NEW YEAR MESSAGE

ISSN 0972-5741 Volume 71 January 2007

INDIRA GANDHI CENTRE FOR ATOMIC RESEARCHhttp://www.igcar.ernet.in/lis/nl71/igc71.pdf

From the Director’s Desk

It gives me a great pleasure in wishing you and your families a veryhappy and blissful New Year and a Happy Pongal.

The Centre visualizes world leadership in Fast Reactor andassociated Closed Fuel Cycle through robust and safe technologiesbased on breakthroughs provided by basic science and engineeringdisciplines. I am a firm believer in seamless science and technology.

I quote Bill Wulff “There is only one nature - the division intoscience and engineering is a human imposition, not a naturalone. Indeed, the division is a human failure; it reflects ourlimited capacity to comprehend the whole”. We thus have tovisualize the totality of the picture and evolve towards thecommon goal of the Centre, with our complementary andcorroborative contributions relating to our specializations. I

take pride in sharing a few achievements of the Centrewith you.

The Fast Breeder Test Reactor (FBTR), thepride of the Centre, has continued to scale newinternational heights by successfully operatingand making the mixed carbide fuel reach a burn-up of 155 GWd/t, without any fuel failure.

FBTR is also acting as a test-bed for the PFBR MOX fuel, whichhas already undergone 60 GWd/t of burn-up as against target burn-up of 100 GWd/t. This will provide very valuable data on theirradiation behavior of the oxide fuel. We have received regulatoryclearances for doing some state-of-art and relevant experiments toenhance safety of future Sodium Cooled Fast Reactors. Analyticaland experimental investigations are being pursued towards lifemanagement of FBTR to ensure that FBTR is available to us fornext twenty years.

The Prototype Fast Breeder Reactor (PFBR) construction hasprogressed as scheduled, and we are sparing no efforts to ensurethat it will be commissioned by September 2010. The Centrecontinues to provide robust design and R & D support to PFBR. A

INSIDETechnical Article

Aerosol Test Facility ForFast Reactor SafetyStudies

Sensors for monitoring oftransformer oil and ethanolmixed petrol as spin-offs

Tailoring of stableferrofluids for variousapplications

Forum for YoungOfficers

When non-linearity makessense: Neural computationin Materials Science

Conference/MeetingHighlights

Workshop on Total QualityManagement

News & Events

Awards & Honors

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(HBNI), having a university status underUniversity Grants Commission, we canhope to further strengthen our humanresources by inducting more youngstudents in various research programmes,besides fulfilling the academic aspirationsof our colleagues. This definitely providesa rich academic atmosphere to our mission-mode research programmes.

While providing the impetus to the R& D activities at IGCAR through carefulplanning and focused execution, we havealso kept in mind the improvements in theresidential environment and holistic healthcare for the residents. Construction ofprotection wall for the Township has beencompleted and the construction of anotherbridge for the township is in progress. Theschools on their part have continued toprovide the right environment for nurturingexcellence in students. All these augur wellfor the overall comfort, safety and blissfulliving of our colleagues.

Fast Reactor Science & Technology isan important area, where continuous questfor knowledge, understanding andinnovations is necessary to enable aquantum leap in our endeavor to be a worldleader. We should evolve and mature fromthe questions of “What ? Why? How ?” toaiming for bigger things and be confidentto ask “Why not ?”. Let me quote AlbertEinstein, “The mere formulation of aproblem is far more essential than itssolution, which may be merely a matter ofmathematical or experimental skills. Toraise new questions, new possibilities, toregard old problems from a new anglerequire creative imagination and marksreal advances in science.” Let us all marchtogether to attain such a state of collectivescientific maturity and wisdom.

Wish you and your family all the bliss,happiness and prosperity during the year2007.

(Baldev Raj)Director

IGCAR & GSO

programme, which has to be pursued inorder to meet these objectives The R&Dprogrammes encompass many areas ofscience and technology including physics,chemistry, structural mechanics,electronics, safety etc. Thus it is obviousthat the entire Centre must focus on theseR&D programmes in order to elevate thefast reactor programme to higher domain.It is very important that we involve all theyoung minds of the Centre to ponder overthe issues related to economics and safetyof the reactors and fuel cycle and take upR&D programmes with commitment andfocus.

We have a unique opportunity to playa leading role in the global development offast reactors and fuel cycle. It is not anexaggeration to state that our success inthe PFBR project and associated closedfuel cycle will be an important ingredient,in subsequent decisions about thedevelopment of fast reactors and theirenhanced contribution to nuclear energyproduction not only in our country, butalso other countries. The world nuclearcommunity is watching with keen interestand admiration our progress in fast reactortechnology. We must make every effort toachieve total success in these programmesand also keep up the momentum of R&Dto reach higher levels of maturity in thistechnology.

We have always believed that quantumjumps in technology can only take placethrough scientific breakthroughs. It is forthis reason that we have a strong andfocused programme of basic research inour Centre, covering a wide spectrum ofactivities such as ab-initio computations,nano coatings, etc. To further strengthenour human resources and the vitality ofour Centre and continuity of knowledge,we have started a Training school atIGCAR in core engineering disciplinesstarting from this year. While, presently itcaters to chemical engineering, electronicsand instrumentation and mechanicalengineering, we hope to add moredisciplines in the years to come. WithIGCAR becoming a constituent institution(CI) under Homi Bhabha National Institute

few important components like SafetyVessel, Main Vessel and Inner Vessel havearrived at site. Many of the reactorcomponents are in advanced stage offabrication. It is a matter of greatsatisfaction for us that we have achievedquality levels better than specified and alsomany international benchmarks.

