Robert W. Albrecht

Neutronic response to two-phase flow in a nuclear reactor

Abstract The neutron noise induced by an air-water loop located in a nuclear reactor is investigated. A simple model of the neutron noise is developed using phenomenological arguments. The model is verified by comparison to experimental results, and three-dimensional, two-energy group diffusion calculations. The aim of the work is to provide the theoretical background for studying two-phase flow using neutron noise analysis.

Measurement of two phase flow properties using the nuclear reactor instrument

Abstract A procedure is introduced for characterizing one dimensional, two phase flow in terms of three properties; propagation, structure, and dynamics. It is shown that all of these properties can be measured by analyzing the response of the reactor neutron field to a two phase flow perturbation. Therefore, a nuclear reactor can be regarded as a two phase flow instrument.

A study of two-phase flow characteristics using reactor noise techniques

Abstract Recent work at the University of Washington has demonstrated the potential for studying two-phase flow characteristics using neutron noise techniques. This method offers the advantage of measuring global characteristics of two phase phenomenon without disturbing the flow or requiring large numbers of sensors. Not only can the presence of the injected air into the flow loops be seen in the neutron spectrum but also the neutron spectrum reflects the type of flow by producing a characteristic signature.

Application of Walsh Functions to Neutron Transport Problems—I. Theory

An approximation to the neutron transport equation is made by representing the angular flux with an expansion of the angular dependence in the orthogonal, complete, and binary valued sets of Walsh function. The Walsh approximation is applied to the one-speed, isotropic-scattering, rectangular-geometry form of the neutron transport equation. Sets of partial differential equations for the expansion coefficients are derived along with appropriate boundary conditions for their solution. The sets of the Walsh expansion to one- and two-dimensional forms of the transport equation are also obtained. The two-dimensional expansion coefficient equations are shown to be not only hyperbolic but also transformable to a set of S/sub N/-like equations that are coupled only through the scattering term. Such transformal sets of equations are termed Walsh-derived quadrature sets.

The Measurement of Dynamic Nuclear Reactor Parameters Using the Variance of the Number of Neutrons Detected

A mathematical model is developed for the ratio of the variance to the mean number of neutrons detected in a point, unloaded reactor as a function of counting time. The model includes the effect of delayed neutrons. An experiment is performed which measured this statistic for counting times between one millisecond and ten seconds. The predictions of the modei and the results of the experiment are compared. It is shown that a reduced two-delay group model predicts the experimental results fairly well. (auth)

In-core/ex-core neutron noise measurements to examine core internal vibrations in an operating PWR

Abstract Simultaneous in-core/ex-core neutron noise measurements are investigated. A signal decomposition scheme is proposed for the ex-core signals. Partial spectral estimates are constructed from the in-core signals. Frequency bands that differentiate modified/baffle jet excited assemblies from ‘normal’ are predicted using a clustering algorithm. A simple phenomenological description of the in-core APSD shape is proposed.

Potential U.S. contributions to in-reactor experiments for fast reactor surveillance systems

Abstract It is maintained that special features of FFTF make it an ideal system to test sodium boiling detection techniques by acoustic/neutronic methods and to test the response of acoustic/neutronic sensors to vibrations. It is shown that accumulated research results indicate that such tests in FFTF are feasible, predictable, promising and safe.

Mobile robotics : a paradigm for complex system engineering

Abstract Mobile robotics is being used as an educational vehicle for teaching the principles of complex system engineering. A mobile robot is a complex system involving mechanical hardware, a suite of transducers, computer control of actuators and sensors, and a hierarchical control system. The operation of an autonomous mobile robot incorporates attributes of artificial intelligence with interfaces via radio links from base computers to on-board computers. A general plan supported by hardware, software shells, senior/graduate courses and graduate research is in place that facilitates the evolution of autonomous mobile robots capable of navigating and performing prototypic tasks in semi-structured environments. A series of projects is designed to enhance the repertoire of skills of the robots to robustly accomplish a range of tasks from simple to complex. The skills are built within a structure that is designed to be cumulative. The result is forecast to be systematic improvement in a generalized knowledge base that is identified as the key to implementation of semi-autonomous mobile robots in semi-structured environments. A university is an educational institution. This means that students are temporary. Students are always on a learning curve and they complete courses and degrees and leave the institution. One important component for achieving the goal of a continually evolving mobile robotic vehicle in the university environment is to document incremental student progress and package this information so that future students can rapidly assimilate previous progress and make a contribution to the continuing evolution of the mobile robotics program. This is accomplished through a set of modules called “robo-tutors”. Robo-tutors are tutorials for students that are written in an expert system shell and provide automated instruction concerning various aspects of the mobile robots program.

Neutronic Fluctuation Analysis as a Characterizing Vehicle for Two-Phase Flow

An exploration of flow regime characterization using measurements of the neutron fluctuations induced by a gasliquid flow passing through a nuclear reactor core has reached a developmental plateau that permits a quantitative evaluation of the method, Albrecht et al. (1982), Crowe et al. (1977). It has been demonstrated that many significant properties of the flow can be determined by analysis of the induced neutronic fluctuations. These characteristics have been categorized as propagation, structure, and dynamics of the flow, Albrecht et al. (1982c).

Application of Walsh functions to neutron transport problems. II. Analysis

The results obtained from the solution of the expansion coefficient equations obtained in the preceding paper for the Walsh approximation are given for both one and two dimensions. Since the one-dimensional analysis was performed mainly to lay a foundation for the two-dimensional analysis, only a brief summary of the one-dimensional results is given. The two-dimensional analysis was performed on a problem type that accentuates ray effects. Solutions obtained with various Walsh and Gauss-Walsh quadrature sets are shown; these solutions provide substantial mitigation of the ray effect, yet retain a reasonable degree of accuracy in the calculation of volumetric reaction rates.