No abstract available

No abstract available

[en] Materials irradiated in the target/blanket region of the Accelerator Production of Tritium (APT) system will contain significantly more hydrogen and helium, for any given displacements per atom (dpa), than typically found in materials irradiated in a fission reactor. The individual effects of helium and hydrogen implantation and displacement damage on structural materials are relatively well established. Helium will increase the strength, decrease the ductility, reduce the creep and stress rupture properties, decrease the fatigue life and weldability, and promote swelling. Hydrogen will also adversely effect the mechanical properties and promote premature fracture along metallurgical interfaces. Displacement damage generally increases the strength and decreases the ductility of single-phase metals and alloys. The adverse effects of hydrogen and helium implantation may couple with displacement damage to limit component lifetime in the target/blanket region of the APT system. This paper provides a technical basis to rationalize potential synergistic effects among displacement damage and the hydrogen and helium embrittlement processes and suggests that such synergistic effects may be of significant importance to component performance in intense spallation neutron sources

[en] Aims: To describe the clinical implementation of interstitial brachytherapy for GYN Cancers.

[en] We examine the melting of commensurate and incommensurate vortex lattices interacting with square pinning arrays through the use of numerical simulations. For weak pinning strength in the commensurate case we observe an order-order transition from a commensurate square vortex lattice to a triangular floating solid phase as a function of temperature. This floating solid phase melts into a liquid at still higher temperature. For strong pinning there is only a single transition from the square pinned lattice to the liquid state. For strong pinning in the incommensurate case, we observe a multistage melting in which the interstitial vortices become mobile first, followed by the melting of the entire lattice, consistent with recent imaging experiments. The initial motion of vortices in the incommensurate phase occurs by an exchange process of interstitial vortices with vortices located at the pinning sites. We have also examined the vortex melting behavior for higher matching fields and find that a coexistence of a commensurate pinned vortex solid with an interstitial vortex liquid occurs while at higher temperatures the entire vortex lattice melts. For triangular arrays at incommensurate fields higher than the first matching field we observe that the initial vortex motion can occur through a correlated ring excitation where a number of vortices can rotate around a pinned vortex. We also discuss the relevance of our results to recent experiments of colloidal particles interacting with periodic trap arrays

No abstract available

[en] The successful prediction of the conditions under which nucleation occurs in metals, as a result of the high concentrations of vacancies and interstitial atoms (and gas atoms) present in reactor environments, has been accomplished by (1) generalizing homogeneous nucleation theory to account for nucleation of matter (i.e., vacancies) in the presence of its antimatter (i.e., interstitials), (2) further generalizing the theory to account for the effects of both trapped and soluble gas, and (3) modifying the theory to describe interstitial loop formation and including the effects of external stress

[en] In this paper the authors present their findings on the isolation and characterisation, including sequence, of two forms of inhibin from bovine follicular fluid (bFF) and the subsequent development of a radioimmunoassay (RIA) procedure which is applicable to follicular fluid and serum. (Auth.)

[en] The propose of this letter is to suggest a mechanism for two dimensional interstitial migration in Mo. (orig./RK)

[en] To provide structural material design data for the Accelerator Production of Tritium (APT) project, a 1 mA, 800 MeV proton beam at the Los Alamos Neutron Science Center (LANSCE) was used to irradiate a large number of metal samples, including a tungsten target similar to that being considered as the neutron source for the tritium production. The maximum proton fluence to the tungsten target was ∼ 10²¹ protons/cm². An unavoidable byproduct of spallation reactions is the formation of large amounts of hydrogen and helium. Postulated accident scenarios for APT involving the use of tungsten rods clad with Alloy 718, raise concerns as to the amount and rate of release of these gases due to temperatures increases from afterheat accumulation, with the major concern being pressurizing and possibly failure of the cladding. To address these issues, portions of the LANSCE tungsten rods were subjected to temperature histories calculated as likely to occur, and the time-dependent evolution of helium and hydrogen gases was measured. Stepped-anneal and total helium/hydrogen measurements were conducted on multiple samples of the tungsten material. Helium measurements were conducted at Pacific Northwest National Laboratory (PNNL) using a high-sensitivity magnetic-sector isotope-dilution helium analysis system. Stepped-anneal measurements were conducted at temperatures from ∼ 25 C to ∼ 1,600 C in ∼ 100 C steps. Total helium measurements were conducted by rapid vaporization after completion of the stepped-anneal process, and are compared with Monte Carlo calculations performed at Los Alamos National Laboratory (LANL) using the LAHET code system. Hydrogen measurements were conducted between ∼ 750 C and ∼ 1,200 C using a high-temperature furnace that had been extensively modified for the application. Hydrogen detection was accomplished by periodic sampling of the furnace gas using a separate quadrupole analyzer. Hydrogen measurements are also compared with LANL calculations