Analysis of the LR-0 benchmark results (WP-3 Final Report)

The lecture gives an overview over the final results of REDOS Work Package 3 (Analytical area - Analysis of calculated and measured data, conclusions).
For a VVER-1000 Mock-up and two VVER-440 Mock-ups and for all positions, where measurements had been carried out, neutron-gamma transport calculations were performed independently by the project participants using deterministic and/or stochastic codes and associated nuclear data libraries, mostly based on ENDF/B-VI. The calculated with different codes and laboratories neutron and gamma flux integrals, DPA-rates and spectra were compared with each other and with experimental values. Seven institutions from 5 countries (Bulgaria, Czech Republic, Germany, Hungary and Spain) delivered calculation results for the VVER-1000 Mock-up, six institutions from 4 countries performed calculations for one or both VVER-440 Mock-ups. More than eight different calculational schemes were used, covering the most important methods used for pressure vessel dosimetry and shielding. The codes used were the stochastic codes MCNP and TRAMO and the deterministic codes ANISN/DORT and TORT. They were associated with different data libraries and data preparation schemes. The BUGLE 47n/20g group structure was used for comparisons of calculated spectra as well as for comparison with experimental spectra. The comparison of the different calculation results showed considerable discrepancies for the calculation of absolute flux spectra normalized to one source neutron per second in the core for thermal neutrons and photons. The attenuation coefficients and spectra related to the spectrum in a special point had slightly lower discrepancies. The measured spectra and attenuation coefficient agree in most cases with the calculated values within the limits of experimental and calculational errors. Considerable discrepancies are found for the gamma to neutron relation at the outer surface of the barrel. The neutron attenuation through the RPV tends to be calculated too small. The uncertainties of the calculations were evaluated on the basis of the dispersion of the participants results, of the discrepancies between calculated and measured results and of the scattering of results obtained with different data libraries and data treatment procedures.