Design, development and performance testing of fast responseelectronics for eddy current flowmeter in monitoring sodium flow

Poornapushpakala S.a,1, Gomathy C.b,2, Sylvia J.I.c,3, Babu B.c,3

a Department of Electronics & Control Engineering, Sathyabama University, Chennai 600119, Indiab Department of Electronics and Communication Engineering, SRM University, Vadapalani, Chennai 600026, Indiac Head, ID&SS, FRTG, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India

a r t i c l e i n f o

Article history:Received 29 March 2013Received in revised form15 March 2014Accepted 2 May 2014Available online 21 May 2014

Keywords:Eddy current flowmeterProgrammable system on chipSodium velocitySignal conditioning circuitFast response

a b s t r a c t

The paper discusses the design, development and performance tests of a fast response processingelectronics for an eddy current flowmeter that has been developed indigenously to measure sodium flowin the primary sodium pump discharge line, pumping liquid sodium to the core consisting of fuel sub-assemblies in the prototype fast breeder reactor at Kalpakkam, India. Liquid sodium is the main coolantin Fast Breeder Nuclear Reactor. Eddy current flowmeters are deployed in liquid metal cooled fastreactors. The measurement of flow rate of the coolant is important to maintain the overall performanceof the pump which in turn is the safety requirement of the system. The faster response of the measuringsystem is required to ensure the protection of the reactor under pump seizer and discharge pipe rupture.This work mainly focuses on the reduction of response time of signal processing electronic delay.

& 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Sodium flow measurement is imperative in the context of FastBreeder Reactors (FBR) to check the operation and safety of thereactors. In sodium cooled FBR, various types of flowmeters areemployed for sodium flow measurement. Permanent MagnetFlowmeters (PMFM) are widely used for sodium flow measure-ment at the primary pump outlet in BN 350 loop type, by pass linein BN 600 and BN 800 pool type reactor [1]. PMFM is also beenused in the primary circuit of Phenix reactor [2]. Fast flux testfacility (FFTF), SNR 300, KNK, MONJU, Rapsodie and Fast BreederTest Reactor (FBTR) [3]. These flowmeters are not suitable for usein regions of high radiation because of the damage to the magnets[4]. In addition, the magnets must be stabilized against theinfluence of demagnetization, temperature and mechanical shocksand these are heavier in nature [5].

In JOYO a loop type reactor, saddle coil flowmeter is in use in theprimary circuit [3] and in the secondary circuit [6]. Saddle coil

flowmeters have been used in the secondary circuit of PrototypeFast Reactor (PFR) [7,8]. Saddle coil flowmeters are comparativelylighter but are lengthy [9]. Hence it is not suitable for remotelocations.

Lehde and Lang [10] patented the flow measurement devicebased on eddy current principle in 1948. The device consists oftwo primary coils excited by an AC generator and is placed in sucha way that their magnetic effects oppose each other. The second-ary coil is placed midway between the other two coils. These areplaced in the insulated material housing. The device is centrallylocated to a tube where the conducting liquid flows. The resultantvoltage induced in the secondary coil is directly proportional tothe speed of the fluid. An alternate design with two primary coilsin series and two secondary coils in series opposition was devel-oped. A modified design adopting the first technique with 3 pri-mary coils and 2 secondary coils was used as speed and distancemeasuring instrument for ships. This concept was proposed as aflow failure alarm in the British PFR in the early 1960s [11]. Probetype eddy current flowmeter (ECFM) has been used in the BritishPFR [12].

ECFM has been developed and used in Hanford EngineeringDevelopment Laboratory (US), Argonne National Laboratory (US)and in Indira Gandhi Centre for Atomic Research (IGCAR, India) formonitoring the flow of sodium through the core in a NuclearReactor. The ECFM is used for void detection in the Liquid MetalFBR (LMFBR) core exit at O-arai Engineering centre (Japan) [13].A conceptual design of a contactless ECFM for liquid metal flows

Contents lists available at ScienceDirect

journal homepage: www.elsevier.com/locate/flowmeasinst

Flow Measurement and Instrumentation

http://dx.doi.org/10.1016/j.flowmeasinst.2014.05.0040955-5986/& 2014 Elsevier Ltd. All rights reserved.

