The Decay of a Thermalized Neutron Pulse

Journal Article · Tue Mar 01 04:00:00 EST 1960 · Nuclear Science and Engineering

OSTI ID:4146367

Nelkin, M. ^[1]

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1. General Atomics, San Diego, CA (United States)

A theoretical basis is presented for the interpretation of the pulsed-neutron technique for measuring thermal neutron absorption cross sections and transport parameters. A procedure is given for the exact solution of the Fourier-transformed, multivelocity transport equation in an infinite medium. The method used is an expansion of the decay constant and neutron spectrum in a power series in the Fourier-transform variable. The procedure is first illustrated for the case of isotropic scattering and then generalized to anisotropic scattering by using the spherical harmonics expansion. The results are given in terms of integral equations whose solution involves a knowledge of the energy-transfer cross sections between thermal neutrons and the moderating material. The approach employed is to extract the maximum amount of information which is independent of these cross sections and to derive explicitly the equations involving them. The relation of the infinite medium Fourier transform variable to the geometric bucking of a finite sample is discussed. The validity of the interpretation of the experiments in terms of the diffusion coefficient and diffusion cooling coefficient by requiring the assignment of an equivalent infinite medium buckling to each finite sample measured is discussed.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Atomic Energy Commission (AEC)
• NSA Number: NSA-14-012319
• OSTI ID: 4146367
• Journal Information: Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Vol. 7; ISSN 0029-5639
• Publisher: Taylor & Francis
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ABSORPTION
ANGULAR DISTRIBUTION
ANISOTROPY
BUCKLING
CROSS SECTIONS
DECAY
DIFFERENTIAL EQUATIONS
DIFFUSION
ENERGY
FOURIER ANALYSIS
GROUP THEORY
INTEGRAL EQUATIONS
INTEGRALS
LIFETIME
MATHEMATICS
MODERATORS
Nuclear Criticality Safety Program (NCSP)
OSCILLATIONS
PULSES
SCATTERING
SHIELDING
SPECTRA
SPHERICAL HARMONICS
THERMAL NEUTRONS
TRANSPORT THEORY
VELOCITY