Closing the fuel cycle is very importantand critical aspect of Fast Reactortechnology and thus reprocessing of thespent fuel is very crucial for this. We aretaking all necessary and urgent stepstowards robust fuel cycle technologies.Integrated Fast Reactor Fuel Cycle Facility(FRFCF) co-located with Prototype FastBreeder Reactor (500 MW(e)) is makinggood progress. Work on plant designengineering consultancy has beencompleted, including the geo-technicalwork, which is important aspect of theplant safety. Activities connected with theHead End Facility are in progress tointegrate with Demonstration FuelReprocessing Plant (DFRP) to becommissioned in 2009. DFRP is designedfor reprocessing irradiated FBTR fuel onregular basis and demonstrating ‘processand plant’ for reprocessing of irradiatedmixed oxide fuel of PFBR.

The full power operation of the SteamWater System of the Steam Generator TestFacility (SGTF) is an event that we arekeenly looking forward to. The operationof the SGTF would provide valuableinsights into the design and operation ofthe steam generators, which are vital forFBRs. Similarly, the testing of variouscomponents in sodium and the setting upof the full scale simulator for PFBR are inexciting periods of progress.

While we note with pride our Centre’sprogress so far, we realize the need toembark on an intense and focused long termR&D programme to introduce innovationsin reactor design, construction andoperation as well as the fuel cycle so thatthe reactors and the fuel cycle facilitiesnot only provide power at an economicaltariff but also operate safely with highavailability factors. Our Centre has alreadyarrived at a framework of R&D

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the containment at various timesfollowing the postulated accident and(ii) the leakage rates from thecontainment stack, ducts and cracks.The time evolution properties ofaerosol mass concentration inside thecontainment building and aerosolmaterial deposition on the walls andfloor of the containment building arealso of great importance. Knowledgeof these properties is required for theanalysis of corrosion of buildingmaterial and equipments and also forthe planning of the subsequentcleaning and calculating the sodiumaerosol exposure for the operatingpersonal. For the post accidentmanagement of fast reactor, the useof validated computer code such asHAARM code is needed. Thecomputer code predicts the followingcharacteristics: (i) the behavior ofsodium, fuel and fission productaerosols inside PFBR containmentand (ii) the subsequent transport intothe atmosphere.

In sodium cooled fast reactor,aerosols are generated in the case ofsodium leak from the secondary loop,apart from the CDA case. The hotcirculating sodium in the secondaryloop may get in contact withatmosphere through cracks and burns

requirements of 10-6 / reactor year forSDS and 10-7 / reactor year for DHRS.Therefore, in case of initiatingtransient event occurring in thenuclear reactor, the CDA can beexpected only when the above twosafety systems fail. In other wordsCDA is viewed as the consequenceof the initiation events followed bythe failure of SDS and DHRS.

In the case of most unlikely event ofCore Disruptive Accident (CDA) inLiquid Metal Fast Breeder Reactor(LMFBR), the sodium slug may impactthe reactor vessel head, causingdamage. This provides a pathway forthe escape of radioactive material(fission products and fuel material)and sodium into the containment. Fueland fission product vapors willcondense and form aerosols. Inaddition, sodium burning will giverise to various compounds of sodiumaerosols. In the bottled condition ofcontainment, it is expected that onlygaseous and aerosol materials mayleak through the containment buildingto the environment. The leak will bemainly through the ducts and wallpenetrations. The amount and typeof aerosol released depends on thefollowing two factors: (i) theconcentration of the aerosols inside

During normal operation of a nuclearreactor, there is a balance between theheat generated in the core and the heatremoved by the heat exchanger. If theheat removal is less than the heatgeneration, the excess heat will bedissipated in the core itself. The causeof this excess heat may be due to thefollowing more probable initiatingevents in the reactor: (i) Transientover power initiated by reactivityaddition (TOP), (ii) Loss of coolantinitiated by reduction in the flow ofcoolant liquid (LOF), and (iii) Loss ofcoolant initiated by loss of heat sink(LOHS). The development of theseinitiating events are detected, and bytaking suitable action, the reactor isbrought to normal condition within asafe period of time. Any failure indetection and prevention measuresmay lead Core disassembly, Core melt-down or both. The after effects of coredisruptive events are called coredisruptive accidents (CDA). In orderto prevent the initiating events ofCDA, the following two safetysystems are provided in the reactors:(i) Shut Down System (SDS) and (ii)Decay Heat Removal System (DHRS).The above systems are normallydesigned to have the failureprobability better than the mandatory

Aerosol Test Facility forFast Reactor Safety Studies

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concentration and the aerosol studiesare being carried out. The materialsused for the generation of aerosolsare of non-radioactive fissionproducts such as strontium peroxide(SrO2), barium oxide (BaO) and cerium(IV) oxide (CeO2) and coolant sodium.A photograph of ATF facility is shownin Fig 1. ATF mainly consists of anaerosol chamber, a plasma torch forthe production of aerosols of fissionproducts and fuel equivalentmaterials, a sodium combustion cellfor the production of sodium oxideaerosols, aerosol measurementapparatus, humidity controller andauxiliary systems such as watercooling, air flow, gas flow, pneumaticcontrol, vacuum, material handlingsystems and on-line data acquisitionsystem for temperature, pressure andrelative humidity (RH) duringexperiments.

Aerosol Generation

A 25 kW thermal plasma torch isoperated in non-transferred arc mode.Plasma torch is based on arc ignitionbetween a thermionic tungsten

cathode and a co-axial copper anode,both of which are water-cooled andimmersed in an axial magnetic field.Nitrogen is used as the plasmagengas. Nitrogen or argon can be usedas the sheath gas. Two methods areemployed in this system for theproduction of aerosol viz., powderfeeder and wire feeder. The powderfeeder is an instrument to introducethe powder into the flame at therequired rate. The wire feeder has astepper motor driving system, wherethe wire or a tube of 6mm diameter,can be fed into the flame at therequired rate. The material introducedin the plasma flame is ensured withhigher dwell time. During the time, thehigh enthalpy available in plasma isutilized to dissociate, melt and/orevaporate finely divided particlesintroduced into the flame to producedispersed aerosols by evaporation-condensation process.

