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where


          erf(x) =2    rx


The mixing ratio based on the hydrogen and uranium distributions is given by

                    -(r-rH)/2bH +  
          R(r) =Ce                 2                (7.9)
                    az-r 2/2b2 a
                  ale      U+ a2

        The hydrodynamic characteristics of the hydrogenuranium coaxial flow are described quantitatively by specifying the radially dependent mixing ratio and the hydrogen and uranium mass flow rates. The mixing ratio and the mass flow rates are directly related to the hydrogen-uranium mixing model based on (7.1) and (7.5). Each of these distributions contains three parameters which can be adjusted to give the specified values of mixing ratio and flow rates. Since the uranium mass flow rate is proportional to the constant Nu (0), adjusting the value of Nu (0) simulates the control of the injected uranium mass flow. The amount of radial dispersion of uranium from the injection region is described by the parameter bu. The extent to which uranium penetrates the coolant annulus is described by the constant Nu (R). An increase in N u(R) corresponds to an increase in fuel loss due to uranium