Heavy Water Production Research Articles

NATURAL OR ARTIFICIAL TRITIUM IN RIVERS – THE ASSESSMENT USING SYMMETRICAL INDEX

Tritium, hydrogen isotope, with a half-life of 12.3 years, is produced in two ways: naturally and artificially. Naturally, tritium is generated through the interaction of cosmic radiation protons and neutrons with gases in the upper atmosphere. Artificially, tritium origins from the atmospheric nuclear tests, production from nuclear reactors, future fusion reactors, fuel reprocessing plants, heavy water production facilities and commercial production for medical diagnostics, radiopharmaceuticals, luminous paints. Elevated concentrations of tritium in the environment are of great public concern. Considering the fact that nuclear power plants are located on rivers, knowing the activity concentration of this isotope in rivers is of great importance. This work presents the results for tritium determination in Danube and Sava River in Belgrade, Serbia. The origin of tritium was estimated using a mathematical parameter, symmetrical index.

Performance of Structured Packing for the Deuterated Water Distillation Process at Above Atmospheric Pressure

The National Research and Development Institute for Cryogenics and Isotopic Technologies (ICSI) was established in 1970 for research focused the industrial pilot plant. ICSI was created with the purpose of developing the heavy water production technology needed mainly for the operation of the CANDU reactors that equip the Cernavoda Nuclear Power Plant in Romania. This technology has been demonstrated and has been successfully transferred to the heavy water production plant. The accumulated experience in the field of isotopic separation allowed for the development of a second pilot plant, also for the purpose of heavy water, but this time for the purpose of separating deuterium and tritium for the recovery of tritium, mainly from the tritiated heavy water of the CANDU reactors. This experimental pilot is based on a technology that combines two hydrogen isotope separation processes: liquid-phase water-hydrogen catalytic isotopic exchange and hydrogen isotope cryogenic distillation. The success of the separation process consists of the technical solution given to the exchange area, its geometry (distillation-isotopic exchange), and last but not least, the performance of the hydrophilic packing, respectively, of the catalyst. Thus, an extensive research program was initiated and carried out over many years for the development of mixed catalytic packages consisting of a hydrophobic Pt/carbon catalyst (with different concentrations of platinum up to 2%) and hydrophilic packing (stainless steel or phosphorous bronze) manufactured within ICSI and made in different configurations (successive layers, random or structured). This program for the improvement of catalytic packages continues by implementing new solutions regarding the improvement of materials that ensure a large contact surface between the liquid and vapors, respectively, vapor and gas, thus increasing the isotopic separation performance. This paper presents an experimental analysis of two types of hydrophilic stainless steel packings developed for the purpose of separating hydrogen isotopes by water distillation to be used in the manufacture of mixed catalytic packages for the catalytic isotopic exchange process. This paper refers to the experiments performed with deuterated water on the hydrophilic packing in conditions of total reflux. The experiments were performed on a column equipped with two types of hydrophilic packing.

From Global to Local: The Development of Heavy Water in International Nuclear Programs (1945–1970)

Abstract Because of how heavy water is produced and used, it has a unique business history and structure. In the late 1940s and 1950s, heavy-water reactors offered the dream of nearly inexhaustible quantities of nuclear power generation. This was because they could operate using natural uranium and also produce plutonium that could be used as fuel in breeder reactors (and also as fissile material for nuclear weapons). Several of the processes and materials used in synthetic fertilizer production could also be used, in somewhat modified form, in the production of heavy water. Yet the production costs for heavy water are exceedingly high, requiring copious amounts of electricity and the infrastructure of an advanced chemical industry. This article suggests that in several countries the fertilizer and heavy-water industries had a close relationship. The governments in those countries, seeking to increase the national trade in fertilizers and to develop domestic nuclear programs, supported both industries. The case of the Spanish Nuclear Board and Energía e Industrias Aragonesas in Sabiñanigo is instructive in this regard.

Drobeta Turnu Severin Heavy Water Plant: Functioning and Shutting Down

Due to the special working conditions in the heavy water plant, an extensive research and program has been developed for the operational safety of the installations, based on specific action methodologies and in situ experimental programs for the evaluation of the long-term behavior of materials and installations. After December 1989, the operation of the modules was stopped for about three years, for the modernization of the technological equipment and the surveillance and environmental protection systems. In September 2015, the production of heavy water was stopped and the plant staff was laid off.

