281 research outputs found
Optimal design of measurement network for neutronic activity field reconstruction by data assimilation
Using data assimilation framework, to merge information from model and
measurement, an optimal reconstruction of the neutronic activity field can be
determined for a nuclear reactor core. In this paper, we focus on solving the
inverse problem of determining an optimal repartition of the measuring
instruments within the core, to get the best possible results from the data
assimilation reconstruction procedure. The position optimisation is realised
using Simulated Annealing algorithm, based on the Metropolis-Hastings one.
Moreover, in order to address the optimisation computing challenge, algebraic
improvements of data assimilation have been developed and are presented here.Comment: 24 pages, 10 figure
Variational assimilation for xenon dynamical forecasts in neutronic using advanced background error covariance matrix modelling
Data assimilation method consists in combining all available pieces of information about a system to obtain optimal estimates of initial states. The different sources of information are weighted according to their accuracy by the means of error covariance matrices. Our purpose here is to evaluate the efficiency of variational data assimilation for the xenon induced oscillations forecasts in nuclear cores. In this paper we focus on the comparison between 3DVAR schemes with optimised background error covariance matrix B and a 4DVAR scheme. Tests were made in twin experiments using a simulation code which implements a mono-dimensional coupled model of xenon dynamics, thermal, and thermal–hydraulic processes. We enlighten the very good efficiency of the 4DVAR scheme as well as good results with the 3DVAR one using a careful multivariate modelling of B
Best linear unbiased estimation of the nuclear masses
This paper presents methods to provide an optimal evaluation of the nuclear
masses. The techniques used for this purpose come from data assimilation that
allows combining, in an optimal and consistent way, information coming from
experiment and from numerical model. Using all the available information, it
leads to improve not only masses evaluations, but also to decrease
uncertainties. Each newly evaluated mass value is associated with some accuracy
that is sensibly reduced with respect to the values given in tables, especially
in the case of the less well-known masses. In this paper, we first introduce a
useful tool of data assimilation, the Best Linear Unbiased Estimation (BLUE).
This BLUE method is applied to nuclear mass tables and some results of
improvement are shown
Differential influence of instruments in nuclear core activity evaluation by data assimilation
The global activity fields of a nuclear core can be reconstructed using data assimilation. Data assimilation allows to combine measurements from instruments, and information from a model, to evaluate the best possible activity within the core. We present and apply a specific procedure which evaluates this influence by adding or removing instruments in a given measurement network (possibly empty). The study of various network configurations of instruments in the nuclear core establishes that influence of the instruments depends both on the independant instrumentation location and on the chosen network
- …