[en] The responsibilities of the Reactor Radiation Division are threefold: to operate the research reactor (NBSR) as a NIST and national resource in a cost-effective manner while protecting the public safety; to conduct a program of materials research using neutron methods, while developing and maintaining state-of-the-art instrumentation to ensure the best utilization of the NBSR neutron scattering facilities; and to develop and operate the Cold Neutron Research Facility (CNRF) as a National center, providing unique measurement capabilities to U.S. researchers. The techniques include nuclear methods for chemical analysis, neutron diffraction and scattering for the characterization of microstructure and dynamics of materials (e.g., hydrogen in metals, polymers, layered materials, surfaces and interfaces, ceramics, alloys, amorphous materials, micelles, microporous materials, and buckminsterfullerene) neturon diffraction metods for determination of residual stress and texture, neutron radiography for the non-destructive examination of large components, neturon autorafiography for art history and restoration, and various techniques for neutron flux calibrations and personnel radiation monitoring. The sections that follow are a summary of the t echnical activities of the Reactor Radiation Division from October 1,1990 through September 30, 1991. A detailed report on work performed at the NIST reactor is available in a NIST Technical Note entitled 'NIST Reactor: Summary of Activities July 1990 through June 1991'

[en] The crystal structure of ammonium nitrate phase III has been studied at room temperature by neutron diffraction using a single crystal containing 5% KNO₃ in solid-solution form. The space group is Pnma, with a = 7.6772 (4), b = 5.8208 (4), c = 7.1396 (5) A, Z = 4. The final residual after full-matrix least-squares refinement was R = 0.042 for 348 observed reflections. The ammonium ions are thermally disordered into two orientations, displaced by an angle of approximately 42⁰ about an axis parallel to the c axis. (Auth.)

[en] The National Institute of Standards and Technology Reactor (NBSR) is a 20 MW research reactor located at the Gaithersburg, MD site, and has been in operation since 1969. In the reactor hall there are 26 experimental facilities which are used for materials science, chemical analysis, nondestructive evaluation, neutron standards work, and irradiations. The reactor had built into it from the beginning a provision for a large volume cold neutron moderator. Utilizing this capability, the Department of Commerce and NIST have begun a project to develop a major national facility for cold neutron research, the CNRF. This $30M project will, when fully completed, provide fifteen new experimental stations with capabilities currently unavailable in this country. It will be operated as a National User Facility, open to all qualified researchers on the basis of scientific merit. One-third of the experimental stations will be provided by sources outside of NIST

[en] Texture measurement as a function of depth with a collimated thermal neutron beam is demonstrated for a 'two-layer plate' geometry sample with preliminary results for a copper cone. (Auth.)

[en] The National Institute of Standards and Technology Reactor (NBSR) is a 20 MW research reactor located at the Gaithersburg, MD site, and has been in operation since 1969. In the reactor hall there are 26 experimental facilities which are used for materials science, chemical analysis, nondestructive evaluation, neutron standards work, and irradiations. The reactor had built into it from the beginning a provision for a large volume cold neutron moderator. Utilizing this capability, the Department of Commerce and NIST have begun a project to develop a major national facility for cold neutron research, the CNRF. This $30M project will, when fully completed, provide fifteen new experimental stations with capabilities currently unavailable in this country. It will be operated as a National User Facility, open to all qualified researchers on the basis of scientific merit. One-third of the experimental stations will be provided by sources outside of NIST. (author)

[en] The NIST Reactor (NBSR) and Cold Neutron Research Facility (CNRF) are located at the Gaithersburg, MD site, and have been in operation since 1969 and 1991, respectively. A total of 26 thermal neutron facilities and 11 cold neutron stations are operating for studies in condensed matter physics and chemistry, materials science, chemical analysis, nondestructive evaluation, neutron standards, fundamental neutron physics, and irradiations. Thermal and cold neutron instruments which have become operational since the 2d IGORR Conference will be described. Major facility upgrades to be implemented in early 1994 will be outlined. (author)

[en] Energy-dispersive neutron diffraction has been developed at the NIST reactor as a probe of sub- and near-surface residual stresses in technological samples. Application of the technique has been made to a variety of metallurgical specimens which includes the determination of triaxial stresses as a function of depth in a number of uranium-3/4wt%Ti samples with different thermo-mechanical histories, and in two types of 7075-T6 aluminum ogives. Preliminary results have been specimen for the SAE

[en] Very recently a new, dedicated, state-of-the-art diffractometer has been installed at the NIST reactor. With it, the residual stress fields in bent steel tubes have been mapped. Two mild steel tubes, of outside diameter 168 mm, wall thickness 8 mm and length 1,000 mm, were subjected to four-point bends. Tube 1 is seamless, tube 2 has a weld parallel to the cylindrical axis. After bending, the central 260 mm, together with end pieces, were cut out of the tubes for neutron diffraction measurements. Using a 2x2x2 mm³ gauge volume, strain components were measured as a function of depth beneath the surface at various locations along the axis and around the circumference of the tubes. Residual stresses were inferred from the measured strains by utilizing Hooke's Law and the appropriate diffraction elastic constants. Features of the new instrument and various experimental results will be discussed

No abstract available

[en] The NIST Reactor (NBSR) and Cold Neutron Research Facility (CNRF) are located at the Gaithersburg, MD site, and have been in operation since 1969 and 1991, respectively. A total of 26 thermal neutron facilities and 11 cold neutron stations are operating for studies in condensed matter physics and chemistry, materials science, chemical analysis, nondestructive evaluation, neutron standards, fundamental neutron physics, and irradiations. Thermal and cold neutron instruments which have become operational since the 2d IGORR Conference will be described. Major facility upgrades to be implemented in early 1994 will be outlined. (author)