E-mail addresses: poornapushpakalas@gmail.com,poornapushpakala.enc@sathyabamauniversity.ac.in,s_ppk@rediffmail.com (S. Poornapushpakala),cgomathy@yahoo.co.uk (C. Gomathy), sylvia@igcar.gov.in (J.I. Sylvia),bbabu@igcar.gov.in (B. Babu).

1 Tel.: þ91 9790956400, þ44 24503165.2 Tel.: þ91 9444287670.3 Tel.: þ91 44 27480500.

Flow Measurement and Instrumentation 38 (2014) 98–107

based on phase-shift measurement is presented in Ref. [14]. Theseused an improved design with single primary coil excited by an ACsource and placed centrally to the two secondary coils. The secondarycoils are connected in series opposition.

The ECFM has been proposed for measurement of sodium flow inFBR where space constraint and high ambient temperature is pre-valent [15–17]. The use of ECFM is appreciable for its small size, abilityto withstand high temperature and resistance to radiation damage [5].The ECFM eliminates the use of permanent magnets and otherferromagnetic parts whose degradation generally tends to affect theperformance of a flowmeter [18,19]. Maintenance of ECFM is mucheasier than any other type of flowmeter. The disadvantage of ECFM isthat it has a slower response time than PMFM and is highly sensitiveto temperature changes and flow turbulence.

2. ECFM and existing electronics

ECFMworks on the principle of change in the magnetic field due toinduced eddy currents as a result of sodium flow. The ECFM consists ofa system of AC operated coils, fixed in space and electromagneticallycoupled conducting fluid. The ECFM has one primary and twosecondary coils placed symmetrically along the flow axis, one inupstream side of primary and other in downstream side of primary.The system has a built in symmetry and hence the output signal of thecoils is zero when fields are stationary. Motion of the fluid causes eddycurrents to move downstream from their symmetrical locations andthe resulting magnetic field imbalance generates an output signalwhich serves as a measure of the fluid velocity.

Fig. 1 represents the schematic of ECFM. The flow sensor used inIGCAR is of 14 mm diameter and 150mm long. It has three coils and iswound over the bobbin made of magnetic material and encapsulatedin stainless steel pocket to maintain physical separation of flowingfluid with primary and secondary coils. Central primary coil is excitedby constant current source at a constant frequency. In British PFR,700 Hz is used as the primary excitation frequency [12]. The FFTFreactors use excitation source of 1000 Hz, 500 mA for the primary

winding of ECFM [20]. It is shown analytically that both the velocity-profile errors and temperature errors can be minimized by selecting asuitable operating frequency [19]. The frequency response test per-formed on ECFM proved that 400 Hz is the optimum primaryexcitation frequency of ECFM for use in Prototype Fast Breeder Reactor(PFBR) [17]. The optimum excitation frequency for MK-3 Probe is375 Hz as described in [13].

The ECFM for this study is developed for use in Prototype FastBreeder Reactor (PFBR) by IGCAR, India. In PFBR, the primarysystem consists of two vertical centrifugal pumps operating inparallel. The flow through the pump is adjusted by changing thepump speed. The flow delivered by each pump is separatelymeasured to monitor the pump performance and to obtain thetotal flow through the core. ECFM is employed in the PrimarySodium Pump (PSP) of the PFBR to measure pump flow and inindividual sub-assemblies before the start up of the reactor inFBTR [21]. Sodium flow is measured in fast reactors mainly atpump outlet in the primary circuits, secondary sodium circuits andat the outlet of the fuel sub-assemblies to detect flow blockage asdescribed in literatures [9,13,22]. The measurement of sodiumflow is important to protect the reactor from events like oneprimary pump seizure, one primary pump trip, off site powerfailure and rupture of pipe joining primary pump to grid plate.Flow monitoring is important to find performance of the sodiumpumps and observing the core cooling.

The output voltage of secondary coil of ECFM has two compo-nents – one due to transformer action and other due to motion ofconducting sodium in the magnetic field. The magnitude ofvoltage in two coils can be thus qualitatively expressed as follows[23]:

S2 ¼ EtransþEmotion ð1Þ

S1 ¼ Etrans�Emotion ð2Þ

where S1 is secondary coil voltage in upstream and S2 is secondarycoil voltage in downstream.

