Recovery Of Isotopes Research Articles

Absorption breakthrough of hydrogen isotopes in inert gas mixture and desorption characteristics with ZrNi alloy particle bed

A metal particle packed bed is one of the most effective methods for the selective recovery of hydrogen isotopes in an inert gas such as argon or helium. An effective and convenient alloy might be ZrNi. ZrNi particles, 80–120 mesh, were packed in a column 20 mm in diameter, through which H 2-Ar or H 2-D 2-Ar gas mixtures at 50 °C were passed. The absorption characteristics were obtained and the desorption rates of the hydrogen isotopes for the alloy were also obtained in flowing argon gas at 400, 600 and 800 °C. It was found that the absorption and desorption rates are very fast, large amounts can be absorbed and the activation of the ZrNi alloy is very easy. Since it is known that the isotopic differences between hydrogen and deuterium in absorption and desorption are very small, it can be concluded that the ZrNi alloy should serve as a good absorbent of the hydrogen isotopes, including tritium, at room temperature.

ChemInform Abstract: Selective Absorption of Hydrogen Isotopes in an Inert gas in a Zirconium Particle Bed.

AbstractThe selective absorption and recovery of hydrogen isotopes at 400°C and their desorption at 800°C were investigated in a Zr particle packed bed using H2 ‐ Ar, D2 ‐ Ar and H2 ‐ D2 ‐ Ar gas mixtures.

Selective absorption of hydrogen isotopes in an inert gas in a zirconium particle bed

The selective absorption and recovery of hydrogen isotopes in an inert gas at 400 °C and their desorption at 800 °C were experimentally investigated using a zirconium particle packed bed. The gases used were H 2-Ar, D 2-Ar and H 2-D 2-Ar mixtures. The absorption rates of the hydrogen isotopes were found to be fast enough for this absorption method to be used as a hydrogen recovery process in the fuel cycle of a fusion reactor. The length of the absorption zone for D 2 in the zirconium bed is about twice that for H 2. The hydrogen isotopes in the H 2-D 2-Ar mixture break through in the sequence D 2, HD and H 2. This is believed to be because the absorption rate and solubility of H 2 are greater than those of D 2. The experimental results for the desorption of hydrogen isotopes are described fairly well by Fick's diffusion equation for a zirconium particle.

The determination of deuterium and tritium in effluent waste water by pulsed nuclear magnetic resonance spectroscopy

A pulsed nuclear magnetic resonance (NMR) procedure was developed for the quantitative determination of deuterium and tritium in radioactive, effluent, wastewater to aid in the design of an efficient combined electrolytic/catalytic exchange system for the recovery of these hydrogen isotopes. The deuterium and tritium NMR signals were observed at 9.210 and 45.7 MHz, respectively. Ten different effluent water samples were analyzed for deuterium and tritium to establish base-line data for the preparation of standard reference samples. The hydrogen isotope concentrations ranged from 0.11 to 2.40 g deuterium and from 2.0 to 21.0 mg tritium per liter of processed sample. The standard deviation of the hydrogen isotope determinations is +- 0.017 g deuterium and +- 0.06 mg tritium per liter of processed effluent water. In the future, the effectiveness of specially prepared and analyzed (calorimetry) effluent samples as tritium standards will be investigated.

Supply and recovery of hydrogen isotopes in high vacuum systems using ZrNi hydride getter pumps

In order to supply and recover hydrogen isotopes in small high vacuum systems, reversible pumps using ZrNi hydride as a getter material have been developed. Since the PC isotherms for the ZrNi–hydrogen system have two different plateau pressures corresponding to the existence of mono- and trihydrides, it is possible for the getter pumps to have two different equilibrium pressures. Because of the rapid decomposition kinetics of ZrNi hydride, these getter pumps are fast and consume little electric energy to supply hydrogen isotopes to high vacuum (HV) systems, e.g., it requires only 3.8 Wh and 150 s from onset of heating to supply 240 Torr liter (200 Torr×1.2 liter) D2 gas. One of the significant features of this getter pump is that, once activated, the gettering action proceeds at room temperature. Using a combination of two ZrNi hydride getter pumps having two different equilibrium pressures, it is possible to recover hydrogen isotopes completely from HV systems, e.g., 10 Torr D2 gas in a 1.2 liter glass HV system, can be pumped to 1×10−4 Torr within 200 s.

