Tritium Facility Research Articles

Four Years of Tritium Operation of the KATRIN Experiment at TLK

The Karlsruhe Tritium Neutrino (KATRIN) experiment measures the tritium β-spectrum close to the maximum decay energy to achieve the value of the electron-antineutrino mass with a sensitivity of 0.2 eV/c2 (90% confidence level). Since only a small fraction of the decay electrons carries nearly all the energy, a high luminous tritium source, with its supporting infrastructure facilities, is necessary. Since the start of the tritium operation of KATRIN back in May 2018, more than 600 days of 24/7 measuring campaigns with a total tritium throughput of ≈18.1 kg and a tritium concentration >95% have been conducted. Despite several technical issues occurring during the run time, the necessary reliable supply of tritium was provided. This contribution will give an overview of the current operational conditions of the Tritium Laboratory Karlsruhe tritium facilities involved, as well as the relevant technical, analytical, and administrative procedures implemented. Furthermore, an analysis will be given for system and component malfunctions in the tritium loop as well as the associated actions for problem-solving and repair. In addition, an end-of-life investigation for the component failure will be presented.

Bioremediation of copper in sediments from a constructed wetland ex situ with the novel bacterium Cupriavidus basilensis SRS

The H-02 constructed wetland was designed to remove metals (primarily copper and zinc) to treat building process water and storm water runoff from multiple sources associated with the Tritium Facility at the DOE-Savannah River Site, Aiken, SC. The concentration of Cu and Zn in the sediments has increased over the lifetime of the wetland and is a concern. A bioremediation option was investigated at the laboratory scale utilizing a newly isolated bacterium of the copper metabolizing genus Cupriavidus isolated from Tim’s Branch Creek, a second-order stream that eventually serves as a tributary to the Savannah River, contaminated with uranium and other metals including copper, nickel, and mercury. Cupriavidus basilensis SRS is a rod-shaped, gram-negative bacterium which has been shown to have predatory tendencies. The isolate displayed resistance to the antibiotics ofloxacin, tetracycline, ciprofloxacin, select fungi, as well as Cu2+ and Zn2+. Subsequent ribosomal sequencing demonstrated a 100% confidence for placement in the genus Cupriavidus and a 99.014% match to the C. basilensis type strain. When H-02 wetland samples were inoculated with Cupriavidus basilensis SRS samples showed significant (p < 0.05) decrease in Cu2+ concentrations and variability in Zn2+ concentrations. Over the 72-h incubation there were no significant changes in the inoculate densities (106–108 cells/ML) indicating Cupriavidus basilensis SRS resiliency in this environment. This research expands our understanding of the Cupriavidus genus and demonstrates the potential for Cupriavidus basilensis SRS to bioremediate sites impacted with heavy metals, most notably copper.

Evaluation of changes in the microbial community structure in the sediments of a constructed wetland over the years.

This study presents the results of the long term (2007-2014) monitoring of the microbial community structure in the surface sediments of the H-02 constructed wetland system, which was built on the Savannah River Site in Aiken, SC, USA, to treat the waste water generated at the Tritium facility. Microbial community structure provides valuable information about the functioning of constructed wetlands and helps understand the biogeochemical cycling of nutrients and contaminants. Phospholipids fatty acid (PLFA) analysis and qPCR were used to identify major bacterial phyla in the sediments. The physiochemical properties of the sediments were also used to deduce potential effects on the microbial community structure over the years. Sulfate-reducing bacteria (SRB) were the most dominant bacterial groups, and their prevalence was progressively increasing throughout the years most likely on the account of methane producers. Concentrations of trace metals (copper and zinc) were negatively associated with methane producers and oxidizer while positively correlated with SRB. Overall, the H-02 wetland system was efficient in immobilizing copper and zinc through the anaerobic respiration of sulfate by SRB and minimizing methane emission through the progressive elimination of methane producers by SRB and Geobacter. The aim of this study was to monitor the changes in the microbial community structure in the surface sediments of a constructed wetland during the first 7years of operation.

