Experimental study of large scale axially heterogeneous LMFBR at FCA - power distribution measurements and their analyses

The power distribution of the large scale axially heterogeneous LMFBR was examined by using the experiments of FCA Assembly XI, XII and XIII and their analyses. The relative power distribution was measured by the γ-scanning method and the distributions of 239Pu and 238U fission rates were measured by the micro fission counters and the foil irradiation method. In addition to the measurements of the reference core, the power distributions were measured in the core inserting the control rod and in the core changing the radial boundary shape of the internal blanket. The calculation was made by using JENDL-2 and JAERI's standard calculation system for the fast reactor neutronics. The power flattening trend which is caused by the decrease of the fat neutron flux was observed in the experiment. The influence on the internal blanket was observed in the power distribution of the control rod insertion core and in that of the core changing the radial boundary shape of the internal blanket. The calculation overpredicts the fast neutron flux in the internal blanket