Towards the development of technical specifications for the production of lithium–lead alloys for the ITER HCLL TMB

The ITER and DEMO projects are developing new Test Blanket Modules (TBM), where the Pb–Li alloy plays a key role in the new commercial fusion reactors functionality. The Breeding Blanket (BB) has to perform several functions which are essential for the reactor operation. The HCLL TBM is one of the Breeding Blanket concepts to be tested in ITER. It is cooled by He and uses the eutectic liquid metal LLE (Lithium–Lead Eutectic) as breeder material (enriched at 90% in ⁶Li).Pb–Li eutectic alloy has no known uses outside of fusion technology, so the available databases of this material are currently incomplete. It is very important, within the material specifications, to have a complete characterization in order to define their chemical and physical properties, because any variation in the alloy composition has significant consequences in their behaviour, and therefore in their regenerative function inside the blanket.The chemical characterization methodology developed and presented in this paper (useful for both Pb–Li alloys as any Pb alloy) is a key tool that allows performing standard quality control procedures for base material and/or monitoring the alloy during the reactor operation. This report provides a procedure to perform a wide material chemical characterization, assessing the concentrations of major elements, as well as a review of trace level elements that can be found both in the eutectic alloy and in starting materials. In this determination plays an important role the ICP-MS technique because, as a highly sensitive technique, allows very low detection limits.     

Subchannel analysis of fuel assemblies of a lead–alloy cooled fast reactor

Lead–alloy cooled fast reactor is one of the six Gen-IV reactors. It has many attractive features such as excellent natural circulation performance, better shielding against gamma rays or energetic neutrons and potentially reduced capital costs. A natural circulation lead–alloy cooled fast reactor with 10 MWth is under design in China (hereafter called LFR-10MW). Fuel assemblies thermal hydraulic analysis is of vital importance for a successful design. A subchannel analysis code with flow distribution model was used to carry out the thermal hydraulic analysis. This work briefly gave the thermal-hydraulic design for the LFR-10MW and analyzed the thermal-hydraulic characteristics under steady-state condition using the subchannel analysis code. Whole core analysis was performed to locate the hottest fuel assembly using the code. The hottest fuel assembly was analyzed to obtain the cladding temperature, fuel temperature and coolant velocity. The maximum cladding temperature, the maximum fuel center temperature and the maximum coolant velocity are all below the design constraints. These results imply that the thermal-hydraulic design of LFR-10MW is feasible.     

Progress on the development of H-concentration probes in eutectic lead–lithium: Synthesis and characterization of electrochemical sensor materials

Dynamic tritium concentration measurement in lithium–lead eutectic (17% Li–83% Pb) is of major interest for a reliable tritium testing program in ITER TBM and for an experimental proof of tritium self-sufficiency in liquid metal breeding systems. Potentiometric hydrogen sensors for molten lithium–lead eutectic have been designed at the Electrochemical Methods Lab at Institut Quimic de Sarria (IQS) at Barcelona and are under development and qualification. The probes are based on the use of solid state electrolytes and works as Proton Exchange Membranes (PEM).In this work, the following compounds have been synthesized in order to be tested as PEM H-probes: BaCeO₃, BaCe_0.9Y_0.1O_3?δ, SrCe_0.9Y_0.1O_3?δ and Sr(Ce_0.9–Zr_0.1)_0.95Yb_0.05O_3?δ. Potentiometric measurements of the synthesized ceramic elements have been performed at different hydrogen concentrations at 500 °C. In this campaign, a fixed and known hydrogen pressure has been used in the reference electrode. The sensors constructed using the proton conductor elements BaCeO₃, SrCe_0.9Y_0.1O_3?δ and Sr(Ce_0.9–Zr_0.1)_0.95Yb_0.05O_3?δ exhibited quite stable output potential and its value was quite close to the theoretical value calculated with the Nernst equation (deviation less than 100 mV). Unstable measurement was obtained using BaCe_0.9Y_0.1O_3?δ as a solid state electrolyte in the sensor.     