The Current Status of the Heavy Water Detritiation Facility at the NRC (Kurchatov Institute) – PNPI

The multifunctional Tritium Removal Facility (TRF) has been designed for the heavy water research reactor PIK in Russia. Along with the extraction of tritium and protium from a heavy water reflector of the reactor, the TRF provides the processing of heavy water waste and the production of tritium-free heavy water. The combined electrolysis catalytic exchange process and hydrogen cryogenic distillation are used at the TRF. A number of investigations have been made to obtain data for the TRF design. At present, the facility is under construction and a detailed design is being completed. The possibility of processing heavy water waste to produce heavy water simultaneously with the extraction of tritium and protium from the heavy water reactor will improve the functionality and economic efficiency of the TRF. The basic technological scheme of the facility and the main modes of its operation are presented along with the progress of the construction of the facility building and engineering systems.

Analysis of the Transient Regimes of a Detritiation Facility Operation

The National Research and Development Institute for Cryogenics and Isotopic Technologies (ICSI Rm. Valcea) was established in 1970 as a research entity with the main goal of developing a heavy water production technology. One of the departments of the institute, entitled ICSI Nuclear, is oriented toward the development of a heavy water detritiation technology with the main beneficiary being the Cernavoda nuclear power plant. Thus, ICSI Nuclear has completed the technical project of the Cernavoda Tritium Removal Facility (CTRF). This paper focuses on the CTRF front end (water detritiation system) and will analyze achievement of the nominal regime at start-up and analysis of the transient regimes that may occur during normal operation and their impact on the water detritiation factor. Analysis results can become input for improvement of the CTRF control and instrumentation system, for subsequent operating facility procedures, and for verification of the isotopic exchange software models corresponding to these modes of operation.

Ni-Based Catalyst Derived from NiAl Layered Double Hydroxide for Vapor Phase Catalytic Exchange between Hydrogen and Water.

A high-efficient and low-cost catalyst on hydrogen isotope separation between hydrogen and water is an essential factor in industrial application for heavy water production and water detritiation. In past studies, Pt-based catalysts were developed but not practical for commercial use due to their high cost for vapor phase catalytic exchange (VPCE), while for impregnated nickel catalysts with a lower cost the problems of agglomeration and low Ni utilization existed. Therefore, to solve these problems, in-situ grown Ni-based catalysts (NiAl-LDO) derived from a layered double hydroxide (LDH) precursor were fabricated and first applied in VPCE in this work. Compared with traditional impregnated Ni-based catalysts, NiAl-LDO catalysts own a unique layered structure, homogeneous dispersed metallic phase, higher specific surface area as well as stronger metal-support interactions to prevent active metal from agglomerating. These advantages are beneficial for exposing more active sites to improve dynamic contacts between H2 and HDO in a catalyst surface and can bring excellent catalytic activity under a reaction temperature of lower than 400 °C. Additionally, we found that the dissociative chemisorption of HDO and H2 occurs not only in Ni (111) but also in NiO species where chemisorbed H(ads), D(ads), OH(ads) and OD(ads) are formed. The results highlight that both of the Ni2+ species and Ni0 species possess catalytic activities for VPCE process.

Determination of tritium levels in tap waters collected from various regions in Thailand using liquid scintillation counting

Tritium can replace a hydrogen atom in water molecules since oxygen atom can react with tritium atoms to form water molecules the same way as for hydrogen atoms, potentially posing hazardous to consumers. This study aims to measure tritium activity concentrations in tap water samples collected from different regions in Thailand, (Phayao, Srisaket, Chanthaburi, Trang and Bangkok) in November 2018. The measurements of tritium activity concentrations were carried out by using electrolytic enrichment and low background liquid scintillation counting (AccuFLEX LSC-LB7), which had a sensitivity of less than 1 Bq/L. The data results of regional distribution of a tendency were discussed according to latitudes and longitudes of the collecting location. The measured tritium concentrations in tap water were in the range of 0.41 – 0.75 Bq/L. Specifically, the results showed that the tritium activity concentrations depended on location, with the highest value obtained from a tap water sample collected from the northern part of Thailand (Phayao). The results could be used as the baseline of tritium levels in tap water in each region of Thailand before building or operating the nuclear facilities such as the first nuclear power plant, fuel reprocessing or heavy water production facilities in the future.