Thermal Stability Testing of LANA.75

Savannah River Site has used the metal hydride LaNi4.25Al0.75 (LANA.75) in the Tritium Facilities for over two decades. LANA.75 beds store significant quantities of tritium but have a limited service life due to the radiolytic decay of tritium to 3He within the metal matrix. It has been shown that the isotherm performance of a tritium-aged LANA.75 sample can be restored by heating under vacuum. Additional investigation is needed to ensure there are no unexpected changes to the hydride before this technique is employed in full-scale beds in the Tritium Facilities. In addition, it is necessary to verify the regenerable behavior and thermal stability of LANA.75 on a small scale prior to it being implemented on a large scale. A non-tritiated bench-scale LANA.75 sample was held at 750°C under vacuum for 200 h to simulate exposure to multiple restoration evolutions. Hydride isotherm performance, chemical composition, crystallinity, and morphology are compared between the pre-restorative and post-restorative testing samples. No significant changes were observed in composition or crystallinity. Comparison of pre-anneal and post-anneal isotherms showed that performance improved rather than deteriorated during the evolution. Scanning electron microscopy analysis showed small growths on the particle surface after exposure to regeneration conditions. Additional testing will be required to determine the cause of these growths.

Expected Environmental Effects of Long-Term Tritium Supply—Lessons Learned

Fusion reactors are considered an almost unlimited source of power for the future, with tritium [deuterium-tritium (D-T) mixture] being the most convenient fuel for these facilities. Due to tritium-specific features and its self-radioactivity there are a number of issues when handling a large amount of tritium for long-term operations of fusion reactors. This paper presents research results of tritium behavior in the D-T mixture and in the environment during operations at tritium facilities. The results provide the basis for an assessment of the future environmental effects of long-term operation of a fusion reactor/tritium facility. The results of experimental and modeling studies include tritium reactions with carbon oxides under radiolysis, radiolysis of DTO, tritium dispersion in atmosphere under rough terrain, tritium oxide washout from atmosphere, tritium oxidation in soil with soil bacteria, tritium oxide migration in the unsaturated soil layer, and tritium uptake by plants, crops, and lichens. Both experimental and observational data have been used to develop models to predict tritium behavior in the environment under similar conditions. The models have been verified and validated.

Preoperational Monitoring of an Experimental Pilot Plant for Tritium and Deuterium in Surface Water at Valcea, Romania

The paper reports the monitoring of the surface water radioactivity variations in the region surrounding the Experimental Pilot Plant for Tritium and Deuterium Separation for an experimental period with a duration of one year. The primary goal of the radioactivity monitoring of the environmental factors in the preoperative stage is to establish the baseline levels of radioactive concentrations present in the environment. Two surface water sampling points in the Olt River, Valcea, Romania were selected. The first was upstream of the discharge point of the “Deversor Olt” as the background location and the second was downstream of the liquid effluent discharge point as the indicator location. The activity concentration measurements were carried out on surface water samples from locations established on the Olt River in the vicinity of the magistrate channel “Deversor Olt” on a weekly basis. The employed analytical methodology was high resolution gamma ray spectrometry with the use of a high purity germanium detector. The observed activity concentration for 40K was less than 1.17 Bq·l−w. The activities of the analyte radionuclides, including 7Be, 51Cr, 60Co, 65Zn, 137Cs, 226Ra, 235U, were below the detection limits. The results recorded for the background location were slightly different compared with the values recorded in the indicator location, but the differences were statistically insignificant. The nuclear activity in the preoperational stage of the Experimental Pilot Plant for Tritium and Deuterium Separation facility has not had any impact on the environment to date. This study creates a unique database that may be relevant for further operational monitoring of the Experimental Pilot Plant for Tritium and Deuterium Separation.

The RMC Method to Handle Tritium Efficiently and Safely

When it comes to the task of handling gaseous tritium, the challenge is to reduce losses of this precious, gaseous, hydrogen isotope. The driving force to achieve this is based on three requests: 1. Improve the safety and efficiency by spotting losses of gaseous tritium. 2. Embed the real-time tritium monitoring in the process and safety automation. 3. Be transparent in the whole workflow for its own safety and for auditable compliance. Many good and accepted single devices and working procedures have been proposed and used already. By introducing the Smolsys Ltd.® Radio Medical Container (RMC) method, a team at Smolsys Ltd. has brought the efficient and safe handling of tritium to a new performance level. The idea of the RMC method is to combine many of those approved single devices for gaseous tritium handling and link the workflow logically and digitally in a well-controllable confinement. In the case of the RMC, the working space or room is a container in which the working places and machines are run; hence, the room itself becomes part of the production process and tritium machine. It is monitored and controlled by the process logic and as such becomes a smart and digitized RMC for more safety and efficiency in tritium handling. This paper presents the RMC based on a realized tritium-processing factory in Switzerland. This RMC is a fully engineered tritium facility with a designed and engineered safety factor and is very flexible to be customized. The RMC is also transportable since standard container sizes are used.

