Tritium Balance Research Articles

A 2D finite element modelling of tritium permeation for the HCLL DEMO blanket module

A local finite element modelling of the tritium permeation through the HCLL breeder unit cooling plates is presented. The tritium concentration in the helium and in the lithium lead are evaluated by solving partial differential equations governing the tritium balance, the thermal field and the lithium lead velocity field in a simplified 2D-geometrical representation of the breeder unit at the mid-equatorial plan. Using a factorial design at two levels as numerical experiments it is shown that the magnetic field and the natural convection are not relevant for the estimation of the permeation. Moreover, numerical analyses showed a developed concentration boundary layer acting as a mass transfer resistance which is equivalent to a PRF of 30.

Tritium balance in macro‐scale river basins analysed through distributed hydrological modelling

AbstractThe recession of bomb tritium in river discharge of large basins indicates a contribution of slowly moving water. For an appropriate interpretation it is necessary to consider different runoff components (e.g. direct runoff and ground water components) and varying residence times of tritium in these components. The spatially distributed catchment model (tracer aided catchment model, distributed; TACD) and a tritium balance model (TRIBIL) were combined to model process‐based tritium balances in a large German river basin (Weser 46 240 km2) and seven embedded sub‐basins. The hydrological model (monthly time step, 2 × 2 km2) estimated the three major runoff components: direct runoff, fast‐moving and slow‐moving ground water for the period of 1950 to 1999. The model incorporated topography, land use, geomorphology, geology and hydro‐meteorological data. The results for the different basins indicated a contribution of direct runoff of 30–50% and varying amounts for fast and slow ground water components. Combining these results with the TRIBIL model allowed us to estimate the residence time of the components. Mean residence times of 8 to 14 years were found for the fast ground water component, 21 to 93 years for the slow ground water component and 14 to 50 years for an overall mean residence time within these basins. Balance calculations for the Weser basin indicate an over‐estimation of loss of tritium through evapotranspiration (more than 60%) and decay (10%). About 28% were carried in stream‐flow where direct runoff contributed about 12% and ground water runoff 13% in relation to precipitation input over the studied 50‐year period. Neighbouring basins and nuclear power plants contributed about 1% each over this time period. Copyright © 2007 John Wiley & Sons, Ltd.

Tritium balance modelling in a macroscale catchment

AbstractTritium concentrations measured in precipitation and discharge are combined with hydrological and meteorological information on a monthly basis over a period of 50 years in order to study tritium balances and hydrological interactions in macroscale catchments. Three subcatchments of the Weser River in Germany (Werra 5410 km2, Fulda 6890 km2 and Weser‐1 15 320 km2) were used to test a tritium balance model, to study residence times, groundwater storage behaviour and tritium load of different water balance components. A comparison of measured and modelled tritium concentrations in discharge showed considerable fits with model efficiencies close to 0·7. The estimated residence times for an estimated fast and slow groundwater component are between 5 to 8 years and 7 to 28 years respectively. The results indicate a tritium load of 12 to 14% of the precipitation input over the whole time period moving through groundwater reservoirs and 13 to 16% transported through direct discharge. Copyright © 2005 John Wiley & Sons, Ltd.

The Prediction of Tritium Level Reduction of Wolsong NPPs by Heavy Water Detritiation with WTRF

The amount of the tritium removed from the Wolsong NPPs after the WTRF operation start was simulated through the modeling of the tritium balance between the Wolsong NPPs and the WTRF. Five WTRF operating scenarios were proposed and the profiles of the tritium level depending on these scenarios were obtained from the simulation. It was predicted that about 9×1017 Bq/yr of tritium would be removed in the beginning of WTRF operation. However the tritium levels in the moderators will be steadily reduced and saturated less than 3×1011 Bq/kg in 2013, and then about 2×1017 Bq/yr of tritium will be removed from the Wolsong NPPs by the WTRF operation.

Tritium particle balance and retention during DT discharges in JET

The tritium balance based on pressure measurements in the divertor was performed for the DTE1 campaign carried out at JET in 1997. This is a complementary analysis to the integrated tritium inventory already reported for a full day of experiments. The particle balance shows that the T flux retention is about 1.26×1021 T s−1 during a plasma pulse (∼65% of the injected flux). Outgasing between pulses reduces this T inventory to about 30% of the injected fluence. This detailed gas balance also shows that the retention of hydrogen species depends on the plasma isotopic ratio. However, during the D clean-up pulses, the amount of T removed by isotopic exchange is shown to be limited to about 2×1023 T. Finally, the total particle balance (D+T) is shown to be independent of the plasma isotopic ratio.

