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Neutron irradiation embrittlement of reactor pressure vessel steels (RPVs) is one of the important material aging issues. In Japan, almost 40 years have past since the first plant started its commercial operation, and several plants are expected to become beyond 40 years old in the near future. Thus, the safe operation, based on the appropriate recognition of the neutron irradiation embrittlement, is inevitable to ensure the structural integrity of RPVs. The amount of the neutron irradiation embrittlement of RPV steels has been monitored and predicted by the complemental use of the surveillance program and embrittlement correlation method. Recent surveillance data suggest some discrepancies between the measurements and predictions of the embrittlement in some old boiling water reactor (BWR) RPV steels with high impurity content. Some discrepancies of pressurized water reactor (PWR) RPV surveillance data from the predictions have also been recognized in the embrittlement trend. Although such discrepancies are basically within a scatter band, the increasing necessity of the improvement of the predictive capability of the embrittlement correlation method has been emphasized to be prepared for the future long term operation. Regarding the surveillance program, on the other hand, only one original surveillance capsule, except for the reloaded capsules containing Charpy broken halves, is available in some BWR plants. This situation strongly pushed establishing a new code for a new surveillance program, where the use of the reloading and reconstitution of the tested specimens is specified. The Japan Electric Association Code, JEAC 4201-2007 'Method of Surveillance Tests for Structural Materials of Nuclear Reactors,' was revised in December 2007, in order to address these issues. A new mechanism-guided embrittlement correlation method was adopted. The surveillance program was modified for the long term operation of nuclear plants by introducing the 'long term surveillance program,' which is to be applied for the operation beyond 40 years. The use of the reloading, reirradiation, and reconstitution of the tested Charpy/fracture toughness specimens is also specified in the new revision. This paper reports the application and practice of the JEAC4201-2007 in reruns of the prediction of embrittlement and the use of tested surveillance specimens in Japan. [DOI: 10.1115/1.4001057]

Neutron irradiation embrittlement of reactor pressure vessel steels is an important aging issue for the long-term operation of light water reactors. A new embrittlement correlation method was developed by Central Research Institute of Electric Power Industry and the Japanese electric utilities in 2007. This method is primarily based on the fundamental understandings on the embrittlement mechanisms, i.e., microstructural changes were modeled by the mathematical form of rate equations, and the predicted microstructural changes were further correlated with the mechanical property changes in transition temperature region. The coefficients of the rate equations were optimized using the Japanese surveillance data of RPV embrittlement. This method was adopted as the revision of the Japanese code, JEAC4201-2007, in 2007. In this paper, after a brief explanation on the new correlation method, the predictions of the new method will be investigated through comparisons with the previous correlation, JEAC4201-2004, and the U.S. surveillance data in order to identify the characteristics of the new method. [DOI: 10.1115/1.4001056] Keywords: nuclear engineering, reactor pressure vessel, embrittlement, surveillance

The National Institute of Standards and Technology (NIST) has developed new gamma-ray and neutron emitting sources for testing radiation detection systems. These radioactive sources were developed for testing of detection […]

Skyrmions represent topologically stable field configurations with particle-like properties. We used neutron scattering to observe the spontaneous formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortex, in the chiral itinerant-electron magnet MnSi. The skyrmion Lattice stabilizes at the border between paramagnetism and long-range helimagnetic order perpendicular to a small applied magnetic field regardless of the direction of the magnetic field relative to the atomic lattice. Our study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of crystalline order composed of topologically stable spin states.

Alternative energy resources such as hydrogen and methane gases are becoming increasingly important for the future economy. A major challenge for using hydrogen is to develop suitable materials to store it under a variety of conditions, which requires systematic studies of the structures, stability, and kinetics of various hydrogen-storing compounds. Neutron scattering is particularly useful for these studies. We have developed high-pressure/low-temperature gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments allowing in situ and realtime examination of gas uptake/release processes. We studied the formation of methane and hydrogen clathrates, a group of inclusion compounds consisting of frameworks of hydrogen-bonded [H.sub.2]O molecules with gas molecules trapped inside the cages. Our results reveal that clathrate can store up to four hydrogen molecules in each of its large cages with an intermolecular [H.sub.2]-[H.sub.2] distance of only 2.93 [Angstrom]. This distance is much shorter than that in the solid/metallic hydrogen (3.78 [Angstrom]), suggesting a strong densification effect of the clathrate framework on the enclosed hydrogen molecules. The framework-pressurizing effect is striking and may exist in other inclusion compounds such as metal-organic frameworks (MOFs). Owing to the enormous variety and flexibility of their frameworks, inclusion compounds may offer superior properties for storage of hydrogen and/or hydrogen-rich molecules, relative to other types of compounds. We have investigated the hydrogen storage properties of two MOFs, [Cu.sub.3][[Co[(CN).sub.6]].sub.2] and [Cu.sub.3][(BTC).sub.2] (BTC = benzenetricarboxylate), and our preliminary results demonstrate that the developed neutron-scattering techniques are equally well suited for studying MOFs and other inclusion compounds. framework-pressurizing effect | hydrogen storage | inelastic neutron scattering | neutron diffraction

The small-angle neutron scattering method is used to investigate the aqueous mixed micellar solutions of perflouropolyether carboxylic salts with ammonium counterions, as their shapes and dimensions are highly affected by the presence of the n3 surfactant. The analysis reveals that a close packing of the tails leads to a decrease in the micellar curvature and repulsions between the polar heads, which ultimately leads to a micellar growth in the ellipsoids with greater axial ratios.