Validation of Tritium Protection Factors of Respiratory Protective Equipment: Setup and Initial Tests

Several types of radiological respiratory protective equipment (RPE) are used in tritiated environments at nuclear facilities and nuclear power plants to protect workers in those environments. It is crucial that the level of protection the RPE provides is well understood. A tritium protection factor (PF) may be assigned to RPE. The PF is often defined as the ratio of the tritium concentration in the ambient air to the tritium concentration in the breathing air. Field observations at Canada Deuterium Uranium (CANDU) nuclear plants indicate that the in-use PFs are too conservative and do not represent actual internal uptakes following work in tritiated atmospheres. To improve radioactive work planning and work execution efficiency, more accurate tritium PFs are needed to cover the variety of personal radiological RPE currently in use. In order to test PFs of RPE, Kinectrics has designed, manufactured, and commissioned a tritium facility, referred to as the tritium exposure box (TEB), through support from the CANDU Owners Group. The TEB is a self-contained enclosure that permits the use of a full-sized mannequin with RPE for testing in a tritium oxide atmosphere. Tritium concentrations of up to 3.7 × 108 Bq/m3 may be achieved and maintained inside the TEB. The clean airflow to an air-supplied suit may range from 420 to 800 standard liters per minute. Following the successful commissioning of the TEB, Kinectrics has performed testing of an air-supplied plastic suit to determine the protection provided.

Genomic Characterization of a Mercury Resistant Arthrobacter sp. H-02-3 Reveals the Presence of Heavy Metal and Antibiotic Resistance Determinants

Nuclear production and industrial activities led to widespread contamination of the Department of Energy (DOE) managed Savannah River Site (SRS), located in South Carolina, United States. The H-02 wetland system was constructed in 2007 for the treatment of industrial and storm water runoff from the SRS Tritium Facility. Albeit at low levels, mercury (Hg) has been detected in the soils of the H-02 wetland ecosystem. In anoxic sediments, Hg is typically methylated by anaerobic microbiota, forming the highly neurotoxic methylmercury (MeHg), which biomagnifies across food webs. However, in surficial oxic wetland soils, microbially mediated demethylation and/or volatilization processes can transform Hg2+ into the less toxic Hg0 form which is released into the atmosphere, thus circumventing MeHg formation. To obtain a deeper understanding on bacterial Hg volatilization, a robust Hg-resistant (HgR) bacteria, called as strain H-02-3 was isolated from the H-02 soils. A draft genome sequence of this strain was obtained at a coverage of 700×, which assembled in 44 contigs with an N50 of 171,569 bp. The genomic size of the strain H-02-3 was 4,708,612 bp with a total number of 4,240 genes; phylogenomic analysis revealed the strain as an Arthrobacter species. Comparative genomics revealed the presence of 1100 unique genes in strain H-02-3, representing 26.7% of the total genome; many identified previously as metal resistance genes (MRGs). Specific to Hg-cycling, the presence of mercuric ion reductase (merA), the organomercurial lyase (merB), and the mercuric resistance operon regulatory protein, were identified. By inference, it can be proposed that the organomercurial lyase facilitates the demethylation of MeHg into Hg2+ which is then reduced to Hg0 by MerA in strain H-02-3. Furthermore, gene prediction using resistome analysis of strain H-02-3 revealed the presence of several antibiotic resistance genes (ARGs), that statistically correlated with the presence of metal resistant genes (MRGs), suggesting co-occurrence patterns of MRGs and ARGs in the strain. Overall, this study delineates environmentally beneficial traits that likely facilitates survival of Arthrobacter sp. H-02-3 within the H-02 wetland soil. Finally, this study also highlights the largely ignored public health risk associated with the co-development of ARGs and MRGs in bacteria native to historically contaminated soils.

