Recovery Of Isotopes Research Articles

Highly efficient and direct recovery of low-pressure hydrogen isotopes from tritium extraction gas by PdY alloy membrane permeator

Low-pressure hydrogen recovery is crucial for the fusion reactor deuterium-tritium fuel cycle, and the usual treatment is achieved through multiple steps of enrichment and separation, which has the drawbacks of complex processes and high energy consumption. In this work, a membrane permeator including 12 sets of Pd92Y8 at% alloy tubes has been investigated for the permeability and extraction of hydrogen in low-pressure mixtures. The hydrogen permeation through dense Pd-based membrane mechanism and corresponding Sieverts’ exponents have been verified. The concentration polarization effect is deducted from the results. Through pure hydrogen permeation test, the cold-rolling 80 μm thick Pd92Y8 at% membrane has hydrogen permeability at 400 °C of 3.43×10−8 mol∙m−1∙s−1∙Pa−0.5, which is higher than that of PdAg alloy membrane under the same conditions. Highly efficient recovery efficiency has been achieved for low hydrogen pressure mixtures, and the PdY alloy membrane permeator with 678 cm2 effective area could reach around 95% hydrogen extraction recovery for 0.1 mol% hydrogen-helium mixture and 97.74% recovery for 0.33 mol% at the rate of 21 standard liter per minute (SLM). It indicates that the PdY alloy membrane permeation can be an alternative solution for efficiently recovering low-pressure hydrogen isotopes in tritium extraction gas.

Four volcanically driven climatic perturbations led to enhanced continental weathering during the Late Triassic Carnian Pluvial Episode

The arid climate of the Late Triassic was interrupted by a particularly humid episode known as the Carnian Pluvial Episode (CPE; ca. 234–232 million years ago). The CPE is often linked to eruptions in the Wrangellia Large Igneous Province (LIP), and is assumed to have led to global warming, enhanced weathering, water deoxygenation, and biotic changes. However, direct evidence for a temporal link between volcanic activity and chemical weathering has not yet been established due to the lack of comprehensive records across the CPE. In this study, geochemical and mineralogical analyses are applied to a lacustrine stratigraphic succession of the Jiyuan Basin (North China) that captures the CPE in high resolution. We identify four distinct pulses of enhanced continental chemical weathering characterized by elevated Chemical Index of Alteration values and kaolinite contents. These peaks in continental weathering coincide with Hg/TOC enrichments and negative organic carbon isotope excursions that mark four short (∼400 kyr) but intense pulses of Wrangellia LIP volcanism. In combination with signs of increased humidity, our findings provide direct and independent evidence that Wrangellia LIP eruptions significantly altered CPE chemical weathering rates in response to global warming and wetting. The lake experienced eutrophication and water deoxygenation after each volcanic pulse but the swift recovery of carbon isotopes suggests that the system rapidly returned to conditions prior to the volcanic perturbation. Organic carbon burial facilitated by widespread dysoxic and anoxic waters, and CO2 consumption via enhanced weathering likely played crucial roles in the rapid climatic recovery after each volcanic pulse.

Fossil‐Bearing Concretions of the Araripe Basin Accumulated During Oceanic Anoxic Event 1b

AbstractFossils from the Araripe Basin (northeastern Brazil) are known for their remarkable preservation of vertebrates and invertebrates, even including soft tissues. They occur in carbonate concretions within organic carbon‐rich strata assigned to the Romualdo Formation. Here we present integrated stable isotope, elemental and microfossil records from the Sítio Sobradinho outcrop, Araripe Basin, northeastern Brazil. Our results imply that black shales hosting fossil‐bearing carbonate concretions within the lower Romualdo Formation were deposited during Oceanic Anoxic Event (OAE) 1b (Kilian sub‐event). Our high‐resolution multi‐proxy approach allows identifying four phases of environmental evolution. After a pre‐event phase, an early phase (onset of the negative carbon isotope excursion—nCIE) of water column stratification and reduced oxygenation likely preconditioned the system for organic carbon burial and preservation. A second phase (peak nCIE) was characterized by an intensified hydrological cycle and continental runoff, as well as increased influx of terrestrial organic matter. High input of continent‐derived nutrients might have enhanced biological productivity in the epicontinental sea, ultimately leading to increased organic carbon fluxes and burial, as well as carbonate dissolution at the seafloor. All together, these paleoenvironmental conditions resulted in expansion of an oxygen minimum zone (OMZ), favoring taphonomic processes that led to the excellent preservation of diverse macro‐ and microfossils. The nCIE recovery phase was characterized by reduced nutrient supply and organic carbon burial. Organic carbon sequestration in such paleoenvironments likely contributed to the recovery (increase) of stable carbon isotope (δ13C) records in the deep ocean during the Kilian sub‐event of OAE 1b.