Qualification of tritium permeation barriers in liquid Pb–17Li

The reduction of tritium permeation from the Pb–17Li, or plasma, into the coolant is of crucial importance in order to reduce the radiological hazard in the steam generator vault as well as in the turbine/condenser area and to optimise the tritium balance in the reactor. The use of aluminium rich coatings has been selected as reference solution for the water cooled lithium lead (WCLL) blanket in order to produce reliable tritium permeation barriers (TPB). TPB qualification activities performed in the past allowed the selection of two reference deposition techniques, the chemical vapour deposition (CVD) process developed on laboratory scale by CEA, and the hot dipping (HD) process developed by FZK. On the basis of the results obtained in the past with the Corelli I–II devices, a new apparatus named Vivaldi was designed to perform comparative tests on two hollow cylindrical specimens in the same operating conditions. The performance of alumina coating on EUROFER 97 steel has been tested in gas and liquid metal phase. The obtained results in terms of permeated fluxes and permeation reduction factors (PRF) are herein presented and discussed. A post experiment examination of coatings was performed by use of optical and SEM microscopy.

Fusion nuclear technology issues studied on the JET facilities

The Joint European Torus (JET) machine was built from the beginning to perform DT studies and is for the next decade the only machine with DT capability. JET is thus the tokamak best suited for studies of various nuclear technology issues that will be of importance for future DT fuelled machines. The Active Gas Handling System (AGHS) built for the supply and reprocessing of tritium is still in operation to detritiate the exhaust gases and to provide the necessary ventilation during vessel openings because >1 g of tritium remain in the machine even 4 years after the DTE1 campaign. The tritium is bound in co-deposited layers and flakes formed mainly on the shadowed inner part of the divertor, and in the bulk of tiles. Areas of erosion and deposition are being identified and preliminary models for the material movement developed. Characterisation of the properties of tiles and flakes is very important to develop the best handling techniques. Due to the activation of the machine and the use of Be and T entry to the torus is limited by the need to minimise worker doses and is currently only possible in full pressurised suite. Work inside it is, therefore, performed with remote handling tools where practicable, e.g. the removal of the divertor septum and the collection of dust and flakes from areas below the divertor to achieve a more accurate tritium balance. Techniques need to be developed to reduce the tritium content in waste to permit disposal as low level waste (<12 kBq/g) and to recover tritium for re-use. Validation of activation models, understanding of the risks due to inhalation of tritiated particles and the local environmental impact of tritium are further important aspects. The paper presents various nuclear issues studied at JET due to activation and tritium.

Strong build nanocoat

The IFMIF Tritium Release Test Module (TRTM) is projected to measure online the tritium release from breeder ceramics and beryllium pebble beds under high energy neutron irradiation. Tritium produced in the pebble bed of TRTM is swept out continuously by a purge gas flow, but can also permeate into the module's metal structures, and can be lost by permeation to the environment. According analyses on the tritium inventory are performed to support IFMIF plant safety studies, and to support the experiment planning. This paper describes the necessary elements for calculation of the tritium transport in the Tritium Release Test Module as follows: (i) applied equations for the tritium balance, (ii) material data from literature and (iii) the topological models and the computation of the five different cases; namely release of tritium from the breeder solid material into the purge gas, loss of tritium over the capsule wall, rig hull, container wall and purge gas return line in detail. The problem of tritium transport in the TRTM has been studied and analyzed by the Tritium Migration Analysis Program (TMAP) and the adapted fusion-devoted Tritium Permeation Code (FUS-TPC). TMAP has been developed at INEEL and now exists in Version 7. FUS-TPC Code was written in MATLAB with the original purpose to study the tritium transport in Helium Cooled Lead Lithium (HCLL) blanket and in a later version the Helium Cooled Pebble Bed (HCPB) blanket by [6] (Franza, 2012). This code has been further modified to be applicable to the TRTM. Results from the computations for the five computational cases concerning safety and experiment analyses are presented.

