Integrative Evaluation of PPRP'S Radionuclide Sampling Program and Database

摘要

The authors completed an analysis of the Power Plant Research Programs (PPRP's)radionuclide database to summarize and integrate data collected over the course of the program. The primary objectives were to develop recommendations for the program with regard to sampling methodology and approach and to define environmental factors that affect the spatial and temporal distribution of radionuclides. Time series analysis indicated amounts of three primary plant-derived radionuclides, including (Sup 58)Co, (Sup 60)Co, and (Sup 134)Cs, have dramatically declined over the last 10 years in sediments collected at Calvert Cliffs Nuclear Power Plant (CCNPP) and Peach Bottom Atomic Power Station (PBAPS). Sediment activity levels of (Sup 137)Cs have remained constant over the same time period, primarily because of its foreign input (from weapons testing) and its long half-life (30 years). A summary analysis of a sub-set of (Sup 60)Co sediment activity data (1990 to 1997) at CCNPP indicated a significant decrease from 1990 to 1997, but no evidence for seasonal differences in (Sup 60)Co activity. To proportion of sediment samples having non-detectable (Sup 60)Co activity levels has differed over time and most recently, these non-detect samples represent approximately 70% of the values recorded annually. Excluding non-detect values in calculating average annual levels may cause mean values to be biased high and estimates of variation to be biased low. At CCNPP, 60CO activity is spatially variable, increasing from the most nearshore site to the second and third stations offshore and thereafter, decreasing with distance offshore, At PBAPS, (Sup 60)Co sediment activity levels decline exponentially with distance downstream of the plant.