Polymer Performance and Aging in a Tritium Environment

In an ideal tritium system, we would be able to remove all polymer components due the damage incurred by the resulting beta decay and reduce the required maintenance of the systems and its components. However, polymers are an integral material used within the Tritium Facility in sealing, joining, and containment and are used in several different systems within the process. With the loss of certain capabilities, such as the Normetex pump, it is necessary to identify and/or develop polymers that can better withstand exposure to beta radiation in tritium environments. This article reviews the various polymer resins and formulations that are used in a tritium environment, their properties, and their performance.

Performance Testing of a Potential Replacement for Normetex Pump

Normetex® Model 15 scroll pump backed by metal bellows (MB) pump made by Senior Aerospace Inc. has been the preferred technology for use in tritium facilities world-wide. Normetex pumps are no longer available and identification of alternate pumps is required for performance and compatibility with tritium gas. Many of the pumps that could be used to meet the functional performance requirements (e.g. pressure and flow conditions) of the Normetex pump have features that include the use of polymers or oils and greases that are not directly compatible with tritium service. Though they are less desirable, alternative pumps may be used in tritium service with appropriate engineered controls to mitigate the impact of degraded organic compounds. These alternative pumps require characterization for potential application in tritium service. One pump that has been identified as a potential replacement for the Normetex pump in some tritium service applications is the Edwards nXDS15iC. A series of pump tests were completed using this pump as a candidate replacement pump. The purpose of the pump testing is two-fold: (1) obtain baseline vacuum pump characteristics for the replacement pump intended for use in tritium service; and (2) verify that low pressure hydrogen gas can be transported over various distances up to 92 meters (300 feet) by the candidate pump. A series of pump tests were performed at various configurations using hydrogen gas (no tritium) and nitrogen to ensure that this pump can meet the performance requirements. The Edwards pump meets the desired functional performance requirements, though there are other tradeoffs that must be considered. As for cost considerations, the Edwards scroll pump costs about ten (10) times less than a Normetex-equivalent scroll pump, which would significantly reduce initial start-up costs in a facility. However, the lifetime of the Edwards pump in a nearly pure tritium process stream is speculated to be only 3–6 months due to the polymer tip seals, whereas the all-metal Normetex pump can last for 5 years. Each application must determine whether the alternative pump considerations outweigh the cost differential. This paper summarizes the results of the tests that have been performed using various pump configurations.

Decontamination of Proton Exchange Membranes After Tritium Exposure

Canadian Nuclear Laboratories (CNL) is developing a Proton Exchange Membrane-based (PEM) electrolyser intended for tritium removal. Commercially available Nafion® N-1110 membranes have been exposed to tritiated water (with a β activity of about 37 GBq/mL) prepared in the Tritium Facility at CNL. Three equivalent batches of Nafion® N-1110 membranes (each with a dimension of 4 cm × 4 cm) were exposed to β-doses of 67 kGy, 155 kGy, and 255 kGy, respectively.The exposed membranes required decontamination for characterization and testing. A few different decontamination methods have been experimentally studied. These methods can be categorized as water elution and chemical soaking. The measured tritium concentration in eluent decreased quickly in the first 30 days of water elution, followed by a slow decay afterwards until reaching a plateau after about 100 days. Chemical soaking proved to be more effective than the water elution method and high temperature facilitated the tritium release.

Design options to minimize tritium inventories at Savannah River

Large quantities of tritium are stored and processed at the Savannah River Site (SRS) Tritium Facilities. In many design basis accidents (DBAs), it is assumed the entire tritium inventory of the in-process vessels are released from the facility and the site for inclusion in public radiological dose calculations. Pending changes in public dose calculation methodologies are driving the need for smaller in-process tritium inventories to be released during DBAs. Reducing the in-process tritium inventory will reduce the unmitigated source term for public dose calculations and will also reduce the production demand for a lower inventory process. This paper discusses process design options to reduce in-process tritium inventories. A Baseline process is defined to illustrate the impact of removing or replacing La-Ni-Al alloy tritium storage beds with palladium (Pd) or depleted uranium (DU) storage beds on facility in-process tritium inventories. Elimination of La-Ni-Al alloy tritium storage beds can reduce in-process tritium inventories by over 1.5kg, but alternate process technologies may needed to replace some functions of the removed beds.