ジルコニウム粒子充てん層による水素同位体の吸収破過および脱離特性

The selective absorption and recovery of hydrogen isotopes in an inert gas at 400°C, and their desorption at 800°C have been experimentally investigated by use of a zirconium particle packed bed. The gases used are H2-Ar, D2-Ar and H2-D2-Ar mixtures. The absorption rates of the hydrogen isotopes are confirmed to be fast enough so that this absorption method can be used as a hydrogen recovery process in the fuel cycle of a fusion reactor. The length of the absorption zone for D2 in the zirconium bed is about twice as long as that for H2.For the breakthrough of hydrogen isotopes in the H2-D2-Ar mixture, the hydrogen isotopes flow out in the sequence of D2, HD and H2. The major reason is believed to be that the absorption rate and the solubility of hydrogen are greater than those of D2 .In the case of desorption process of the hydrogen isotopes, Fick's law diffusion equation in a zircorium particle can describe the experimental results fairly well.

Drainage of interstitial fluid from different regions of rat brain.

Studies were carried out in anesthetized rats comparing dynamics and pathways of interstitial fluid (ISF) drainage from different regions of brain. Rates of drainage from brain and flow into cerebrospinal fluid (CSF) were estimated from the efflux from brain and influx into CSF of radioiodinated albumin (RISA) following microinjection into caudate nucleus, internal capsule, or midbrain: pathways of flow through the subarachnoid space and into lymph were traced from the distribution of horseradish peroxidase and/or Evans blue-labeled albumin after injection into brain. ISF drainage rates (mul X g brain-1 X min-1) estimated for the three injection sites were 0.18, 0.19, and 0.29, respectively. Flow of ISF into bulk CSF sampled from the cisterna magna accounted for 60-75% of efflux from midbrain but only 10-15% of efflux from caudate nucleus or internal capsule. RISA was concentrated in the subarachnoid space, relative to bulk CSF, in sleeves of adventitial tissue surrounding pericerebral arteries, possibly accounting for the low recovery of isotope from bulk CSF. From the subarachnoid space, some fluid drained via olfactory nerve sheaths to retropharyngeal lymph nodes.

Nitrogen‐15 Recovery for Five Years after Application of Ammonium Nitrate to Crested Wheatgrass

AbstractAlthough perennial grasses usually respond to N fertilization if there is adequate water, fertilizer N recovery is usually relatively low. This research was conducted to understand better the fate of fertilizer N applied to grasslands. Twenty open‐ended cylinders (102‐mm diam by 637‐mm length) were pressed into each of two main plots containing 4‐year‐old stands of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.]. One plot had received no fertilizer N, and the other plot had received 22.4 g N/m2 each year since seeding. Enriched 15N was applied at the rate of 8.4 g N/m2 to a different replicated set of cylinders each of the 5 years of this study. Remaining cylinders received 8.4 g nonenriched N/m2 each year. Aboveground vegetation was harvested, and, after the fifth year, cylinders were removed from the soil. Roots were screened dry, and all plant material, roots, and soil were analyzed for total N and N‐isotope ratio.Average annual top growth varied fivefold as a result of highly variable precipitation and evaporation rate. Plant N concentration and uptake the first several seasons were about 25% greater from previously fertilized than from previously unfertilized soil. Cumulative recovery of 15N in tops increased with time, but considerable variation existed because of varied growing conditions between years. From 12 to 52% of the 15N applied was recovered in top growth in the season of application, representing about 75% of total isotope recovery in tops after four additional growing seasons. About 15% of the 15N was in roots after the first growing season, and about two‐thirds of this N appeared in plant tops within 3 y. Soil 15N varied from 29 to 49% of that applied, present mostly as organic N after the first season. About 70 to 95% of the 15N applied was accounted for in tops, roots, and soil, with little apparent relationship between 15N accounted for and either dry‐matter production or seasonal precipitation. Although uptake of soil N was initially 20 to 25% greater from previously fertilized than from unfertilized soil, this difference disappeared after the third year of fertilization, suggesting that at least 3 y of fertilization were required for the N cycle to readjust to a new steady state. Growing conditions the first few months after fertilizer application appear to have a major, but largely undefined, effect upon the fate of fertilizer N.