Hydrogen Isotope Effects during Water Electrolysis Using Liquid and Polymer Membrane Electrolytes

Hydrogen isotope separation is highly important and equally challenging. Annual production of heavy water (D2O) is over a thousand tons to supply nuclear reactors and for medical and research applications worldwide. Current D2O production methods are expensive due to the low natural abundance of deuterium and high complexity of separation techniques. Demand for low-cost production of heavy water is inevitable with increased usage of nuclear power. Therefore, it is important to develop novel and economically viable methods to concentrate deuterium in water to overcome these demands. The purpose of this project is to study hydrogen isotope effects during the electrolytic decomposition water. Water electrolysis occurs via an oxygen evolution reaction (OER) at the anode and a hydrogen evolution reaction (HER) at the cathode. We have located OER and HER as the two main reactions that can have an isotope effect. Custom-built electrolyzers are used for the water electrolysis experiments where IrO2 is used as the catalyst layer at the anode and Pt on Carbon is used as the catalyst layer at the cathode. Results from using sulfuric acid in H2O and deuterated sulfuric acid in D2O as the liquid electrolytes for water electrolysis in a three-electrode conventional cell will be presented and discussed in the context of hydrogen isotope effects on the OER and HER. A similar comparison is made to study isotope effects at OER and HER in a proton exchange membrane (PEM) cell using Nafion 212 as the solid polymer electrolyte in a custom electrolyzer. Monolayer graphene in its pristine form has been shown to act as a selective barrier allowing proton transmission at rates much higher than deuteron transmission. We have incorporated a graphene layer in between two Nafion membranes to study the effect of graphene on the ability to separate deuterium from a hydrogen/deuterium gas mixture and also from H2O vs D2O electrolysis. Monolayer graphene’s barrier character together with isotope effects of OER and HER of the membrane electrode assembly (MEA) could contribute to a potential low-cost method to separate deuterium from a H/D isotope mixture.

Separation process study of liquid phase catalytic exchange reaction based on the Pt/C/PTFE catalysts

Abstract The liquid phase catalytic exchange (LPCE) reaction is an effective process for heavy water detritiation and production of deuterium-depleted potable water. In the current study, hydrophobic carbon-supported platinum catalysts (Pt/C/PTFE) with high efficiency as reported previously for LPCE were prepared and comprehensive performance evaluation method is applied to evaluate the separation behaviors of LPCE systematically. Experimental results indicate that the optimum reaction temperature of 60–80 °C and the molar feed ratio G/L of 1.5–2.5 would lead to higher separation efficiencies. As to the packing method, a random packing mode with a packing ratio of hydrophobic catalysts 0.25 is recommended. In addition, thermodynamic analysis corresponds well with experimental results under lower temperature and G/L, while the suppression of kinetic factors should not be neglected when T > 80 °C and G/L > 1.5.

History and General Characteristics of the Adaptive Control System of the Deuterium Pre-concentration Stage in Heavy Water Production

History and General Characteristics of the Adaptive Control System of the Deuterium Pre-concentration Stage in Heavy Water Production

Nuclear Archaeology to Distinguish Plutonium and Tritium Production Modes in Heavy-Water Reactors

Several nuclear archaeology techniques have been proposed to determine historic plutonium production in dedicated nuclear reactors. These methods rely on sampling materials from the reactor core, or specially designed monitor tags, to examine suited isotopic ratios and deduce the amount of plutonium produced. However, some production reactors are capable of producing isotopes other than plutonium, such as tritium. If a reactor was declared to produce tritium, it would be crucial to confirm that it was in fact producing tritium, and not plutonium. In this paper, we describe how isotopic ratios discrepancies could be used to distinguish between plutonium and tritium production modes. We present results obtained from the simulation of reactor lattices inspired by Savannah River Site heavy-water production reactors and show that elements such as hafnium and tungsten can detect undeclared production of plutonium.

The Trails of Memory – Remembering the Heavy Water Raid in Norway

A Second World War sabotage act targeting the production of Heavy Water (D20, deuterium oxide) in inland Norway, figure among the best known and best-remembered acts of sabotage in Norwegian history. This article considers the various acts of remembrance regarding this event and explores the intermedial intertwining of its trails of memory. It looks at the semi-documentary film released in 1948, the industrial factory turned World Heritage Site, and lastly the different hiking activities known as the Saboteur Marches. A central point is how these different acts of remembrance interact and reinforce each other, resulting in a plethora of media concerned with commemoration.