A New Hydrogen Processing Development System

The design of many of the process systems at the Savannah River Site (SRS) Tritium Facilities were developed at the Savannah River National Laboratory (SRNL) in the 1980’s and early 1990’s for Cold War production requirements. Most of the process systems developed used cold (non-radioactive) test systems to reduce the cost of developing pilot and full-scale test systems. The metal hydride (MH) based process technologies developed for the Replacement Tritium Facility (RTF) allowed tritium process equipment to be confined in tritium stripped glovebox systems which greatly reduced tritium emissions to the public. Facility start-up in 1994 was considered state-of-the art technology for the world’s largest metal hydride based tritium process facility. The end of the Cold War reduced production requirements, but increased maintenance is needed for the 20 year old process systems. The Hydrogen Processing Development System (HPDS) is a new, non-radiological R&D system to be built for testing and demonstrating improved process systems for SRS Tritium Facilities. Experience gained from facility operations and new concepts from fusion fuel cycle development programs will be used to develop improved processes and restore base capabilities of the SRS Tritium Facilities. The HPDS will be designed to test systems such as a Revised Unloading Purification System (RUPS), an optimized advanced storage and isotope separation (OASIS) System, a Reduced Area Confinement and WAter Processing (RACWAP) System, and some components of a separate breeding and extraction program. New processes would retain the desirable features of the current/existing technologies while creating “right-sized” and flexible advanced or hybrid system to meet current and future tritium processing needs. Testing in the HPDS will reduce the cost and risk of deploying new technologies into the SRS tritium production process.

Production of Highly Tritiated Water for Tritium Exposure Studies

From inception to completion, this paper provides a brief description of the design and processes used in the production and dispensing of highly tritiated water in the Tritium Facility at Chalk River Laboratories.

Thermal Release of 3He from Tritium Aged LaNi4.25Al0.75 Hydride

Recently, the demand for He-3 has increased dramatically due to widespread use in nuclear nonproliferation, cryogenic, and medical applications. Essentially all of the world’s supply of He-3 is created by the radiolytic decay of tritium. The Savannah River Site Tritium Facilities (SRS-TF) utilizes LANA.75 in the tritium process to store hydrogen isotopes. The vast majority of He-3 “born” from tritium stored in LANA.75 is trapped in the hydride metal matrix. The SRS-TF has multiple LANA.75 tritium storage beds that have been retired from service with significant quantities of He-3 trapped in the metal. To support He-3 recovery, the Savannah River National Laboratory (SRNL) conducted thermogravimetric analysis coupled with mass spectrometry (TGA-MS) on a tritium aged LANA.75 sample. TGA-MS testing was performed in an argon environment. Prior to testing, the sample was isotopically exchanged with deuterium to reduce residual tritium and passivated with air to alleviate pyrophoric concerns associated with handling the material outside of an inert glovebox. Analyses indicated that gas release from this sample was bimodal, with peaks near 220 and 490°C. The first peak consisted of both He-3 and residual hydrogen isotopes, the second was primarily He-3. The bulk of the gas was released by 600 °C.

Thermal Enhancement Cartridge Heater Modified Tritium Hydride Bed Development. Part II — Experimental Validation of Key Conceptual Design Features

Thermal Enhancement Cartridge Heater Modified (TECH Mod) tritium hydride bed is an interim replacement for the 1st generation (Gen 1) process hydride beds currently in service in the Savannah River Site (SRS) Tritium Facilities. Three new features are implemented in the TECH Mod hydride bed prototype: internal electric cartridge heaters, porous divider plates, and copper foam discs. These modifications will enhance bed performance and reduce costs by improving bed activation and installation processes, in-bed accountability measurements, end-of-life bed removal, and He-3 recovery.A full-scale hydride bed test station was constructed at the Savannah River National Laboratory (SRNL) in order to evaluate the performance of the prototype TECH Mod hyd ride bed. Controlled hydrogen (H2) absorption/desorption experiments were conducted to validate that the conceptual design changes have no adverse effects on the gas transfer kinetics or H2 storage/release properties compared to those of the Gen 1 bed. Inert gas expansions before, during, and after H2 flow tests were used to monitor changes in gas transfer rates with repeated hydriding/dehydriding of the hydride material. The gas flow rates significantly decreased after initial hydriding of the material; however, minimal changes were observed after repeated cycling. The data presented herein confirm that the TECH Mod hydride bed would be a suitable replacement for the Gen 1 bed with the added enhancements expected from the advanced design features.