Corrosion of Fe9Cr1Mo steel in stagnant liquid lead–lithium eutectic

The corrosion behaviour of Fe9Cr1Mo steel samples in a static Pb₈₃Li₁₇ eutectic melt at 823 K in a specially designed necked quartz capsule is investigated. The samples are kept isothermally for 500, 1000, 1500 and 2000 h. The changes in microstructure and depletion of alloying components of the sample kept for 2000 h have been studied using scanning electron microscope (SEM), energy disperses X-rays (EDS) and electron probe beam microanalysis (EPMA). Weight loss and thinning of the walls has been calculated by gravimetric analysis method for all the samples. Using this data the change in thickness per year is calculated. Preferential dissolution of major constituent elements namely iron and chromium from the samples with the formation of a ferritic–martenstic layer is observed. Percentage mass loss with respect to time follows a parabolic curve which indicates non linear mechanism of corrosion.     

Flow characteristics of natural circulation in a lead–bismuth eutectic loop

Lead and lead-alloys are proposed in future advanced nuclear system as coolant and spallation target.To test the natural circulation and gas-lift and obtain thermal-hydraulics data for computational fluid dynamics(CFD) and system code validation, a lead–bismuth eutectic rectangular loop, the KYLIN-Ⅱ Thermal Hydraulic natural circulation test loop, has been designed and constructed by the FDS team. In this paper, theoretical analysis on natural circulation thermal-hydraulic performance is described and the steady-state natural circulation experiment is performed. The results indicated that the natural circulation capability depends on the loop resistance and the temperature and center height differences between the hot and cold legs. The theoretical analysis results agree well with,while the CFD deviate from, the experimental results.     

A comprehensive study on neutronics of a lead–bismuth eutectic cooled accelerator-driven sub-critical system for long-lived fission product transmutation

The aim of this study is to investigate the high-level waste (HLW) transmutation and fissile breeding potentials of a lead–bismuth eutectic (LBE) cooled accelerator-driven system (ADS) for the various configurations (the target radius, R_T = 10–50 cm and the radial thickness of the sub-critical core, δ_SC = 50–80 cm) and for the various fuel compositions (the fuel volume fraction, VF_F = 10%, 12%, 15% and 20% and the fissile fraction, FF = 10–24%) under sub-critical condition. The long-lived fission products (LLFPs: ⁹⁹Tc, ¹²⁹I and ¹³⁵Cs nuclides) and the uranium mono carbide (UC) ceramic fuel are considered as the HLW and the fissile fuel, respectively. The neutronic calculations have been performed per the incident proton (1000 MeV) with the high-energy Monte Carlo code MCNPX in coupled neutron and proton mode using the LA150 library. The numerical results bring out that the case of R_T = 30 cm, δ_SC = 80 cm, VF_F = 10% and FF = 23% is the optimum configuration and fuel composition, from the energy gain point of view, and has a high neutronic performance for an effective LLFP transmutation and fissile breeding.     

On the 24Mg(t,p) Reaction in the Incident Energy Range of 1.65–3.4 MeV

Previously, cross sections and angular distributions of the ²⁴Mg(t, p) reaction were measured in the incident triton energy range of 1.65–3.4 MeV. Presently, the analysis of the reaction is made with a combined model of the resonance and direct reactions. Almost good agreement was obtained between the experiment and the analysis. Some excited states of the compound nucleus ²⁷Al in Ex = 19:68–21:23 MeV were determined by the resonance analysis.     

On the electrochemical formation of Pu–Al alloys in molten LiCl–KCl

Properties of Pu–Al alloys were investigated in connection with development of pyrochemical methods for reprocessing of spent nuclear fuel. Electroseparation techniques in molten LiCl–KCl are being developed in ITU to group-selectively recover actinides from the mixture with fission products. In the process, actinides are electrochemically reduced on solid aluminium cathodes, forming solid actinide–aluminium alloys. This article is focused on electro-chemical characterisation of Pu–Al alloys in molten LiCl–KCl, on electrodeposition of Pu on solid Al electrodes and on determination of chemical composition and structure of the formed alloys. Cyclic voltammetry and chronopotentiometry were used to study Pu–Al alloys in the temperature range 400–550 °C. Pu is reduced to metal in one reduction step Pu³⁺/Pu⁰ on an inert W electrode. On a reactive Al electrode, the reduction of Pu³⁺ to Pu⁰ occurs at a more positive potential due to formation of Pu–Al alloys. The open circuit potential technique was used to identify the alloys formed. Stable deposits were obtained by potentiostatic electrolyses of LiCl–KCl–PuCl₃ melts on Al plates. XRD and SEM–EDX analyses were used to characterise the alloys, which were composed mainly of PuAl₄ with some PuAl₃. In addition, the preparation of PuCl₃ containing salt by carbochlorination of PuO₂ is described.     