Tritium Issues Toward Fusion Plants

ABSTRACTTechnical issues on tritium technology are investigated from the aspects of processing, safety and fuel supply, considering the concept of DEMO plant following ITER as the next target. Fusion plant equipped with power blanket will contain high temperature heat transfer medium and bred tritium in a tritium cycle. Although the inventory and throughput may not increase drastically from ITER, tritium plant will require significant technical improvements characterized by the self-consistent tritium fuel cycle and safety function to maintain the tritium level in the power train at adequately low level. Tritium balance issue will be one of the most important features because it will strongly affect the fusion in energy market by supplying initial loading. Tritium processing for coolant that will be mainly used for normal operation will dominate the safety feature of the entire plant by its technical difficulty and importance. Under off-normal conditions, this coolant tritium process can remove possible spill within the confinement, and thus fusion plant will not have any major process dedicated for accidents. Tritium technology is essential to make fusion energy attractive from the aspect of socio-economics, and its success in development is of vital importance toward fusion power plant as viable energy source for future.

A New Approach for Assessing the Required Tritium Breeding Ratio and Startup Inventory in Future Fusion Reactors

Accurately estimating the required tritium breeding ratio (TBR) λr in fusion reactor systems is necessary to guide fusion research and development and to assess the feasibility of fusion reactors as a self-sufficient energy source. This is especially true when one considers the limits imposed by the present-day breeding performance of breeder blanket candidates. Studies of this subject have been performed in the past, with particular emphasis on developing appropriate dynamic simulations of the fuel cycle. In the last few years, development of new dynamic and integrated fusion fuel cycle tritium computer codes has moved away from general residence-time models and instead incorporated more comprehensive and realistic models. Furthermore, detailed and rigorous computer codes that model the dynamic retention behavior of individual components inside the fuel cycle, in particular the torus plasma-facing components in a tokamak, have been vastly improved with uncertainties identified. A more efficient and intuitive methodology for tritium self-sufficiency analyses is developed based on an analytical scheme that makes use of different types of tritium inventories inside the fuel cycle as calculated from detailed numerical simulations. Short-term and long-term tritium inventories are differentiated as well as tritium lost through waste material. Also, the tritium fuel cycle is split into a number of independent tritium migration paths to aid in the development of an integrated tritium balance for which λr or other parameters of interest can be solved analytically. Tritium startup requirements are also examined. An important side benefit derived from using the aforementioned methodology is that the uncertainty in λr for a given reactor design can easily be calculated from uncertainty ranges characterizing a number of relevant reactor operation and fuel cycle parameters. Maximum tritium inventory limits were considered from safety and operational standpoints. A wide range of parametric studies were conducted with various scenarios to forecast changes in λr when the reactor design is modified. For example, it was determined that with most current estimates of the achievable TBR λa, ranging from 1.04 to 1.07, a small design window for both the fuel fractional burnup and the downtime of tritium reprocessing components severely limits any proposals for a reactor operating scenario that will be valid for a reasonably paced fusion growth rate.

Control Methods of Cryogenic Distillation Column Processing Plasma Exhaust Gas

Two control methods of the column processing the plasma exhaust gas are proposed in the present study. A method is that the flow rate of the middle product stream is adjusted from the tritium balance around the column. The flow rate of bottom product stream is adjusted by a feedback control loop. In the other method, the flow rate of middle product stream is adjusted by a feedforward control loop from the tritium feed rate by the plasma exhaust gas. The flow rate of bottom product stream is adjusted by a feedback control loop. The later method always gives successful results against the appreciable fluctuations for the flow rate and composition of the plasma exhaust gas.

Radiocarbon speciation and distribution in an aquifer plume and groundwater discharge area, Chalk River, Ontario

The storage of low level radioactive waste in trenches overlying an unconfined groundwater flow system in sands has generated a contaminant plume (with chemical characteristics of dilute sanitary landfill leachate) containing 14C both as dissolved inorganic and organic C. In the groundwater, dissolved organic compounds account, on average, for 22% of the total C and 10% of the 14C. Approximately 300 m from the waste management site, the groundwater discharges to the surface in a wetland containing up to 3 m of peat and an extensive tree cover. Drainage from the wetland passes through a gauged stream. Radiocarbon input to the groundwater discharge area in 1991 was determined to be between 3.3 and 4.2 GBq, based on data from a line of sampling wells along the groundwater input boundary of the wetland, with control provided by water and tritium balance data. During the 1991 study year, only 1.5–2% of both the inorganic and organic 14C inputs left the wetland in surface water drainage. Vegetation growth in the wetland during the study year contained 8–10% of the released radiocarbon. If the rate of 14C accumulation in the peat has been constant, 7–9% of the annual radiocarbon input has been retained in the organic soil. Much of this soil accumulation can be attributed to litter from standing vegetation, making distribution coefficients an inappropriate model for 14C partitioning between groundwater and soil. The plant/soil 14C concentration ratio was 24 to 33, but application of a concentration ratio to describe the transfer of radiocarbon to plants is also believed to be inappropriate. This study indicates that over 80% of the groundwater radiocarbon is rapidly lost to the atmosphere when the groundwater comes to surface, and we infer that most of the 14C accumulation in vegetation occurs by CO 2 transfer from the air to the plant.