Thermal Enhancement Cartridge Heater Modified (Tech Mod) Tritium Hydride Bed Development Part I – Design and Fabrication

The Savannah River Site (SRS) tritium facilities have used 1st generation (Gen1) LaNi4.25Al0.75 (LANA0.75) metal hydride storage beds for tritium absorption, storage, and desorption. The Gen1 design utilizes hot and cold nitrogen supplies to thermally cycle these beds. Second and 3rd generation (Gen2 and Gen3) storage bed designs include heat conducting foam and divider plates to spatially fix the hydride within the bed. For thermal cycling, the Gen2 and Gen 3 beds utilize internal electric heaters and glovebox atmosphere flow over the bed inside the bed external jacket for cooling.The currently installed Gen1 beds require replacement due to tritium aging effects on the LANA0.75 material, and cannot be replaced with Gen2 or Gen3 beds due to different designs of these beds. At the end of service life, Gen1 bed desorption efficiencies are limited by the upper temperature of hot nitrogen supply. To increase end-of-life desorption efficiency, the Gen1 bed design was modified, and a Thermal Enhancement Cartridge Heater Modified (TECH Mod) bed was developed. Internal electric cartridge heaters in the new design to improve end-of-life desorption, and also permit in-bed tritium accountability (IBA) calibration measurements to be made without the use of process tritium. Additional enhancements implemented into the TECH Mod design are also discussed.

A Low Tritium Hydride Bed Inventory Estimation Technique

A nominal 1500 STP-L Passively Cooled, Electrically heated hydride (PACE) Bed was developed and deployed into tritium service in Savannah River Site (SRS) Tritium Facilities. Process beds to be used for low concentration tritium gas were not fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory measurement method: In-Bed Accountability (IBA). In some instances, two physical beds, or canisters, were joined together with one process line connection, creating a bed with a total capacity of nominally 3000 STP-L or up to 815 grams of tritium. The IBA detection limit for these beds was estimated to be 9.75 grams tritium. After deployment of these low tritium beds, the need arose to estimate tritium inventories of these beds without installation of IBA instrumentation. Two methods have been developed to estimate the tritium inventory of these low tritium content beds. The first approach assumes the bed is half-full and uses a gas composition measurement to estimate the tritium inventory and uncertainty. The second approach utilizes the bed’s hydride material pressure-composition-temperature (PCT) properties and a gas composition measurement to reduce the uncertainty in the calculated bed inventory.

Honeycomb Palladium Catalyst for the Oxidation of Tritiated Hydrocarbons Produced in Tritium Facilities

We have developed a honeycomb palladium catalyst to be used for the oxidation of tritiated hydrocarbons. Since the suitable loading rate of palladium deposited on the base material is a technical point, honeycomb-shaped palladium catalysts of three different loading rates—2, 5, and 10 g/L—were prepared to investigate the effect of loading rate of palladium on reaction rate in this study. Tritiated methane was selected as the typical hydrocarbon. A 12 m3 tank was prepared to prevent tritiated methane at tracer concentration fed to the catalytic reactor from fluctuating. The overall reaction rate constant for tritiated methane oxidation on the honeycomb palladium catalyst was determined with a flow-through system as a function of space velocity from 1000 to 6300 h−1, methane concentration in carrier from 0.004 to 100 ppm, and temperature of catalyst from 322 to 673 K. The honeycomb palladium catalyst without pretreatment for activation initially lowers the overall reaction rate constant at lower temperatures. However, the constant recovers steeply to the original value during the continuous combustion of tritiated methane. The loading rate of palladium deposited on the base material has little effect on reaction rate for tritiated methane combustion. The overall reaction rate constant is proportional to the space velocity. The overall reaction rate constant is independent on the methane concentration when it is less than 10 ppm.