Nucleation,growth and transport modelling of helium bubbles under nuclear irradiation in lead–lithium with the self-consistent nucleation theory and surface tension corrections

Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio.A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM^® CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process.Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and reinforces the idea that nucleation may not be a remote phenomenon, may have a large impact on the system's design and reveals the necessity to conduct experiments on He cavitation.     

Estimate of the Efficiency of Hydrogen–Metal Hydride (Intermetallic Compound) Systems in the Separation of the Three-Isotope Mixtures H–D–T

A method is developed for calculating apparatus for separating a three-isotope mixture H–D–T by the sorption method using hydrides of metals or intermetallic compounds. Relations are established between the partition coefficients and mass-transfer characteristics, determined for binary isotopic mixtures of hydrogen, and the parameters determining the isotopic equilibrium and the kinetics of mass transfer in the system gas–solid hydride phase with three isotopes. The efficiencies of various sorbents for deprotization of deuterium–tritium mixture are compared. 4 figures, 2 tables, 7 references.     

An optimized numerical method to pre-researching the performance of solid-phase oxygen control in a non-isothermal lead–bismuth eutectic loop

In the present work, a new transient calculation method for parameters that can be used to evaluate the ability of oxygen control in a non-isothermal lead-bismuth eutectic(LBE) loop with solid-phase oxygen control was proposed. It incorporates the dissolution process of PbO particles and the oxygen mass transfer process, and an optimized method was used for finding out the optimized oxygen mass transfer coefficient. In numerical terms, three mass transfer models were simultaneously applied, and ...     

An optimized numerical method to pre-researching the performance of solid-phase oxygen control in a non-isothermal lead–bismuth eutectic loop

In the present work, a new transient calculation method for parameters that can be used to evaluate the ability of oxygen control in a non-isothermal lead-bismuth eutectic(LBE) loop with solid-phase oxygen control was proposed. It incorporates the dissolution process of PbO particles and the oxygen mass transfer process, and an optimized method was used for finding out the optimized oxygen mass transfer coefficient. In numerical terms, three mass transfer models were simultaneously applied, and ...     

On the problem of the metabolic exchange of cesium,strontium, and a mixture of α-emitters in cows

The results are presented of an Investigation of the distribution and excretion of the radioactive isotopes Cs¹³⁷, sr^89,90, and of a mixture of ß -emitters in 6 cows after peroral administration. It is shown that cesium and strontium are resorbed well from the intestines and that a considerable portion of the amount of emitters resorbed is excreted into milk. Resorbed cesium is almost exclusively deposited in the muscles, while strontium is in the skeleton. The results of the work indicate the danger of widespread application of radioactive fertilizers and of the maintenance of cows in pastures contaminated by the radioactive particles resulting from fission. The results can be used in calculating the maximum permissible contents of cesium, strontium, and mixtures of ß-emitters in products intended for feeding cows.     

Design and analysis on tritium system of multi-functional experimental fusion–fission hybrid reactor (FDS-MFX)

As early application of fusion technology, the fusion–fission hybrid systems/reactors could be used to transmute long-lived radioactive waste and produce fissile nuclear fuel. A fusion–fission hybrid reactor named FDS-MFX was designated for checking and validating the DEMO reactor blanket relevant technologies. The reactor design is based on easy-achieved plasma parameters extrapolated from the successful operation of tokamaks and the subcritical blanket is designed based on the well-developed technologies of fission reactors. In this contribution, a concept of the tritium system was designed for the FDS-MFX: the tritium was extracted from LiPb by the helium purge gas which contains a small amount of hydrogen gas, then the impurity gas was removed by cold trap, finally tritium was separated from hydrogen isotope by the cryogenic distillation and supply to reactor core. On the basis of data obtained by present design and experimental research, the system parameters were presented and discussed in detail. The results preliminarily demonstrated the engineering feasibility of the design.     