Sodium combustion cell is used forthe generation of sodium compoundaerosols. A Bunsen burner (capacity~ 150 gm) is kept inside a vacuumcompatible chamber. An externalheater energizes the burner. Thetemperatures of the sodium and atlocations just above the sodium aremonitored using thermocouples. Thesodium combustion cell is flushedwith argon and it is isolated from theaerosol chamber through apneumatically operated gate valve.Sodium is loaded in the burner and itis heated in argon environment. Afterheating the sodium to the requiredtemperature (say 550oC), compressedair is passed in to the cell through avalve. The sodium burns and formsinto aerosols and the sodiumcompound aerosols are injected intothe aerosol chamber.

Aerosol Characterization

Characterization of aerosols is doneby (i) Real-time and (ii) Cumulative

Fig.1 Photograph of Aerosol Test Facility showing plasma torch, aerosol chamber and aerosoldiagnostic equipments.

to give aerosols. In atmosphere, hotsodium burns to give sodiummonoxide (Na2O) when sodium is inexcess and peroxide (Na2O2) whenoxygen is in excess. The oxideaerosols quickly react with watervapor present in the atmosphereforming sodium hydroxide (NaOH)and then sodium carbonate (Na2CO3)upon further reaction with carbondioxide in the atmosphere. Sodiumcompound aerosol is a mixture of allthe above compositions and theproportion depends on oxygen,atmospheric moisture and CO2.

For the aerosol studies of fast reactorsafety analysis, an Aerosol TestFacility (ATF) has been designedfabricated and Commisioned atRadiological Safety Division (RSD).The test facility is used for thegeneration of input data for HAARMcode and for the studies on co-agglomeration processes of themixture of sodium, fuel and fissionproduct aerosols. The aerosols ofsodium, fuel and fission product willbe generated with the requisite mass

r

AerosolChamber

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samplings. The aerosol deposits areanalyzed in SEM, EDAX and XRDanalyzer. Using light scatteringdevices such as Mastersizer (M/sMalvern UK), Aerosol Dust Monitor(M/s Grimm Aerosolteknic, GmbH,Germany) and Quartz CrystalMicrobalance (QCM) (M/s CaliforniaInstrument, Inc., USA), real timemeasurements are carried out. Filterpaper sampler and Low PressureImpactor (M/s Andersen Inc., USA)are used for cumulativemeasurements.

Experiments

The initial (at a time t=20s) volume-sized distribution of sodiumcompound aerosol measured byMastersizer at 50% Relative Humidity(RH) is shown in Fig.2. The initialsized distribution is a Gaussian log-normal distribution having MassMedian Diameter (MMD) of 1.02 μmwith Geometric Standard Deviation(sg) (GSD) 1.2. Mass-size distributionwas measured by QCM at the instantof 20s and it is also a log-normaldistribution with Aerodynamic MassMedian Diameter (AMMD) at 1.58μmwith GSD (sg) of 2.75. Upon convertingAMMD to MMD by using the density(2.2 g/cm3) of the sodium hydroxide(the nature of the aerosol), the MMDwas found to be almost equal to 1.0μm. The initial MMD was obtainedfor various ignition temperature ofsodium and found to be nearly 1.0 μm.The initial MMD was also determinedby various RH% inside the chamber.It was observed that, the initial MMDvalue is nearly 1.0 μm up to 50% andthen it increases with increase in RHvalue.

The depletion of mass concentrationwith time inside the closed vessel forthe sodium oxide aerosol, SrO2 andFe2O3 aerosols is shown in Fig 3. Thedepletion rate of mass concentrationof the sodium compound aerosols is

Fig.2 The initial Mass-size distribution (20s) of sodium compound aerosols for the ignitiontemperature of 550 °C at 50%RH measured by Mastersizer.

Fig.3 The depletion of mass concentration of sodium compound aerosol alongwith Fe2O3 and SrO2 aerosols

Fig.4: Depletion of suspended sodium compound aerosol mass concentration with time in theabsence of gamma field

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concentration (sodium compound )inside the chamber under the gammafield was studied for the dose rates of8.0, 4.0, 1.0 and 0.5 mGy/h and theseresults are shown in Fig. 5. It isobserved from the Figure 5 that, theaerosol mass concentrationdecreases faster in the presence ofgamma field. The faster depletion rateis attributed to enhanced Browniancoagulation due to bi-polar chargingof aerosols.

SummaryAerosol study is one of the importantareas of interest in the fast reactorsafety analysis. The environmentalsource term and consequences ofsodium leakage depend on theamount of aerosol released and theircharacteristics. In this context ATF isused to generate input data forvarious analyzing codes and predictmodels in the case of such leakages.Further experiments are beingcontinued with composite aerosols.

(Reported by R. Baskaran,V. Subramaniam and R. Indira

Radiological Safety Division,SafetyGroup)

I. Transformer oil degradationmonitoring

Slow build up of oxidation productsas a result of chemical reactions withoxygen and moisture fromenvironment under the prevailingservice conditions and physicalingress of polar molecules such as

performing real-time instrumentationsystems for general as well as forspecial purpose applications relevantto our reactor and associated fuelcycle programmes. Here we report twospin-off developments which are ofwider significance to the energysector.

