14C studies in the vicinity of the Czech NPPs

The Czech Republic has two nuclear power plants (NPPs) equipped with light water pressurized reactors (LWPR). Annual sampling of biota for 14C activity monitoring by Nuclear Physics Institute in cooperation with the National Institute of Radiation Protection started in 2002. We present the results of biota monitoring covering two sampling periods 2002–2005 and 2007–2008. The considerable problem in the case of biota sampling for monitoring purpose is given by a relatively short period of biota accumulation for prevailing types of biota samples (leaves of deciduous trees or agricultural plants), which usually lasts from several weeks to 2 months. The short period of sample accumulation can also be partly overlapped by a service period of reactor outage in a given NPP. On the base of our several years’ experiences we have changed a type of the sampled material to reduce variations of observed activities and to precise reference levels in the exposed and reference sites.