Recovery of hydrogen isotopes using a uranium bed

A breakthrough experiment was used to investigate the recovery of hydrogen isotopes from contaminated inert gases by using a reactive uranium powder bed column under various conditions. Before the break point the partial pressure of hydrogen in the outlet gas is almost equal to the plateau pressure of UH 3 at the column temperature. The breakthrough curve can be described by Meienschein's gas phase mass-transfer-limited model. The column is still effective at 273 K where the partial pressure of hydrogen at the outlet is 10 −5 Pa.

Toxicity, tissue distribution, and excretion of benzyl chloride in the rat.

The tissue distribution and excretion of [14C]benzyl chloride was investigated in adult male and female Fischer 344/N rats after administration of a single oral dose of [14C]benzyl chloride in corn oil at 25 mg/kg, data was correlated with histopathologic and toxicity findings elicited from a 27-37-wk repeated-dose oral toxicity study of benzyl chloride. Radioactivity was detected in all tissues selected for examination. Elimination of the isotope occurred predominantly in the urine. Female rats excreted the isotope at a faster rate than the males and also maintained slightly lower tissue concentrations (with the exception of the blood and kidneys). Isotope recovery was achieved at 90% in the urine and feces of female rats at 24 h, compared with an 80% recovery rate in males. Concentrations of radioactivity were high in the gastrointestinal tract, reflecting the route of administration; however, the squamous stomach and the small intestine consistently retained higher concentrations of isotope than the glandular stomach. Results of acute toxicity and organ histopathology studies in animals dosed with benzyl chloride for 27-37 wk are compatible with the organ distribution and excretion of [14C]benzyl chloride. Histopathologic findings included severe acute and chronic gastritis, hyperkeratosis and hyperplasia of the squamous stomach, and progressive lesions of the heart ranging from proliferation of interstitial cells to acute necrosis of myocardial fibers. Both of these studies suggest that the squamous stomach is a target organ for benzyl chloride or one of its metabolites.

Anodic oxidation — an improved technique in the chemical recovery and refinement of isotopic thallium

The Electromagnetic Isotope Separations Program of the Oak Ridge National Laboratory has been involved in the seperation, chemical recovery and refinement of the stable isotopes of thallium since 1947. The initial interest was in obtaining chemically pure, isotopically enriched samples of each of the stable isotopes of thallium for basic physical research. Recently, the major emphasis has shifted to 203Tl which is used to produce the radiopharmaceutical isotope 201Tl. Two persistent problems in the chemistry of isotopic thallium have been the production of unoxidized, homogeneous ingots of thallium metal and the elimination of sulfur contamination in thallic oxide. The application of anodic oxidation in the chemistry has resulted in a significant reduction of the problems previously encountered as well as considerable improvement in the chemical purity of the product. The details of this procedure and a general description of all of the appropriate thallium chemistry will be presented. In addition, the generalization of the technique to the refinement of other elements will be discussed.

Estimation of Plasma Histidine Flux in Cows

A tracer method is described for estimating the plasma amino acid flux in animals during steady state, and its application is illustrated using lactating cows that were injected intravenously with 14C- or 3H-labeled histidine. The method involves an extension of the occupancy principle in which the fraction of tracer recovered in a metabolic sink, casein or hemoglobin, provides the basis for calculating the amino acid flux. The plasma histidine flux was 25 g/day based on recovery of istope in milk casein and 31 g/day based on recovery of isotope in hemoglobin.histidine flux cows casein hemoglobin

Separation of plutonium in urine without sample ashing for determination by alpha-spectrometry.

Present methods for the analysis of plutonium in urine require ashing the organic constituents of the sample, a time-consuming procedure and a major source of error. A method was developed to quantitatively separate 25 fCi of plutonium directly from 800 cm/sup 3/ of urine by coprecipitation with calcium oxalate. Without ashing, the oxalate precipitate is directly dissolved in 7.2 M HNO/sub 3/ and the plutonium is isolated by anion exchange, electrodeposited, and then measured by ..cap alpha..-spectrometry. The results are in excellent agreement with results obtained by existing procedures, and for 194 samples the average recovery of the plutonium tracer was 91% with a standard deviation of +- 10. The average recovery of the plutonium isotope in quality control samples was 101% when corrected for the /sup 242/Pu tracer recovery.