Novel approaches in thedevelopment of Sensors fordiverse applications at the

Centre led to the creation of a varietyof pulsating sensors. The in-housedeveloped sensors of unique designsare facilitating development ofreliable, inexpensive and high

Fig.5: Depletion of suspended sodium compound aerosol mass concentration with time undergamma field

faster than that of SrO2 and Fe2O3

aerosols. This is attributed to the factthat sodium oxide reacts with humidityand size grows, which enhances thecoagulation resulting particle size.The larger particles undergo fastergravitional settling. The initial aerosolmass concentration inside thechamber is nearly 2 g/m3. Using initialMMD and mass concentration asinput, the time evolution of

suspended mass concentration of thesodium compound aerosols inside thechamber was predicted by HAARMcode. Both experimental and HAARMcode predictions are presented inFig. 4.

A 137Cs source of strength 60 GBq wasused for the panoramic exposure ofthe aerosol chamber. The timeevolution of suspended aerosol mass

Sensors for monitoring oftransformer oil and ethanolmixed petrol as spin-offsfrom the pulsating sensorsdevelopment programme

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water cause the dielectric permeabilityof the service oil in any transformerto increase with time. A pulsatingsensor has been developed formonitoring transformer oildegradation. The sensor is basicallycapable of detecting minor shift indielectric permeability of the oil duringservice. A laboratory made stainlesssteel electrode assembly consistingof uniformly spaced multiple numberof SS electrode discs, immersed in themineral oil of interest, serves as thetiming capacitor of an oscillator circuitwhich is driven by a DC supply. Withall other factors remainingunchanged, the digital pulsefrequency at the output is governedby the dielectric permeability of theoil that acts as the dielectric mediumin the capacitor assembly. The pulsefrequency changes sensitively withthe change in dielectric permeabilityand, hence, the shift in measured pulsefrequency with respect to the freshoil is a measure of dielectricdegradation of the used oil duringservice.

The measurement set up is shownschematically in Fig.1. Frequency canbe measured by any of thecommercially available hand-heldfrequency meter. However, for adetailed study hardware and softwareinterfaces have been developed torecord the frequency data as afunction of time through a PC.Photographs of a typical fieldmonitoring kit and a PC basedmeasurement device, both developedat IGCAR, are shown in Fig. 2a andFig. 2b respectively.

The digital pulse frequency data as afunction of time for fresh oil as wellas for a slightly degraded oil using atypical device is shown in Fig. 3.Decrease in pulse frequency for theused oil corresponds to increase inthe dielectric permeability by about

Fig. 1 : Schematic representation of the oil monitoring device.

Fig. 2 : a) A typical pulsating sensor based transformer oil field monitoring kit. b) A PC based dataacquisition system for the oil monitoring device.

Fig. 3 : Pulse frequencies recorded as afunction of time for fresh oil and a sample of

service oil. Fig. 4 : A prototype on-line transformer oilmonitoring probe.

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of a portable battery operated deviceat IIS for rapid and non-destructiveassay of ethanol in ethanol-mixedpetrol. This development was inanticipation of a possible need forsuch devices in view of the plan forprogressive introduction of ethanolblended petrol throughout thecountry.

Ethanol, being polar in nature, hasdielectric permeability significantlyhigher than that of petrol. Hence, thedielectric permeability of ethanol-mixed petrol changes as a function ofethanol content. In this device thepetrol to be monitored serves as thedielectric medium of a laboratory madecapacitor assembly that acts as thetiming capacitor of a miniatureoscillator circuit. Digital pulsefrequency at the output, which canbe measured by any hand-heldgeneral purpose digital multi-meter,changes sensitively with small changein dielectric strength. An assembly ofuniformly spaced rectangularelectrodes, immersed in petrol, wasused for exploitation of the capacitiveeffects, and proved to be adequatefor monitoring minor shifts indielectric permeability caused byprogressive increase in ethanol level.Thus, for a given device, the shift infrequency from that measured forpure petrol is related to ethanolcontent.

Based on the successful laboratorystudy, a prototype battery operatedunit has been made for field use, aphotograph of which is shown inFig. 5. The measured shift infrequency as a function of ethanolcontent, in the range of 0 – 5 volumepercent, is given in Fig. 6. Consideringthe precision of frequencymeasurement with a general purposehand-held multi-meter, the measuredfrequency shifts are quite large, and,therefore, permits sensitive

pulsating sensor based oil monitoringdevices. Thus, seven parameters weredetermined experimentally on everyoil sample.

It was observed that the pulsefrequency, as measured by the IGCARdevices, reduced by about sevenpercent for service oils nearingrejection compared to that for thefresh oil. As the devices permit precisemeasurement of frequency shifts lessthan 0.2%, onset of degradation isdetectable at an early stage. Further,the correlations among the standardcharacteristics, ie among interfacialtension, neutralization value,dielectric dissipation factor, resistivity,breakdown voltage and watercontent, were comparable with thosebetween the digital pulse frequencyand the standard parameters. Theconclusion of the joint evaluation byIIS, ESD and CPRI was that, as thepulsating sensor based newtechnique of IGCAR is simple, thetransformer maintenance personnelmay use it as a screening test fordeciding whether the oil sampleshould be sent to a central laboratoryfor full evaluation towards furtheractions with respect to treatments forreuse or disposal.

Success of the off-line devicesprompted design and development ofthe rugged on-line monitoringdevices at IIS in collaboration withESD. Photograph of an on-lineprototype device which is inoperation for over one year with an11-kV transformer in IGCAR is shownin Fig. 4. Industrial grade productshave also been made and they areundergoing laboratory tests.

II. Ethanol assay in ethanolmixed petrolThe laboratory developed digitalapproach, enabling capture of minorvariations in dielectric permeability ofliquid dielectrics, led to development

Fig. 5 : The schematic diagram with aphotograph of the portable field monitoring kit

for assay of ethanol in petrol.

Fig. 6 : Response of the device to ethanol.

1.6 %. Thus, extremely high precisionin frequency data permits monitoringof very minute shifts in dielectricpermeability, hence enabling earlydetection of onset and progress ofdegradation in the quality of serviceoil.