Scalable and efficient separation of hydrogen isotopes using graphene-based electrochemical pumping

Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination. The existing technologies remain extremely energy intensive and require large capital investments. New approaches are needed to reduce the industry’s footprint. Recently, micrometre-size crystals of graphene are shown to act as efficient sieves for hydrogen isotopes pumped through graphene electrochemically. Here we report a fully-scalable approach, using graphene obtained by chemical vapour deposition, which allows a proton-deuteron separation factor of around 8, despite cracks and imperfections. The energy consumption is projected to be orders of magnitude smaller with respect to existing technologies. A membrane based on 30 m2 of graphene, a readily accessible amount, could provide a heavy-water output comparable to that of modern plants. Even higher efficiency is expected for tritium separation. With no fundamental obstacles for scaling up, the technology’s simplicity, efficiency and green credentials call for consideration by the nuclear and related industries.

Improved Recovery in H<sub>2</sub>S–H<sub>2</sub>O Exchange Process for Increasing Heavy Water Production

GS process is the most widely used bi-thermal exchange process for production of heavy water. This paper describes how recovery of deuterium from natural water can be increased in a GS process plant, from existing limit of 19.6% to 25% by incorporating cold and hot stripper sections in the first stage exchange towers. By increasing recovery, production can be increased and operating costs reduced substantially, leading to enhanced and cheaper heavy water production from similar size plant. These concepts and novel flow sheet changes can be applied to new as well as existing plants by reassigning some of the available contacting stages to stripper sections, and still enhance production rates. They can also be applied to any other bi-thermal exchange process.

ICIT activities related to tritium management

National Research and Development Institute for Cryogenics and Isotopic Technologies (ICIT) was established in 1970 as a research focused Industrial Pilot Plant. This new Institute was created with the purpose to develop the heavy water production technology. This technology has been successfully transferred to the heavy water production plant in 1988 (with a capacity of 360t/year). Currently, research within ICIT is focused on the following main objectives: support for the National Nuclear Program, hydrogen and fuel cells, cryogenics, environment.Within ICIT it has been built an Experimental Pilot Plant having as the main objective the development of a technology for heavy water detritiation. The purpose of this Pilot Plant is to obtain technological data and functional characteristics of specific equipment in order to design a Detritiation Facility used for Nuclear Power Plants with CANDU reactors.This work is focused on the presentation of ICIT research activities, perspectives and its capability related to water detritiation technologies and also to on issues in the field of nuclear fusion.

Development of Hydrophobic Platinum-Doped Carbon Aerogel Catalyst for Hydrogen-Deuterium Exchange Process at High Pressure

The use of catalysed exchange of deuterium (D) between hydrogen (H) gas and liquid water using the bithermal hydrogen water (BHW) process is a promising and environment-friendly approach for the production of heavy water. However, the use of this approach is limited by the lack of a suitable catalyst that has good activity at high operating pressures required for practical applications. We report the development of hydrophobic platinum-doped carbon aerogel (PtCA) catalyst which shows good catalytic activity for H/D isotope exchange reactions at operating pressures up to 20 bar.

A New Challeng for Hydrogen Isotope Electrolytic Separation System Combined with Fuel Cell

1. Introduction Hydrogen isotopes are important elements for nuclear and fusion reactors. The technique of hydrogen isotope separation has been investigated in several approaches [1-3]. However, the most methods are ineffective processes and shows low separation factor. That is, a large scale plant is generally necessary to deal with enormous water for the isotope enrichment. In Japan, a novel separation technology of tritium in Fukushima Daiichi nuclear power plant is urgently required. Although water electrolysis has been mainly used for heavy water production since the 1930s, it is no longer used except in the final separation stage. The reason is that water electrolysis consumes an enormous amount of the electric energy for a large-scale production. However, the electrolysis process is still attractive due to the highest separation factor and less polluted exhausts. In the conventional electrolysis process, no attempts have been made to recover energy from the gases evolved from the water electrolysis cell. The gases evolved from the electrolysis are recombined in a burner or catalytic exchange tower, and the left water vapor is condensed and fed to a lower stage. Supposed that the evolved hydrogen and oxygen gases are fed into a fuel cell as seen in Fig. 1, a large amount of energy will be recovered as electricity. For exploring this new concept [4], we have comprehensively investigated the electrochemical kinetics of hydrogen electrode reactions and separation factors in fuel cell and water electrolysis [5]. 2. Experimental The kinetic study was conducted by the rotating electrode with the rotation rate of 900, 1600, 2500 and 3600 rpm. The working electrode was a 0.785 cm-2 polycrystalline Pt disk and the counter electrode was coiled Pt wire. The reference electrode was Hg/Hg2SO4 saturated with K2SO4. The polarization curves were recorded by linear sweep voltammetry at the scan rate of ±0.01 V s-1. The electrolytes of 0.05 M D2SO4and 0.05 M KOD were maintained at 298 K. 3. Results and discussion Figure 2 shows Tafel plots of mass transfer corrected currents for the hydrogen oxidation reaction (HOR) and deuterium oxidation reaction (DOR) at low anodic overpotential (η ≤ 0.08 V). The Tafel region of HOR began to be observed at η ≈ 0.04 V. The slope value of HOR was 0.091 V dec-1, which was larger than that of DOR (0.055 V dec-1). Concerning on the exchange current density, the ratio of i 0(H2) / i 0(D2)was 0.46. The present kinetic comparison of deuterium with protium data supported the isotope effect by which the deuterium was more easily dissociated on platinum electrode, pointing out a new separation by fuel cells. We will calculate the total energy consumption in fuel cell and water electrolysis and discuss the possibility of new separation system for heavy water production. ACKNOWLEGMENT The authors appreciate the financial aid given by the Ministry of Education, Culture, Sports, Science and Technology (Project NO. 26870234). One of the authors, H. Matsushima, wishes to express his sincere gratitude to Inamori Foundation in Japan. REFERENCES [1] C. Banglin et al., J. Am. Chem. Soc., 130, 6411 (2008). [2] I. Cristescu et al., Fusion Eng. Des., 82, 2126 (2007). [3] I. A. Alekseev et al., Fusion Sci. Technol., 41, 1097 (2002). [4] H. Matsushima, T. Nohira, T. Kitabata, Y. Ito, Energy, 30, 2413 (2005). [5] S. Shibuya, H. Matsushima, M. Ueda, in preparation. Figure 1