Effects of protein deficiency on muscle myofibrillar protein turnover in adult rats.

The rates of gain, catabolism, synthesis and reutilization of myofibrillar protein were measured in adult rats fed a protein-free diet, low protein diet (2% lactalbumin) or control diet (10% lactalbumin) for 14 to 31 days. Two forms of synthesis were measured: exogenous synthesis (nitrogen derived from diet) and endogenous synthesis (nitrogen derived from catabolized body protein). The rate of gain of myofibrillar protein was measured as the rate of increase in its weight and the rate of catabolism was determined from urinary 3-methylhistidine excretion. The rate of total synthesis was calculated as the sum of these two rates. Exogenous synthesis was calculated from the recovery of isotope in protein 24 h after oral administration of 15N-leucine and endogenous synthesis was calculated as the difference between the total synthesis and exogenous synthesis. Reutilization was calculated as the ratio of endogeneous synthesis to catabolism. The rate of catabolism was slightly decreased in protein deficiency (2.1, 2.1 and 2.6% in the protein-free, low protein and control groups, respectively), while that of synthesis was significantly decreased in protein deficiency (1.3, 2.0 and 3.3% in the respective groups). Restriction of protein intake resulted in a decrease in the rate of exogenous synthesis, without appreciable change of endogenous synthesis. The reutilization rate of endogenous N was estimated to be about 70% in rats with restricted protein intakes and about 50% in those with a normal protein intake.

Availability of monoglutamyl and polyglutamyl folates in normal subjects and in patients with coeliac sprue.

Intestinal folate absorption was assessed in six normal subjects and in four patients with coeliac sprue who were studied before and after treatment by dietary gluten exclusion. Comparisons were made of the luminal disappearance from the perfused jejunum of 3H-pteroylmonoglutamate and pteroyl 14C-glutamylhexaglutamate, and of the 48-hour urinary recovery of each isotope after perfusion and a tissue saturating dose of folic acid. The labelled urinary folates consisted of folic acid, 10-formyltetrahydrofolate, and 5-methyltetrahydrofolate. In each group urinary recovery of 3H was significantly greater than that of 14C, confirming the evidence from jejunal perfusion that the availability of monoglutamyl folate is greater than that of polyglutamyl folate. According to the urinary recovery data, both folates were poorly absorbed in untreated coeliac sprue, but were normally absorbed after treatment. Assuming uniform displacement of the absorbed labelled folates by the parenteral flushing dose, the finding of greater urinary isotope recovery than of luminal folate disappearance from the perfused proximal jejunal segment suggests an adaptation of the distal small bowel for folate absorption in coeliac sprue.

Dietary protein and lead retention

The effects of dietary protein content on lead retention were studied in young rats. In experiments lasting between 3 and 6 weeks, rats given diets containing lead and 20% casein were fed ad libitum or were pair fed with rats given diets containing 6.5 or 7.5% casein. Among rats given 20% casein, lead retention was inversely related to growth rate. A reduction of dietary protein either had no effect or reduced lead retention. In other experiments lasting 4 days and using 203Pb, given orally or intraperitoneally, the recovery of isotope in the gutfree carcass was unaffected or reduced by a reduction in dietary protein. Blood and liver lead often increased when kidney and carcass lead decreased in response to a reduction of dietary protein. Conflicting observations on the effect of low-protein diets on lead retention may thus be due to opposing effects of low dietary protein and decreases of growth rate and to different responses of different tissues.

Aerobic and Anaerobic Fermentation of Glucose by Echinostoma liei

Echinostoma liei was incubated in vitro aerobically and anaerobically with various species of 14C glucose. From the recovery of isotope in the respired CO2, it appeared that glucose was incompletely oxidized. The major portion of the CO2 arose from the 3 and 4 carbons of glucose. In addition to CO2, a number of volatile fatty acids accumulated as end-products both aerobically and anaerobically. Lactate and succinate were also isolated. Of these, n-valerate was recovered in the highest concentrations. Qualitatively, the same products were demonstrated after both aerobic and anaerobic incubations, but quantitatively considerably more fatty acids accumulated anaerobically.