An integrated structural and paleomagnetic study was carried out on Neogene-Quaternary elastic sedimentary sequences exposed in north Calabria to define the brittle postorogenic evolution of the inner sector of the Calabrian arc. The structural, mineralogical, and magnetic fabric data presented in this paper suggest that the post-orogenic basins of north Calabria originated and developed under an extensional tectonic regime that has been active since the middle Miocene. Results were used to define the spatial and temporal evolution of the extensional fault systems in the framework of extensional processes active in the backarc region of the southeastward-migrating Apennine subduction system. Our data indicate that regional backarc extension operated in the brittle crust, and the data trace a continuous evolution from low- to high-angle extensional faulting. Paleomagnetic data show that this continuous extensional process was accompanied by complex interactions among fault-bounded crustal blocks. In fact, the extensional domain is subdivided into different structural compartments, separated by the adjustment in the fault strike imposed by the regional rotation pattern. Keywords: extension tectonics, Calabria, Italy, paleomagnetism, magnetic susceptibility, anisotropy, neutron diffraction analysis.

Small angle neutron scattering and UV titration is used to study effect of the ratio of negative to positive charges on the structure of complexes formed by short negatively charged polyelectrolyte chains (PSS) and globular positively charged proteins (lysozyme). It is observed that the primary complexes reach a finite size, controlled by electrostatic repulsion, and then aggregate at a higher scale with a fractal dimension of 2.1 characteristic of reaction-limited colloidal aggregation.

Dissociation temperatures of gas hydrate formed in the ethane-water system are studied at pressures up to 1500 MPa. In situ neutron diffraction analysis and X-ray diffraction analysis in a diamond anvil cell showed that the gas hydrate formed in the ethane-water system at 340, 700, and 1840 MPa and room temperature belongs to the cubic structure I (CS-I).

The neutron back scattering technique is used to search for land mines. Advantages of this technique are: the speed of detection, the ability to detect metal free mines, and the insensitivity to metal and pebbles. The method is sensitive to soft moisture, therefore a desert environment is perfectly suited for application of the neutron backscattering technique. Tests were performed using various dummy mines and real defused mines in the Egyptian desert. Index Terms--Land mine detection, neutron generator, neutron scattering.

Cation ordering in two important iron nickel sulfide minerals, pentlandite and violarite, was studied by neutron powder diffraction using samples prepared with isotopically enriched [sup.60]Ni. Pentlandite of composition [Fe.sub.4.8][Ni.sub.4.2][S.sub.8], annealed at 150[degrees] C for 1 month has a disordered Ni/Fe distribution with Ni occupying 57(2)% of the octahedral site and 46(1)% of the tetrahedral site with a unit cell repeat of 10.1075(1) [Angstrom]. After annealing for a further 2 months at 150[degrees]C the Ni/Fe distribution is still disordered with 53(2)% Ni in the octahedral site and 48(2)% Ni in the tetrahedral site and the cell parameter increased by 0.21% possibly due to slight readjustment of the Fe/Ni ratio. Synthetic violarite, Fe[Ni.sub.2][S.sub.4], prepared at 300[degrees]C, exhibits ordering of Ni onto the tetrahedral site, with Fe and the remaining Ni sharing the octahedral site. In situ neutron diffraction heating experiments in which pentlandite and violarite were heated up to 300[degrees]C for 12 hours did not alter the Ni/Fe distribution between tetrahedral and octahedral sites. Violarite did not exhibit any evidence of magnetic ordering upon cooling to -173[degrees]C. The interatomic distances in the two structures indicate that in pentlandite [Fe.sup.2+] and [Ni.sup.2+] are high spin and in violarite [Fe.sup.2+] is low spin with [Ni.sup.3+] with an inverted spinel structural type. Keywords: Neutron diffraction, cation ordering, [sup.60]Ni isotope, pentlandite, violarite, thiospinel

A highly viscoelastic wormlike micellar solution of nonionic surfactants in a dilute region is reported. The results of structural investigations with small-angle neutron scattering (SANS) and the observations using dynamic light scattering (DLS) are presented.

Neutron scattering experiments are performed on fully deuterated liquid N-methylformamide at various temperatures and under pressure. The recorded data at atmospheric pressure and room temperature are analyzed to yield the molecular form factor and the distinct pair correlation function.