Fig. 1. Schematic of ECFM (Courtesy [IGCAR]).

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107 99

ðS2�S1ÞðS2þ S1Þ

¼ Emotion

Etransð3Þ

Etrans represents the component of voltage due to transformeraction and Emotion represents the component of voltage due tomotion induced voltage. Emotion polarity in the downstream andupstream coils is opposite, since the direction of primary magneticfield in radial direction is opposite in the downstream andupstream coils. When temperature of surrounding sodiumincreases, its electrical resistance increases. This results in lesseddy currents and an increase in both Etrans and Emotion voltage.The effect of temperature is compensated by using normalizedoutput signal (NS) as given in Eq. (4) which is a scalar quantity andthis output is a function of velocity as reported in Ref. [24].

NS ¼jS2�S1jjS2þS1j

100 ð4Þ

Wiegand et al. [18] performed dry and sodium loop test onECFM and inferred that there was a residual signal which con-tributed to measurement errors even though an external arrange-ment was used to balance that signal. In addition, found 10%discrepancy in the sensitivity of ECFM with theoretical value fromthe sodium loop test and suggested implementation of filteringtechniques to reduce the noise pick up voltage that are very highin ECFM. When there is no sodium flow, the differential outputof the ECFM should be zero but experimentally it is found to give2–3 mV offset voltage due to the misalignment of the secondarycoils as discussed in Ref. [17,23]. The wet and dry performanceevaluation in sodium inferred that the sensitivity of ECFM in Drydesign test housing is better than the wet design. The Probe typeECFM used in FFTF has electrical unbalance which was nullified byadjusting the voltage and gain of the amplifier used in theelectronics supporting the sensor [20]. The ECFM has responsetime limitations due to the low carrier frequency for very largechannels [5,18].

The response time of ECFM is found by reducing the sodiumvelocity (V0) to zero at time t¼0, and computed from the transientresponse [25]. When there is sodium flow the magnetic force linesare distorted due to the formation of eddy currents as shown inFig. 2. The distortion of magnetic force line changes depending onthe sodium flow. For no sodium flow, the magnetic force line is astraight line.

Initial, electromotive force (EMF) before step change is given bythe following equation:

E0 ¼ V0 Bd ð5Þ

B – magnetic flux density of the applied magnetic field; d – diameterof the pipe; E0 – electromotive force at time, t¼0; and V0 – velocity ofthe sodium flow at t¼0.

Response time of ECFM can be defined by Eq. (6), which iscomputed from the transient response after the sodium flow is

stopped.

τ¼Z 1

0E d t=E0 ¼ L=V0 ð6Þ

Z 1

0E d t ¼ LBd ð7Þ

where τ – time constant; E – electromotive force; L – distance ofthe displacement from the original straight magnetic force line

From Eqs. (5)–(7), it is described that the response time of theEMF is proportional to the electric conductivity of sodium and tothe square of the pipe diameter. Hence response time of the ECFMfor a 0.6 m diameter pipe at sodium temperature of 400 1C isfound to be 0.1 s [25].

Simulation of finite element method (FEM) analysis of eddycurrent water flowmeter was done using MagNet software foroptimizing the configuration of the device to enhance the brakingtorque [26]. Similar simulation of ECFM is performed usingCOMSOL software and subjected it to various temperatures ran-ging from 150 1C to 550 1C and found the optimum operatingfrequency and flow characteristics [27]. It is observed that thesimulation results have an average of 4.8% and 2.7% error with theexperimental results for 500 1C and 400 1C respectively. TheCOMSOL model used zero conductivity cable for modeling ECFMcoils against the actual mineral insulated cables that has conduc-tivity. Hence an average deviation of 71.24 mV was observed withthe experimental results.

