Total Tritium Content Research Articles

Influence of Tritium Exposure Route on Vegetation Types at the Savannah River Site

Plant, soil, water, and other media from various locations at the Savannah River Site were measured for total tritium (T) content and T speciation to characterize T in these areas,...

Tritium generation, release, and retention from in-core fluoride salt irradiations

Further understanding of tritium transport mechanisms in the combined molten fluoride salt and graphite environment is necessary for the design and licensing of a Fluoride-Salt-Cooled High-Temperature Reactor (FHR). The three in-core fluoride salt irradiations completed at the Massachusetts Institute of Technology Reactor (MITR) are a useful parallel for studying transport phenomena expected in a FHR environment. During the irradiations, evolution of tritium from the flibe salt was monitored and compared to the calculated total generation rate. A difference of 22 ± 10% between the integrated calculated tritium generation rate and the total release was measured for the third MITR irradiation (FS-3). The fraction of tritium which was not released from the salt could be explained by tritium retention in graphite. For post irradiation examination, a thermal desorption furnace was used to heat nuclear graphite samples in order to release and measure retained tritium. The desorption analysis in this work utilized seven subsections of graphite from the second salt irradiation (FS-2); three from a disc of IG-110U and four from ARB matrix graphite. Observed desorption versus temperature as well as total tritium content in the samples after irradiation indicate that the graphites were not volumetrically saturated with tritium, but rather tritium retention was likely limited to the near-surface region. Measurements of the samples resulted in 2.90 ± 0.29 μCi/mm2 of tritium retained by IG-110U and 1.83 ± 0.31 μCi/mm2 for ARB during the 300 h FS-2 in-core irradiation. Based on the desorption measurements, the estimated total tritium retention in graphite from the FS-2 samples is consistent with the tritium release measurements from the FS-3 experiment.

BIXS for tritium analysis with Ar gas and Al thin film as β-ray stopping layers and comparison with EBS

β-ray induced X-ray spectrometry (BIXS) and elastic backscattering spectrometry (EBS) were utilized in this study for the tritium analysis of samples of tritium/deuterium-containing titanium films with thick Mo substrates. Using the BIXS method which incorporates Monte Carlo simulated data, we used Ar gas filler (BIXS-Ar) or placed Al film (BIXS-Al), respectively, between the sample and X-ray detector as β-ray stopping layers. Using the EBS method to confirm whether or not the tritium will volatilize under the impact of the proton beams, we conducted two measurements at the same point of the sample surfaces. A TiH film sample with thick Mo substrate was used in our EBS experiment to remove the influence of the Mo spectrum on the EBS experimental spectra of tritium/deuterium-containing samples. We well fit using the SIMNRA code the tritium and deuterium EBS spectra that were obtained by removing the Mo spectra. The tritium content and depth profiles in the titanium films were obtained via these different methods and the results were compared. It was found that the total tritium content measured using the EBS, BIXS-Al, and BIXS-Ar methods were in agreement within the experimental uncertainties, and the BIXS-Al method may be better at measuring the tritium depth profiles than the BIXS-Ar method.

Novel method for determination of tritium depth profiles in metallic samples

Tritium accumulation in fusion reactor materials is considered a serious radiological issue, therefore a lot of effort has been concentrated on the development of radiometric techniques. A novel method, based on gradual dissolution, for the determination of the total tritium content and its depth profiles in metallic samples is demonstrated. This method allows for the measurement of tritium in metallic samples after their exposure to a hydrogen and tritium mixture, tritium containing plasma or after irradiation with neutrons resulting in tritium formation. In this method, successive layers of metal are removed using an appropriate etching agent in the controlled regime and the amount of evolved gases are measured by means of chromatography (gas composition and release rate) and a proportional gas flow detector (tritium). Results for the tritium profiles in neutron irradiated, plasma exposed and gas loaded beryllium are reported.

