Hot discussion on nuclear reactor

A few days before, we had a hot discussion on nuclear reactor. The two sides stand for the Very High Temperature Reactor and Sodium cooled fast Reactor. These types of reactor are generation four reactors and our solution to future fuel issues. We carried on the discussion on three factors: security, cost, performance.

People still worry about the radioactivity a reactor sends out and they think the sodium cooled reactor is safer.Sodium is very chemically active and it can react with the core material and then the lifespan of the reactor will be less. Moreover, the sodium will get radioactive and we cannot imagine what it will be when the coolant is exposed to the outside. The VHTR has great advantages of security over other reactors like the sodium cooled fast reactor. First of all, it uses helium as coolant. Helium is an inert gas, it will not chemically react with any other materials. Meanwhile, helium is radioactive when it is radiated, unlike the other coolants. Even if all helium comes out of the reactor, it still causes little effects on the environment. We control the speed of the atoms to slow down the speed of the reaction. If the system loses control, its core temperature will rise and finally it melts. The possibility of a sodium cooled reactor to melt is about per reactor per year. The one of a VHTR is about per reactor per year. When the system finds something wrong, it will automatically stop working and cool down the temperature to a safe level.

Some people think the cost of the sodium cooled reactor is much cheaper. Apparently, the cost of VHTR is really high. But the economic rent of the reactor does not only depend on the cost to build the plant, but also depends on the efficiency of the reactor. We spend more money initially, but we can get more interests as it runs, so we still benefit. The VHTR has an average heat efficiency of 40%. The heat efficiency of sodium cooled reactor is only 20%. For example, one spends 1 billion dollars to build a 200MW VHTR and one builds a 100MW sodium one that costs 0.5billion dollars. The price of 1kw.h electricity is 8 cents. Then a 200MW VHTR will have an advantage of 1 billion dollars after 20 years run over the sodium cooled reactor. Then, the overall benefit of the sodium reactor is too little compared to the Very High Temperature Reactor.