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abstracts
Polarized neutron scattering is a very useful method of determining spin densities and magnetic structures. It can also be used to separate nuclear coherent scattering from spin-incoherent scattering. When compared to other neutron polarizing techniques like Heusler crystals and polarizing supermirrors, polarized 3He neutron spin filters provide several unique advantages: First, polarized 3He can effectively polarize neutrons over a broad range of energies. Second, it has a large acceptance angle for incoming neutron beams. Third, it does not change direction of, or add divergence to, neutron beams. At Oak Ridge National Laboratory (ORNL), a polarized 3He program has been established to meet the increasing needs from various neutron beamlines. 3He is polarized through spin-exchange optical pumping at ORNL. Both ex situ and in situ systems have been developed to accommodate the requirements of different instruments. We report the current status of our development and present test results on several neutron beamlines at ORNL. Future application in small angle neutron scattering will also be discussed.
abstracts
Residual stresses are expected in monolithic, aluminum clad uranium 10 weight percent molybdenum (U-10Mo) nuclear fuel plates because of the large mismatch in thermal expansion between the two bonded materials. Previous high energy x-ray diffraction measurements successfully profiled the residual stresses in the U-10Mo, but were unable to probe either the Al cladding or the 15micron Zr diffusion prevention barrier due to poor grain statistics. Neutron diffraction, with its inherently more divergent incident be alleviates this problem and, moreover, allowed for the determination of the dislocation density and texture in all three phases. Several samples were examined as a function of processing step and the phase stresses, dislocation density and texture are monitored with respect to the processing conditions.
