Kerma factor evaluation and its application in nuclear heating experiment analysis

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The accuracy of calculating ‘kerma factor’, which is the response function for nuclear heating is very important in many applications, particularly fusion systems. A computer code, called MAZE, has been developed primarily for evaluating neutron and gamma kerma factors based on an improved modeling and a capability to analayze basic data and evaluate consistency in preserving energy. Kinematics equations and energy conservation considerations are modeled in the code. The code has features that allow comparison and analysis among different methods of calculating the kerma factor and it provides users with data information needed to make user-oriented selections from two to three, often different, results. A kerma factor library, called MAZE-LIB, has been generated with MAZE for most of the materials of interest in fusion based on the most recent and accurate data available, FENDL library, which is the nuclear data library selected by ITER. The kerma factor library provided in this work is the result of an extensive analysis of nuclear data and careful selection from among often different results from the different calculational methods. It was shown that some data inconsistency problems in preserving the energy still exist in the FENDL library. Some problems with the widely used computer code NJOY were exposed during the process of the kerma factor evaluation, which is crucial at this stage of fusion research, since NJOY is the primary nuclear data processing code selected by ITER. Comparison with nuclear heating experimental data, derived from very recent integral experiments with 14 MeV neutrons and the analysis of the uncertainty in prediction have been carried out using the newly developed kerma factors. Comparative analysis shows that the new kerma factors generated in this work results in better agreement with the experiments than those obtained from previous work. The calculated-to-experimental values (C/Es) obtained in this work indicate an overestimation of the gamma production in the basic nuclear data library for certain elements. The integral and differential heating profiles along with knowledge of the contributing partial kerma factors, which are generated in this work, could in principle, provide input for sensitivity analysis and be used to improved the basic nuclear data and kerma factor evaluations.