Finally, sodium, unlike water, is not corrosive to many structural materials. Reactor components immersed in liquid sodium for years appear like new after the excess sodium has been washed off. However, sodium also has some undesirable properties. Its melting point much higher than room temperature, so the entire coolant system must be kept heated at all times to prevent the sodium from solidifying. This is accomplished by winding a spiral of insulated heating wire along coolant piping, valves, and so forth.
Sodium is also highly chemical reactive.
Hot sodium reacts violently with water and catches fire when it comes in contact with air, emitting dense clouds of white sodium peroxide smoke. Sodium which passes through the reactor core therefore becomes radioactive. However, because of the radioactivity of the sodium and because sodium reacts so violently with water, it is not considered sound engineering practice to carry the sodium coolant directly from the reactor to the steam generators. Leaks have often occurred in steam generators between the sodium on one side and the water on the other, and such leaks could lead to the release of radioactivity. All primary loop components, the reactor, pumps, heat exchangers, and so on, are separate and independent.