Biomedical subjects

R D Spence

Publications and source records attributed to R D Spence.

6 recordsLinked to original sources

PubMed2004

Laboratory stabilizations/solidification of tank sludges: MVST/BVEST.

Oak Ridge tank sludges that have been collected over several decades are being combined for treatment and disposal. Stabilization of the highly radioactive, mixed-waste sludges in the different tank sets has been evaluated prior to the proposed combination and treatment. This paper documents the testing of a Melton Valley Storage Tank (MVST)/Bethel Valley Evaporator Storage Tank set. Subsequent papers will discuss continued work on other tank sets and efforts to maximize the sludge loading. Grout formulations were tested in the laboratory both with a surrogate and with a sample of an actual mixed waste tank sludge from MVST W-25. Wet-sludge loadings of 50-60wt% resulted in strong wasteforms with no free water and gave a volume increase of about 40-50vol%. Resource Conservation and Recovery Act (RCRA) metals included in the surrogate testing were cadmium, chromium, lead, selenium, thallium, and mercury. The actual sludge sample was only characteristically hazardous for mercury by the Toxic Characteristic Leaching Procedure but exceeded the Universal Treatment Standard (UTS) limit for chromium. The grout formulations stabilized these two RCRA metals within UTS limits. In addition, a grout leachability index of about 9.0-10.0 was measured for both (85)Sr and (137)Cs, meeting the recommended requirement of >6.0.

Conservation of Natural Resources↗

PubMed2004

Laboratory stabilization/solidification of tank sludges: GAAT, OHF, and combined tank sets.

Highly radioactive, mixed-waste sludges that have been collected at Oak Ridge over several decades are being combined for treatment and disposal. Stabilization of the sludges in the different tank sets was tested prior to the proposed combination and treatment. This paper, which follows a previous article on the Melton Valley Storage Tank/Bethel Valley Evaporator Storage Tank set, documents the testing of the Gunite and Associated Tank and Old Hydrofracture Facility tank sets, as well as the combined sludges of all the Oak Ridge National Laboratory tank sets; the third paper on this subject will discuss efforts to maximize the sludge loading. The grout formulations were tested in the laboratory with surrogates. A wet-sludge loading of 60wt% resulted in strong wasteforms with no free water and gave a volume increase of about 30-40vol%. The Resource Conservation and Recovery Act metals included in the surrogate testing were silver, cadmium, chromium, lead, selenium, thallium, zinc, and mercury. The grout formulations stabilized these metals within the Universal Treatment Standards limits. In addition, a grout leachability index of about 10.0-12.0 was measured for both (85)Sr and (137)Cs, meeting the recommended requirement of >6.0.

Conservation of Natural Resources↗

PubMed2004

Laboratory stabilization/solidification of tank sludges: maximizing sludge loading.

Highly radioactive, mixed-waste sludges that have been collected in tanks at Oak Ridge over several decades are being combined for treatment and disposal. Stabilization of the sludges in the different tank sets was tested prior to the proposed combination and treatment. This paper is the third one in a series on the laboratory stabilization/solidification of these tank sludges. It discusses efforts to maximize the sludge loading with no strength criterion for the grout formulation. Grout formulations were tested in the laboratory both with surrogates and with actual samples of tank sludge. Hydrogels eliminated free water generation, even at sludge loadings of >90wt%, albeit strong monoliths did not form at such high loadings. Correlations established the dependence of the chromium and mercury performance in the Toxicity Characteristic Leach Procedure for the surrogates on the slag content of the grout while the lead performance depended on the extract pH. The surrogate sludge loading was limited by the chromate content to about 90wt%, meeting Universal Treatment Standard limits. However, tests with actual sludges at such high loadings revealed problems with lead and silver stabilization that were not experienced with the surrogate testing.

Chromium↗

PubMed1990

Ozone alters carbon allocation in loblolly pine: assessment with carbon-11 labeling.

Loblolly pine (Pinus taeda L.) seedlings were exposed to 0.120 micromol mol(-1) (ppm) ozone for 7 h per day, 5 days per week for 12 weeks. No visible damage resulted from this regime. A short-lived radioisotope of carbon ((11)C) was used to characterize changes in plant physiology caused by ozone, the first time this technique has been used for ozone exposure studies. In comparison to plants kept in charcoal-filtered air, pines exposed to ozone exhibited reductions in photosynthesis (16%), speed of phloem transport (11%), phloem photosynthate concentration (40%) and total carbon transport toward roots (45%). Photosynthate not transported to the roots appeared to accumulate in the stems. Primary branches of pines exposed to ozone were some 50-60% heavier than those of control pines. Ozone was thus shown to have a significant short-term impact on phloem transport processes that results in a shift in allocation of photosynthate favoring stems.

Journal Article↗

PubMed1985

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles.

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.

Biological Transport↗

PubMed1981

High-temperature Disruption of Guard Cells of Vicia faba: EFFECT ON STOMATAL APERTURE.

Increased variability in stomatal aperture at high temperatures can be attributed, in part, to the differential sensitivity of guard cells to thermal damage. Individual stomata become increasingly open at higher temperatures until guard cells are lethally damaged; at that temperature, apertures decrease. The extent of irreversible damage causing closure was estimated by K(+) uptake, neutral red accumulation, and visual scoring of chloroplasts.This study found that visual scoring of chloroplast disruption provided the best estimate of guard cell viability at high temperature. Removal of the damaged guard cells from the population sample resulted in a constant coefficient of variability for apertures over the temperature range 25 to 50 C.

Journal Article↗