The existing electronic circuitry for the ECFM sensor has a driveunit which supplies a constant current output of 200 mA at 400 Hzto the primary winding. It also has a signal processing unit withtemperature compensating circuits. Occurrence of changes in flowrate is detected by the existing module with a response time of1.5 s. The time delay is due to the filter and AC to DC conversion asper the published literatures [17,23]. Since the ECFM sensor itselfhas response time limitations, improving the response time of thismeasuring unit is essential to protect the reactor from nuclearmeltdown. This work presents the improvements in the designmethods of the signal conditioning circuit with quicker responsetime. It also discusses the use of Programmable System on Chip(PSoC) microcontroller for improving the performance of themeasuring and monitoring system.

3. Design and development of measuring electronics

ECFMs are housed in the primary pump discharge line of liquidsodium pumps to measure the flow to the reactor core consistingof fuel sub-assemblies. Two incidents of major safety concern inthe reactor vessel are seizer of primary sodium pump and ruptureof pump discharge lines connected to the core. In such a situationthere will be a sudden drop in discharge pressure that results insudden flow reduction, and hence sudden rise in temperature ofthe core which may lead to core melt down. To prevent such anoccurrence of flow reduction, it has to be detected and the reactorhas to be scrammed (emergency shutdown) within 1 s. Consider-ing the overall time taken for the shutdown mechanism to operateand complete the scram, it is required that the response time ofECFM and signal processing delay for detection of flow reduction,should be limited to less than 100 ms.

The objective of this work is to design an electronics that aids acontinuous monitoring of sodium flow rate and detects the changesin flow rate within a very shorter span of time. In addition, the designalso ensures that the flow characteristics are not affected due tovariations in temperature. The main requirement of this work is toreduce the response time of the measuring electronics excluding theECFM sensor response time. The challenge of the new design is toFig. 2. Distortion of magnetic force line caused by eddy currents (Courtesy [25]).

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107100

minimize the delay due to filter, AC to DC conversion and processingtime in the existing electronics used in IGCAR, Kalpakkam. Fig. 3shows the schematic of the Fast Response Electronics, developed forprocessing ECFM signal.

3.1. Design of signal conditioning circuit

The nature of the signal from the secondary coils of the ECFM isvery low in the range of mill volt, which necessitates pre-amplification. Instrumentation amplifier is generally preferred insuch applications. For this application, Integrated Circuit (IC)INA128 is used. According to the design Eq. (8), Rg is selected as5 KΩ to give a gain (G) of 11.

G¼ 1þ 50KRg

ð8Þ

The instrumentation amplifier has settling time of 6 ms. Since theapplication has low input voltage and the signal is sinusoidal innature, slew rate does not have much effect on the response. Anisolation amplifier is included to electrically isolate the ECFMsensor from the associated electronics, IC ISO120 is used. The

isolation amplifier contributes a settling time of 50 ms based on thedesign. A band pass filter is used to maintain a natural frequencyand to eliminate noise. From the design Eq. (9) of IC UAF42, bandpass gain (ABp)¼1, gain setting resistor, RG is calculated to be50 KΩ. A center frequency of 400 Hz with a bandwidth of 100 Hz isconsidered for the design calculation. From Eq. (10), Q is calculatedto be 4. From Eq. (11) the Q setting resistor, RQ is calculated to be8.3 KΩ assuming the external filter resistor RF1, RF2 to be 400 KΩ.

ABp ¼R4

RGð9Þ

Q ¼ f mf 2� f 1

ð10Þ

fm¼Band pass mid frequency; f2� f1¼bandwidth

Q ¼ 1þðR4ðRGþRQ Þ=ðRGRQ ÞÞ1þðR2=R1Þ

R2RF1C1

R1RF2C2

� �1=2

ð11Þ

The challenge of the new design is to minimize the delay dueto filter and AC to DC conversion. For AC to DC conversion, initi-ally design was made using precision rectifier and RC Filter. With

Signal Conditioning Circuit

Signal Conditioning Circuit

PSoCECFM Secondary

Output 2

ECFM Secondary Output 1 Monitoring

in Personal Computer

Fig. 3. Schematic of the fast response electronics.

