Hendrik_2000
Lieutenant General
That is true but because it generate high temperature overall it will produce high efficiency up to 50% which is unheard of. The conventional power plant has very low efficiency around 30% and relatively low temperature producing wet steam(saturated steam) necessitating very large steam turbine .
But the main reason why helium is selected is because it doesn't absorb contaminant and more important it doesn't absorb neutron so it doesn't become radioactive itself . So in theory you can use it to drive turbine . But in reality and regulatory requirement. You need to pass it to heat exchanger (Steam generator) to generate steam that drive the turbine.
This type of reactor is attractive because it is the only one that has negative loop and prevent run away reaction like in Fukushima
It does so because so called Doppler broadening
When the increases in temperature, the rapid motion of the atoms in the fuel causes an effect known as . The fuel then sees a wider range of relative neutron speeds. , which forms the bulk of the uranium in the reactor, is much more likely to absorb fast or epithermal neutrons at higher temperatures. This reduces the number of neutrons available to cause fission, and reduces the power of the reactor. Doppler broadening therefore creates a negative feedback because as fuel temperature increases, reactor power decreases. All reactors have reactivity feedback mechanisms, but the pebble-bed reactor is designed so that this effect is very strong. Also, it is automatic and does not depend on any kind of machinery or moving parts. If the rate of fission increases, temperature will increase and Doppler broadening will occur, decreasing the rate of fission. This creates passive cooling.
Another attractive feature is it doesn't use water as the primary coolant which eliminate a lot of the complicated high pressure cooling system and safety shutdown system with their attendance of complicated control system that need powered control valve
That is exactly what went wrong in Fukushima when the valve of the safety shut down system cannot be open because the electrical system is located in the basement and flooded by water.Causing run away reaction.
This type of reactor can also use Thorium as fuel the most plentiful on earth
The German are the pioneer of this type of reactor But they abandoned it because of accident caused by human failure and the general aversion of anything nuclear after Chernobyl. The Chinese license some of their system and buy the fuel
The Chinese claim they solved the problem in their 10 MW pilot plant and improve on the German design.
This design would make and excellent Nuclear Submarine power plant because of their simplicity and safety. It doesn't need need noisy high pressure pump all you need is low pressure circulating compressor
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They already have 10 MW design all they need is double it and make it more compact
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