Under an MoU between IGCAR andCentral Power Research Institute(CPRI), the devices made in IIS forESD of IGCAR were tested at CPRIalong with the conventional standardtechniques for degradationassessment. Two hundred oil samplesfrom power transformers of differentratings were collected and evaluatedby the Dielectric Laboratory of CPRIfor the standard characteristics viz.,interfacial tension, neutralizationvalue, dielectric dissipation factor,resistivity, breakdown voltage andwater content following theprescribed procedures. The digitalpulse frequencies were also recordedby CPRI on each sample using the

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quantitative assay of ethanol inpetrol. The range is extendable.

It is to be noted that petrol, beinginflammable and highly volatile, wasnot handled in the laboratory. Allmeasurements related to above datawith respect to pure and mixedsolutions, including preparation ofblended solutions of differentcompositions for calibration, werecompleted in about half-an-hour in anopen area with this battery operatedsystem, demonstrating itsapplicability, simplicity and speed forfield measurement.

The kit was used to measure the pulsefrequencies corresponding to purepetrol samples drawn from sevendifferent petrol bunks aroundKalpakkam belonging to Indian Oil,Bharat Petroleum and HindustanPetroleum companies. The pulsefrequencies were practically same andlied within the standard deviation of±20 Hz ( ie ~ 0.06% of the measuredpulse frequency). It is seen from thedata given in Fig. 6 that the pulsefrequency shifts by more than 200 Hzper volume percent of ethanol. Hence,the ethanol content can be

determined easily with good accuracyand precision.

The indigenously developed aboveinexpensive and non-destructivemonitoring devices can be adoptedfor large scale use in the country foroff-line / on-line / field assessment oftransformer oil degradation as well asfor rapid assay of ethanol in ethanolmixed petrol.

(Reported by B. Saha, InnovativeInstrumentation Section,

Electronics & InstrumentationGroup)

nanoparticles from 2.3 to 6.5 nm bycontrolling the properties of thesolvent media. The nanoparticles withdifferent sizes are prepared bycontrolling the solubility and reactionrates. The equilibrium critical radius(r*) of particles during nucleation insupersaturated solution is defined as

)ln(2*

STkVr

B

σ= (1)

where, V is the molecular volume ofthe precipitated species,σ is thesurface free energy per unit surfacearea, kB is the Boltzmann constant, Tis the absolute temperature and S isthe saturation ratio, which is definedas ratio between soluteconcentrations at saturation (X) andequilibrium (XS), i.e. S = X/XS. For a

nanoparticles used in the ferrofluidvaries with applications. Therefore,the methodologies to control thephysical properties of nanoparticlesare very important. Among variousreproducible synthesis routes for thepreparation of nanoparticles, theprecipitation technique is one of themost convenient and versatilemethods. In precipitation, thenucleated particle size depends onparameters related to reactionconditions, solubility and interfacialenergy. Over the last few years, aresearch programme is being pursuedat IGCAR to tailor stable ferrofluidsfor various applications such asoptical sensors, NDT probes and leakfree sealant.

Recently, a simple method hasdeveloped for tuning the size of the

Ferrofluid is a nanofluid containingmagnetic nanoparticles in the sizerange of 5-10nm. The nano-particlesused in ferrofluids are functionalizedwith organic molecules to preventagglomeration of particles. The easeof manipulating these fluids by anexternal field has led to manyinnovative applications inmechanical, biomedical, electronicand optical systems. Ferrofluids arenow used as dynamic mechanicalseals, airborne seals for protection ofoptical devices and sensitiveelectronic instrumentation in militaryand surveillance aircraft, heat removalagent, medical applications such ascancer treatment, drug delivery, MRIcontrast agents and cell sorting.

The requirement of size, morphologyand the magnetic properties of

Tailoring of stable ferrofluidsfor various applications

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dielectric constant and ε0 is thepermittivity in vacuum. Therefore, thesaturation ratio is inverselyproportional to the solvent dielectricconstant and the equilibrium criticalradius is directly proportional to thesolvent dielectric constant. Bycontrolling the dielectric constant ofsolvent with suitable ratio of ethanolto water, it is possible to vary thecritical nuclei size and hence theparticle size.

By controlling the ratio of ethanol towater, the size of the particles obtainedhas been varied from 2.3 to 6.5nmwhere the alkali used for precipitationwas NaOH. Table 1 shows thecompositions of the solvent, thecorresponding particle size andsaturation magnetization for thesamples S1, S2, S3 and S4. The TEMimage of a magnetite sample and thesize distribution are shown in Fig 1.

The XRD results show that thesamples S1-S4 are magnetite withinverse spinel structure. The inversespinel structure consists of oxide ionsin the cubic close-packedarrangement in which 1/3 oftetrahedral interstices and 2/3 ofoctahedral interstices coordinate withoxygen. All Fe(II) ions occupy theoctahedral interstices, and half of theFe(III) occupies the tetrahedralinterstices and remaining half of theFe(III) in octahedral interstices.Electron spins of Fe(III) ions inoctahedral interstices are aligned anti-parallel to those in tetrahedralinterstices. The Fe(II) ions align theirspins parallel to Fe(III) ions in adjacentoctahedral sites leading to a netmagnetization. The measured valuesof lattice constant for the sample areabout 0.838nm. Fig. 2 shows themagnetization curves of samples S1,S2, S3 and S4. All the samples showsuperparamagnetic behavior with zeroremanence and coercivity.

given value of S, all the particleswhose radius is below r* will dissolvein the solution whereas others willgrow. The concentration XS of ionsforming a saturated solution inequilibrium with the solid is given by

(2)

Where, i is the free energy change,a+ and a- are radii of ions with chargesz1 and z2 , respectively, e is theelementary charge, ε is the solvent

Table 1The compositions of the solvent, the precipitated particle size and

saturation magnetization..

