A particular weakness of the commercial liquid-metal fast breeder reactor is the design of the steam generator (SG). Any small leak in the SG allows the hot sodium (Na) to come into contact with the water/steam, and this results in a violent reaction and SG damage. A secondary circuit is normally used to prevent such reactions causing damage to the reactor core and primary vessel.

NNC Ltd. has developed a copper (Cu)-bonded SG system, the objective of which is to provide three separate solid boundaries (two steel and one Cu) between the primary sodium coolant and the water/steam and hence eliminate the possibility of contact between Na and water/steam. The design uses a hot isostatic pressure method of construction to bond all three barriers to aid heat transfer. This highly reliable system allows the elimination of the secondary circuit, greatly reducing the cost of the reactor system and increasing availability.