Light weight radioisotope heater unit (LWRHU) production for the Cassini mission

The Light-Weight Radioisotope Heater Unit (LWRHU) is a [sup 238]PuO[sub 2] fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. The heat sources are required to maintain the temperature of specific components within normal operating ranges. The heat source consists of a hot- pressed [sup 238]PuO[sub 2] fuel pellet, a Pt-3ORh vented capsule, a pyrolytic graphite insulator, and a woven graphite aeroshell assembly. Los Alamos National Laboratory has fabricated 180 heat sources, 157 of which will be used on the Cassini mission

High temperature thermodynamics and vaporization of the zirconium--niobium--oxygen system

The vaporization behavior of the Zr--Nb--O system was studied by means of successive vaporization, Knudsen effusion-target collection experiments, and mass spectrometric analysis of the vapors effusing from a Knudsen crucible. The successive vaporization experiments were performed on two ternary samples in open crucibles. X-ray powder diffraction patterns of the residues and x-ray fluorescence analysis of the condensates and residues indicated the preferential vaporization of niobium-containing species with the composition of the residue subsequently becoming closer to that of congruently vaporizing ZrO/sub 2-x/. The Knudsen effusion-target collection experiments were employed on two samples, pure NbO/sub 2/(s) and a two-phase ZrO/sub 2/--NbO/sub 2/ mixture, in order to obtain information on the activity of NbO/sub 2/ in the two-phase mixture. Second law enthalpies and entropies of sublimation as well as third law enthalpies were obtained for both systems. The vaporization behaviors of five compositions in the Zr--Nb--O system, NbO/sub 2/, NbO, a ZrO/sub 2/--NbO/sub 2/ two-phase mixture, Nb/sub 2/O/sub 5/, and Zr/sub 6/Nb/sub 2/O/sub 17/, were investigated. Above Nb/sub 2/O/sub 5/ and the fully oxidized Zr/sub 6/Nb/sub 2/O/sub 17/ oxygen is preferentially lost; over NbO/sub 2/, the two-phase ZrO/sub 2/--NbO/sub 2/ system, and NbO the principal gaseous species is NbO/sub 2/

Light Weight Radioisotopic Heater Unit (LWRHU) production for the Galileo Mission

The Light Weight Radioisotopic Heater Unit (LWRHU) is a /sup 238/PuO/sub 2)minus/ fueled heat source designed to provide a thermal watt of power for space missions. The LWRHU will be used to maintain the temperature of various components on the spcaecraft at the required level. The heat source consists of a /sup 238/PuO/sub 2/ fuel pellet, a Pt-30Rh capsule, a pyrolytic graphite insulator, and a woven graphite aeroshell assembly. Los Alamos National Laboratory (LANL) has fabricated 134 heater units which will be used on the Galileo Mission. This report summarizes the specifications, fabrication processes, and production data for the heat sources fabricated at LANL. 4 figs., 15 tab

Milliwatt Generator Project

This report covers progress on the Milliwatt Generator Project from April 1986 through March 1988. Activities included fuel processing and characterization, production of heat sources, fabrication of pressure-burst test units, compatibility studies, impact testing, and examination of surveillance units. The major task of the Los Alamos Milliwatt Generator Project is to fabricate MC2893A heat sources (4.0 W) for MC2730A radioisotope thermoelectric generators (RTGS) and MC3599 heat sources (4.5 W) for MC3500 RTGs. The MWG Project interfaces with the following contractors: Sandia National Laboratories, Albuquerque (designer); E.I. du Pont de Nemours and Co. (Inc.), Savannah River Plant (fuel); Monsanto Research Corporation, Mound Facility (metal hardware); and General Electric Company, Neutron Devices Department (RTGs). In addition to MWG fabrication activities, Los Alamos is involved in (1) fabrication of pressure-burst test units, (2) compatibility testing and evaluation, (3) examination of surveillance units, and (4) impact testing and subsequent examination of compatibility and surveillance units

Milliwatt generator project: Progress report, April 1983--March 1984

This report covers progress on the Milliwatt Generator Project during April 1983--March 1984. Activities included (plutonium 238 oxide) fuel processing and characterization, production of heat sources, fabrication of pressure-burst test units, compatibility studies, impact testing, examination of surveillance units, Inconel weld development, and qualilty assurance