Effect of geometrical parameter’s uncertainty of BIXS experimental setup for tritium analysis

In this paper, the effect of geometrical parameter’s uncertainty of experimental setup in β-decay induced X-ray spectroscopy (BIXS) method has been studied. By varying deliberately the distance between the X-ray detector and the sample surface, the change of the tritium content and the tritium depth distribution obtained by the BIXS method has been observed. Both Monte Carlo simulations and experimental measurements were carried out for our BIXS experimental setup. It is found that the BIXS method will not give reliable tritium content and depth distribution of the sample if the sample-detector distance of the experimental setup is not measured accurately, i.e., the deviation of 1mm of the sample-detector distance will cause ∼10% error of total tritium content besides of the distortion of the shape of tritium depth distribution. This indicates that the geometrical parameters of the experimental setup in the BIXS method must be accurately determined, especially the internal configuration of the X-ray detector used in the BIXS method. The measurement of the internal configuration of an X-ray detector used in the BIXS method by an industrial computed tomography (CT) has been shown in this paper.

Tritium analysis in titanium films by the BIXS method

In this paper, tritium analyses in titanium films has been carried out by β-decay induced X-ray spectroscopy (BIXS), based on Monte Carlo simulations and the Tikhonov regularization. In our analysis, for the first time the internal bremsstrahlung of tritium β-decay has been taken into account in the BIXS method. Meanwhile, parallel computation using the Monte Carlo code PENELOPE has been realized within the frame of a message passing interface. The tritium depth distributions, surface homogeneity and the total tritium content of the analyzed samples have been obtained. The total tritium contents obtained by the present BIXS method are found to be in good agreement with those obtained by the PVT method.

Formation and release of [3H]acetylcholine in the rat urinary bladder strip.

The relationship between different frequencies of loading stimulation and [3H]acetylcholine (ACh) formation and release from nerve terminals has been investigated in extratrigonal strips of the urinary bladder of the rat. An increase in frequency (0.2, 0.4 and 0.8 Hz) for the 30 min incubations with [3H]choline produced an enhancement of storage of [3H]ACh from 19.5 to 34% of total tritium content in the tissue. Higher frequencies (1.6 and 3.2 Hz) failed to increase storage further on. The [3H]choline content did not vary significantly. Electrical field stimulation at 2 Hz (360 shocks) produced a release of tritium. The evoked outflow was higher when the strip was loaded at 0.8 Hz than at the other frequencies tested. Both [3H]ACh and [3H]choline were measured in the perfusate of strips preloaded at 0.8 Hz. Most of the induced outflow was found to be [3H]ACh, as in previous experiments carried out using 0.2 Hz as a loading frequency. The findings suggest that in the rat urinary bladder strip loading at 0.8 Hz is suitable for increasing the formation and the resulting release of [3H]ACh during electrical stimulation.

Self-catalyzed Tritium Incorporation in Amorphous and Crystalline

AbstractTritiated amorphous and crystalline silicon is prepared by exposing silicon samples to tritium gas (T2) at various pressures and temperatures. Total tritium content and tritium concentration depth profiles in the tritiated samples are obtained using thermal effusion and Secondary Ion Mass Spectroscopy (SIMS) measurements. The results indicate that tritium incorporation is a function of the material microstructure rather than the tritium exposure condition. The highest tritium concentration attained in the amorphous silicon is about 20 at.% on average with a penetration depth of about 50 nm. In contrast, the tritium occluded in the c-Si is about 4 at.% with a penetration depth of about 10 nm. The tritium concentration observed in a-Si:H and c-Si is higher than reported results from post-hydrogenation experiments. The beta irradiation appears to catalyze the tritiation process and enhance the tritium dissolution in silicon material.

