Overnight Cost
About
Overnight Cost captures the capital required to build a reactor, excluding financing costs, interest during construction, and inflation. It is a critical factor in reactor selection because it directly shapes project feasibility, financing requirements, and risk tolerance for purchasers. High overnight costs can increase exposure to cost overruns, lengthen payback periods, and limit the pool of potential investors. The total Overnight Cost score is driven by two distinct indicators: the overnight cost of major nuclear components and the overnight cost of construction. These are estimates and projections; actual costs depend on deployment conditions, technical requirements, scale, and other implementation-specific factors.
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Indicator Breakdown
Weight 40%
Component Cost
Core question
What is the expected cost of the reactor’s major components?
Component Cost measures the cost (in U.S. dollars) of major nuclear island and balance of plant components such as the reactor vessel, steam generator, heat exchangers, primary pumps, and instrumentation and control systems. This indicator reflects manufacturing complexity, material availability, and reactor footprint.
Coding rules
- 1 — Greater than $1 billion
- 2 — $500 million-$999 million
- 3 — $100 million-$500 million
- 4 — Less than $100 million
Weight 60%
Construction Cost
Core question
To what extent does the design reduce construction cost and risk through modular fabrication and limited nuclear-grade specialization?
Construction costs can vary by site and jurisdiction owing to labor and regulatory differences, making direct dollar comparisons unreliable. The Construction Cost indicator evaluates overnight construction cost using the design features that most drive it: modularity and specialization. This approach enables consistent comparison across reactor designs without site-specific assumptions. Construction Cost captures labor intensity, nuclear-grade scope, construction sequencing complexity, and predictability. The indicator adds Modularity and Specialization scores from Deployment Timescale criterion into a single measure, where the lowest possible combined score is 2.
Coding rules
- 1 — Sum of Modularity and Specialization indicators equals 2
- 2 — Sum of Modularity and Specialization indicators equals 3
- 3 — Sum of Modularity and Specialization indicators equals 4
- 4 — Sum of Modularity and Specialization indicators equals 5
- 5 — Sum of Modularity and Specialization indicators equals 6
- 6 — Sum of Modularity and Specialization indicators equals 7
