New axial geometry model of the SRS K reactor

In order to predict the worth of control rod moves in a reactor, one must have the capability to accurately model both the axial and radial flux profiles. At the Savannah River site (SRS), the GRIMHX three-dimensional diffusion theory code is used for these purposes. While GRIMHX predictions of the radial flux profile compare favorably to those observed during reactor operation, the same cannot be said for the axial flux shape. Significant discrepancies between predicted and observed axial flux shapes were identified during the Startup Testing and Power Ascension Program conducted during operation of the K-14 charge in the summer of 1992. Investigation of these discrepancies led to the development of a new axial model for the GRIMHX code. The model is based on new information on the axial fuel geometry and has been modified to obtain agreement with axial flux shapes observed during the operation of the K-14 charge