Quasielastic neutron scattering (QENS) spectra of water-filled MCM-41 samples are measured over the temperature range 238-298 K and the momentum transfer range 0.31-0.99 A(sup -1) to investigate the dynamics of confined water molecules. Using the Lorentzian and the stretched exponential functions, the spectra, which consist mainly of contributions from the transational diffusion of water molecules, are analyzed.

Quasielastic neutron scattering measurements have been performed, to investigate the dynamics of homologous disaccharide aqueous solutions. Neutron spectra have been collected by using the spectrometer OSIRIS at the ISIS pulsed neutron source of the Rutherford Appleton Laboratory.

The aggregation properties of single-chain cationic surfactants bearing one, two and three pyridinium headgroups are studied by using detailed small-angle neutron scattering (SANS). The critical micellar concentration (cmc) of these surfactants is estimated by measuring the specific conductance of the aqueous solution of the surfactants.

Small-angle neutron-(SANS) and X-ray-scattering (SAXS) patterns obtained at 40 degree C from 0.0729 m D2O solution of cesium dodecyl sulfate (CsDDS) is evaluated in terms of the conventional two-shell model, a three-shell model created for demonstration purposes. Findings suggest that the most reliable information on the aggregate structure is obtained when fitting the four-component model to the combined SANS + SAXS patterns.

Uranium doping and thermal neutron irradiation effects on flux-pinning of silver Bi-Sr-Ca-Cu-O tapes were studied.

Incorporation of the triangular mu(super 3) )[(C(CN)(sub 3)](sub -) ligand into polymeric arrays has led to a new class of spin-frustrated molecule-based magnets of the type M(super II)[(C(CN)(sub 3)](sub 2) (M = V, Cr). The crystal structure of Cr(super II)[(C(CN)(sub 3)](sub 2) (M = V, Cr) was determined from neutron powder diffraction at low temperature and was seen that it adopts an interpenetrating rutile-like topology.

MICROSCOPY IMAGING NOW 10X FASTER Scientists at the National Synchrotron Light Source II (NSLS-II) developed a transmission x-ray microscope (TXM) that can image samples 10 times faster than previously possible. [...]

A study was conducted to examine the effects of neutron irradiation to phase-pure (Hg(sub 1-x)Bix)Ba2Ca2Cu3Oy superconductor. By measuring the magnetization and thermal conductivity of neutron-irradiated-superconductor, it was found that the inclusion of point-defects form irradiation diminishes transition temperature and destroys the coupling between neighboring superconducting grains.

AMPING UP ACCURACY OF RESIDUAL STRESS MAPPING Researchers from the University of Virginia, Charlottesville, are using neutrons to explore fundamental work in residual stress mapping that promises more precise science [...]

Introduction Neutron logging has found extensive application in a number of earth science-related fields. It is a technique that takes advantage of the properties of the hydrogen atom in thermalizing [...]

The structural parameters of [Hg.sup.2} hydration were studied by neutron diffraction with isotopic substitution. It was fond that [Hg.sup.2} is hydrated by a first solvent shell of six water molecules and the Hg-O distance obtained in the neutron diffraction experiment is larger by approximately 0.1 Angstrom than that obtained by X-ray diffraction.

Neutron scattering is used for examining the layered A-type antiferromagnet Pr0.5Sr0.5MnO3. A gap of 2.3 plusminus 0.2 meV at the zone center [0.5 0 0.5] is observed in the spin-wave excitations.

Elastic neutron scattering is used to examine the peculiar structure of charge and spin ordering in the half-doped layered perovskite oxide La1.5Sr0.5CoO4. The spin structure is a damped flat spiral polarized in the a-b plane with the propagation vector Q=(zeta, zeta, 1).

Magnetic measurements and neutron diffraction techniques were used for examining the magnetic structure of high purity MnBi low temperature phase. A coercivity of 2.0 T at 400 K and a positive temperature coefficient from 0 to at least 400 K is observed in the low temperature phase of the MnBi alloy.

The direct visualization of deuterium molecules adsorbed on isoreticular metal organic frameworks (IRMOF-1) is presented by using reverse Monte Carlo simulation based on first principle molecular dynamics simulation and neutron diffraction. The studies have shown that the average distance of deuterium molecules adsorbed onto IRMOF-1 is longer than that in a solid state but much shorter than that in the corresponding gas state.

Several studies are conducted to explain the annealing nature of the defects present in the depletion region, as well as the neutral base of the neutron damaged silicon bipolar transistors. The generation/recombination currents exhibited by the base-emitter junctions are shown to be the main factor leading to large, damage-induced base currents.

Neutron diffraction is used for showing cholesterol' s orientational preference in different lipid bilayers. The results have provided credibility to DMPCEs aversion for polyunsaturated fatty acids (PUFAs), which has supported the notion that domain formation is primarily driven by lipids.

The predicted structure and molecular trajectories from molecular dynamics simulation of the solvated Double-Super Helix (DSH) model of nascent high-density lipoprotein (HDL) are determined and compared with reconstituted nascent HDL. The analysis of salt bridge persistence during simulation helped in understanding the structural features of apoA1 that has formed the backbone of the lipoprotein.