Effects of external energetic factors on tritium release from the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles

Tritium release from samples of 9–13 mg of the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles under the separate and simultaneous action of temperature 490–770 K, 5 MeV fast-electron radiation 14 MGy h −1 for 3 h and magnetic field (MF) of 1.7 T was investigated. The pebbles were found to be very dissimilar with respect to their total tritium content—2.5–9 MBq g −1. The batch contained also some coarse agglomerates of the pebbles containing 10–19 MBq g −1 of tritium having also a high tritium release. For the pebbles having the total tritium 2.5–5.3 MBq g −1, the electron radiation for 3 h caused the fractional tritium release 17–26% ( B = 0) and 21–29% ( B = 1.7 T), the temperature of the pebbles being <550 K. The annealing of the pebbles at the temperature ramp at 5 K/min to 553 K and at 553 K for 3 h caused the fractional tritium release 10–19% ( B = 0) and 14% ( B = 1.7 T). For the pebbles having the total tritium 3.6–5.8 MBq g −1, the annealing of the pebbles at the temperature ramp at 5 K/min to 770 K and at 770 K for 1 h caused the fractional tritium release 17–24% ( B = 0) and 25% ( B = 1.7 T), but with the simultaneous additional action of the electron radiation for 3 h the fractional tritium release was 24–42% ( B = 0) and 32–37% ( B = 1.7 T).

DISTRIBUTION OF TRITIUM IN THE LEACHATES AND METHANE GAS CONDENSATES FROM MUNICIPAL WASTE LANDFILLS IN KOREA

In this paper, the tritium levels in the leachates and methane gas condensates which have occurred at 13 sanitary landfills of municipal solid wastes (MSW) are investigated and reported. During the 6 months investigation period, the mean tritium concentrations of the raw leachates were distributed from 17 to 1,196 TU. They corresponded to several scores or hundreds higher tritium levels than that of the normal environmental level except for two cases. High tritium levels were also detected in the effluents of the leachate treatment facilities. Generally, the tritium existed in the dissolving fraction of the leachate but for some cases about 10% of the total tritium content was present as colloidal particles of over 0.45 μm in size. In general, the relationship between the tritium and other contaminants in the raw leachate was low, but it was relatively high between the tritium and TOC. Thus, it is predicted that the dissolving state of the tritium in the leachates would be affected by the tritium sources of the tipped wastes in a MSW.

Tritium imaging of JET wall tile exposed to D-T shots

Tritium imaging was used to determine the lateral distribution of residual tritium in an X-point carbon-carbon composite tile taken from the JET tokamak after the Preliminary Tritium Experiment of November 9, 1991. Substantial variation in image brightness was observed in different parts of the tile. Features of the fine scale morphology that were visible by optical microscopy were also observed in the tritium images. Alternate sputtering and imaging of tile speciments indicates the presence of tritium at depths beyond the implantation range that would be expected under tokamak operating conditions, suggesting that tritium is being codeposited with carbon. The total tritium content of two specimens were assessed by destructive means. Analysis suggests that most of the tritium present in the tile specimens was codeposited during the post-PTE cleanup.

A small volume tritium monitor and fill system

Environmental concerns demand that all tritium releases be minimized. In particular an experiment recently fielded at Los Alamos National Laboratory required a 4 mm 3 volume to be dynamically filled to a pressure of 7 MPa, while keeping the total tritium content (and potential release) below 20 Ci (1 Ci = 3.7 × 10 10 Bq). We describe the system which was designed and built for this purpose, complete with a low volume fiberoptic monitor and pressure transducers.

Gas recovery system for the first JET tritium experiment

Abstract Gas recovery during the first JET tritium experiment was mainly based on the use of a cryopump designed earlier [1] for collection of torus exhaust gas. This cryopump system was extended to include collection of gas from the neutral injectors and to provide sampling and diagnostic facilities such as an ionisation chamber for on-line tritium accounting, a mass spectrometer for gas analysis and a sampling manifold for off-site tritium accounting. The cryopump was backed by a collection system comprising a reservoir, recirculation pump and 4 uranium beds originally designed for the JET Active Gas Handling System [2]. During operation of the system from start of the experiment on 04.11.91 until 20.12.91 a total of 1450 bar 1 of gas with a total tritium content of 4.3 × 10 13 Bq (1162 Curies) were collected. A small exhaust detritiation system was installed to reduce emissions in case of accidents such as major torus or neutral injector air or water leaks. As no major problems were encountered during the experiment, it was not used.