Fig. 4. Signal conditioning circuit design.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107 101

R and C in parallel, time constant of the response is found to be8.5 ms, whereas the ripples were more than 1%. With R and C inseries the ripples were within 1% whereas, the time constant ofthe response is 35 ms. Design has been tested for various combi-nations of RC values for 1% ripple (γ) calculated using the formulagiven by the following equation:

γ ¼ 1

4√3f RCð12Þ

To improve the response time without compromising on the ripplefactor a design with True Root Mean Square (RMS) to DC converter(IC AD736) has been employed by replacing the precision rectifierand RC filter. This design gave better result with time constant of4.23 ms and ripple of less than 1%. The selection of averagingcapacitor in the design contributes to a settling time of 18 ms.Design of signal conditioning circuit and its simulation is done inCadence ORCAD software [28]. The output at each stage of thesimulated circuit is compared with the theoretical value obtainedas per the design of the signal conditioning circuit. Simulatedresults are linear and have an average of 70.02 V deviations withthe theoretical value. Fig. 4 shows the signal conditioning circuitdesign.

3.2. Hardware development

The printed circuit boards are developed for the measuringelectronics using Altium Designer. For enabling easy troubleshooting and for ease of handling the fast response electronicssystem is split into four modules, namely power supply, signalconditioning, control and bus.

The power supply module generates two þ12 V, two �12 Vand one þ5 V supplies. One pair of þ12 V and �12 V supply isused for providing power supply for the electronic components insignal conditioning board before isolation and another pair is usedfor those after isolation and þ5 V supply is used for the controllerIC, LED, LCD, Keyboard, etc., The signal conditioning module asdescribed in Section 3.1 has Instrumentation Amplifier (INA128),Isolation Amplifier (ISO120), Active Band pass Filter (UAF42), TrueRMS to DC converter (AD 736) and the supporting electroniccircuits. The controller module has CY8C3866AXI-040 PSoCs3processor IC and 74HCT138 decoder IC for key selection. Fig. 5shows the circuit diagram of the controller board.

Mother board module interconnects all the three modules forsharing power supply, input signal and output signal using euroconnector. The mother board is provided with 6 pin circularconnector for getting the input from the ECFM sensor, RS232connector for sending the signal via serial port, the Zigbee modulefor wireless transmission and 3.3 V regulated supply for poweringthe Zigbee. Fig. 6 shows the circuit diagram of the mother board.

3.3. Design of PSoC microcontroller

The DC output of the signal conditioning circuit correspondingto both the secondary output of ECFM are acquired and processedby a Programmable System on Chip (PSoC) Microcontroller.Initially the hardware is designed using PSoCs1, with analog todigital converter (ADC) of 10 bit resolution at a sampling rate of1000 samples per second (sps). With this design, the responsetime of the microcontroller was 3.9 ms. An advanced design usingPSoCs3 with increased sampling rate of 48000 sps and ADC

Fig. 5. Circuit diagram of controller board.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107102

Fig. 6. Circuit diagram of mother board.

Fig. 7. Screenshot of PSoC design.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107 103

resolution of 16 bit, achieved a response time of 1 ms. PSoCs3 isprogrammed on a PSoCsCreator platform. A linear relationbetween the normalized output signal (NS) and velocity is estab-lished from the experimental data. The sodium velocity (VSO) iscomputed based on the relation, given by Eq. (13). For eliminatingthe error due to misalignment in the secondary coils, offsetadjustment is done on the normalized output signal through PSoC

programming. Fig. 7 shows the screenshot of PSoC Design for thisapplication.

Vso ¼ NS

2:247ð13Þ

The components used in the design of PSoCs 3 are, 16 bit deltasigma ADC, Multiplexer, Timer, key module, LCD module, UARTand EEPROM. This design use delta sigma ADC, configured for16 bit resolution with a sampling rate of 48000 sps. The twosecondary signals are given to the ADC through a multiplexer.1 mstimer is configured using 8 bit timer. This 1 ms timer is used fordisplay and transmission timing calculations. The PSoC LCD driversystem is designed to allow PSoC to directly drive LCD glass. LCD oftwo rows and 16 characters are used for this work. This design useEEPROM which stores the threshold value and offset valueenabling the microcontroller to use the last updated thresholdvalue and offset value for the calculation of normalized outputsignal mentioned in Eq. (13). The UART is configured for fullduplex transmission with a baud rate of 9600. Two UART are used,one for wired transmission via RS232 and the other for wirelesstransmission via Zigbee. The microcontroller response time iscalculated using counter.

