Use In Blankets Research Articles

Modeling of hydrogen isotopes release from lithium ceramics Li2TiO3 during in-situ experiments using vacuum extraction method

Lithium ceramics Li2TiO3 in spherical granules (pebbles) is one of the most promising functional material for use in breeder blankets of a fusion reactor. In paper the experiments on a study of tritium and helium release from lithium ceramics Li2TiO3 (pebbles with a diameter of 1 mm, enrichment in 6Li is 96 %, weight ~ 0.37 g) under irradiation at the WWR-K research reactor (Almaty, Kazakhstan) are presented. The experiments showed that the main amount of tritium is released as HT molecules (the HT yield is an order of magnitude higher than T2 molecules yield). The release of tritium in the form of tritium water molecules was not recorded. The HT molecule yield's significant growth occurs at the initial moment with an increase in the ceramic temperature (while the T2 molecule release drops), after which the release flux decreases to the average level.The experimental results were evaluated by a qualitative model based on the obtained analytical expression for the tritium flux from a spherical ceramic sample for the given experimental conditions.

The thickness and deposition rate effects on structural and optical properties of aluminized PET

In this study, we used the PVD method by thermal evaporation technique, in which aluminum deposited on a 13 microm polyethylene terephthalate substrate. The aluminum deposition was carried out in different thicknesses (100, 150, 200, 250, 300 nm) on both sides of the substrate and two different deposition rates (a high rate of 6 nm/s and a low rate of 0.4 nm/s). Absorptance and emittance analyses were done. These analyses were evaluated by ECSS-Q70-71A standard for use in thermal blankets. According to analyses and evaluation, it was found that the sample with a thickness of 150 nm has the optimum values of absorptance and emittance for use in the thermal layers. Surface morphologies of the samples with the thicknesses of 100, 150, 200, 250, and 300 nm were investigated using AFM analysis. Other structural properties of the Al-PET sample with a thickness of 150 nm were determined by structural analyses, including XRD, FTIR, and FESEM.

Effects of test environment on high temperature fatigue properties of reduced activation ferritic/martensitic steel, F82H

Reduced activation ferritic/martensitic (RAFM) steels are assumed as structural material of blanket design activities. Determining the design limit is essential for the RAFM steels to qualify their use in fusion blankets. This work investigates fatigue properties of a RAFM steel, F82H at elevated temperature up to 823 K in the air and a vacuum condition. The tests were carried out with axial strain controlled condition using cylindrical specimen, and the results were summarized using the Manson’s modified universal slope method, which can describe fatigue lifetime as a function of tensile properties. Manson’s modified universal slope method gives good estimation for lifetime of F82H at temperature below 823 K. However, F82H-IEA demonstrated shorter lifetime than the estimation. The lifetime at vacuum condition was successfully described using universal slope method. On the other hand, the lifetime in the air was 1/3 or shorter than that in vacuum condition. It is notable that a heat of F82H prepared for IEA round robin tests demonstrated 1/5 of shorter lifetime than the latest F82H.

Avian Cholera emergence in Arctic-nesting northern Common Eiders: using community-based, participatory surveillance to delineate disease outbreak patterns and predict transmission risk

Emerging infectious diseases are a growing concern in wildlife conservation. Documenting outbreak patterns and determining the ecological drivers of transmission risk are fundamental to predicting disease spread and assessing potential impacts on population viability. However, evaluating disease in wildlife populations requires expansive surveillance networks that often do not exist in remote and developing areas. Here, we describe the results of a community-based research initiative conducted in collaboration with indigenous harvesters, the Inuit, in response to a new series of Avian Cholera outbreaks affecting Common Eiders (Somateria mollissima) and other comingling species in the Canadian Arctic. Avian Cholera is a virulent disease of birds caused by the bacterium Pasteurella multocida. Common Eiders are a valuable subsistence resource for Inuit, who hunt the birds for meat and visit breeding colonies during the summer to collect eggs and feather down for use in clothing and blankets. We compiled the observations of harvesters about the growing epidemic and with their assistance undertook field investigation of 131 colonies distributed over >1200 km of coastline in the affected region. Thirteen locations were identified where Avian Cholera outbreaks have occurred since 2004. Mortality rates ranged from 1% to 43% of the local breeding population at these locations. Using a species-habitat model (Maxent), we determined that the distribution of outbreak events has not been random within the study area and that colony size, vegetation cover, and a measure of host crowding in shared wetlands were significantly correlated to outbreak risk. In addition, outbreak locations have been spatially structured with respect to hypothesized introduction foci and clustered along the migration corridor linking Arctic breeding areas with wintering areas in Atlantic Canada. At present, Avian Cholera remains a localized threat to Common Eider populations in the Arctic; however expanded, community-based surveillance will be required to track disease spread.