Decrease of Acetylcholine Release from Cortical Slices in Aged Rats: Investigations into Its Reversal by Phosphatidylserine

The release of total acetylcholine (ACh) and [3H]ACh was investigated in electrically stimulated cortical slices prepared from 4- and 18-month-old male Wistar rats. The slices were prelabeled with [3H]choline ([3H]Ch) and perfused with Krebs solution containing physostigmine. Total ACh was measured and the nature of the tritium efflux identified by HPLC. The total tritium content in the slices at the end of the incubation period was half as great in the old as in young rats. A linear relationship was found between stimulation frequencies (2, 5, and 10 Hz) and fractional [3H]ACh release in both young and old rats. In the latter the release was significantly smaller. At 10 Hz stimulation frequency the ratio between the two 2-min stimulation periods, S2/S1, was higher in the 18-month-old rats than in the young rats. Specific activity of the evoked ACh release was significantly smaller in S2 than in S1 in 4-month-old rats only. These findings indicate that the young synthetize ACh from endogenous unlabeled Ch more than older rats. In 18-month-old rats both the evoked total ACh and [3H]ACh release, expressed as picograms per minute, showed an approximately 50% decrease in both S1 and S2 stimulation periods, with no significant difference in specific activity. Phosphatidylserine (PtdSer) administration (15 mg/kg, i.p. daily) for 1 week to 18-month-old rats prevented the reduction in total evoked ACh release but not the reduction in evoked [3H]ACh release. The specific activity of ACh release was therefore significantly smaller than that of the young and untreated old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple apparatus for separating and trapping tritiated water from multiple biological samples

The effective use of tritiated compounds in biological systems often requires determination of the extent to which the tritium label has been removed from the compound and equilibrated with biological fluids. (1) This usually is accomplished by first determining the total tritium content of a water-containing sample and then determining either the tritiated water separated by evaporation or the tritium content of the dried sample. The former method gives a direct measure of tritiated water but involves isolating the tritiated water. In the latter method, the amount of tritium in the water is calculated as the difference between the tritium contents of the water-containing and dried samples. Although this indirect method is less accurate than the direct method, it does not require isolating the tritiated water. In both cases, it is important that very mild conditions be used for separating water from the aqueous sample in order to prevent further removal of tritium from the compound. This is accomplished conveniently by a freeze-drying procedure. Although this method is old and likely to be in common use, a convenient apparatus for processing large numbers of samples has not been described in the literature. The apparatus described in this report has been used routinely in several of our laboratories for many years to separate and collect tritiated water from biological samples, usually urine.

Effect of hypophysectomy on estrogen conjugation and on plasma and tissue concentrations of tritium after administration of 3H-estradiol-17β

Estradiol-17β-6,7- 3H was injected into ovariectomized (control) and ovariectomized, hypophysectomized (hypox) rats in order to study the binding of estradiol in the brain. Hypophysectomy resulted in a significant increase in the concentration of tritium in the hypothalamus and preoptic area, as well as cortex, muscle, plasma and liver. However, since the liver was lighter in hypox rats, the total tritium content in the liver was unchanged from controls. Part of the weight reduction in the liver was due to a loss of stainable glycogen, which took place within 24 hours of hypox. The increase in circulating tritiated estradiol after hypox led us to investigate hepatic metabolism of estradiol. In vitro studies on liver slices from control and hypox rats demonstrated a significant reduction in the formation of conjugates of estrogen. Specifically, estradiol glucuronide and estrone sulfate formation were reduced in hypox rats and conversely the unmetabolized estradiol concentration was higher. Hypophysectomy for 24 hours results in a significant decrease in hepatic metabolism of estradiol-17β.