4. Performance test

The signal conditioning circuit is initially tested in the PSpicesimulation environment. The simulation results have an average of70.02 V deviation from the theoretical value. A variable sinusoidalsignal of 0–360 mV at 400 Hz is generated by using PSoC

Table 1Output voltage at each stage of signal conditioning circuit.

Input to instrumentation amplifier (V) Output of instrumentation amplifier (V) Output of filter (V) DC output (V)

Theoretical Experimental Theoretical Experimental Theoretical Experimental

0.047 0.51 0.51 0.51 0.52 0.18 0.180.066 0.72 0.69 0.72 0.65 0.25 0.220.083 0.91 0.84 0.91 0.81 0.32 0.280.106 1.16 1.10 1.16 1.10 0.41 0.380.137 1.50 1.44 1.50 1.41 0.53 0.520.142 1.56 1.50 1.56 1.50 0.55 0.540.160 1.76 1.71 1.76 1.71 0.62 0.600.246 2.70 2.62 2.70 2.70 0.95 0.92

Fig. 8. Performance of instrumentation amplifier.

Fig. 9. Performance of band pass filter.

Fig. 10. Performance of true RMS to DC converter.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107104

microcontroller. This signal is used for testing the fast responseelectronics and the output at each stage of the signal conditioningcircuit is recorded. Table 1 shows the experimental and theoreticalvalues at each output stage of signal conditioning circuit. Figs. 8–10 show the comparison of experimental results with theoreticaloutput of Instrumentation amplifier, Band pass filter and true RMSto DC converter respectively. It is observed that the experimentalresults have an average of 70.05 V deviation from the theoretical

value. The theoretical values are also tabulated. Fig. 11 shows theresponse of signal conditioning circuit for a burst of signal. It isobserved that the average delay time is 0.72 ms with a standarddeviation of 0. 212 and average rise time is 7.88 ms with thestandard deviation of 2.2.

The fast response electronics is tested for various signalsincluding the worst case condition arise due to maximum differ-ence between two secondary outputs of ECFM. The system istested by giving a burst of input signal of varying magnitude andthe time taken to detect the changes is recorded. Table 2 shows themeasure of rise time and fall time for various strengths ofsecondary voltages. The output voltage corresponds to sodiumvelocity in m/s. The average rise time is found to be 13.9 ms withthe standard deviation of 6.18 and the average fall time is 14.65 mswith standard deviation of 0.747. Fig. 12 shows the DC resultantvoltage of fast response electronics for burst of signal.

Fig. 11. Response of signal conditioning circuit.

Table 2Output characteristics of fast response electronics.

S1 (mV) S2 (mV) Differentialvoltage (mV)

Risetime (ms)

Falltime (ms)

Outputvoltage (V)

115 155 40 25.4 15.3 6.59120 153 33 19.1 16.0 5.37123 150 27 9.9 14.4 5.10127 148 21 10.0 14.2 3.39130 145 15 9.8 14.0 2.42133 140 7 9.2 14.0 1.14

Fig. 12. DC output of fast response electronics for burst of signal.

Fig. 13. Performance of fast response electronics for ECFM.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107 105

5. Results and discussion

Based on the comparison of results, more than 3% devia-tion is observed between the theoretical and experimentalvalues of true RMS to DC converter above the operating rangeof 250 mV. This is because of the selection of averagingcapacitor and the feedback capacitor in the design circuit ofTrue RMS to DC converter. Since the maximum output fromthe secondary coils of ECFM is 100 mV, the circuit is designedfor the input range of 0–200 mV and a cut off frequency of400 Hz. The characteristic of signal conditioning circuit islinear in this range and the error increases above 3% withthe theoretical value above this range. The selection of thesecapacitors can widely be varied according to the requirementbased on the application.

The measuring module is tested by giving a burst of inputsignal and the time taken to detect the changes is recorded. Themeasurements shown in Table 2 indicate the characteristics of thefast response electronics which is influenced by the signal con-ditioning circuit, microcontroller hardware and software. It isobserved that the rise time is not consistent and has a standarddeviation of 6.18 but the fall time is very much consistent with alow standard deviation of 0.747. This is due to the averagingalgorithm used in the ADC programming for processing the inputsignals.