Reducing beryllium content in mixed bed solid-type breeder blankets

Beryllium (Be) is a precious resource with many high value uses, the low energy threshold (n,2n) reaction makes Be an excellent neutron multiplier for use in fusion breeder blankets. Estimates of Be requirements and available resources suggest that this could represent a major supply difficulty for solid-type blanket concepts. Reducing the quantity of Be required by breeder blankets would help to alleviate the problem to some extent. In addition, it is important that the reduction in the Be quantity does not diminish the blanket's performance in key aspects such as the tritium breeding ratio (TBR), energy multiplication and peak nuclear heating.Mixed pebble bed designs allow for the multiplier fraction to be varied throughout the blanket. This neutronics study used MCNP 6 to investigate linear variations of the multiplier fraction in relation to blanket depth, in order to better utilise the important multiplying Be(n,2n) and breeding reactions. Blankets with a uniform multiplier fraction showed little scope for reduction in Be mass. Blankets with varying multiplier fractions were able to simultaneously use 10% less Be, increase the energy amplification by 1%, reduce the peak heating by 7% and maintaining a sufficient TBR when compared to the performance achievable using a uniform composition.

ChemInform Abstract: Recent Developments of Solid Breeder Fabrication

AbstractReview: 25 refs.

Recent developments of solid breeder fabrication

Worldwide research and development has been performed on solid breeder materials as a tritium source for future fusion power reactors. These ceramic materials will be used in the International Thermonuclear Experimental Reactor (ITER) to check their performance and screen their applicability for use in fusion blankets. While all members of the ITER project are engaged in the development of solid breeder blanket concepts, five are actively involved in the fabrication of tritium breeding ceramics for the different test blanket modules to be tested in ITER.All solid breeder concepts proposed for ITER are based on the use of ceramics in the form of pebble beds with pebble diameters of about 1mm or smaller. Although alternative materials are still under investigation, the main candidates for tritium breeding ceramics are lithium metatitanate and lithium orthosilicate. Recent developments and preparatory work for ITER are presented.

Novel mixed-oxide ceramic for neutron multiplication and tritium generation

Beryllium and lithium titanate (Li2TiO3), have limited use in blankets due to the swelling of beryllium and low thermal conductivity of Li2TiO3. A novel mixed oxide composite of beryllium oxide and lithium titanate (BeO–Li2TiO3) is proposed, which utilizes the high thermal conductivity of BeO and its favourable neutronics. Li2TiO3 was prepared using two different routes, one employing a solid-state reaction and the other through sol–gel route. The sintered BeO–Li2TiO3 is found to have no intermediate products and its thermal conductivity decreased from 36 to 14W/m/K with the increase in temperature from 127°C to 927°C. The coefficient of thermal expansion (CTE) of BeO–Li2TiO3 is less than that of Li2TiO3. Thermodynamic calculations show that tritium cannot be trapped in BeO unless beryllium monotrioxide (BeOT) is formed. The merits of BeO are compared with beryllium metal and neutronic calculations on tritium production in this novel mixed oxide are also presented.

Fusion materials development program in the broader approach activities

Breeding blankets are the most important components in DEMO. The DEMO blanket has to withstand high neutron flux typically 15–30 dpa/year under continuous operation. Therefore integrated and effective development of blanket structural materials and breeding/multiplying materials is essential in the blanket development for DEMO. In parallel to the ITER program, broader approach (BA) activities are initiated by EU and Japan. Based on the common interest of each party towards DEMO, R&D on reduced activation ferritic martensitic (RAFM) steels as a DEMO blanket structural material, SiC f/SiC composites which have potential for use in DEMO blankets, advanced tritium breeders and neutron multiplier for DEMO blankets, and tritium technologies including tritium behavior studies in advanced materials for DEMO blanket applications will be carried out as a part of the BA activities.

Adhesion Energy Estimation of some Composite Materials

In this paper the technique of adhesion energy estimation for materials having heterogeneous structure in particular, multi-component materials is offered. The adhesion energy estimation for material combinations which are promising for use in liquid-metal blankets of fusion reactor has been carried out and results of multilayer composites test in liquid lithium at T=600 °C and 650 °C are shown.

Calcium Oxide Coating on Vanadium Alloys in Liquid Lithium

AbstractWe have fabricated CaO coatings on vanadium metal and various vanadium alloys (V-10Cr, V-1Ti, V-4Cr-4Ti, and V-5Cr-5Ti), for use in liquid metal blankets of fusion reactors. Initially, by monitoring weight change as a function of time, oxygen was charged into the vanadium alloys (rectangular sample, 2 x 1 x 0.1 cm) at 710°C by flowing Ar-O2gas. Oxygen-charged samples were exposed in 2.8 at.% Ca-Li at temperatures of 600 and 700°C for times between 50 and 120 h. The thickness of the in-situ-formed CaO was 13 to 30 m in the experimental conditions. Thicker CaO films were formed at higher oxygen contents and 700°C, while thinner CaO films were formed at lower oxygen contents and 600°C. The data show promise for in-situ formation of CaO layers on V alloys for the fusion blanket application.

On the use of tin–lithium alloys as breeder material for blankets of fusion power plants

Tin–lithium alloys have several attractive thermo-physical properties, in particular high thermal conductivity and heat capacity, that make them potentially interesting candidates for use in liquid metal blankets. This paper presents an evaluation of the advantages and drawbacks caused by the substitution of the currently employed alloy lead–lithium (Pb–17Li) by a suitable tin–lithium alloy: (i) for the European water-cooled Pb–17Li (WCLL) blanket concept with reduced activation ferritic–martensitic steel as the structural material; (ii) for the European self-cooled TAURO blanket with SiC f/SiC as the structural material. It was found that in none of these blankets Sn–Li alloys would lead to significant advantages, in particular due to the low tritium breeding capability. Only in forced convection cooled divertors with W-alloy structure, Sn–Li alloys would be slightly more favorable. It is concluded that Sn–Li alloys are only advantageous in free surface cooled reactor internals, as this would make maximum use of the principal advantage of Sn–Li, i.e., the low vapor pressure.

Comparison of lithium and the eutectic lead-lithium alloy, two candidate liquid metal breeder materials for self-cooled blankets

Abstract Liquid metal blankets are attractive candidates for both near-term and long-term fusion applications. The subjects of this comparison are the differences between the two candidate liquid metal breeder materials Li and LiPb for use in breeding blankets in the areas of neutronics, magnetohydrodynamics, tritium control, compatibility with structural materials, heat extraction system, safety, and required research and development program. Both candidates appear to be promising for use in self-cooled breeding blankets which have inherent simplicity with the liquid metal serving as both breeder and coolant. Each liquid metal breeder has advantages and concerns associated with it, and further development is needed to resolve these concerns. The remaining feasibility question for both breeder materials is the electrical insulation between the liquid metal and the duct walls. Different ceramic coatings are required for the two breeders, and their crucial issues, namely self-healing of insulator cracks and tolerance to radiation-induced electrical degradation, have not yet been demonstrated.

A Comparative Study of Thermal Neutron Fusion Blanket Arrangements

Four basic configurations, block, homogeneous, multilayered, and heterogeneous systems, for tritium breeding in natural lithium water-reflected fusion blankets are compared. A 14-MeV point neutron source is used with a lead multiplier. All the calculations are done in rectangular geometry with the Monte Carlo code MORSE-E and Los Alamos National Laboratory's 30-group neutron cross-section set CLAW-IV in P/sub 3/ scattering approximation. The homogeneous system gives the best and the block concept gives the lowest tritium breeding, but neither of these concepts is practical for use in fusion blankets. Among the practical blanket arrangements, for equal amounts of natural lithium and water, the heterogeneous and multilayered arrangements give almost identical tritium breeding.

Compatibility of materials for use in liquid-metal blankets of fusion reactors

A review of corrosion and environmental effects on the mechanical properties of austenitic and ferritic steels for use with liquid metals in fusion reactors is presented. The mechanisms and kinetics of the corrosion processes in liquid lithium and Pb-17Li systems are examined and their influence on degradation of structural material is discussed. Requirements for additional data are identified.

Performance of ceramic materials in high temperature steam and hydrogen

Materials considered for use in fusion blankets for synthetic fuel production were exposed to flowing steam and a combination of steam and hydrogen at temperatures up to 1668 K and flow velocities of 10 meters per second, which are characteristic of blanket design conditions. The penetration rate of 2mm per year on silicon carbide in steam at 1400 K increased to 6mm per year at 1600 K, while alumina, zirconia, and magnesia were below 0.1mm per year.Steam containing 32 to 44 volume percent hydrogen caused a large increase in the erosion rate of alumina, zirconia, and magnesia at elevated temperatures. The temperature above which the erosion rate greatly increased was 1400 K for magnesia, 1550 K for alumina, and 1600 K for zirconia. The penetration rates below these temperatures were less than 0.1 mm per year; however, 100 K above these temperatures, the penetration rate increased four to six times and continued to increase with temperature. The erosion rate on silicon carbide was unaffected by the presence of hydrogen in the steam.Carbon dioxide was substituted for steam and hydrogen in several runs up to 1670 K, and no significant weight losses occurred. The silicon carbide acquired a porous-glassy coating at the highest temperature.