The reactor startup rate (SUR) is defined as the number of factors of ten that power changes in one minute. The units of SUR are powers of ten per minute, or decades per minute (DPM). Equation (4-10) shows the relationship between reactor power and startup rate.

where:

The relationship between reactor period and startup rate can be developed by considering Equations (4-6) and (4-10).

Changing the base of the exponential term on the right side to "e" (10 = e^2.303) and solving the result yields the following.