Accession Number : AD0674888

Title :   EXPERIMENTAL STUDY OF THE PROPAGATION OF SLOW NEUTRONS CLOSE TO THE SOURCE IN THE UNBOUNDED ATMOSPHERE (EKSPERIMENTALNOE IZUCHENIE RASPROSTRANENIYA MEDLENNYKH NEITRONOV V BESKONECHNOI VOZDUSHNOI SREDE VBLIZI ISTOCHNIKA),

Corporate Author : FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO

Personal Author(s) : Degtyarev,S. F. ; Kukhtevich,V. I. ; Tarasov,V. V.

Report Date : 04 JAN 1968

Pagination or Media Count : 10

Abstract : The density of thermal neutrons is experimentally studied to provide data for computing capture gamma-radiation in air. A Po-Be fast neutron source was used in a paraffin block having walls 20 cm thick. Thermal neutrons are taken as those with an energy below the cadmium threshold E sub n < 0.4 Mev and neutrons with greater energies are called fast neutrons. An SNM-O boron counter was used for measuring the density of thermal neutrons. The source and detector were located at an altitude of 60 m to eliminate the effect of neutrons scattered from the earth. Three quantities were measured directly: (1) the density of neutrons throughout the entire spectrum escaping from the paraffin block; (2) the density of thermal neutrons formed from the fast neutrons; (3) the density of fast neutrons escaping from the source and propagated in the atmosphere. The results show that the fraction of thermal neutrons produced by attenuation in the atmosphere is small in comparison with the thermal neutrons for the given spectrum. A comparison of experimental and theoretical data for thermal neutron distribution shows excellent agreement at a source temperature of 293 degrees K with some discrepancy when the source temperature is increased to 440 degrees K.

Descriptors :   (*NEUTRON CAPTURE GAMMA RAYS, IONOSPHERIC PROPAGATION), (*THERMAL NEUTRONS, DENSITY), NEUTRON COUNTERS, FAST NEUTRONS, TRANSPORT PROPERTIES, REACTOR SHIELDING CALCULATIONS, NEUTRON SCATTERING, USSR

Subject Categories : Nuclear Radiation Shield, Protection & Safety
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE