5/9/2023 0 Comments Nuclear fission power plant![]() Many of the components, especially the generators, require regular, sometimes quite difficult, maintenance. This doesn’t mean that these reactors are maintenance-free, however. Even the HTGR is being talked about more, despite the fact that it’s been deployed in the UK fleet for decades, for many of the same reasons these other reactor designs are being investigated: it’s possible to make each of these designs “walk-away safe”, among other safety features inherent in their design, making nuclear accidents far more unlikely. Terms like “Liquid Metal Fast Breeder Reactor,” “Aqueous Homogeneous Reactor,” the ubiquitous “Molten Salt Reactor,” and others are being discussed, each with their own set of advantages and disadvantages over the current PWRs and BWRs that have been deployed worldwide. However, as many readers of this blog are familiar, nuclear power is going through a renaissance worldwide right now, with many reactor concepts that were proposed, but never deployed, being heavily investigated once again. However, the systems are very similar: heat water, produce steam, run turbines, cool the water, return it to the core. This much simpler system is called a boiling water reactor (BWR), and has the advantage of mechanical simplicity but adds the challenge of the turbine becoming radioactive over time, making maintenance more difficult. Another version actually produces the steam for the generators in the reactor vessel itself, and then runs this through the generator. This is known as a two-loop pressurized water reactor (PWR), and is the most common type of nuclear reactor in the world. Most reactors use what’s known as a two-loop system, meaning that the water that goes through the generator never enters the reactor core, instead the water from the core is run through a heat exchanger that transfers this heat to a second loop of water (the primary and secondary loops, respectively), to prevent the generator from becoming radioactive over time, while greatly simplifying the maintenance of the power plant. That water is then run through a cooling system (either cooling towers or a body of water), before being returned to the reactor core to start the process over again. ![]() This steam then drives a set of steam turbines, which spin a generator and produce electricity. Many people are familiar with the way a nuclear power plant works on Earth: a reactor heats up water from the heat generated by fission in fuel elements (rods, bundles, or pellets, usually), which then goes through a steam generator. So how is nuclear electricity generated in space? When these designs were first flown, photovoltaic panels were not nearly as efficient as they are today, so they weren’t considered a practical option, or the altitude of the satellite was so low that the air resistance on the panels would cause it to deorbit too soon to be useful. Radar is a notorious power hog, since resolution and power supply are directly proportional to each other. In the case of the US it was an experimental version of the Agena spacecraft and for the USSR and Russia, it was used for RORSATs (Radar Ocean Reconnaissance SATellites). All of these systems were designed to provide electrical power for a satellite. The US has flown one nuclear reactor (SNAP-10a) and the USSR and Russia have flown over thirty, using two different designs. Most people that have looked into in-space nuclear power know that using a nuclear reactor for electrical power is nothing new. This does not directly using the heat of the reactor like in a nuclear thermal rocket. Let’s look at the most popular way to use nuclear power in space. Systems for Nuclear Auxiliary Propulsion.Subscale Active Filtration of Exhaust (SAFE).Full Exhaust Capture and Stennis Space Center Testing Plans.CFEET (Compact Fuel Element Environmental Test).Fuel Elements: Design and Considerations.Nuclear Testing: Critical Geometry and Fuel Element Irradiation.General Purpose Heat Source RTG (GPHS-RTG).Arcjets, and Their Similarities to MPD Thrusters.VASIMR, the VAriable Specific Impulse Magnetoplasma Rocket.Induction, Radio Frequency and Microwave Thermal Thrusters.SNAP-2/10B and SNAP Improvement Program.Systems for Nuclear Auxiliary Power (SNAP).Low Enriched Uranium Nuclear Thermal Propulsion.
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