Sample Ethanol: Average particle SaturationWater ratio size (nm) magnetization (emu/g)

S1 60:40 2.3 6.23

S2 40:60 3.3 14.57

S3 20:80 4.8 18.36

S4 0:100 6.5 26.27

Fig 2: The magnetization curves of samples prepared at different ethanol-water ratio

Fig 1. The TEM image of magnetitenanoparticles and the size distribution (inset).

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For sealant applications,nanoparticles are functionalized witha monolayer of surfactant molecules.It has been found that, under dynamiccoating, a close-packed monolayer ofcoordinating ligand is formed on theparticles, where the surfactant has anability to control the size and shapeof the growing particles. Thesurfactants provide a primary coatingon the magnetite particles, which inturn stabilize the particles against vander Waals and magnetic attraction.The surfactant coated magnetitenanoparticles show a two-stepweight loss, where the first weightloss belongs to the weakly boundsecondary layer as well as someweaker bound molecules within theprimary surfactant layer and thesecond weight loss belongs tostrongly bound primary surfactantlayer. The experimental values ofweight loss in sample S1 (2.3 nm) andsample S4 (6.5 nm) are 27.6 and 13.6% respectively. The first loss isobserved at ~250oC with small dropof weight and a large drop is observedat ~375oC. Assuming that thesurfactant forms a close-packedmonolayer on the nanoparticles, thetotal weight loss due to the loss ofsurfactant is calculated theoretically.The calculated values of weight loss

Fig 3: Photograph of magnetite (nanoparticles of average diameter of 6.5 nm) based ferrofluid undermagnetic field (i) unstable (A&B) (ii) stable ferrofluid (C&D).

based ferrofluids under magnetic fieldis shown in Fig 3. The samples A & Bare unstable under field, due toimproper surfactant coating, whereassamples C & D are stable due to amonolayer coating of surfactant oneach particle. The nanoparticlessuspensions obtained by dynamiccoating have shown remarkablestability, in a variety of carrier fluidsover very long periods. The in-housedeveloped magnetite basedferrofluids are being used forfundamental studies and sealantapplications.

(Reported by John Philip, SMARTS,Non-Destructive Evaluation Division,

Metallurgy & Materials Group)

are found to be 30 and 13.17 %respectively for 2.3 and 6.5 nm sizedparticles. The experimentallyobserved amount of surfactant insample S1 was about 2.03 times morethan S4, which was in reasonableagreement with the theoreticalcalculations (i.e.2.27). The differencebetween theoretical and experimentalvalues should be attributed topolydispersity of the particles,hindrance effect of surfactantmolecules at the interface of small sizeparticles, shape of the particles (in thecalculations, particles are assumed tobe spherical) and excess freesurfactant molecules available in S4.A photograph of magnetite (6.5 nm)

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Young OfficersYoung OfficersYoung OfficersYoung OfficersYoung OfficersFFFFForum fororum fororum fororum fororum for

When non-linearitymakes sense: Neuralcomputation inMaterials Science

Sumantra Mandal

Mr. Sumantra Mandal obtained hisB.E. degree in MetallurgicalEngineering from B.E. College,Shibpur in 2002 and M.Tech degreein Materials and MetallurgicalEngineering from IIT, Kanpur in2004 under DAE GraduateFellowship Scheme (DGFS). He isfrom DGFS-2002 batch and joinedIGCAR as Scientific Officer (SO/C)in September 2004.

Artificial neural network (ANN) is ahighly simplified model of thestructure of a biological network[Fig.1]. The fundamental unit orbuilding block of ANN is theprocessing element, also called anartificial neuron or simply a neuron.Some neurons interact with the realworld to receive input, and someprovide the real world with the output.Rest of the neurons remain hidden.Neurons are connected to each otherby synapses; associated with eachsynapse is a weight factor.

ANN is basically an advancestatistical technique that links inputdata to output using a particular setof nonlinear basis functions. Being anon-linear statistical technique, anANN can be applied to solveproblems that can not be efficientlysolved by other conventionalstatistical model. The basic advantageof employing an ANN approach liesin the fact that they do not requireany external manifestation ofparametric relationships an ANNlearns from examples and recognizesthe patterns in a series of input andoutput values without any priorassumptions about their nature andinterrelations. Therefore, ANN canautomatically map the complicatedrelationships between variousparameters. These advantages haveled to an increased interest in the useof ANN in various fields of materialsscience.

Constitutive behavior: ANNapproach

The constitutive behavior of steel isusually expressed by empirical andsemi-empirical relations. However,

Sumantra Mandal and Colleagues,Materials Technology Division,Metallurgy & Materials Group

Fig.1: Schematic diagram of feed-forward multilayer neural network

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ANN model to predictmicrostructural evolutionduring hot working

A model for the microstructuralevolution, including the fraction ofdynamic recrystallization (DRX) andgrain size, in D9 has been establishedemploying artificial neural network.Microstructural data have beengenerated through different industrialscale metal forming processes likeforge hammer, hydraulic press androlling in the temperature range1173K-1473K for various strains.These data have been used todevelop the model. The network hasbeen optimized employing resilient

due to complicated microstructuralchanges (like work hardening,dynamic recovery and dynamicrecrystallization) associated with hightemperature deformation processing,it is very difficult to describe thecomplete hot deformation behaviorusing a single relationship.Furthermore, development of thesemodels are always time consumingand usually have low accuracy inprediction. In this context, ANN canbe considered as an efficientalternative. We have successfullyapplied ANN to predict constitutivebehavior of austenitic stainless steelunder hot torsion and compression.

