Process for Establishing Release Limits and Action Levels at Nuclear Facilities: Text Equivalent
Figure 1 depicts a nuclear facility releasing liquid effluent into the middle of a flowing surface water body. A contaminant plume extends from the end-of-pipe to a location downstream and becomes lighter, representing dilution of the plume until it reaches some mixing zone. The image is a visual representation of how an exposure-based release limit can be back calculated in order to meet surface water quality critiria at the end of the mixing zone to the end-of-pipe final discharge point (i.e., point of compliance), taking into account some dilution factor.
Figure 2 depicts a scatter plot for two years of historical releases sampled weekly. The data from this plot is used to generate a frequency distribution plot and the statistical quantities that can be used to calculate the action level and the frequency to exceed.
Figure 3 depicts a frequency distribution plot for the dataset displayed in Figure 2. The data from this plot is used to identify the type of distribution so that the appropriate statistical equations can be used to calculate the action level based on the 95th percentile as well as the corresponding frequency to exceed. In this graph the distribution appears to be logarithmic and positively skewed.
Figure 4 depicts a scatter plot of new releases over a 46 week period of normal operation of a nuclear facility. The plot demonstrates the application of the action level and frequency to exceed that were calculated in graph 2. The graph shows several values above the action level based on 95th percentile and demonstrates that the action level would be triggered automatically if a single exceedance was above the 99.9th percentile, or would trigger on the fourth exceedance of the year.
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