Pb-Zn liquid metal diffusion

The Lead-Zinc binary equilibrium system is currently being investigated. Ground based studies of this system were performed to examine the possibility of obtaining a couple which, after diffusion, could be examined continuously along the diffusion axis by quantitative metallography to determine the extent of diffusion. The specimens were analyzed by X-ray fluorescence in the scanning electron microscope to provide exact information on the chemical composition gradient. Two diffusion experiments were run simultaneously in the multipurpose furnace, each in its own isothermal cavity. Two flight samples, two flight backup samples, and two flight space samples were generated

Acoustic Emission Study of Twinning in Indium Crystals and Lead-Tin Alloys

Dr. Evans\u27 lecture has been an excellent introduction to my presentation. I would like to say, however, that at one time we were asked if we were for or against evaluation by acoustic emission, and we said that we were against it. The reason we were against it was because of a doubt that some of the test procedures were actually telling us anything about cracking. We, therefore, accepted as a chore to try to do what Dr. Evans said should be done, that is, see if we can discriminate between slip, twinning, fracture in acoustic emission signals

Third Annual Report of the Farm Management Service for Farmers in Soil Conservation Demonstration Areas for the year 1937 (April 1937 to March 1938)

Farm Management,

Dopamine Cell Loss within the Nigrostriatal Pathway Due to Oxidative Stress from Chronic Methylphenidate

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder that affects 11% of children in the US alo­ne. Methylphenidate (MPH) is the most commonly prescribed drug for the treatment of ADHD. Given the fact that ADHD symptoms persist in up to 50% of patients, many children receive MPH from childhood to early adulthood. Unfortunately, most of the scientific literature focuses on the short-term consequences of MPH, even though individuals are taking MPH for many years. MPH acts by blocking dopamine (DA) transporters and norepinephrine transporters, preventing the reuptake of these catecholamines following release. Previous research has shown that long-term exposure to MPH causes dopaminergic neurons within the nigrostriatal pathway to be more sensitive to the Parkinsonian toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We hypothesize that oxidative stress caused by the spontaneous oxidation of the excess DA in the synaptic cleft is what’s rendering dopaminergic neurons within the nigrostriatal pathway to be more sensitive to MPTP. Adolescent male Swiss-Webster mice were divided into three cohorts and administered either saline (control), 1 mg/kg MPH (normal dose) or 10 mg/kg (abusive dose) via intraperitoneal (IP) injections for 12 weeks. Mice were injected twice daily, Monday through Friday, mimicking a school-week dosing schedule. After 12 weeks, all animals received a drug washout period of 7 days. Then, half of each cohort was treated with MPTP (4 x 20mg/kg, every 2 hours), while the other half was administered 4 injections of sterile saline. Seven days after MPTP or saline treatment, the mice were sacrificed, brains were removed, and the substantia nigra (SN) and striatum (STR) were collected. Oxidative stress related to increased DA levels was determined using the glutathione assay to measure glutathione (GSH) content and near-infrared fluorescence dot blots to measure free and protein-bound ortho-quinones. GSH is an important antioxidant and thus its depletion would be indicative of oxidative stress. Additionally, since DA may be oxidized to a quinone, increases in free and protein-bound ortho-quinones also indicate oxidative stress. Interestingly, we observed a significant decrease in GSH as the dose of MPH increased with both saline and MPTP samples. Furthermore, there was a significant increase in quinones as the dose of MPH increased. In conclusion, it appears that long-term exposure to MPH sensitizes dopaminergic neurons within the nigrostriatal pathway to oxidative stress, rendering them vulnerable to further insults, such as MPTP exposure. As such, these studies provide insight into the risks of long-term psychostimulant exposure

A neutronic feasibility study for LEU conversion of the high flux beam reactor (HFBR).

A neutronic feasibility study for converting the High Flux Beam Reactor at Brookhaven National Laboratory from HEU to LEU fuel was performed at Argonne National Laboratory. The purpose of this study is to determine what LEU fuel density would be needed to provide fuel lifetime and neutron flux performance similar to the current HEU fuel. The results indicate that it is not possible to convert the HFBR to LEU fuel with the current reactor core configuration. To use LEU fuel, either the core needs to be reconfigured to increase the neutron thermalization or a new LEU reactor design needs to be considered. This paper presents results of reactor calculations for a reference 28-assembly HEU-fuel core configuration and for an alternative 18-assembly LEU-fuel core configuration with increased neutron thermalization. Neutronic studies show that similar in-core and ex-core neutron fluxes, and fuel cycle length can be achieved using high-density LEU fuel with about 6.1 gU/cm{sup 3} in an altered reactor core configuration. However, hydraulic and safety analyses of the altered HFBR core configuration needs to be performed in order to establish the feasibility of this concept

A neutronic feasibility study for LEU conversion of the Budapest research reactor.

A neutronic feasibility study for conversion of the Budapest Research Reactor (BRR) from HEU to LEU fuel was performed at Argonne National Laboratory in cooperation with the KFKI Atomic Energy Research Institute in Hungary. Comparisons were made of the reactor performance with the current HEU (36%) fuel and with a proposed LEU (19.75%) fuel. Cycle lengths, thermal neutron fluxes, and rod worths were calculated in equilibrium-type cores for each type of fuel. Relative to the HEU fuel, the LEU fuel has up to a 50% longer fuel cycle length, but a 7-10% smaller thermal neutron flux in the experiment locations. The rod worths are smaller with the LEU fuel, but are still large enough to easily satisfy the BRR shutdown margin criteria. Irradiation testing of four VVR-M2 LEU fuel assemblies that are nearly the same as the proposed BRR LEU fuel assemblies is currently in progress at the Petersburg Nuclear Physics Institute

Argonne National Laboratory Reports

The reactor physics studies performed in the gas cooled fast reactor (GCFR) mockup on ZPR-9 are covered. This critical assembly, designated Phase II in the GCFR program, had a single zone PuO₂-UO₂ core composition and UO₂ radial and axial blankets. The assembly was built both with and without radial and axial stainless steel reflectors. The program included the following measurements: small-sample reactivity worths of reactor constituent materials (including helium); ²³⁸U Doppler effect; uranium and plutonium reaction rate distributions; thorium, uranium, and plutonium alpha and reactor kinetics. Analysis of the measurements used ENDF/B-IV nuclear data; anisotropic diffusion coefficients were used to account for neutron streaming effects. Comparison of measurements and calculations to GCFR Phase I are also made