Light-Weight Radioisotope Heater Unit (LWRHU) sequential impact tests

The light-weight radioisotope heater unit (LWRHU) is a {sup 238}PuO{sub 2}-fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. Los Alamos National Laboratory designed, fabricated, and safety tested the LWRHU. The heat source consists of a hot-pressed {sup 238}PuO{sub 2} fuel pellet, a Pt-30Rh vented capsule, a pyrolytic graphite insulator, and a fineweave-pierced fabric graphite aeroshell assembly. A series of sequential impacts tests using simulant-fueled LWRHU capsules was recently conducted to determine a failure threshold. Sequential impacting, in both end-on and side-on orientations, resulted in increased damage with each subsequent impact. Although the tests were conducted until the aeroshells were sufficiently distorted to be out of dimensional specification, the simulant-fueled capsules used in these tests were not severely deformed. Sequential impacting of the LWRHU appears to result in slightly greater damage than a single impact at the final impact velocity of 50 m/s. Postimpact examination revealed that the sequentially impacted capsules were slightly more deformed and were outside of dimensional specifications

Light-weight radioisotope heater impact tests

The light-weight radioisotope heater unit (LWRHU) is a {sup 238}PuO{sub 2}-fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. Los Alamos National Laboratory designed, fabricated, and safety tested the LWRHU. The heat source consists of a hot-pressed {sup 238}PuO{sub 2} fuel pellet, a Pt-30Rh vented capsule, a pyrolytic graphite insulator, and a fineweave-pierced fabric graphite aeroshell assembly. To compare the performance of the LWRHUs fabricated for the Cassini mission with the performance of those fabricated for the Galileo mission, and to determine a failure threshold, two types of impact tests were conducted. A post-reentry impact test was performed on one of 180 flight-quality units produced for the Cassini mission and a series of sequential impact tests using simulant-fueled LWRHU capsules were conducted respectively. The results showed that deformation and fuel containment of the impacted Cassini LWRHU was similar to that of a previously tested Galileo LWRHU. Both units sustained minimal deformation of the aeroshell and fueled capsule; the fuel was entirely contained by the platinum capsule. Sequential impacting, in both end-on and side-on orientations, resulted in increased damage with each subsequent impact. Sequential impacting of the LWRHU appears to result in slightly greater damage than a single impact at the final impact velocity of 50 m/s

Recycle of scrap plutonium-238 oxide fuel to support future radioisotope applications

The Nuclear Materials Technology (NMT) Division of Los Alamos National Laboratory has initiated a development program to recover and purify plutonium-238 oxide from impure feed sources in a glove box environment. A glove box line has been designed and a chemistry flowsheet developed to perform this recovery task at large scale. The initial demonstration effort focused on purification of {sup 238}PuO{sub 2} fuel by HNO{sub 3}/HF dissolution, followed by plutonium(III) oxalate precipitation and calcination to an oxide. Decontamination factors for most impurities of concern in the fuel were very good, producing {sup 238}PuO{sub 2} fuel significantly better in purity than specified by General Purpose Heat Source (GPHS) fuel powder specifications. The results are encouraging for recycle of relatively impure plutonium-238 oxide and scrap residue items into fuel for useful applications. A sufficient quantity of purified {sup 238}PuO{sub 2} fuel was recovered from the process to allow fabrication of a GPHS unit for testing. The high specific activity of plutonium-238 magnifies the consequences and concerns of radioactive waste generation. This work places an emphasis on development of waste minimization technologies to complement the aqueous processing operation. Results from experiments allowing more time for neutralized solutions of plutonium-238 to precipitate resulted in decontamination to about 1 millicurie/L. Combining ultrafiltration treatment with addition of a water-soluble polymer designed to coordinate Pu, allowed solutions to be decontaminated to about 1 microcurie/L. Efforts continue to develop a capability for efficient, safe, cost-effective, and environmentally acceptable methods to recover and purify {sup 238}PuO{sub 2} fuel

Running the routes together: co-running and knowledge in action

The mundane, concrete practices of social life have remained underanalyzed, unproblematized, even taken for granted by some social theorists, despite their being constitutive of the very foundation of social life. Despite a growing corpus of ethnographic studies within the sociology of sport, little analytic attention has been devoted to the concrete practices of actually “doing” sporting activity. Based on data derived from a collaborative auto-ethnographic study of distance runners, this article analyzes the ways in which two runners jointly accomplish running-together. The article also examines and “marks” some of the knowledge in action that underpins the production of running-together, analyzed in relation to three specific areas: ground and performance, safety concerns, and “the other,” in the form of training partner(s), highlighting the importance of aural and visual components. It concludes with a call for more detailed analytic descriptions of sporting practices to better ground more abstract generalizations about sporting phenomena