Abstract: Nuclear beta decay currently provides the most precise extraction of the CKM matrix element | V_ud |. The lifetime of a beta emitter receives radiative corrections and these must be included when extracting fundamental physics constants. 

In this talk I will describe how to organize these corrections using effective field theory, and how to compute ``outer'' corrections in an effective theory in which nuclei are treated as point-like heavy particles. Along the way we will see how the Fermi function emerges as an infinite sum of diagrams in the effective field theory, and how to use renormalization group methods to systematically resum logarithms.