Low temperature hydrogen superpermeation in vanadium composite metal foil pumps

Palladium-based foil membranes are an effective option for hydrogen isotope recovery from the plasma exhaust of future fusion plants, but cost and availability are concerns. Vanadium (V) is a relatively low cost, neutron tolerant material with high hydrogen permeability. It has been well-studied as a superpermeable membrane at high temperature (>500 °C), but V displays negligible superpermeation at low temperature (75–200 °C) due to catalytic limitations. Composite membranes were fabricated by depositing thin layers (∼100 nm) of either Pd or BCC PdCu on sputter-cleaned vanadium foils (100 μm). Symmetric membranes elevated superpermeation to levels approaching bulk Pd or PdCu foils, with ∼5X higher flux in the latter reflecting the superior properties of PdCu. Asymmetric membranes revealed that the Pd-based catalyst layer was critical for both efficient absorption of superthermal hydrogen upstream as well as catalyzing re-combinative desorption downstream. At T ≥ 150 °C composite membrane superpermeation was equivalent to the Pd-based foils, but the flux was attenuated by a factor of 2-3X as the temperature was reduced. This deviation from pure foil performance coincided with the formation of vanadium hydride (β-V2H), which also impacted the transient response. Nevertheless, no embrittlement was observed under the conditions examined and elevating the temperature >150 °C removed the hydride and restored full performance. The achievement of palladium-level performance with a >99% reduction in Pd inventory makes these V composite metal foils pumps an attractive option for low temperature hydrogen isotope recovery in future fusion plants.

Supplementing branched-chain volatile fatty acids in dual-flow cultures varying in dietary forage and corn oil concentrations. I: Digestibility, microbial protein, and prokaryotic community structure

Branched-chain amino acids are deaminated by amylolytic bacteria to branched-chain volatile fatty acids (BCVFA), which are growth factors for cellulolytic bacteria. Our objective was to determine the dietary conditions that would increase the uptake of BCVFA by rumen bacteria. We hypothesized that increased forage would increase cellulolytic bacterial abundance and incorporation of BCVFA into their structure. Supplemental polyunsaturated fatty acids, supplied via corn oil (CO), should inhibit cellulolytic bacteria growth, but we hypothesized that additional BCVFA would alleviate that inhibition. Further, supplemental BCVFA should increase neutral detergent fiber degradation and efficiency of bacterial protein synthesis more with the high forage and low polyunsaturated fatty acid dietary combination. The study was an incomplete block design with 8 dual-flow continuous cultures used in 4 periods with 8 treatments (n = 4 per treatment) arranged as a 2 × 2 × 2 factorial. The factors were: high forage (HF) or low forage (LF; 67 or 33%), without or with supplemental CO (3% dry matter), and without or with 2.15 mmol/d (which included 5 mg/d of 13C each of BCVFA isovalerate, isobutyrate, and 2-methylbutyrate). The isonitrogenous diets consisted of 33:67 alfalfa:orchardgrass pellet, and was replaced with a concentrate pellet that mainly consisted of ground corn, soybean meal, and soybean hulls for the LF diet. The main effect of supplementing BCVFA increased neutral detergent fiber (NDF) degradability by 7.6%, and CO increased NDF degradability only in LF diets. Supplemental BCVFA increased bacterial N by 1.5 g/kg organic matter truly degraded (6.6%) and 0.05 g/g truly degraded N (6.5%). The relative sequence abundance decreased with LF for Fibrobacter succinogenes, Ruminococcus flavefaciens, and genus Butyrivibrio compared with HF. Recovery of the total 13C dose in bacterial pellets decreased from 144 µg/ mg with HF to 98.9 µg/ mg with LF. Although isotope recovery in bacteria was greater with HF, BCVFA supplementation increased NDF degradability and efficiency of microbial protein synthesis under all dietary conditions. Therefore, supplemental BCVFA has potential to improve feed efficiency in dairy cows even with dietary conditions that might otherwise inhibit cellulolytic bacteria.

