Hydrogen gas is produced. The extraordinary heat transfer properties of liquid metals make them attractive reactor coolants for both thermal and fast reactors. In addition, liquid metal systems operate at low pressure require the minimum of pumping power and are capable of operating at the high temperatures required to generate steam for modern turbine generators. Two liquid metals, sodium and eutectic mixtures of sodium and potassium have been used extensively in nuclear reactors. No moderator required.
Full advantage is taken of excellent heat removal characteristics of sodium.
Sodium doesn't react with uranium and thorium. Fuel can be bonded to container with liquid metal. Electromagnetic pumps can be used with fair efficiency. Sodium reacts violently with water and actively with air. Radiation damage a serious problem, except with molten fluid.