Comparative study of 2-group P1 and diffusion theories for the calculation of the neutron noise in 1D 2-region systems

• In this paper, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its meanvalue, is calculated in 2-group P1 and diffusion theories for a 2-region slab reactor using Green’sfunction technique. The applicability of diffusion theory for different types and locations of the perturbation,as well as different frequencies, is assessed. Material data, i.e. nuclear cross-sections and kineticparameters, representative of a Light Water Reactor (LWR) and of a Heavy Water Reactor (HWR),respectively, are used in this work. It is demonstrated that for practical situations in LWRs and HWRs,there is no significant advantage to use P1 theory since diffusion theory gives acceptable results. Thelargest deviations between the two formalisms are observed in regions of large gradients of the staticneutron flux, such as close to the reflector interface and close to the perturbation. Such observationsare in agreement with theoretical expectations. This study also indicates that neglecting the effect ofcross-section perturbation on the diffusion coefficient gives a rather small impact on the solution. Thisallows drastically simplifying the determination of the neutron noise. When using numericaltechniques for such a determination the memory requirements and computational effort can be significantlyreduced.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Annan teknik -- Övrig annan teknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Other Engineering and Technologies -- Other Engineering and Technologies not elsewhere specified (hsv//eng)

Publication and Content Type

art (subject category)

ref (subject category)