Design optimization of first wall and breeder unit module size for the Indian HCCB blanket module

The Indian test blanket module（TBM） program in ITER is one of the major steps in the Indian fusion reactor program for carrying out the R＆D activities in the critical areas like design of tritium breeding blankets relevant to future Indian fusion devices（ITER relevant and DEMO）.The Indian Lead–Lithium Cooled Ceramic Breeder（LLCB） blanket concept is one of the Indian DEMO relevant TBM,to be tested in ITER as a part of the TBM program.Helium-Cooled Ceramic Breeder（HCCB） is an alternative blanket concept that consists of lithium titanate（Li_2TiO_3） as ceramic breeder（CB） material in the form of packed pebble beds and beryllium as the neutron multiplier.Specifically,attentions are given to the optimization of first wall coolant channel design and size of breeder unit module considering coolant pressure and thermal loads for the proposed Indian HCCB blanket based on ITER relevant TBM and loading conditions.These analyses will help proceeding further in designing blankets for loads relevant to the future fusion device.

Comparative studies for two different orientations of pebble bed in an HCCB blanket

The Indian Test Blanket Module（TBM） program in ITER is one of the major steps in its fusion reactor program towards DEMO and the future fusion power reactor vision. Research and development（RD） is focused on two types of breeding blanket concepts： lead–lithium ceramic breeder（LLCB） and helium-cooled ceramic breeder（HCCB） blanket systems for the DEMO reactor. As part of the ITER-TBM program, the LLCB concept will be tested in one-half of ITER port no. 2, whose materials and technologies will be tested during ITER operation. The HCCB concept is a variant of the solid breeder blanket, which is presently part of our domestic RD program for DEMO relevant technology development. In the HCCB concept Li_2TiO_3 and beryllium are used as the tritium breeder and neutron multiplier, respectively, in the form of a packed bed having edge-on configuration with reduced activation ferritic martensitic steel as the structural material. In this paper two design schemes, mainly two different orientations of pebble beds, are discussed. In the current concept（case-1）, the ceramic breeder beds are kept horizontal in the toroidal–radial direction. Due to gravity, the pebbles may settle down at the bottom and create a finite gap between the pebbles and the top cooling plate, which will affect the heat transfer between them. In the alternate design concept（case-2）, the pebble bed is vertically（poloidal–radial） orientated where the side plates act as cooling plates instead of top and bottom plates. These two design variants are analyzed analytically and 2 D thermal-hydraulic simulation studies are carried out with ANSYS, using the heat loads obtained from neutronic calculations.Based on the analysis the performance is compared and details of the thermal and radiative heat transfer studies are also discussed in this paper.

Nanofluids:Critical issues,economics and sustainability perspectives

According to the Scopus database,every year several hundreds of new research papers are published in the field of nanofluids.This area is attracting growing attention because of the significant improvement in the heat transfer and energy efficiency of the systems working with nanofluids.However,as results from numerous scientific studies conducted by independent laboratories,there are several fundamental problems related to the unambiguous determination of their physical properties,their production,and economic use.Although most studies often focus on one issue or cover one kind of research or math-ematical correlation,this review paper provides insights into many problems during nanofluids research by proposing solving possibilities,which is the strength of our work.The paper discusses the case of nanofluids quality,and morphology,thermal conductivity enhancement and the discrepancies in mathematical modelling,errors in dimensional and similarity analysis,nanofluid erosion,safety guide-lines,and toxicology tips.Moreover,the sustainability and economics of nanofluids usage are also being discussed.

Effect of Li^(+)ion mobility on the grain boundary conductivity of Li_(2)TiO_(3) nanoceramics

Lithium titanate(Li_(2)TiO_(3))is one of the most promising candidates among the tritium breeding materials because of its good tritium release capacity.Li concentration has much significance on the diffusivity of tritium in the material.The nanocrystalline single-phase Li_(2)TiO_(3) with monoclinic structure has been prepared by high energy ball milling followed by calcination at 700℃for 2 h.The field emission scanning electron microscopy(FESEM)studies confirmed uniform distribution of nanocrystalline phase with particle size below 100 nm.The study of the Li^(+)ion diffusion on the sintered sample was investigated by means of electrical conductivity measurements.Electrical properties of the samples were studied in wide temperature(50-500℃)and frequency(100 Hz-1 MHz)ranges.The complex impedance spectroscopy(CIS)studies showed the presence of both bulk and grain boundary effects in nanocrystalline Li_(2)TiO_(3).The bulk resistance of the samples has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance(NTCR)behavior.The low activation energies of the samples suggested the presence of singly ionized oxygen vacancies in the conduction process.The hopping frequency shifted toward higher frequency with increase in temperature.Activation energy of 0.86 eV was calculated from AC conductivity.

Electrical properties of bulk and nano Li_(2)TiO_(3) ceramics:A comparative study

Nanocrystalline and bulk Li_(2)TiO_(3) having monoclinic structure were prepared by mechanical alloying as well as conventional ceramic route.Complex impedance analysis in the frequency range of 100 Hz-1 MHz over a wide range of temperature(50-500℃)indicates the presence of grain boundary effect along with the bulk contribution.The frequency-dependent conductivity plots exhibit power law dependence,suggesting three types of conduction in the material:low-frequency(100 Hz-1 kHz)conductivity showing long-range translational motion of electrons(frequency independent),mid-frequency(1-10 kHz)conductivity showing short-range hopping of charge carriers and high-frequency(10 kHz-1 MHz)conductivity showing conduction due to localized orientation of hopping mechanism.The electrical conductivity measurement of nanocrystalline and bulk Li_(2)TiO_(3) with temperature shows the negative temperature coefficient of resistance(NTCR)behavior.The activation energy(0.77 eV for nano sample and 0.88 eV for bulk sample)study shows the conduction mechanism in both samples.The low activation energies of the samples suggest the presence of singly ionized oxygen vacancies in the conduction process.