moderated, gas-cooled, very high temperature designs.
Terra-Power is developing a sodium-cooled system. In 2020, the company was chosen by the Biden Administration as a recipient of a grant to build a demonstration reactor.
The molten-salt reactor, is safer than earlier designs since it can cool itself even if the system loses power. Canadian company Terrestrial Energy plans to build a plant in Ontario by 2030.
A Gen IV reactor was connected to the Chinese grid in 2021. The Helium-cooled reactor runs at 1,000°C and generates 210 MW.
Following is a comparison of small modular reactors and Gen IV large-scale designs.
Advanced Reactor Demonstration Program | Department of Energy
There is nothing standing in the way of a nuclear future except an irrational fear of atoms. This despite the fact that our bodies contain a billion-billion-billion atoms, every one with a nucleus.
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
