Firepit Chats Encouraging Conversation 73C
Nuclear Reactors: Controlled Power
Nuclear reactors are used to generate electricity using a controlled and sustained nuclear chain reaction (fission) to create heat. That heat turns the water in a reactor core into steam; that steam spins a turbine, the turbine is attached to a generator which produces electricity. There are two types of light water reactors currently used in the US: Pressurized Water Reactors and Boiling Water Reactors.
Heat to steam: This atom-split heat is used to boil water, creating high-pressure steam.
Steam powers the turbine: The high-pressure steam is directed to a turbine, causing the turbine to spin.
Electricity generation: The spinning turbine is connected to a generator, which converts the mechanical energy into electrical energy.
Key Components of a Nuclear Reactor:
Fuel Rods: Contain the fissile material, typically enriched uranium, in the form of ceramic pellets encased in metal tubes. These are where the fission reactions occur.
Moderator: In a reactor, the high-energy neutrons produced in the fission of a uranium 235 nucleus must be slowed down by a moderator. When the neutrons are slower moving, they are more likely to cause further fission in an uranium-235 nucleus, thus sustaining the chain reaction. Materials that are useful for a moderator are normal water (H2O), heavy water (D2O, with deuterium atoms replacing the standard hydrogen atoms), and ultra-pure graphite. These materials slow down neutrons through collisions with their nuclei1. Light nuclei are needed in order to slow down neutrons efficiently, and they should not strongly absorb the neutrons during the collisions; otherwise the chain reaction would be cut off. These two requirements make these three materials useful moderators.
Control Rods: Made of neutron-absorbing materials (like boron, cadmium, or hafnium), these rods are inserted into or withdrawn from the reactor core to regulate the rate of the chain reaction. Lowering them into the core absorbs more neutrons, slowing the reaction; raising them allows more neutrons to pass, causing more fissions, and thus increasing the reaction rate.
Coolant: A fluid (like water, heavy water, or liquid metal) that circulates through the reactor core to remove the immense heat generated by fission. This heat is then used to produce steam, which drives turbines to generate electricity.
Reactor Core: The central part of the reactor where the fuel rods, moderator, and control rods are located, and where fission takes place.
Pressure Vessel: A robust container that houses the reactor core and coolant, designed to withstand high pressures and temperatures.
Containment Building: A thick, reinforced concrete and steel structure enclosing the entire reactor system. Its primary purpose is to prevent the release of radioactive materials into the environment in the event of an accident.
Safety Issues Distinct to Nuclear Reactors
The primary safety concern with nuclear reactors is preventing the uncontrolled release of radioactive materials.
Core Meltdown: If the reactor’s cooling system fails and the chain reaction is not adequately controlled, the fuel rods can overheat and melt, potentially breaching the containment vessel. This is the most severe type of reactor accident (e.g., Chernobyl, Fukushima Daiichi).
Radioactive Waste Management: Spent nuclear fuel remains highly radioactive for thousands of years, requiring secure, long-term storage and disposal. This is a persistent environmental and security challenge.
Accidental Release of Radioactivity: Even without a full meltdown, component failures or human error can lead to the accidental release of radioactive gases or liquids.
Security and Proliferation: Reactors contain fissile material that could potentially be diverted for illicit purposes, raising proliferation concerns. Robust security measures are essential.
1The relevant nuclei are: hydrogen (a proton), deuterium (a proton and neutron bound together), or in the case of graphite, a carbon nucleus (6 protons and 6 neutrons).
Next on “Firepit Chats” – Nuclear Bombs: What you need to know.
(Much of this Primer is based on or quoted from information in the Manhattan Project Interactive History, which was produced by the Department of Energy and is available on the internet. ) For a Deeper Dive please see “The Nuclear Realm” https://thesteadystate.org/media-and-posts/
Margaret Henoch was born in Los Alamos and developed her understanding of the nuclear world, nuclear reactors and nuclear weapons by listening to her father at the dinner table over about a decade and a half. After college she worked for SRI, International assessing the technical capabilities of airborne advanced radar and communication systems on fighter and bomber aircraft, and after five years of that, joined the Clandestine Service of the CIA, where she served for 25 years. She is a member of The Steady State.
Dr. Tony Fainberg has spent a career in basic and applied research in physics, as applied to national security issues, such as counter terrorism and nuclear nonproliferation. He received his PhD from University of California Berkeley in 1960. He has served on congressional staff, in several agencies of the Executive Branch and with a government-sponsored research institution. Mr. Fainberg is a member of The Steady State.
Founded in 2016, The Steady State is a nonpartisan, nonprofit 501(c)(4) organization of more than 300 former senior national security professionals. Our membership includes former officials from the CIA, FBI, Department of State, Department of Defense and Department of Homeland Security. Drawing on deep expertise across national security disciplines including intelligence, diplomacy, military affairs and law, we advocate for constitutional democracy, the rule of law and the preservation of America’s national security institutions.