Molybdenum isotopes separation using squared-off optimized cascades

Recently molybdenum alloys have been introduced as accident tolerating materials for cladding of fuel rods. Molybdenum element has seven stable isotopes with different neutron absorption cross section used in various fields, including nuclear physics and radioisotope production. This study presents separation approaches for all intermediate isotopes of molybdenum element by squared-off cascades using a newly developed numerical code with Salp Swarm Algorithm (SSA) optimization algorithm. The parameters of cascade including feed flow rate, feed entry stage, cascade cut, input feed flow rate to gas centrifuges (GCs), and cut of the first stage are optimized to maximize both isotope recovery and cascade capacity. The squared off and squared cascades are studied, and the efficiencies are compared. The results obtained from the optimization showed that for the selected squared off cascade, Mo94 in four separation steps, Mo95 in five steps, Mo96 in six steps, Mo97 in seven steps, and Mo98 in two steps are separated to the desired concentrations. The highest recovery factor is obtained 63% for Mo94 separation and lowest recovery factor is found 45% for Mo95.

Experimental and Numerical Analysis of a Pd-Ag Membrane Unit for Hydrogen Isotope Recovery in a Solid Blanket.

The interest of the fusion community in Pd-Ag membranes has grown in the last decades due to the high value of hydrogen permeability and the possibility of continuous operation, making it a promising technology when a gaseous stream of hydrogen isotopes must be recovered and separated from other impurities. This is the case of the Tritium Conditioning System (TCS) of the European fusion power plant demonstrator, called DEMO. This paper presents an experimental and numerical activity aimed at (i) assessing the Pd-Ag permeator performance under TCS-relevant conditions, (ii) validating a numerical tool for scale-up purposes, and (iii) carrying out a preliminary design of a TCS based on Pd-Ag membranes. Experiments were performed by feeding the membrane with a He-H2 gas mixture in a specific feed flow rate ranging from 85.4 to 427.2 mol h-1 m-2. A satisfactory agreement between experiments and simulations was obtained over a wide range of compositions, showing a root mean squared relative error of 2.3%. The experiments also recognized the Pd-Ag permeator as a promising technology for the DEMO TCS under the identified conditions. The scale-up procedure ended with a preliminary sizing of the system, relying on multi-tube permeators with an overall number ranging between 150 and 80 membranes in lengths of 500 and 1000 mm each.

Zinc Absorption Estimated by Fecal Monitoring of Zinc Stable Isotopes Validated by Comparison with Whole-Body Retention of Zinc Radioisotopes in Humans

Knowledge about zinc availability from human diets is limited due to methodological difficulties. Recently developed stable isotope techniques for estimating dietary zinc abosrption were compared with radioisotope techniques in five men and three women. Stable and radioactive zinc isotopes were simultaneously administered. Fecal excretion of the isotopes as well as whole-body retention of the radioactive zinc isotope was monitored. Concentration of stable zinc isotope label in fecal samples was determined by inductively coupled plasma mass spectrometry by fully quantitative measurements and from inductively coupled plasma mass spectrometry isotope ratios combined with analysis of total zinc content using atomic absorption spectrometry. Zinc absorption estimated from whole-body retention was 27 ± 6% (x̄ ± SD), estimated zinc absorption obtained by fecal monitoring of radioisotope was 26 ± 9%, and the two stable zinc measurements resulted in values of 29 ± 12 and 33 ± 12%, respectively. There was no signfiicant difference in zinc absorption estimated from whole-body retention and with the fecal monitoring methods. Recovered stable zinc isotope label was significantly lower than recovered radiolsotope. For individual fecal samples, systematic differences of 16% and 12%, respectively (P < 0.05), between the radioisotope recovery and the recovery of stable isotopes with the two methods for measurement was observed. The stable zinc isotope technique for measurement of zinc absorption resulted in mean results similar to those of the radioisotope technique, but with a larger variation in the measurements.

Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes 32P, 33P around Balaklava Coast.

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)3 obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)3 with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)3 with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin 32P and 33P were used. Volumetric activity profiles of 32P and 33P in particulate and dissolved forms were obtained. Based on 32P and 33P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters.

Photonuclear Alchemy: Obtaining Medical Isotopes of Gold from Mercury Irradiated on Electron Accelerators.

In our work, the photonuclear production of 198,199Au isotopes for nuclear medicine purposes was studied, and a method for their recovery from irradiated mercury was developed. The yields of the corresponding nuclear reactions were determined, and a comparison of various methods of obtaining gold radioisotopes was provided. New sorbents based on benzo-15-crown-5, which selectively binds gold, were studied, and the optimal conditions for Au recovery with a high degree of purification from mercury were found. It was established that, for the fast and quantitative recovery of Au isotopes, it was necessary to add at least 0.1 mg of the carrier. As a result, the developed method can be regularly used to obtain 198,199Au for the research of radiopharmaceuticals based on them.

Optimization Criterion for Two-Stage Cascade for Iterative Molybdenum Isotopes Recovery by the method of laser-assisted retardation of condensation(SILARC)

In this paper, application of the method of laser-assisted retardation of condensation has been considered for molybdenum isotope separation. Enrichment factor as a function of pressure and temperature of gas flow cold core have been evaluated. Since the maximal value of enrichment factor is not high(~ 1.8), to achieve desired enrichment level in products an iterative procedure is applied. To reduce the amount of wastes and increase performance of the SILARC method, introduction of the second stage into the separation cascade is considered. Relations between molar and isotopic fractions of target isotopologues on the first and second stages of the cascade at each iteration are found. Optimization problem is formulated to evaluate optimal physical parameters of a two-stage cascade for molybdenum isotopes enrichment.

Evolution of the Enrichment Factor for an Iterative Scheme of Zirconium Isotopes Separation

In this paper evolution of the enrichment factor for zirconium isotopes separation by the laser assisted retardation of condensation has been found for specific choice of iterative policy of isotopes recovery. It has been evaluated for a set of gas flow temperatures, corresponding to its maximal value, provided all values of other important parameters of the system such as gas flow pressure, target gas molar fraction, laser intensity, laser beam radius, irradiation chamber length, and nozzle throat height are fixed. Enrichment factor has been found by solving a set of transport equations for molar fractions of four characteristic groups represented in the gas flow (monomers, dimers, excited monomers, and epithermals) in a static approximation on each iteration.

Comparison analysis of wet digestion and stripping methods on recovery of lithium isotopes in the loaded phase

Abstract 6Li and 7Li play important roles in the nuclear industry. In this study, the recovery of lithium isotopes in the loaded phase after extraction was compared for the first time between the stripping and wet digestion method. The results showed non-significant differences in the data obtained after processing in the two methods. The recovery of lithium isotopes by wet digestion is simple and complete. But it destroys the organic phase and requires heating at high temperatures, making it suitable for handling small amounts of samples. The stripping method is recommended for sample processing because it involves lesser chemical reagents and related hazards without damaging the sample.

Study on CH4 Oxidation and H2O Adsorption for Hydrogen Isotope Recovery

This study deals with the processes of converting trace CH4 in the oxidation reaction and adsorbing H2O. The conversion of CH4 was confirmed at various reaction temperatures and flow rates by injecting O2 above the equivalence ratio of CH4 in Ar. The conversion was higher at a higher reaction temperature and a lower flow rate. Also, the impurity effects of CO2, CO, and H2O coexisting in the feed gas with CH4 were investigated. When CO2 and H2O were included in the feed gas, CH4 conversion was decreased, and CO contained in the feed gas increased CH4 conversion by the heat of oxidation reaction. When CH4 is converted to CO2 and H2O through oxidation and H2O is adsorbed on the adsorbent, complete recovery of hydrogen isotopes can be obtained. Molecular sieve was used as the adsorbent, and the water adsorption capacity of the adsorbent was confirmed by generating water through the generator. Finally, it was confirmed that converted H2O from CH4 was adsorbed on the absorbent.

Adsorption of hydrogen and deuterium on A-type zeolites at 77 K after various heat treatments

Abstract Molecular sieves (MSs) are a potentially useful means of hydrogen isotope recovery as well as the temporary storage and supply of such isotopes. In this study, the hydrogen adsorption isotherms for various MS samples were acquired after applying different water removal processes to activate the MSs. MS-3A sample was found not to adsorb hydrogen regardless of the activation conditions. MS-4A sample adsorbed hydrogen at 77 K after heating at 473, 513, and 673 K. However, the adsorption amount after heating at 473, 513 K was considerably less than that at 673 K. Consequently, heating at 673 K was required to activate this type of MS. In the case of an MS-5A sample, the presence of residual water had little effect on hydrogen isotope adsorption at 77 K. From these results, it is evident that MS-5A is the most suitable hydrogen adsorption material because it is readily activated and is less affected by water adsorption.

Effects of structural and concentration polarization on the efficiency of Pd membrane permeator

For the processes of extracting hydrogen from the mixed gas of fusion reactors, it is of benefit to find an efficient method for hydrogen isotopes recovery and cyclic utilization. To enhance the hydrogen extraction efficiency, the properties of hydrogen permeation under various operating conditions in the tubular Pd membrane reactor system have been first investigated using the computational fluid dynamics (CFD) and material diffusion model. The results show that the predominated factor for the hydrogen extraction efficiency of tubular Pd membrane reactor is the fluid field of permeation pipe, further the effects of flux velocity, membrane length and thickness on the extraction efficiency at different pressures, as well as the concentration polarization effect at different conditions have been evaluated. The results could be significant for improving the engineering design of a highly efficient extraction Pd reactor by greater aspect ratio reactor. In addition, this method can also be used to simulate isotope separation process in Pd membrane reactor.

Interesterification Does Not Alter Postprandial Absorption or Oxidation of Dietary Fats, as Measured Using Stable Isotopes Analysis (P08-104-19)

ObjectivesAltering the structure of lipids by interesterification is largely replacing partial hydrogenation in the production of solid form vegetable-based fats. While proposed to be much healthier than the trans-fat containing alternatives, very little mechanistic work has been done to determine how these interesterified (IE) fats act in the human body. This study aimed to describe the physiological handling of commonly consumed IE fats during and after digestion compared to a non-IE equivalent and a control oil. MethodsIn a randomized, double-blinded controlled trial, healthy adults (n = 20) aged 45–75 years were assessed for postprandial triglyceride (TG) responses following consumption of 3 test meals (897 kcal, 50 g fat, 16 g protein, 88 g carbohydrate). Each meal contained 50 g of IE fat (80:20 palm stearin/palm kernel fat), the equivalent non-IE fat, or high-monounsaturated oil (canola oil, CO). A subsample of the study group (n = 9) consumed 75 mg of 1–13C glyceryl tripalmitate to trace the metabolic fate of the saturated fats consumed. Blood and breath samples were collected at baseline, and hourly thereafter for 8 h. Samples were analyzed for 13C:12C ratio by isotope ratio mass spectrometry and expressed as % dose recovered (PDR). ResultsNo differences were observed for palmitate oxidation as measured by PDR in breath CO2. Similarly, no difference in PDR of plasma 13C-palmitate in the postprandial period was observed between IE or non-IE fats (P = 0.439). Recovery of 13C-palmitate was ∼2.5-fold higher for the CO versus non-IE and IE treatments (P < 0.0001). We speculate this difference was due mainly to the differences in total solid fats at body temperature (37°C) and possibly the higher 13C-palmitate: total palmitate ratio in the CO meal. The levels of solid fat at 37°C were 21%, 16% and 0% for non-IE, IE and CO, respectively. As a function of the total palmitate found in the 50 g of fats consumed, non-IE, IE and CO were labelled with 13C palmitate at 0.26%, 0.26%, and 2.3%, respectively. While it is unlikely tracer enrichment was responsible, both factors may have collectively contributed to the higher isotope recovery in the CO meal. ConclusionsRates of palmitate absorption and oxidation were not affected by interesterification. The degree of saturation likely affect absorption due to the proportion of solid fat at body temperature. Funding SourcesBBSRC DRINC (UK). Supporting Tables, Images and/or Graphs▪▪

Evidence of microalgal isotopic fractionation through enrichment of depleted uranium

Resulting from the nuclear fuel cycle, large amounts of depleted uranium (DU) tails are piling up, waiting for possible use or final disposal. To date, the recovery of the residual 235U isotope contained in DU has been conducted only marginally by physical processes. Relative isotope abundances are often mediated by biological processes, and the biologically driven U isotopic fractionation has been previously identified in reducing bacteria. Our results indicate that the cells of two microalgal strains (freshwater Chlamydomonas sp. (ChlGS) and marine Tetraselmis mediterranea (TmmRU)) took up DU from the exposure solutions, inducing U isotopic fractionation with a preference for the fissile 235U isotope over 238U. The n(235U)/n(238U) isotopic fractionation magnitudes (δ235) were 23.6 ± 12.5‰ and 370.4 ± 103.9‰, respectively. These results open up new perspectives on the re-enrichment of DU tailings, offering a potential biological alternative to obtain reprocessed natural-equivalent uranium. Additionally, the findings present implications for identifying biological signatures in the geologic records.

Synthesis, characterization and application of a new nano-structured samarium(III) ion-imprinted polymer

This work presents the synthesis of a new nano-structured samarium ion-imprinted polymer (Sm(III)-IIP) by precipitation polymerization. The Sm(III)-IIP nanoparticles were prepared by the copolymerization of Sm(III)–acrylic acid–4-vinylpyridine ternary complex with ethylene glycol dimethacrylate and methyl methacrylate, and then, Sm(III) was leached to obtain Sm(III)-IIP leached particles. Moreover, non-imprinted polymer particles were similarly prepared without Sm(III) ions. The characterization of polymers was carried out by Fourier transform IR spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) and surface analysis. The effect of several parameters such as solution’s pH, sorption and desorption time, type, concentration and volume of eluent on the extraction of the polymers was investigated and optimized by one variable at the time. Optimized parameters were as follows: pH 4; mass sorbent 0.1 g; sorption time, 120 min; desorption time, 120 min; aqueous phase volume, 10 mL. Moreover, it is found that 30 mL of HCl (3 M) provided the most effective elution of Sm3+ ion from IIP beads. The maximum sorbent capacity of the IIPs is 14.91 mg g−1. The sorbent was used for purification of samarium-152 stable isotope. The samarium-152 stable isotope recovery yield was % 99.67. The detection limit of the method was evaluated to be 0.27 ng mL−1. The precision of the method (%RSD, n = 6) was % 0.47.

Adsorption kinetics on the recovery of hydrogen isotopes from helium using palladium particle bed

The recovery and separation of hydrogen isotopes from helium purge gas is one of the critical steps in nuclear fusion based fuel cycle. In the present study, the adsorption kinetics of hydrogen and deuterium from helium using palladium particle bed is generated at different temperatures varying from 30 °C to 150 °C in a recirculating packed bed batch adsorption system. The system is modeled as a combination of packed bed adsorber and a mixing vessel connected in closed loop. The overall mass transfer coefficient is estimated at different temperatures by minimizing the error between the simulated results and the experimental data. The apparent activation energy is estimated for both the hydrogen isotopes using Arrhenius plot. Based on the estimated values of apparent activation energies, it is concluded that the overall adsorption rate is limited by internal diffusion for both hydrogen and deuterium.