Life-cycle impacts from novel thorium–uranium-fuelled nuclear energy systems

Electricity generated from nuclear power plants is generally associated with low emissions per kWh generated, an aspect that feeds into the wider debate surrounding nuclear power. This paper seeks to investigate how life-cycle emissions would be affected by including thorium in the nuclear fuel cycle, and in particular its inclusion in technologies that could prospectively operate open Th–U-based nuclear fuel cycles. Three potential Th–U-based systems operating with open nuclear fuel cycles are considered: AREVA’s European Pressurised Reactor; India’s Advanced Heavy Water Reactor; and General Atomics’ Gas-Turbine Modular Helium Reactor. These technologies are compared to a reference U-fuelled European Pressurised Reactor. A life-cycle analysis is performed that considers the construction, operation, and decommissioning of each of the reactor technologies and all of the other associated facilities in the open nuclear fuel cycle. This includes the development of life-cycle analysis models to describe the extraction of thorium from monazitic beach sands and for the production of heavy water. The results of the life-cycle impact analysis highlight that the reference U-fuelled system has the lowest overall emissions per kWh generated, predominantly due to having the second-lowest uranium ore requirement per kWh generated. The results highlight that the requirement for mined or recovered uranium (and thorium) ore is the greatest overall contributor to emissions, with the possible exception of nuclear energy systems that require heavy water. In terms of like-for-like comparison of mining and recovery techniques, thorium from monazitic beach sands has lower overall emissions than uranium that is either conventionally mined or recovered from in-situ leaching. Although monazitic beach sands (and equivalent placer deposits) only form 30% of the overall known thorium ore deposits, it is expected that such deposits would generally be utilised first if thorium becomes a viable nuclear fuel. Overall, for these four nuclear energy technologies, the range of CO2(eq) emissions per kWh generated (6.60–13.2 gCO2(eq)/kWh) appears to be low in comparison to the majority of electricity-generating technologies.

Investigation of the Dynamic Strain Aging and Mechanical Properties in Alloy-625 with Different Microstructures

Tensile tests were carried out on service exposed Alloy 625 ammonia cracker tube used at heavy water production plant to study the effect of microstructure on the serrated yielding and mechanical properties of the material. Owing to temperature gradient during service exposure, the microstructure was different in top, middle, and bottom sections of the tube. Variation of flow stress, ductility, and average work hardening were monitored with temperature. In the present work, emphasis was given on the study of serrated yielding in the service exposed Alloy 625. Detail investigations were made to study the effect of microstructure on the underlying mechanism of dynamic strain aging of the material. The study revealed that both the normal and the inverse Portevin–Le Chatelier effect (PLC) occured in the material at lower and higher temperature regime, respectively. While the normal PLC dynamics was associated with locking of dislocations by interstitial carbon atoms, the inverse one was accomplished by the dislocation pinning by substitutional Mo atoms. Further analyses identified that the basic deformation mechanism was different in middle and bottom samples as that in the top samples which was reflected in the difference in their respective activation energy and stress drop magnitude.