Calculation of two-dimensional lambda modes

Conference · Tue Jan 01 00:00:00 EST 1991 · Transactions of the American Nuclear Society; (United States)

OSTI ID:5764074

Belchior, A Jr ^[1]; Moreira, J M.L. ^[2]

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1. Empresa Gerencial de Projetos Navais, Sao Paulo (Brazil)
2. IPEN-CNEN/SP, Sao Paulo (Brazil)

A system for on-line monitoring of power distribution in small reactors (known as MAP) is under development at COPESP-IPEN. Signals of self-powered neutron detectors are input to a program that estimates the power distribution as an expansion of lambda modes. The modal coefficients are obtained from a least-mean-squares technique adequate for real-time analysis. Three-dimensional lambda modes are synthesized out of one- and two-dimensional lambda modes. As a part of this project, a modification of a computer code was carried out in order to obtain the lambda modes. The results of this effort are summarized. The lambda modes are the solutions of the time-independent multigroup neutron diffusion equation, an eigenvalue equation. Normally, the computer codes produce the fundamental mode corresponding to the largest eigenvalue; their respective interpretations are neutron flux distribution and effective multiplication factor. For calculating higher order lambda modes it is usually necessary to eliminate the contribution of the lower modes from the fission source.

• OSTI ID: 5764074
• Report Number(s): CONF-910603-; CODEN: TANSA
• Journal Information: Transactions of the American Nuclear Society; (United States), Vol. 63; Conference: Annual meeting of the American Nuclear Society (ANS), Orlando, FL (United States), 2-6 Jun 1991; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
POWER DENSITY
CALCULATION METHODS
REACTOR CORES
ON-LINE MEASUREMENT SYSTEMS
SELF-POWERED NEUTRON DETECTORS
PERFORMANCE
C CODES
COMPUTER CODES
CONVERGENCE
EIGENVALUES
IEAR-1 REACTOR
MULTIGROUP THEORY
MULTIPLICATION FACTORS
NEUTRON DIFFUSION EQUATION
NEUTRON FLUX
REACTOR MONITORING SYSTEMS
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE
TWO-DIMENSIONAL CALCULATIONS
DIFFERENTIAL EQUATIONS
ENRICHED URANIUM REACTORS
EQUATIONS
MEASURING INSTRUMENTS
NEUTRON DETECTORS
NEUTRON TRANSPORT THEORY
ON-LINE SYSTEMS
POOL TYPE REACTORS
RADIATION DETECTORS
RADIATION FLUX
REACTOR COMPONENTS
REACTORS
RESEARCH AND TEST REACTORS
RESEARCH REACTORS
SELF-POWERED DETECTORS
THERMAL REACTORS
TRANSPORT THEORY
WATER COOLED REACTORS
WATER MODERATED REACTORS
220400* - Nuclear Reactor Technology- Control Systems
440101 - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments