Tritiated Hydrogen Gas Research Articles

Experimental investigation of D2 conversion to DHO in soil near the Cernavoda nuclear power plant site in Romania

The current Canadian and Romanian model predictions for tritium dose following an atmospheric tritiated hydrogen gas (HT) release is based on a default Canadian Standards Association (CSA) conversion factor of HT to tritiated water (HTO) of 4.3%. The determination of an empirical site specific value for the conversion factor was essential for the CANDU Cernavoda Nuclear Power Plant (NPP) in Romania to verify if the CSA value is appropriate for use at this site. Given the role of soil characteristics on the conversion of HT to HTO, on-site experiments would provide the best evaluation of the conversion factor.The objective of the study was to define the soil HT to HTO conversion parameters specific to the Cernavoda NPP site. In June 2016, a series of experiments were conducted to meet this objective. First, the in situ deposition velocity of D2 gas, as a surrogate for HT gas, was obtained using an exposure chamber. Diffusion of D2 into the soil was then evaluated based on the measurements of DHO concentrations in the exposed soil. As soil microbes play a role in the conversion of HT to HTO, this work included a microbiological characterization of the soil, which targeted total soil bacteria (cultivable and gene-based) and hydrogen oxidizing bacteria (cultivable and gene-based). The fraction of hydrogen oxidizing cultivable soil bacteria represented 14–20% of the total cultivable bacteria population estimated as 2.8–29.2 × 105 cfu/g of soil. The empirically derived HT to HTO conversion factor was lower than the default value (4.3%). It fell between 0.9% and 2.0%. The default value is therefore more conservative than the Cernavoda site-specific derived value obtained from the study.

Pebble fabrication and tritium release properties of an advanced tritium breeder

Li2TiO3 with excess Li (Li2+xTiO3+y) has been developed as an advanced tritium breeder. With respect to the tritium release characteristics of the blanket, the optimum grain size after sintering was less than 5μm. Therefore, an emulsion method was developed to fabricate pebbles with this target grain size. The predominant factor affecting grain growth was assumed to be the presence of binder in the gel particles; this remaining binder was hypothesized to react with the excess Li, thereby generating Li2CO3, which promotes grain growth. To inhibit the generation of Li2CO3, calcined Li2+xTiO3+y pebbles were sintered under vacuum and subsequently under a 1% H2–He atmosphere. The average grain size of the sintered Li2+xTiO3+y pebbles was less than 5μm. Furthermore, the tritium release properties of Li2+xTiO3+y pebbles were evaluated, and deuterium–tritium (DT) neutron irradiation experiments were performed at the Fusion Neutronics Source facility in the Japan Atomic Energy Agency. To remove the tritium produced by neutron irradiation, 1% H2–He purge gas was passed through the Li2+xTiO3+y pebbles. The Li2+xTiO3+y pebbles exhibited good tritium release properties, similar to those of Li2TiO3 pebbles. In particular, the released amount of tritiated hydrogen gas for easier tritium handling was greater than the released amount of tritiated water.

Tritium Contamination and Decontamination of Sealing Oil for Vacuum Pump

In the decommissioning project of tritium handling laboratories or/and facilities, oils such as used in the vacuum pumps have been left conventionally in their comprehensive facilities. Existence of oils, especially highly-contaminated with tritium, is becoming one of the serious problems in projects for decommissioning tritium handling laboratories because of no disposal way of the tritiated waste oils. Experiments using bubblers were carried out to examine the tritium contamination and decontamination of a volume of rotary-vacuum-pump-oil. Contamination of pump oil was observed by bubbling with tritiated water vapor and tritiated hydrogen gas. And then, subsequent decontamination of tritiated oil was processed by bubbling with pure water vapor and dry argon gas. The bubbling with water vapor was more effective than with the dry gas. Experimental results show that the water vapor bubbling in an oil bottle can remove tritium efficiently from the contaminated oil into another water-bubbling bottle.

HT to HTO conversion and field experiments near Darlington Nuclear Power Generating Station (DNPGS) site

The Canadian input parameters related to tritiated hydrogen gas (HT) used in tritium dose models are currently based on experiments performed at the Chalk River Laboratories (CRL) site in 1986, 1987 and 1994. There is uncertainty in how well other sites experiencing atmospheric HT releases are represented by these data. In order to address this uncertainty, HT to HTO conversion factors were evaluated at different locations near the Darlington Nuclear Power Generating Station (DNPGS) site using various experimental approaches. These were D2 gas exposure chamber experiments, atmospheric tritium measurements, and HTO and OBT measurements in vegetation and soil. In addition to these field experiments, chamber experiments were conducted using HT gas on field soil samples. The suggested Canadian input parameters for atmospheric tritium releases estimate the total fraction of HT oxidized in air and in soil, at the site, to be up to a maximum of 2.4%. Based on the more limited data obtained near DNPGS in early spring, this fraction would likely be closer to 0.5%. The result suggests that current parameters provide a conservative estimate for the DNPGS site.

Temperature-Programmed Elimination of Tritium in Coal Labeled by Tritiated Gaseous Hydrogen

The hydrogen exchange of an Argonne Pocahontas #3 (POC) coal with tritiated gaseous hydrogen in the presence of a Pt/Al2O3 catalyst was carried out using a fixed-bed reactor at a temperature range of 200−250 °C. Then, the tritiated coal sample was re-exchanged with hydrogen in a gaseous hydrogen atmosphere at different raising temperature rates. The changes in radioactivity of tritium releasing from the tritium-labeled coal sample in the temperature-programmed elimination (TPE) of tritium was monitored by a radioanalyzer in situ. The release profile of tritium was fit using three Gaussian distribution functions in TPE. On the basis of the waveform analysis, the amounts and activation energies of the hydrogen exchange for every type of exchangeable hydrogen were estimated. The values of exchange activation energies are 8.8 ± 0.5, 10.7 ± 0.5, and 16.3 ± 0.5 kcal/mol for three types of exchangeable hydrogen, respectively. The amount of type-I hydrogen was independent of the exchange reaction temperature. In contrast to this, the amount of types II and III of exchangeable hydrogen increased with an increasing exchange temperature, suggesting that the amount of types II and III of hydrogen in the coal is dependent upon the exchange temperature.

Study on the technology of CECE–GC system for water detritiation

Based on the thorough study of electrolysis enrichment, gas–liquid phase catalytic exchange, gas chromatography for hydrogen isotope separation, and hydrogen–oxygen recombination technologies, a CECE–GC prototype system with disposal capability of 10 ton/a of tritiated water was set up in the middle of 2004 at China Academy of Engineering Physics (CAEP). It has successfully fulfilled the demonstration experiment of recovering deuterium from deuterium contained water and simulation operation of recovering tritium from tritiated water. Total concentration factor of CECE about 4, and the separation factor of tritium around 10 for operation time of 240 h with this system. The GC system of 50 m 3/d has successfully recovered 90% hydrogen from 10 m 3 tritiated hydrogen gas in 6 h and the tritium concentration in this part was depleted more than 1000 times. This experimental system served as an important step stone for further engineering works.

Disposal Pathway for Tritiated Reactive Metals and Tritiated Hydrogen Gas

Kinectrics and its predecessor company Ontario Hydro Research Division (a division of Ontario Hydro) had a fully operational tritium laboratory on site since the early 1980’s. During those years numerous projects and experiments were undertaken using hydrogen and tritium for the most part. Metals with an affinity for hydrogen are commonly employed as scavengers of hydrogenic gases from process streams or as hydrogen storage mediums. The two most common of these metals used were depleted uranium and a zirconium-iron alloy (SAES St198). The break-up of Ontario Hydro through deregulation activities resulted in the building of a new, smaller, tritium laboratory and the decommissioning of the original tritium laboratory. Decommissioning activities resulted in the need to safely dispose of these reactive metals. Disposal of these metals is not straight forward. For safe, long term, disposal it has been decided to oxidize the metals in a controlled fashion. The oxidized beds, containing the metals, will be sent to a radioactive waste site for long term storage. Options for disposal of tritiated hydrogen gas are presented and discussed. This paper provides a disposal pathway for tritiated reactive metals and hydrogen thereby closing the loop in tritium handling.

Effect of demineralization on hydrogen transfer of coal with tritiated gaseous hydrogen

Roles of mineral matters and oxygen functional groups of coal on hydrogen transfer reaction with gaseous hydrogen were investigated by using a tritium tracer technique in a fixed-bed reactor system. Mineral matters in coal were removed by HCl or HCl/HF treatments. Alkali metals and a part of pyrite were removed by HCl treatment. SiO 2 and Al 2O 3 were removed only by HCl/HF treatment. A large part of pyrite was removed by HCl/HF treatment but about 20% of them still remained even after the treatment. It was observed that the efficiency of hydrogen transfer of coal decreased to some extent when cations and mineral matters were removed by HCl treatment. Further decrease in hydrogen transfer was observed after HCl/HF treatment. These results suggested that iron species from pyrite may catalyze the hydrogen transfer reaction with H 2 gas. Mineral matters assist the H-transfer to the carbon network of coal but does not promote hydrogen transfer to hydroxy groups.

Elucidation of hydrogen transfer behavior of coal with tritiated gaseous hydrogen in the absence and the presence of a catalyst using a fixed-bed reactor ☆

Hydrogen transfer behaviors of four Argonne coals with gas phase tritiated H 2 in thermal (non-catalytic) and catalytic reactions (in the presence of 3 wt% Pt/Al 2O 3) in temperature range from 250 to 400 °C have been investigated using a fixed-bed reactor. The result showed that the efficiency of hydrogen transfer reaction of coal with the gas phase in the thermal run increased with increasing oxygen functionalities, providing the indication that some oxygen functional groups have a role for effective promotion of hydrogen transfer reaction with the gas phase H 2 under mild condition. When the reaction was run in the presence of the catalyst, the efficiencies of hydrogen transfer reaction for the all coals, except for the POC coal, were significantly enhanced even at temperature as low as 250 °C. The results for the catalytic reaction have provided indications into the reactive sites (formation of free-radicals) in coal and patterns for coal matrix degradation reactions.

Elucidation of Hydrogen Mobility in Coal Using a Fixed Bed Flow Reactor -Hydrogen Transfer Reaction between Tritiated Hydrogen, Coal, and Tetralin-

Hydrogen transfer reactions of coal with tritiated gaseous hydrogen in the presence of tetralin were performed using a flow reactor under the following conditions: pressure 50 kg/cm2, temperature 200−400 °C, and reaction time 120−420 min. When Wandoan coal (WA) was used as a coal sample, functional groups participated in the hydrogen transfer reaction even at 200 °C and then decomposed at 250 °C. At 300 °C, ether bonds were cleaved to generate hydroxy groups which were decomposed at 350 °C. When the higher rank Pocahontas coal (POC) was used, functional groups participated in the hydrogen transfer reaction even at 250 °C and then decomposed at 300 °C. Further, ether bonds were cleaved at 350 °C to generate hydroxy groups which were decomposed at 400 °C. These results showed that in the case of POC coal, a 50 °C higher temperature was needed to obtain functional group behavior similar to the case of WA coal.

Elucidation of hydrogen behaviour in coal by using a tritium tracer method: hydrogen transfer reaction of coal with tritiated gaseous hydrogen in a flow reactor

The hydrogen transfer reactions of three Argonne coals with tritiated gaseous hydrogen were carried out using a flow fixed-bed reaction system in the presence of Pt/Al2O3 catalyst at a temperature range 200−300 °C and under pressure of 1.5−5.0 MPa to trace the behavior of hydrogen in coal. In the reactions under a constant pressure of 5.0 MPa, it was found that the hydrogen exchange between tritiated hydrogen atoms generated from the Pt catalyst and hydrogen in functional groups such as hydroxy groups proceeded at temperatures as low as 200 °C for all coals studied. The results also indicate that hydrogen transfers to decompose ether linkages and reduce carbonyl groups in coal proceeded substantially at temperatures as low as 200 °C for lignite Beulah-zap (ND) and middle rank Illinois No. 6 (IL) coals. The amount of functional groups in the tritiated coal achieved a maximum at 250 °C for all coals examined. Hydrogen exchanges with hydrogen in the benzylic position and the phenoxy ring were observed at a p...

Diffusion Coefficient of Tritium in Ni-Based Alloy

ABSTRACTHydrogen diffusivity and solubility in Inconel 600 were determined with a gas-absorption method using tritiated hydrogen gas in a temperature range from 573 K to 973 K. The temperature dependence of diffusivity D and solubility S were obtained as,D (cm2s−1) = 1.3 x 10−2 exp(−50.6/(RT / kJ)),S (cm3(NTP)cm−3Pa−0.5) = 4.7 x 10−3 exp(−11.7 /(RT / kJ)).

Elucidation of hydrogen mobility in coal under reductive atmosphere using a tritium tracer method

Hydrogen exchange reaction of three Argonne coals (Illinois No. 6, Upper Freeport and Pocahontas #3) and Wandoan coal with tritiated gaseous hydrogen were performed at several temperatures. Hydrogen exchange reaction was performed in a flow reactor packed with 0.4 g of coal and 0.05 g of catalysts under the following conditions: pressure 15 kg/cm 2, temperature 200, 250, 300 °C, carrier gas H 2 or N 2 5 ml/min. When a pulse of [ 3H]H 2 was introduced into a coal in H 2 carrier gas at several temperatures, the delay of [ 3H]H 2 pulse observed increased with increasing the reaction temperature and decreased with increasing coal rank. Further in the reaction of tritiated coals with gaseous hydrogen at constant temperature, the hydrogen exchange rate was estimated from the release rate of [ 3H]H 2. The apparent hydrogen exchange rate at 200 °C was higher than that at 250 °C. This shows that the hydrogen with low reactivity came to participate in the reaction at high temperature. When the reaction of tritiated coal with gaseous hydrogen was performed during heat treatment, one, two or three peaks of tritium concentration were observed in the outlet of the reactor depending on temperature (200, 250 or 300 °C, respectively) at which tritium was incorporated into coal initially. It was suggested that there were at least three kinds of hydrogen with different reactivity in coal.

Tritium doses from chronic atmospheric releases: a new approach proposed for regulatory compliance.

Regulatory models for atmospheric releases of tritium approved by the Environmental Protection Agency (CAP88, AIRDOS-PC, and COMPLY) calculate doses only from tritiated water (HTO) taken into the body. They do not deal with dose from emissions of tritiated hydrogen gas (HT) and conversion of HT to HTO in the environment, nor do they address the dose from ingesting tritium incorporated into organic compounds. A simple model (NEWTRIT) is proposed that accounts for all pathways to dose from atmospheric releases of HT and HTO. The model is formulated in terms of the tritium-to-hydrogen ratio in each environmental compartment. With each transfer, a small reduction in the ratio is introduced to reflect the dilution that occurs in nature. Conversion of HT to HTO in the environment is modeled using the latest experimental data. Concentrations of organically bound tritium are calculated in foodstuffs based on amounts of hydrogen in proteins, fats, and carbohydrates. Concentrations in foodstuffs and doses calculated by NEWTRIT are consistent with the predictions of existing regulatory models. In addition, the HTO component of NEWTRIT is tested using public bioassay data and the HT component is tested using results from a model intercomparison study for a hypothetical HT release. Although tritium doses probably have not been underestimated by regulatory models that account only for HTO (due to the high degree of conservatism built into these models), the explicit treatment of HT and organically bound tritium proposed here will make the dose assessments more comprehensive, defensible, and scientifically acceptable. Because NEWTRIT includes all pathways to dose and predicts conservative doses, it is a suitable model to replace the tritium models currently used for compliance.

Elucidation of Hydrogen Mobility in Functional Groups of Coals Using Tritium Tracer Methods

Hydrogen exchange reactions of coal with tritiated water and gaseous hydrogen were investigated to estimate the mobility of hydrogen in coal using not only a batch type reactor but also a flow type reactor. Specifically, the reactivities of functional groups were traced in these reactions. In the reaction of coal with tritiated water at 100 °C the hydrogen exchange of functional groups such as hydroxyl group in coals could be estimated. In the pressurized system using stainless batch type reactor aromatic hydrogen at ortho- and para-positions of a functional group could also be estimated by the hydrogen exchange reactions of coal and tritiated water at higher temperature. In hydrogen exchange reactions of coals with tritiated gaseous hydrogen using a flow reactor, reaction temperature was controlled exactly. The use of a Pt/Al2O3 catalyst promoted the generation of hydrogen radicals which reacted with coal. This method enables us to estimate the reactivity of a functional group with a hydrogen radical. Fu...

Elucidation of Hydrogen Behavior in Coal Using a Tritium Tracer Method: Hydrogen Transfer Reaction of Coal with Tritiated Gaseous Hydrogen in a Flow Reactor

The hydrogen transfer reactions of three Argonne coals with tritiated gaseous hydrogen were carried out using a flow fixed-bed reaction system in the presence of Pt/Al2O3 catalyst at a temperature range 200−300 °C and under pressure of 1.5−5.0 MPa to trace the behavior of hydrogen in coal. In the reactions under a constant pressure of 5.0 MPa, it was found that the hydrogen exchange between tritiated hydrogen atoms generated from the Pt catalyst and hydrogen in functional groups such as hydroxy groups proceeded at temperatures as low as 200 °C for all coals studied. The results also indicate that hydrogen transfers to decompose ether linkages and reduce carbonyl groups in coal proceeded substantially at temperatures as low as 200 °C for lignite Beulah-zap (ND) and middle rank Illinois No. 6 (IL) coals. The amount of functional groups in the tritiated coal achieved a maximum at 250 °C for all coals examined. Hydrogen exchanges with hydrogen in the benzylic position and the phenoxy ring were observed at a perceptible extent at 300 °C. Substantial decarboxylation of lignite ND coal was also observed at 300 °C. When the pressure dependence was investigated at a constant temperature of 250 °C, it was found that the amount of hydroxy groups in tritiated coal increased with both the decomposition of ether linkages and the reduction of carbonyl groups.

Reactions of Tetralin with Tritiated Molecular Hydrogen on Pt/Al2O3, Pd/Al2O3, and Pt−Pd/Al2O3 Catalysts

Reactions of tetralin with tritiated gaseous hydrogen were carried out at 5.00 MPa and at 200−400 °C on several noble metal catalysts prepared: Pt/Al2O3, Pd/Al2O3, and Pt−Pd/Al2O3. Hydrogenation and dehydrogenation activities of the catalysts were compared. By tracing changes in the radioactivities of 3H in the products before and after reaction, amounts of the hydrogen exchange between tetralin and tritiated hydrogen were measured to determine the behavior of hydrogen in the reaction. Further, effects of sulfur present in the feedstocks on the catalytic performance were investigated and resultant differences in the sulfur tolerance among the catalysts were clarified.

Hydrogen Exchange Reactions of Coal with Tritiated Gaseous Hydrogen and Water. Effects of Particle Size of Coal on Hydrogen Exchange

The hydrogen exchange reactions of Argonne Premium coals and Wandoan coal with tritiated gaseous hydrogen and tritiated water were carried out to investigate the effect of the particle size of coal on the hydrogen exchange reaction. Coals with several particle sizes (< 100 mesh and <20 mesh for Argonne Premium coals, <250 mesh, 250-150 mesh, and 20-22 mesh for Wandoan coal) were used, and it was found that the particle size of coal only slightly affected the hydrogen exchange ratio of coal in both cases of tritiated gaseous hydrogen and water. These results suggest that most of hydrogen exchanged with gaseous hydrogen or water, e.g., hydrogen in functional groups, is located on not only the exterior surface but also interior surface of coal, where hydrogen atom generated in the presence of the catalyst or proton generated from water can easily approach, even in the case of larger particle size of coal.

Elucidation of hydrogen mobility in coal using a tritium pulse tracer method. Hydrogen exchange reaction of coal with tritiated gaseous hydrogen

The hydrogen exchange of coal with gaseous hydrogen was carried out between 200 and 300°C using a pulse flow reaction system in the absence and presence of a Pt/Al2O3 catalyst to estimate the mobility of hydrogen in coals. In the absence of the catalyst, hydrogen exchange hardly occurred and hydrogen exchange ratio (HER) was fewer than 1% in most of coals used. Hydrogen exchange reaction between coal and gaseous hydrogen was enhanced remarkably in the presence of Pt/Al2O3 catalyst and HER was increased with temperature. The hydrogen mobility in coal was lower for higher rank of coals at each temperature. Further, the amount of hydrogen in functional groups of coal, which is contributed to the hydrogen exchange with tritiated gaseous hydrogen, could be estimated by the treatment of the tritiated coals with water. It was suggested that almost all hydrogen of functional group in coals were exchanged with gaseous hydrogen at high temperatures over 250°C in the presence of the catalyst.

Elucidation of coal liquefaction mechanisms using a tritium tracer method: hydrogen exchange reaction of solvents with tritiated molecular hydrogen in the presence and absence of H 2S

To estimate the hydrogen mobility of solvents quantitatively, reactions of tetralin, decalin and naphthalene with tritiated gaseous hydrogen in the presence and absence of H 2S were performed under the conditions generally used for coal liquefaction (400°C, initial hydrogen pressure 60 kg/cm 2). The conversions of tetralin and decalin to other organic structures in the presence and absence of H 2S were very close to each other. However, the conversion of naphthalene in the presence of H 2S was promoted about four times of that in the absence of H 2S. In the absence of H 2S, the hydrogen exchange ratio (HER: the ratio of hydrogen exchanged in a solvent to total hydrogen in the solvent) of naphthalene was highest among the solvents. However, in the presence of H 2S, the HERs of tetralin and decalin were promoted about 10 times. In the presence of H 2S, the HER of tretalin was highest in comparison with those of decalin and naphthalene. It was suggested that H 2S promoted the hydrogen exchange through tetralyl radical.