Some Features of Spatial Neutron Kinetics for Multiplying Systems

Abstract The paper considers some physical aspects of the neutron space kinetics of critical and source-driven subcritical systems. The possibility of introducing some indicators to qualify the spatial nature of neutronic transients is investigated. It is shown theoretically and then proved by numerical examples that the separation of the eigenvalues of the mathematical operator defining the problem can be taken as a good indicator of the importance of space effects in time-dependent conditions. To obtain good physical insight into the phenomena, paradigmatically simple configurations are considered, and whenever possible, a fully analytical approach is used. The presented results evidence the limits of applicability of classic simplified models for transient analyses, such as point kinetics. In a second part, the paper considers the open problem of the choice of the weighting function to be used either for the generation of the kinetic parameters of pointlike models or for the exploitation of quasi-static procedures, analyzing comparatively the effect of different options on the results of transient calculations.

[1]  Keisuke Kobayashi.  A relation of the coupling coefficient to the eigenvalue separation in the coupled reactors theory , 1998 .

[2]  K. Nishina,et al.  Verification of more general correspondence between eigenvalue separation and coupling coefficient , 1996 .

[3]  S. B. Brumbach,et al.  Spatial kinetics studies in liquid-metal fast breeder reactor critical assemblies , 1988 .

[4]  Piero Ravetto,et al.  Multigroup Diffusion Kinetics Benchmark of an ADS System in Slab Geometry , 2002 .

[5]  Roger A. Rydin,et al.  Noise and Transient Kinetics Experiments and Calculations for Loosely Coupled Cores , 1971 .

[6]  Hugo van Dam.  Inhour equation and kinetic distortion in a two-point reactor kinetic model , 1996 .

[7]  J. Devooght.  Spectrum of the multigroup-multipoint diffusion operator with delayed neutrons , 1976 .

[8]  Imre Pázsit,et al.  Theory of neutron noise induced by source fluctuations in accelerator-driven subcritical reactors , 1999 .

[9]  Toshikazu Takeda,et al.  Analysis of First-Harmonic Eigenvalue Separation Experiments on KUCA Coupled-Core , 1998 .

[10]  Toshio Sanda.  Interpretation of Noise Coherence Function Measurements in Liquid-Metal Fast Breeder Reactor Critical Assemblies , 1990 .

[11]  Kojiro Nishina,et al.  Measurement of Flux Tilt and Eigenvalue Separation in axially Decoupled Core , 1997 .

[12]  D. G. Cacuci,et al.  ON PERTURBATION THEORY AND REACTOR KINETICS: FROM WIGNER'S PILE PERIOD TO ACCELERATOR DRIVEN SYSTEMS , 2002 .

[13]  A. Rineiski,et al.  ON APPLICATION OF QUASISTATIC AND POINT-KINETICS SCHEMES FOR SUBCRITICAL SYSTEMS WITH EXTERNAL NEUTRON SOURCE , 2003 .

[14]  Imre Pázsit,et al.  On the kinetic response of a reactor with delayed neutrons II: Spatial effects , 1996 .