Fig. 13 shows the comparison of fast response electronics testresult with the experimental data. This indicates the sodiumvelocity measured by the system is linear but have an average of70.11% error for the data. As the differential voltage increases, theerror increases up to an average of 71.3%. The relation between

Fig. 14. The photograph of fast response electronics.

Fig. 15. Photograph of the inner chasis of fast response electronics.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107106

the normalized output signal and sodium velocity is obtained fromthe data corresponding to a single operating temperature which isshown in Eq. (13). For various operating temperature, a relationcan be derived by linear regression technique which will lead thereduction in error.

The average response time of the signal conditioning circuit isfound to be 25 ms. The microcontroller response time is found tobe 1 ms. Figs. 14 and 15 show the photograph of the fast responseelectronics for ECFM and the inner chassis of the electronicsrespectively.

6. Conclusion

The probe type ECFM is used for the measurement of sodiumflow in fuel sub-assemblies and primary pump by-pass line inPFBR. In this work, the fast response electronics is developed foruse in monitoring the sodium velocity from the ECFM sensoroutput. The system is tested for various types of generated signaland the test results have an average rise time of 13.9 ms and falltime of 14.65 ms with an overall response time of 25 ms as againstthe response from the existing system of 1.5 s. The error in themeasurement can be further minimized by improving the designof the system by introducing digital signal processing algorithms.In future, the fast response electronics can also be tested for actualECFM sensor signal for further analysis.

Acknowledgment

This work was supported by Indira Gandhi Centre for AtomicResearch, Indira Gandhi Centre for Atomic Research (IGCAR/FRTG/C&IDD/BKK/SBU/09/01), Department of Atomic Energy, Kalpak-kam, India. The authors are thankful to the Director and all thescientists of IGCAR, Kalpakkam for the support extended.

References

[1] Kamanin YL, Kuzavkov. Measurement of coolant flow rate through the fuelassemblies in BN-350 and BN-600 reactors. In: Proceedings of IAEA/IWGFRSpecialists. Meeting on Instrumentation for Supervision of Core-Cooling inFast Breeder Reactors, Kalpakkam, India, 1989; p. 143–53.

[2] Fontaine B, Martin L. Core flow measurement at Phenix. In:' Proceedings ofCEA-IGCAR Technical Seminar on Liquid Metal Fast Reactor – Safety AspectsRelated to Severe Accidents, Kalpakkam; 2007.

[3] Hans R, Knaak J, Weiss HJ. Flow measurement in main sodium pipes. AtomicEnergy Rev 1979;17(4):833–42.

[4] Sackett, John I.. Measurements of thermal – hydraulic parameters in liquidmetal cooled fast breeder reactors. In: Symposium on Measurement Techni-ques in Power Engineering, International Center for Heat and Mass Transfer,Beograd, Yugoslavia, August 29–September 3; 1983.

[5] Turner GE. Liquid Metal Flow Measurement (Sodium) State-of-the-Art Study.Liquid Metal Engineering Center, U.S. Atomic Energy Commission by AtomicsInternational Issued: June 28, 1968.

[6] Araki H, Horikoshi S, Sekiguchi N, Kitagwa H, Sano K, Uno O. Design criteriaand current status of research and development on LMFBR large pipe sodiumflowmeter in Japan. IAEA specialists meeting on sodium flowmeasurements inlarge LMFBR pipes. Bensberg, W. Germany: Interatom; 1980; 161–71.

[7] Thatcher C, Bentley PG, McGonigal G. Sodium flow measurement in PFR. NuclEng Int 1970:822–5.

[8] Thatcher G. Electromagnetic flowmeters for large sodium flows. Proceedingsof IAEA specialists meeting on sodium flow measurements in large LMFBRpipes. Bensberg, W. Germany: Interatom; 1980; 21–33.

[9] Baker Roger C. Electromagnetic flowmeters for fast reactors. Nucl Energy1977;1:41–61.

[10] Lehde H, Lang WT. AC electromagnetic induction flowmeter 1948, US Patent2,435,043.

[11] Shercliffe JA. Theory of electromagnetic flow measurement. UK: CambridgeUniversity Press; 1962.