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H2S and H2O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

To elucidate the effect of H2S and H2O on hydrogen exchange reactions between tetralin and gaseous hydrogen, the reactions of tetralin with tritiated hydrogen in the presence of H2S or H2O were performed under practical coal liquefaction conditions. The amounts of hydrogen exchange between tetralin and tritiated hydrogen were estimated from hydrogen and tritium balance. The conversions of tetralin in the presence and absence of H2S at 400 °C for 300 min were 4.1 and 3.9%, respectively, while the hydrogen exchange ratio (HER) of tetralin remarkably increased from 4.6% to 40.4% in the presence of H2S and reached 71% at 400 °C for 600 min. It was suggested that the hydrogen exchange mechanism of tetralin with hydrogen in the presence of H2S would include a different mechanism from that in the absence of H2S. It was considered that the H2S molecule acted as both an initiating species and an HS• radical and rapidly abstracted and added hydrogen atom reversibly, promoting the hydrogen exchange in both an aromatic ring and a naphthene ring. In addition to the radical mechanism, the electrophilic exchange with a proton formed from hydrogen sulfide was proposed for the hydrogen exchange mechanism. On the other hand, the conversion and HER of tetralin in the presence of H2O at 400 °C for 300 min were 1.7 and 1.3%, respectively. These values were smaller than those in the absence of H2O. It was considered that H2O inhibited the formation of tetralyl radicals and the hydrogen transfer from tritiated hydrogen to tetralyl radicals. The tritium distribution in H2S reached equilibrium at the initial stage of the reaction, and the hydrogen exchange reaction between gaseous hydrogen and H2S rapidly occurred. However, it was estimated that the hydrogen exchange reaction between gaseous hydrogen and H2O was slower than that with H2S.

Methodical Aspects of Modelling the Water and Tritium Balance of the Unsaturated Zone

Abstract Detailed investigations of the unsaturated zone in regard to water and tritium balance and tritium input into groundwater are necessary especially in the case of thick and inhomogeneous aeration zone (different soil layers, clay horizons etc.) and inhomogeneous land utilization. The paper shows a method to quantify water and tritium movement and storage in unsaturated zone by means of a two-dimensional conceptual box model called BOWAM(T). The model was tested on 4 sandstone aquifers in the Finne region (brink of the Thuringia basin). The results show that water balance depends strongly on surface morphology and infiltration capacity, non- or semiconducting layers within aeration zone, land usage (forest, agriculture, meadow…) and atmospheric conditions. Especially runoff, evapotranspiration and groundwater recharge at Finne region have a sensitive variation. Naturally, the tritium balance is connected with water balance. There is a difference in tritium input functions into groundwater between c...

The control of tritium in ETHEL

The operation of the European Tritium Handling Experimental Laboratory (ETHEL) will require the implementation of means and procedures for allowing tritium control within the facility. For that purpose, account must be taken of the particular characteristics of tritium, such as its high mobility, capacity to dissolve in materials, often limited precision when performing inventory measurements. This paper estimates the influence of these effects on the overall tritium balance in ETHEL. By employing available models for predicting tritium hold-up, it is estimated that three to four grams of tritium may potentially remain irreversibly fixed in various plant items of the standard laboratory infrastructure (exclusive of experimental circuits). On the other hand, the highest overall precision that may be attained with the present plant regarding inventory measurements is estimated to be of the order of few percent. On the basis of the above estimates, the allowable limits for the Material Unaccounted For (MUF) are discussed.

Environmental tritium near the Ignalin nuclear power plant

The objective of this investigation was to examine the tritium content in the waters near the Ignalin nuclear Power Plant (RBMK-1500) in Lithuania. This is an important environmental problem due to the weak circulation of the cooling reservoir (Lake Drukshya) and has been investigated for a number of years. In this study, the environmental sources of tritium into the reservoir were examined and the tritium balance was obtained. The results agreed with the tritium content of the surface water as well as the yearly emission figures from Ignalin. Additionally, well samples demonstrated that tritium also leaked into the soil. The study concluded that tritium was ecologically significant in this area.

