The KORPUS irradiation experiment has been used to test and demonstrate improvements of the pressure vessel dosimetry methodology developed in Rossendorf. The Monte Carlo Code TRAMO has been recently supplied with extended geometries and with a new data treatment procedure for elastic scattering. The new code version has been used to accurately calculate absolute neutron fluence spectra at detector positions in the KORPUS irradiation facility at the RIAR in Dimitrovgrad. The sensitivity of the obtained fluences to various approximations in the calculations was investigated using calculations for different model variants.

The activation rates calculated with these spectra have been compared with results of activation measurements with detectors irradiated at the International Dosimetry Benchmark at the KORPUS facility. Based on the measured data the calculated fluence spectra have been adjusted with the help of the adjustment code system COSA3, a newly extended multi-spectrum version of COSA2. A comprehensive uncertainty analysis was accomplished for the fluence calculations and the measurements.