Determination of the power density peak factor from out-of-core detector signals in small reactors

This paper aims to show that in small reactors the power density peak factor can be determined from the power axial offset, measured from out-of-core detector signals, and from signals indicating the control rod positions in the core. The response of out-of-core detector signals were measured in experiments performed in the IPEN/MB-01 zero-power reactor. Several reactor states with different power density distribution were obtained by positioning the control rods in different configurations. The power distribution and its peak factor were calculated with the CITATION code for each of these reactor states. The obtained results show that for the small reactors there is a correlation between the peak factor, the control rod position and power axial offset. The analysis shows that a complex pattern exist between the peak factor and the power axial offset. In order to improve the accuracy, the results indicate that the peak factor should be determined through a correlation which takes into account the power axial offset and the quadrant power tilt. (author)