The largest contributor to steam line radiation at a BWR is N-16. This is a neutron activation product and is extremely short lived. We limit access to Steam Tunnels, Turbines, and Feedwater Heaters to minimize exposure from this nuclide. Once we shutdown, N-16 decays away in a minute or so.
If a plant has cladding pinhole leaks, you'll see some Noble Gas activity in the steam lines. Kr-88, and Xe-133 are the big guys here. The fuel reliability engineers can use short lived / long lived Noble Gas activity ratios to determine the size of a cladding defect. These Noble Gases end up decaying away in Charcoal Adsorbers located in the Off Gas System.
Most BWRs are pretty clean plants, the indicator to look at is Reactor Coolant Dose Equivalent Iodine activity. Many plants are near zero, the ones that are not have - or have had- fuel cladding defects.
Hope that helped.