Sodium is such a nightmarish coolant. Yes, there are advantages in building and engineering a sodium cooled reactor, but from an operating point of view... oh boy.
Sodium catches fire when exposed to air.
Sodium reacts violently with water (used in some designs as secondary cooling cycle).
Sodium absorbing a neutron creates a strong gamma emitter with a low half time.
Sodium reactors have always had low availability times, caused by constant technical problems.
However unlike lead as coolant, no advances in material sciences are required to get an operational Gen 4 reactor. On the upside, you can pretty much use Sodium (fast) reactors right now... but maybe you shouldn't?
Sodium catches fire when exposed to air.
Sodium reacts violently with water (used in some designs as secondary cooling cycle).
Sodium absorbing a neutron creates a strong gamma emitter with a low half time.
Sodium reactors have always had low availability times, caused by constant technical problems.
However unlike lead as coolant, no advances in material sciences are required to get an operational Gen 4 reactor. On the upside, you can pretty much use Sodium (fast) reactors right now... but maybe you shouldn't?