[12] Dean SA, Harrison E, Stead A. Sodium flow monitoring. Nucl Eng Int1970:1003–7.

[13] Nakamoto K, Tamura S, Ishii K, Kuwahara H, Ohayama N, Muramatsu T.Application of an eddy-current type flowmeter to void detection at LMFBRcore exit. Nucl Eng Des 1984;82:393–404.

[14] Priede Janis, Buchenau Dominique, Gerbeth Gunter. Contactless electromag-netic phase-shift flowmeter for liquid metals. Meas Sci Technol 2011;22(055402):11, http://dx.doi.org/10.1088/0957-0233/22/5/055402.

[15] Farrington BJ, Hughes G. A theoretical analysis applied to electromagneticinstruments used in liquid sodium. Nucl Energy 1978;17(1):57–64.

[16] Veerasamy R, Sureshkumar S, Asokane C, Sivakumar NS, Padmakumar G, DashSK, et al. Eddy current flow sensor development and testing for LMFBR sodiumpumps. In: Proceedings of the 15th International Conference on NuclearEngineering Nagoya, Japan, April 22–26, 2007.

[17] Veerasamy R, Asokane C, Narayanan K, Dhanasekaran R, Swaminathan K,Prabhakar R. Eddy current flowmeter for in-core flow measurement in fastreactors. In: Proceedings of the 8th National seminar on Physics Technology ofsensors (NSTPS-8) at IGCAR, Kalpakkam; 2001.

[18] Wiegand David E, Michels Charles W. Performance tests on an eddy-currentflowmeter. IEEE Trans Nucl Sci 1969;16(1):192–5, http://dx.doi.org/10.1109/TNS.1969.4325106.

[19] Wiegand David E. Summary of an analysis of the Eddy current flowmeter. IEEETrans Nucl Sci 1968;15(1). http://dx.doi.org/10.1109/TNS.1968.4324826.

[20] Costello TJ, Laubham RL, Miller WR, Smith CR. FFTF probe type eddy currentflowmeter-wet vs dry performance evaluation in sodium. American NuclearSociety International Meeting, Washington D.C, December, 1972.

[21] Chetal SC, Balasubramaniyan V, Chellapandi P, Mohanakrishnan P, Puthiyavi-nayagam P, Pillai CP, et al. The design of the prototype fast breeder reactor.Nucl Eng Des 2006;236:852–60.

[22] Hess B, Ruppert E. Instrumentation for core and coolant monitoring in LiquidMetal Fast Breeder Reactors (LMFBRs). Atomic Energy Rev 1975;13:93–9.

[23] Sharma Prashant, Kumar SSuresh, Nashine BK, Veerasamy R, Krishnakumar B,Kalyanasundaram P, et al. Development, computer simulation and perfor-mance testing in sodium of an eddy current flowmeter. Ann Nucl Energy2010;37:332–8, http://dx.doi.org/10.1016/j.anucene.2009.12.009.

[24] Dohi A, Oda M, Iida S. Development of an in-core flowmeter for the LMFBR. In:Proceedings of the International Conference on Liquid Metal Technology inEnergy Production, Pennsylvania, 1976; p. 796–801.

[25] Kawabe Ryuhei. Analysis on response time of electromagnetic flow meters. JNucl Sci Technol 1982;19(2):169–72.

[26] Vidal N, Aguirre-Zamallo G, Barandiaran JM, Garcia-Arribas A, Gutierrez J. FEManalysis of an eddy current water flowmeter. J Magn Magn Mater 2006;304(2):e838–40, http://dx.doi.org/10.1016/j.jmmm.2006.03.010.

[27] Sharma P, Dash SK, Nashine BK, Suresh Kumar S, Veerasamy R, KrishnakumarB, et al. Performance prediction of eddy current flowmeter for sodium. In:Proceedings of the COMSOL Conference, Bangalore, India; 2009.

[28] Poornapushpakala S, Gomathy C. Design, development and performanceanalysis of signal conditioning circuit of fast response electronics for eddycurrent flowmeter in PFBR. Int J Intell Electron Syst 2012;6(1):24–30.

S. Poornapushpakala et al. / Flow Measurement and Instrumentation 38 (2014) 98–107 107