First wall/blanket/shield design and optimization system

A first wall/blanket/shield design and optimization system (BSDOS) has been developed to provide a state-of-the-art design tool for fast, accurate analysis. In addition, it has been designed to perform several other functions: (a) allowing comparison and evaluation studies for different concepts using the same data bases and ground rules, (b) permitting the use of any figure of merit in the evaluation studies, (c) optimizing the first wall/blanket/shield design parameters for any figure of merit under several design constraints, (d) permitting the use of different reactor parameters in the evaluation and optimization analyses, (e) allowing the use of improved engineering data bases to study the impact on the design performance for planning future research and development, and (f) evaluating the effect of the data base uncertainties on the design performance. BSDOS is the first design and optimization system to couple the highly interacting neutronics, heat transfer, thermal hydraulics, stress analysis, radioactivity and decay-heat analyses, tritium balance, and capital cost. A brief description of the main features of BSDOS is given in this paper. Also, results for using BSDOS to perform design analysis for several reactor components are presented.

Tritium balance in the Baltic Sea during the years 1972?1982

Tritium balance in the Baltic Sea during the years 1972?1982

LAKE WATER MIXING AND TRITIUM BALANCE ON LAKE CHUZENJI

Both mixing processes in a fresh-water lake and residence time of groundwater in its drainage basin have been made clear by using environmental tritium as a tracer on Lake Chuzenji. The lake covers an area of 11.97 km2 at an altitude of 1, 269m, having a large drainage basin of about 119.68 km2. The mean depth is 95m and the maximum 172m. A field survey was carried out from July 29 to August 3, 1978. Water samples for tritium analysis were collected at eleven stations, as shown in Figure 1. The sampling of lake water was made every 20m vertically. Temperature, ply, and electrical conductivity of the water were determined on the spot. The values obtained are indicated in Figure 2. Tritium concen-trations of lake water are shown in Figure 3 and those of stream water and groundwater in Figure 4. The mean tritium concentration of lake water was 34.7 TU, and a significant variation was not found throughout the all vertical profiles of the stations. Concerning the vertical profiles of tritium concentration in lake water, the lake water would be well mixed at least vertically. The tritium concentration of Shirakumo Falls, 37.8TU, showed nearly the same value to the lake, which shows that the Falls would be poured out as the seepage of the lake. Spring water from elevator shaft, which was drilled near Kegon Falls for the sight-seeing of the Falls, showed 33.3 TU. This figure was also the same as that of the lake. Those of spring water in Jigoku-zawa and of the well near the lake shore were 21.5 and 26.9 TU, respectively, showing lower than the lake water. This fact seems to reflect the influence of recent precipitation. Yukawa River, 37.9 TU, showed higher tritium concentration than both precipitation and the stream water flowing into Senjuga-hama. The annual water balance of the lake was calculated in the period from 1952 to 1977 (Table 3). Meteorological data at the Chugushi Meteorological Station were used as basic data in the calculation, and evapotranspiration from the drainage basin and evaporation from the lake were calculated by Penman's method. The tritium concentrations of precipitation in Tokyo and Tsukuba from 1952 to 1977 were used to estimate the mean tritium concen-tration of the lake water. The calculation was carried out on the assumption that lake water is completely mixed every year. As a result, the following conclusions were obtained. 1. The mean inflow to the lake is about 1.92×108m3•yr-1, that is, 6.09m3•sec-1, and the mean residence time of the lake water is determined to be about 5.9 years. In spite of the huge volume of lake water, the mean residence time is shorter than expected, because the area of drainage basin is about ten times as large as that of the lake. 2. The discharge from the lake depends upon groundwater outflow which is about 4.76m3•sec-1 and 79% of the total outflow. The propotions of evaporation and surface outflow are about 4% and 17%, respectively. 3. The vertical profile of tritium concentration in lake water and the result of the simula-tion of tritium balance support that the lake water would be well mixed in a year. 4. As a component of precipitation on the drainage basin, groundwater flow into the lake takes an average time of less than 4 years.

Estimation of groundwater accession to and evaporation from a South Australian lake using environmental tritium

Groundwater throughflow in a small lake (volume = 9.6 x 104 m3) which penetrates a limestone aquifer in southern Australia, is estimated to be c. 3.0 x 104 m3/yr. To make this estimate, use was made of both a short-term and a long-term tritium balance for interpreting the environmental tritium concentration of lake water and surrounding groundwater. This value compares well with estimates made using groundwater isopotentials and lake and groundwater chemistry. Knowledge of the groundwater component of the water balance has enabled an estimate of lake evaporation to be made.