Partial Purification and Some Properties of Oxalacetase from Aspergillus niger

1. Oxalacetase from Asperigillus niger was found to be an inducible enzyme, the induction being dependent not only on neutralisation of the acidic growth medium but also on the presence of carbonate. An explanation is proposed. 2. Three methods were established for the quantitative determination of oxalacetase activity. These are based on the determination of the product acetate, on the absorbance of oxaloacetate and on coupling the hydrolysis of oxaloacetate to the oxidation of malate by NAD in the presence of malate dehydrogenase. 3. Oxalacetase was purified about 50-fold from cell-free extracts of A. niger and used to determine some of its properties such as kinetic constants. 4. 2S-[U-14C, 3-2H2] Malate in the presence of oxalacetase, NAD and malate dehydrogenase was partially converted to acetate and oxalate. The 3H/14C ratio of the isolated acetate was nearly twice as high as that of the malate used initially. The result demonstrates that the keto form of oxaloacetate, not the enol, is the substrate of the enzyme. 5. Equimolecular mixtures of 2S, 3S-[3-2H1] malate + 2S-[2-2H1] malate (mixture 1) and 2S, 3R-[3-2H1, 3H1] malate + 2S, 3R-[2-2H1, 3-3H1] malate (mixture 2) were prepared from 2S-[3-3H2] malate by incubation with fumarase in normal and tritiated water, respectively. The isolated mixture 1, in the presence of oxalacetase, NAD and malate dehydrogenase was incubated in tritiated water for formation of acetate and oxalate; the isolated mixture 2 was treated likewise in normal water. 6. The mixtures of symmetrically labelled [3H1] acetate and chiral acetates thus produced were isolated and the configuration of the [3H1, 3H1] acetate specimens was determined in the sequence acetate leads to malate leads to fumarate, as usual. The [2H1, 3H1] acetate derived from 2S, 3S-[3-2H1] malate (present in mixture 1( yielded a malate which on incubation with fumarase retained 65.0% of its total tritium content. This chiral acetate, therefore, had the R configuration. The [2H1, 3H1] acetate derived from 2S, 3R-[2-2H1, 3-3H1] malate produced a malate which retained 35% of its total tritium content, and therefore had the S configuration. 7. It was concluded that the detachment of the oxaloyl residue from oxaloacetate and its replacement by a proton proceed with inversion of configuration at the methylene group which becomes methyl during the hydrolysis.

Enzymic generation of chiral acetates. A quantitative evaluation of their configurational assay.

1. R-Acetate was generated enzymically from R-acetate in the sequence acetate leads to malate leads to oxaloacetate leads to acetate, and S-acetate likewise from S-acetate. It was concluded that the formation of malate on malate synthase involves the operation of a normal isotopic effect combined with inversion of configuration. The malate synthase kH/k2H was determined as 3.7 +/- 0.5 by a method which yields results independently of the stereochemical purity of the chiral acetates used initially. 2. R-Acetate was also generated from R-acetate in the sequence acetate leads to citrate leads to malate leads to oxaloacetate leads to acetate, and S-acetate likewise from S-acetate. The conclusion is the same as given above, but refers to the formation of citrate on the re-synthase. 3. 2S,3R-[2-2H1,3-2H1,3H1]Malate and 2S,3S-[2-2H1,3-2H1]malate were prepared from 2S-[2,3-2H3]malate by treatment with fumarase in tritiated water and normal water, respectively. It was assumed that these malate specimens were pure with respect to chirality as generated by isotopic labelling. 4. These two malate specimens were partially converted (about 9%) to acetates in conditions where no racemization at the level of transiently formed oxaloacetate occurred. That no racemization took place was demonstrated experimentally. Oxidative enzymic hydrolysis of 2S,3R-[2-2H1,3-2H1,3H1]malate in normal water and of 2S,3S-[2-2H1,3-2H1]malate in tritiated water produced S-[2H1,3H1]acetate and R-[2H1,3H1]acetate, respectively. 5. The isolated R-[2H1,3H1]acetate and S-[2H1,3H1]acetate on configurational analysis yielded malates which in the presence of fumarase retained 79.7 +/- 0.7% and 20.3 +/- 0.9%, respectively, of their total tritium content. The symmetric deviation from the 50% value found with [3H1]acetate strengthens the conclusion that stereochemically pure chiral acetates were analyzed. The malate synthase kH/k2H was determined from the data of this study as 3.9 +/- 0.2. 6. The average of the values given under paragraphs 1 and 5 for the isotopic discrimination on malate synthase corresponds to kH/k2H=3.8 +/- 0.1. It was concluded that the configurational analysis of stereochemically pure R-[2H1,3H1]acetate and S-[2H1,3H1]acetate yields malates which in the presence of fumarase retain 79 +/- 2% and 21 +/- 2%, respectively, of their total tritium content. Hence, a deviation of 29 +/- 2% from the 50% value represents the actual amplitude of the configurational assay. 7. Outlines are given for an enzymic generation of chiral acetates in preparative scale.

