MEASUREMENT AND CALCULATION OF NEUTRON FLUX DISTRIBUTION IN KARTINI REACTOR USING SELF-POWERED NEUTRON DETECTOR (SPND) AND MCNPX CODE

Abstract

The neutron flux is one of the important parts of the fission reaction. Recently, the fuel configuration at the Kartini reactor has been changed, and now it has 71 fuel elements. SPND  has small cladding so this detector can reach a narrow gap in-core area. The output of SPND is a very small electric current. To convert from electric current to neutron flux, the value of the detector sensitivity is required, for this purpose, it is done by neutron flux measurement using gold foil activation method at the same location as SPND detector. MCNPX simulation is calculated through scanning area at the axial and radial direction from ring central thimble (CT), H7, H10, H12, H14, and H16. Using the Visual Editor (Vised) module of the MCNPX, the location of SPND measurement can be performed by MCNPX version 2.6.0, and nuclear data was used in ENDF/B-VI. The amount of axial data difference between SPND and gold foil activation measurements for location H16 is 8%. The trend of the graphs between SPND measurements and MCNPX simulations axially and radially are almost the same. However, there are differences in the data between the two. Such differences are caused due to the fact that the detectors are not modeled in MCNPX but using tally F5 instead. SPND data and gold foil activation at location H16 have almost the same neutron flux value for axial direction. This is a reference that the SPND detector is in good condition and valid for use.