FOAK, NOAK, BOAK Explained

First-, next-, and buy-of-a-kind name the build stages: the first integrated unit, its refined successor, and fleet units carrying the learning.

Three build stages

Fusion programs, like other first-of-their-kind infrastructure, improve build-to-build. Kronos names the stages FOAK, NOAK, and BOAK to keep the maturity honest — a first unit is not a fleet unit, and should not be described as one.

What each stage means

• FOAK — first-of-a-kind: the first integrated commercial build, carrying the most uncertainty and the fewest completed learnings.
• NOAK — next-of-a-kind: the second builds, incorporating what FOAK taught about fabrication, assembly, and operation.
• BOAK — buy-of-a-kind: fleet units built with a stabilized design and mature supply chain.

The breeder walks this ladder first (FOAK first tritium ~2030, then NOAK and BOAK). The burner walks its own ladder after the ~2032 test unit, with a commercial FOAK on the path to a fleet near 2036.

Why the naming matters

Performance and reliability legitimately differ across these stages. A FOAK unit may need more maintenance and show more variability than a BOAK unit. Naming the stage keeps any performance figure attached to the maturity it actually reflects.

MetroVolt fleet properties — firmness, availability, small water footprint at scale — are BOAK expectations, validated stepwise from FOAK onward.