Urate reabsorption in proximal convoluted tubule of the rat kidney.

Urate reabsorption was examined in the rat utilizing clearance and in vivo microperfusion techniques. In control rats, the fractional excretion of urate averaged 12.5 +/- 1.3% of the filtered load, with 60-70% of perfused urate reabsorbed at 2 mm of perfused tubule length (urate efflux). Increasing the perfusion concentration of urate to 6, 12, and 25 mg/100 ml did not alter the fractional rate of reabsorption. The acute administration of chlorothiazide resulted in a fall in GFR and Curate such that the fractional excretion was unchanged from controls and averaged 13.3 +/- 2.0%, without an associated change in urate reabsorption from proximal perfusates despite the presence of significant inhibition of sodium and water reabsorption. By contrast, the chronic administration of chlorothiazide accompanied by a low-sodium diet resulted in a significantly lower fractions excretion rate of urate of 7.95 +/- 0.5% and a significant increase in reabsorption of sodium and water as well as urate from microperfusates, In control rats receiving an infusion of 5% mannitol in isotonic saline, urate secretion was demonstrated by the urinary precession of [2-14C]urate from [methoxy-3H]inulin following placement of these isotopes on the surface of the kidney. The additional infusion of chlorothiazide did not alter this pattern of isotope recovery in the urine.

Hormone Induced Lactation in the Bovine. II. Dynamics of Injected and Endogenous Hormones

Three lactations were induced in two cows in two trials by twice daily subcutaneous injections for seven days. Each injection contained .05 mg/kg body weight of estradiol-17β and .125 mg/kg body weight of progesterone. Included with the hormones in trial 1 was a combination of 233μCi of [6,7-hydrogen-3] estradiol-17β and 12μCi of [4-carbon-14] progesterone. During trial 2, 2050μCi of [2,4,6,7 hydrogen-3] estradiol- 17)β were incorporated with the hormones for one cow and 2344μCi of [1,2,6,7 hydrogen-3] progesterone for the other. Radioactivity from hydrogen-3 and carbon-14 was detected in urine and feces but not in mammary secretion during trial 1. Isotope recovery from [hydrogen-3] estradiol-17β was too low to quantify. By day 17, 90% of the carbon-14 from progesterone was accumulated in feces and 8.0% in urine. For trial 2, recoveries of radioactivity by day 28 from urine, feces, and mammary secretions were, respectively, 32.4, 56.2, and <.002% from [hydrogen-3] estradiol-17β and 6.0, 87.7, and .25% from [hydrogen-3] progesterone. Estrogen and progesterone in plasma averaged 1.83 and 2.61ng/ml during days 2 to 7. Estrogen decreased more rapidly than progesterone post-treatment, but both had decreased by days 16 to 19 when average prolactin of plasma increased. Quantitative measures of estradiol 17-β and progesterone absorption, whether in plasma or excreta, were correlated.

Characteristics of urate influx in the rat nephron.

Permeability of the tubular epithelium to urate presented on the peritubular side was studied in anesthetized rats during mannitol diuresis by capillary microinjections of [14C]urate and [3H]inulin, [14C]PAH and [3H]inulin, or [14C]urate and [3H]PAH. Recovery of isotopes was determined in urine collected serially from the injected and contralateral kidney. Appearance and peak excretion of urate in the experimental but not in the contralateral kidney preceded inulin and coincided with PAH, indicating proximal permeability to urate. Recovery of urate was higher from the injected than from the contralateral kidney. Urate precession and recovery did not change after addition of PAH (1.5-6.4 mm) to [14C]urate-[3H]inulin solutions, whereas they decreased significantly in the experimental kidney after pyrazinoate (1.6-3.2 mM) addition. On the other hand, no effect of urate on [14C]PAH-[3H]inulin injections was detectable. These findings are suggestive of a carrier-mediated transtubular influx of urate in rat proximal tubule. Absence of competition with PAH may suggest differences in the secretory mechanisms for organic acids.