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Neutron spectrum from a uramium-235 sphere bombarded by 14-MeV neutrons

Journal Article · · Nucl. Sci. Eng.; (United States)
OSTI ID:7140327

A benchmark measurement of the neutron leakage spectrum from a pulsed 38-kg uranium (93.5 percent /sup 235/U) sphere has been made using time-of-flight techniques. The sphere had a multiplication of approximately 11 for 14-MeV neutrons, and a neutron hold-up time of approximately 40 nsec. The centrally located source of 14.1 +- 0.8-MeV neutrons, produced by bombarding a tritium gas target with pulses of low-energy deuterons, was isotropic to +-7.7 percent. Neutrons in the 0.180- to 16.0-MeV energy range were detected at the end of a 39-m flight path by an Ne-213 liquid scintillator employing pulse-shape discrimination. The detector efficiency was measured over this same energy range using monoenergetic neutrons from the T(p,n) T(d,n), and D(d,n) reactions. The measured neutron flux as a function of energy is compared with the results of Monte Carlo calculations performed with the MCN code. Uranium cross sections from ENDF/B-IV and an older set from Lawrence Livermore Laboratory were used in the calculations. The results calculated using the ENDF/B-IV cross sections are in good agreement with the measurements, especially in the 1- to 6-MeV energy region where the uncertainties in both the calculated and experimental results are the smallest.

Research Organization:
Los Alamos Scientific Lab., NM
OSTI ID:
7140327
Journal Information:
Nucl. Sci. Eng.; (United States), Journal Name: Nucl. Sci. Eng.; (United States) Vol. 61:1; ISSN NSENA
Country of Publication:
United States
Language:
English