A three layer feed forward networkwith eight neurons in a single hiddenlayer and back-propagation learningalgorithm has been employed todevelop ANN model to predict flowstress under hot compression of alloyD9. Experimental data to train and testthe network has been obtained byperforming hot compression tests inservohydraulic compression testingmachine. The input parameters of theneural network are strain, strain rateand temperature while flow stress isobtained as output. The result of thisstudy shows that coefficient ofdetermination (R2) for training andtest dataset are 0.9937 and 0.9960respectively. The ANN model forprediction of torsional flow stress fortype 304L has been developedemploying resilient propagationalgorithm. Experimental data to trainand test the network has beenobtained by performing hot torsiontests in the temperature range 600°Cto 1200°C and in the maximum surfacestrain rate range 0.1 s-1 to 100 s-1. Theperformance of the network fortorsional flow stress prediction hasbeen demonstrated in Fig.2.

propagation and superSAB learningalgorithms. The correlation coefficient(R) for test dataset in %DRXprediction is found to be 0.984. Thedeviation in correlation for grain sizedata is found to be 5%. However, thismagnitude of the error in prediction,in fact, is less than the error thatnormally arises during grain sizemeasurement. Therefore, it issuggested that the developed modelcan efficiently predict themicrostructural evolution duringthermomechanical processing. Aninstantaneous microstructure,therefore, can be designed in order tooptimize the process parametersbased on microstructural evolution.

Fig.2: Performance of the network to predict the constitutive behavior of 304L under hot torsion (a)training data set (b) all data set

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IGC Newsletter

ANN model for tensileproperty prediction

The mechanical properties of alloy D9depend on its chemical compositionas well as work temperature. It istherefore important to understand thecorrelation “chemical composition⇒ work temperature⇒ properties”,which would eventually help to

Fig.3: Performance of the ANN model for yield strength (YS) prediction in alloy D9(a) training data (b) All data

optimize the alloy composition inorder to achieve the desiredcombinations of properties.

Basically there are two ways tounderstand such correlations. Firstly,one can construct a physical modelthat describe the relation betweenparameters and validate this modelwith experimental findings. However

an explicit physical model thatquantitatively describes all thecorrelations between alloycomposition, work temperature andmechanical properties of austeniticstainless steel does not exist.Alternatively, model can be developedapplying statistical technique likemultilinear regression methods.However, due to synergistic effect ofindividual alloying elements, thecorrelation between alloying elementsand mechanical properties are highlycomplex and not simply the sum ofthe influence of individual element.An artificial neural network modeltherefore has been developed tosimulate the correlation between alloycompositions, test (work) temperatureand tensile properties of alloy D9. Theinput parameters in the model are fivealloying elements, C, Ni, Mn, Cr andMo as well as test temperature. Outputparameters are three important tensileparameters namely yield strength(YS), ultimate tensile strength (UTS)and uniform elongation (UE).Different models have been tried andthe optimum model has been used forsimulation. It has been observed thatthe developed network is well capableof predicting tensile properties of D9alloy with sufficient accuracy. Theperformance of the model for YSprediction is depicted in Fig.3. It canbe seen that correlation is quite goodand predicted data can efficientlytrack the experimental findings. Themodel is recommended for use as aguide line for optimization of alloycomposition of alloy D9 in order toachieve desired combination ofmechanical properties at differentworking temperature.

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News & Events

October 2, 2006

As part of the Centre’s sustainedinitiatives towards improving the qualityof science education in universities, andalso towards motivating, attracting andretaining the bright young talents in activescientific research, IGCAR organized anawareness tour and a brain stormingsession with Dr.Baldev Raj, Director,IGCAR for about 140 academia fromMadras and Anna Universities,Government and private / Governmentaided colleges situated in and aroundChennai city, in line with the DAE’s oneof the six key drivers for majorprogrammes viz. mutual strengthening ofeducation and research in nuclear scienceand technology and allied disciplines. TheChennai team was lead by Dr.S.Mani,Director of Collegiate Education,Government of Tamil Nadu.Shri P. V. Ramalingam, Director, ReactorOperation & Maintenance Group andalso the Chairman of Public RelationsActivities Implementation Committee(PRAIC) of IGCAR welcomed theaugust gathering and presented anoverview of DAE. Dr. P. R. VasudevaRao, Director, Chemistry, Metallurgy &Materials Groups highlighted thechemistry and physics researchprogrammes of IGCAR. Dr. P.Mohanakrishnan, Head, Reactor PhysicsDivision outlined the reactor physics andsafety research activities, Dr. C. S.Sundar, Head, Materials Science Divisioncovered the materials science programmeand Dr. K. S. Viswanathan, Head,

Analytical Chemistry and SpectroscopySection spoke on the Centre’s chemistryresearch activities.A brain storming session was conductedby Dr. Baldev Raj and Dr. S. Manifollowed the technical presentations. Dr.Baldev Raj appreciated and complimentedthe academia for their keen interest andcommitment to have participated in theevent, despite it being a holiday onaccount of Gandhi Jayanthi. He sharedthe concern of the teaching communityregarding the declining interest in studentsto take up science as a career. He criticallyanalyzed the issue and outlined theroadmap to inculcate the scientific temperin the younger generation. He exploredthe avenues of sharing the excitements ofadvanced research in physics andchemistry being pursued at IGCAR, andextending the unique and the state-of-theart facilities and infrastructure of IGCARto the academic world. In his response,Dr. S. Mani appreciated the initiativesand efforts taken by IGCAR, and pledgedfull support of the TN Directorate ofCollegiate Education towards achievingthis noble cause. The familiarization touralso identified the domains that requireimmediate attention, like the need toenhance the employability of science PGsin Indian context.

