Measurement of Reaction Rate Distribution and Neutron Spectrum in China Experimental Fast Reactor

China Experimental Fast Reactor (CEFR) has completed physics start-up tests in 2010 and connected the grid on 40%FP in 2011. The reaction rate distribution, neutron spectrum are some important parameters for CEFR neutron field. In order to measure these parameters some low power irradiation tests using foil activation method have been done in CEFR core. Two kinds of special irradiation test subassemblies have been developed and fabricated for irradiation in CEFR core. And a digital high purity Germanium gamma-ray spectrometer system has been established for foil activity measurement. After dozens of low power irradiation tests in CEFR core, the radial and axial distribution of ²³⁵U and ²³⁸U fission reaction rate have been measured. The distribution of ²³⁸U capture reaction rate in CEFR core was also obtained in these tests. The experimental values of reaction rate are according with the calculation values well. Neutron spectrum was measured by means of multifoil activation method. And a neutron spectrum adjusting code was also compiled to determine the neutron spectrum.