The creation of an historical meteorological database for environmental dose assessment.

Abstract

The focus of this study is to develop wind data for the Savannah River Site (SRS) between 1955 and 1961 to be used in an assessment of estimates of atmospheric dispersion and downwind risk at the Savannah River Site. In particular, a study of the uncertainties of radioiodine dosimetry from the late 1950s provides the underlying motivation for developing historical windroses at the Savannah River Site (SRS). Wind measurement towers did not exist at the SRS until the early 1970s. Three relatively simple methods were used to create a 1955-1961 meteorological database for the SRS for a dose reconstruction project. The winds were estimated from onsite measurements in the 1990s and National Weather Service (NWS) observations in the 1990s and 1950s using (1) a linear regression method, (2) a similarity theory approach, and (3) a simple statistical differences method. The criteria for determining success were based on (1) how well the mean values and standard deviations of the predicted wind speed agree with the known SRS values from the 1990s, (2) the shape of the predicted frequency distribution functions for wind speed, and (3) how closely the predicted windroses resembled the SRS windrose for the 1990s. The linear regression model's wind speed distribution function was broad, flat, and skewed too much toward higher wind speeds. The similarity theory approach produced a wind speed distribution function that contained excess predicted speeds in the range 0-1.54 m s(-1) (0-3 kts) and had 'excluded' bins caused by predictions being made from integer values of knots in the NWS data. The distribution function from the mean difference method was smooth with a shape like a Weibull distribution with a shape parameter of 2 and appeared to resemble closely the SRS 1992-1996 distribution. The wind directions for all three methods of approach were successfully based on the mean difference method. It was difficult to discern differences among the wind roses produced by the three methods so the wind speed distribution functions need to be examined in order to make an informed choice for dose reconstruction.