Critical Heat Flux Ratio (DNBR)
A transparent ratio calculation using your supplied heat flux values.
DNBR = critical heat flux ÷ actual heat flux
What this calculates
DNBR is the ratio of the predicted critical heat flux to the actual local heat flux at the same location. For example, 3 MW/m² divided by 2 MW/m² gives 1.500.
This tool does not predict critical heat flux, determine a design limit, or assess equipment safety. The critical value must come from a validated correlation or data applicable to your conditions. A ratio alone is not an operating recommendation.
The previous version used an unsupported approximation for critical heat flux. That approximation has been removed.
Reference: NRC AP1000 review, section 4.4.1.1.