A Caltech Library Service

Pulsed Neutron Measurements in Two Adjacent Finite Media


Giraudbit, Georges Pierre Alexis (1966) Pulsed Neutron Measurements in Two Adjacent Finite Media. Engineer's thesis, California Institute of Technology. doi:10.7907/JP3Y-CR96.


The pulsed neutron technique has been used to investigate the decay of thermal neutrons in two adjacent water-borated water finite media. Experiments were performed with a 6x6x6 inches cubic assembly divided in two halves by a thin membrane and filled with pure distilled water on one side and borated water on the other side.

The fundamental decay constant was measured versus the boric acid concentration in the poisoned medium. The experimental results showed good agreement with the predictions of the time dependent diffusion model. It was assumed that the addition of boric acid increases the absorption cross section of the poisoned medium without affecting its diffusion properties: In these conditions, space-energy separability and the concept of an “effective” buckling as derived from diffusion theory were introduced. Their validity was supported by the experimental results.

Measurements were performed with the absorption cross section of the poisoned medium increasing gradually up to 16 times its initial value. Extensive use of the IBM 7090-7094 Computing facility was made to analyze properly the decay data (Frantic Code). Attention was given to the count loss correction scheme and the handling of the statistics involved. Fitting of the experimental results into the analytical form predicted by the diffusion model led to

Ʃav = 4721 sec-1 (±150)

Do = 35972 cm2sec-1 (±800) for water at 21˚C

C (given) = 3420 cm4sec-1

These values, when compared with published data, show that the diffusion model is adequate in describing the experiment.

Item Type:Thesis (Engineer's thesis)
Subject Keywords:(Mechanical Engineering)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Shapiro, Jerome L.
Thesis Committee:
  • Unknown, Unknown
Defense Date:28 March 1966
Funding AgencyGrant Number
French Ministry of Foreign AffairsUNSPECIFIED
Alliance Francaise of New YorkUNSPECIFIED
Fulbright CommissionUNSPECIFIED
Record Number:CaltechTHESIS:09292015-093522074
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9181
Deposited On:30 Sep 2015 15:54
Last Modified:28 Feb 2024 17:27

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page