05 Nuclear fuels (scientific, technical)
05/01015 Identification of reactor internals' vibration modes of a Korean standard PWR using structural modeling and neutron noise analysis Park, J. el al. Progress in Nuclear Energy, 2003, 43, (1-4), 177-186. The vibration characteristics of a Korean standard PWR reactor internals have been estimated through a three-dimensional finite element analyses and verified by using the mode separated power spectral density functions obtained from the ex-core neutron noise signals. Also the natural vibration modes of the fuel assembly have been identified measuring both the ex-core and the in-core neutron noise signals, which are close to each other. As a result, the fundamental bending mode frequency of the reactor internal structure is found to be around 8 Hz and the fundamental shell mode frequency 14.5 Hz, respectively. It is also shown that the fundamental bending mode frequency of the fuel assembly is 2.3 Hz and the 2nd bending mode frequency 5.8 Hz, respectively. These results can be used for the supplements of tile Korean standard PWR's CVAP (Comprehensive Vibration Assessment Program) data.
05101016 Lesson learnt from mathematical modeling of primary circuit of VVER 440/213 reactors Pecinka, L. et al. Progress in Nuclear Energy, 2003, 43, (1-4), 167-175. For the analysis of flow induced vibrations of a VVER 440/213 unit, a generalized model has been developed which consists of the reactor as a lumped mass model with 77 degrees of freedom. Linking of the loops to the reactor pressure vessel is modelled using translational and rotational stiffnesses. Main results obtained: eigenfrequencies and mode shapes of the whole system and dynamic response of the whole system generated by the main circulating pump pressure pulsations.
0501017 Lessons learned with vibration monitoring systems in German nuclear power plants Kolbasseff, A. and Sunder, R. Progress in Nuclear Energy, 2003, 43, (1- 4), 159-165. Compared to international standards, vibration diagnosis of German pressurized water reactors ranks high. Based on the Condition Monitoring System COMOS a lot of operational experiences could be gathered meanwhile and led to knowledge of long-term experiences. Meanwhile a successor system called 'COMOSnt' is developed and installed in several plants. After a brief description of COMOS system features, a case study based on PWR internal vibrations is presented. In German BWRs, until now no multi-sensorial vibration monitoring comparable to PWR standards is established. Reasons for this can be related to constructional characteristics, differences in neutron-flux instrumentation and variable speed-driven operating mode of reactor recirculation pumps. However, current issues with regard to core internals were reasons to investigate BWR vibration monitoring principles, taking into account for example vibration sensors at reactor recirculation pumps, self-powered neutron detectors and aceeler- ometers from loose parts monitoring. Noise analyses of incore-neutron flux signals showing specific modes of fuel assembly vibrations are presented in detail. The correlation analyses could be verified by means of accompanying structure model calculations. At present, specific systems for recirculation pump monitoring are running in three BWRs, an overall vibration monitoring concept including core internals is tested in a reference plant.
05/01018 Materials for high performance light water reactors Ehrlich, K. et al. Journal of Nuclear Materials, 2004, 327, (2-3), 140 147. A state-of-the-art study was performed to investigate the operational conditions for in-core and out-of-core materials in a high performance light water reactor (HPLWR) and to evaluate the potential of existing structural materials for application in fuel elements, core structures and out-of-core components. In the conventional parts of a HPLWR- plant the approved materials of supercritical fossil power plants (SCFPP) can be used for given temperatures (_