IGCAR Awareness Tour and Brain Storming session

for Science Teachers of Chennai Colleges

Visits were conducted in the post-lunchsession to the radiochemistry andmaterials science laboratories and also tothe Fast Breeder Test Reactor to enablethe academia get first hand knowledge ofthe experimental facilities andcompetence of IGCAR. The awarenesstour concluded with the panel discussion/feed-back session conducted by thetechnical experts consisting of Shri P. V.Ramalingam, Dr. P. R. Vasudeva Rao, Dr.C. S. Sundar and Dr. K. S. Viswanathan.The professors actively participated inthe discussion and submitted their writtenfeedback with suggestions forconsideration and implementation byIGCAR for reversing the presentunhealthy trend. Their suggestions arebeing compiled and consolidated by thePRAIC. The participants thankedIGCAR for the excellent arrangements inorganizing the event and making themfamiliar with the experimental facilitiesof IGCAR. Shri J.Daniel Chellappa,Head, Technical Co-ordination & PublicAwareness, Chennai and also theConvener of PRAIC proposed vote ofthanks and acknowledged the valuablecontributions by various agenciesinvolved in this initiative.

(Reported by J.Daniel Chellappa andP.V.Ramalingam, PRAI Committee)

Principals, HODs of Physics and Chemistry colleges of Chennaialong with Dr. Baldev Raj, Director, IGCAR and Dr. S. Mani, DCE, Government of Tamilnadu.

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IGC Newsletter

Dr P.R.Vasudeva Rao, Chairman, Editorial Committee Members: Dr.G.Amarendra, Shri M.Ganapathy, Dr.K.V.G.Kutty, Dr.Mary Mohankumar, Shri G.Padma Kumar, Shri Shekar Kumar,Shri M.Somasekharan, Shri R.Srinivasan, Shri R.V. Subba Rao, Shri K.V.Suresh Kumar. Published by Scientific Information Resources Division, IGCAR, Kalpakkam - 603 102

Dr. Baldev Raj has been conferred with the honorary Doctor of Science (D.Sc.) by Sathyabama Institute ofScience & Technology (Deemed University), Chennai. He has been elected as Honorary Member of IndianInstitute of Metals and Honorary Fellow of Indian Welding Society. He has deliverd the following honour lectures,Stanley Ehrlich Distinguished Lecture and Gold Medal, Acoustical Foundation for Education and CharitableTrust, India (2006), International Recognition Award, Indian Society for Non-Destructive Testing (2006)Dr. P. V. Sivaprasad, Materials Technology Division has been awarded the “Metallurgist of the Year” for the year2006 by the Ministry of Steel, GOI.Dr A. K. Bhaduri, Material Technology Division has been elected as the Fellow of Indian National Academy ofEngineering from January 2007.Shri P Sukumar, Non-Destructive Evaluation Division and Shri N. Vinayagam, Central Workshop Division,have been awarded the “DAE Meritorious Service Award” for the year 2005.Shri R.Subbaratnam, QA&NDTS won the prestigious “NDE man of the year Award” for the year 2006.STAR Quality Circle of CWD has got the “Distinguished Award” during 20th National Convention of QualityCircle (NCQC-2006) presentations at IIT, Kanpur, during December 2006.

AWARDS AND HONOURS

introductory note. Shri M. Rajan, Director,Safety Group inaugurated the workshop andstressed the need to evolve TQM inLibraries. Prof. A. Amudhavalli, President,MALA & Head, Department of InformationScience, University of Madras proposedthe vote of thanks. Commodore S. Shekar,Managing Director, Sanjeevini HumanResource Institute, Chennai and his teamconducted the workshop.

The TQM workshop was designed to givethe participants an overview of the all-pervasive nature of Total Quality

Management. The workshop was dividedinto three sessions: Session-1: IntroducingTQM, Session-2: TQM Tools andTechniques and Session-3: Putting TQMto work. The workshop was highlyinteractive and participative. During thefinal session participants formed fivegroups and case studies of their choicewere presented. The studies werepresented and critically evaluated. About120 delegates from various institutionsparticipated in the workshop. Theworkshop was highly appreciated by allthe participants.

(Reported by M. Somasekharan, SIRD)

Workshop on “Total Quality Management” - November 18, 2006

A one-day workshop on “Total QualityManagement (TQM)” was organized bythe Madras Library Association,Chennai & MALA-Kalpakkam Chapteron 18-11-2006 at AnupuramConvention Centre. The workshopprovided an excellent opportunity tothe participants to get to know theevolution and emergence of TQM intheir working environment.

Shri M. Somasekharan, President,MALA-KC & Head, SIRD, IGCARwelcomed the gathering and delivered

Visit of Japanese delegation from Japan Council on Energy andSecurity (JCES) - November 22-23, 2006

Dr. Osamu Saito, Senior Fellow of JCES,Mr. Makio Tsuji, Senior Fellow of JCES,Mr. Kazuya Ochiai, Fellow of JCES andDr. Naoyuki Takaki, Fellow of JCES.

The delegation had deliberations with seniorscientists of the centre. Dr. Baldev Raj,

Distinguished Scientist & Director ofIGCAR in his address highlighted theactivities of the centre. He alsoemphasised on R&D approach to FBRwith improved economy and safetyfeatures. Prof. Kaneko, the leader of theJapanese delegation, talked about thecurrent status of Japanese fast reactorprogram. The Japanese delegationexpressed the hope that the cooperationbetween India and Japan would beenhanced considerably in the comingyears. The delegation visited the FastBreeder Test Reactor, facilities of the FastReactor Technology Group, SafetyGroup, Structural Mechanics Laboratory,Materials Science Laboratory and PFBRsite.

(Reported by M. Sai Baba, SHRPS)

A Japanese delegation led by Prof.Kumao Kaneko from Japan Council onEnergy and Security (JCES) visitedIGCAR on 22nd and 23rd November,2006. The members of the delegationswere: Prof. Kumao Kaneko, President,JCES,

Japanese delegation from Japan Council on Energy and Security,led by Prof. Kumao Kaneko during a discussion meeting with Dr. Baldev Raj, Director,

IGCAR and other senior colleagues of the Centre

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