Disposition of digitoxin in renal failure.

The disposition of digitoxin was studied for a period of 8 days in 6 uremic patients given a single oral dose of 1 mg 3H-digitoxin. In plasma, the time-course of radioactivity indicated a diminished absorption velocity of tritium compared to that of control subjects already reported and, after reaching of a pseudostate-equilibrium at 24 hr, an exponential decline with a mean half-life of 8.0 days. In urine, smaller amounts of tritiated compounds were eliminated in uremic patients (8.7% of the dose) than in controls (22.5%). The average fecal excretion of digitoxin and its metabolites was not significantly increased. Chloroform extraction and thin-layer chromatography in plasma, urine and feces suggested no qualitative alteration in the metabolism of digitoxin. Calculations of the total body tritium content (body stores) after each 24-hr interval and its pharmacokinetic behavior showed that the elimination of digitoxin is determined by the transfer constant from tissue to plasma. The differences in elimination kinetics of digitoxin and its metabolites of uremic patients and healthy subjects were not significant.

Substrate Stereochemistry of the Acetyl‐CoA Acetyltransferase Reaction

1. A specimen of symmetrically tritiated 3S-3-hydroxy[2-3H2]butyryl-CoA was prepared from acetoacetyl-CoA by incubation in tritiated water, followed by enzymic reduction using 3S-specific 3-hydroxyacyl-CoA dehydrogenase. In addition, a specimen of dideuterated, racemic 3RS-3-hydroxy-[2-2H2]butyryl-CoA was prepared chemically from 3RS-3-hydroxy[2-2H2]butyric acid. 2. These acyl-CoA derivatives were incubated respectively with deuterium oxide and tritated water in presence of enoyl-CoA hydratase. Stereospecifically tritiated compounds, respectively 2S,3S-3-hydroxy[2-2H1,3H1]butyryl-CoA and 2R,3S-3-hydroxy[2-1H1,3H1]butyryl-CoA (plus 3R-diastereomer) were formed and isolated. 3. 3S-3-Hydroxy[2-3H2]butyryl-CoA and the 3S-[2-3H2,3-14C]-labelled material were also prepared as described in the preceding paper. The latter substrate was used to establish conditions in which little loss of tritium would occur (found; about 7%) on cleavage to acetyl-CoA in the presence of 3-hydroxyacyl-CoA dehydrogenase and acetyl-CoA acetyltransferase. Little loss of tritium indicates a small degree of racemization of the stereospecifically 2-tritiated 3-hydroxyacyl-CoA derivatives at the level of transiently formed acetoacetyl-CoA and acetyl-CoA. This ensures high optical purity of the chiral acetates generated from the stereospecifically tritiated hydroxybutyryl-CoA specimens listed in paragraph (2). 4. These two acyl-CoA derivatives and the symmetrically tritiated 3S-3-hydroxy[2-3H2]butyryl-CoA listed in paragraph (3) were converted to the acetates enzymically in the sequence hydroxy-butyryl-CoA leads to acetoacetyl-CoA leads to acetyl-CoA leads to acetate. The isolated acetates were assayed for chirality by conversion to the malates and fumarates as usual. 5. The malate formed from 3S-3-hydroxy[2-3H2]butyryl-CoA on incubation with fumarase lost nearly 50%, that derived from 2R,3S-3-hydroxy[2-2H1,3H1]butyryl-CoA (plus 3R-diastereomer) retained about 26% and that derived from 2S,3S-3-hydroxy[2-1H1,3H1]butyryl-CoA retained about 78% of its total tritium content. 6. It was concluded that the detachment of acetyl-CoA from acetoacetyl-CoA on acetyl-CoA acetyltransferase occurs with inversion of configuration at the methylene group which becomes methyl.