Evaluation of the calibration factors of neutron dose rate meters in a ~(241)Am–Be neutron field

Calibrations were performed for three types of neutron ambient dose equivalent rate meters, i.e., Aloka TPS-451C (Hitachi), KSAR1 U.06(Baltic Scientific Instruments), and Model 12-4(Ludlum), using a standard field of a ~(241) Am–Be source. The measured total neutron ambient dose equivalent rates, H*(10)'_( tot), were analyzed to obtain the direct neutron ambient dose equivalent rates,H*(10)'_(dir), using the ISO 8529-2-recommended generalized-fit method, semiempirical fit method, and reducedfitting method(RFM) fit methods. The calibration factor(CF), defined as the ratio between the conventional true value of the neutron ambient dose equivalent rates in a free field, H*(10)'_(FF), and H*(10)'_(dir), was evaluated as one of the important characteristics of the neutron meters in the present work. The fitting results show that the H*(10)'_(dir) values of the meters are in good agreement within the theoretical data within 4%. The averaged CFs of the three neutron meters were evaluated as 0:99±0:01, 1:00±0:03; and0:99±0:08, respectively. The largest standard uncertainty of these values was determined to be approximately18.47%(k=1). The standard uncertainty of the CFs obtained using the RFM method was less than 4.23%(k=1), which is the smallest uncertainty among the three methods.     

Experimental Investigation of Processes Occurring in the Plasma of a Cesium–Barium Tasitron

The results of measurements of plasma parameters in different regions of a nonstationary discharge in a cesium–barium tasitron with 1-sec time resolution are presented. Data analysis made it possible to determine the quenching mechanism of a discharge in a three-electrode system with large-structure grid. 7 figures, 12 references.     

Active oxygen control by a PbO mass exchanger in the liquid lead–bismuth eutectic loop: MEXICO

Accurate control of dissolved oxygen concentration is crucial in order to use liquid lead alloys as a coolant of advanced nuclear systems. An oxygen control system based on PbO mass exchanger (PbO MX) technology was implemented in order to control the dissolved oxygen concentration in the liquid lead--bismuth eutectic (LBE) loop MEXICO. The oxygen control system consisted of a packed bed of PbO spheres, an oxygen sensor and a pneumatic control valve. The concentration of dissolved oxygen in the loop was controlled by regulating the LBE flow through the PbO MX using a proportional–integral–derivative (PID) controller with feedback from the oxygen sensor. Highly accurate control of the dissolved oxygen concentration in the loop was achieved by this system.     

Evaluation of the irradiation dose rate for marine biota in the region of the destroyed fukushima reactor (japan) in march–may 2011

The irradiation dose rate in March–May 2011 is evaluated for marine biota in the coastal zone near the destroyed Fukushima reactor and in the open sea. It is shown that for representative marine organisms (fish and mollusks) the irradiation dose rate did not exceed the safe level 0.4 mGy/h (10 mGy/day). In the open sea, 30 km from the nuclear power plant, the irradiation of marine biota is much lower than in the coastal zone near the nuclear power plant. A comparative evaluation is made of the irradiation dose rate for water organisms in the exclusion zones of the Eastern-Urals track of radioactivity and the Chernobyl and Fukushima nuclear power plants.     

Engineering-scale test on the thermal–hydro–mechanical behaviors in the clay barrier of a HLW repository

The thermo–hydro–mechanical (T–H–M) behaviors of a clay barrier are of importance from a performance and safety viewpoint of the engineered barrier system (EBS) for a high-level waste (HLW) repository. An engineering-scale test was carried out to investigate the T–H–M behaviors in the buffer of the Korean reference disposal system (KRS). The test started on May 31, 2005 and is still in operation. The experimental data obtained allowed a preliminary and qualitative interpretation of the T–H–M behavior in bentonite blocks. The temperature was higher as it became closer to the heater, while it became lower as it was farther away from the heater. The water content had a higher value in the part close to the hydration surface than that in the heater part. The relative humidity data suggested that a hydration of the bentonite blocks might occur by different drying–wetting processes, depending on their position. The total pressure was continuously increased by the evolution of the saturation front in the bentonite blocks and thereby the swelling pressure. There was also a contribution of the thermal expansion of the bentonite blocks near the heater and the capillary force in the dry bentonite blocks which the water did not reach from the hydration surface.