Design & Development of Ultrasonic Vessel Inspection System (ULTVIS) for

TAPS-1&2 Reactor Pressure Vessel (RPV) Weld Joints

S.K.Lalwani1,a, R.K.Jain1, A.A.Agashe1, P.P.Nanekar2,

Rites Ranjon3, G.D.Randale1, P.Jyothi1 and Gopal Joshi1

1Electronics Division, BARC, Mumbai, India

2Atomic Fuels Division, BARC, Mumbai, India 3Refueling Technology Division, BARC, Mumbai, India

aemail: skl@barc.gov.in

Abstract. TAPS-1&2 have completed 45 years of successful operation. As per the regulatory

requirements, it is mandatory to inspect the Reactor Pressure Vessel (RPV) welds of these two

reactors for detection and characterization of flaws that can affect its structural integrity. An

automated UT based RPV inspection system has been developed to carry out in-service inspection

of RPV weld joints at TAPS. The system comprises of three major components: an automated

mechanical manipulator carrying the ultrasonic probes, multi channel ultrasonic data acquisition

system and data analysis software. This paper deals with data acquisition system named Ultrasonic

Vessel Inspection System (ULTVIS) which has been designed and developed at Electronics

Division, BARC. ULTVIS acts as interface between the other two components of the RPV

inspection system. The RPV inspection system employs 8 ultrasonic transducers for inspection of

welds and parent metal. ULTVIS acquires data from all the 8 transducers as well as positional

information of the probe holder while the manipulator carrying this probe holder is in motion. It

saves the C-scan data in a pre-defined file format which is understood by the analysis software.

ULTVIS comprises of in-house developed 8-channel ultrasonic pulser-receiver, digitizer, GUI

based control, C-Scan data acquisition software and potentiometer & encoder interface for sensing

the position of manipulator. The ULTVIS has been successfully tested along with the mechanical

manipulator and the analysis software at an underwater mock-up facility at TAPS-1&2. C-scan data

were acquired and analyzed using the analysis software.

Keywords: Ultrasonic Testing, Reactor Pressure Vessel, C-scan data acquisition, In-service inspection,

Pulser-Receiver.

Introduction

Multi-channel ultrasonic imaging systems typically comprise of multi-channel ultrasonic pulser-

receiver for excitation of ultrasonic transducers and amplification of received echo signals, digitizer

for data acquisition, automated mechanical manipulator for area scanning and software for

imaging/analysis. Reactor Pressure Vessel (RPV) inspection system for TAPS-1&2 employs 8

ultrasonic transducers (45°, -45°, 60°, -60°, 70°, -70°, 0° Normal Beam and 0° Dual) for inspection

of welds and parent metal. These transducers are mounted on a probe holder. The RPV inspection

system comprises of three major components: an automated mechanical manipulator carrying the

probe holder (BARVIS for core belt region and WIM-2M for upper shell region), an 8-channel

ultrasonic data acquisition system (named Ultrasonic Vessel Inspection System- ULTVIS) and data

analysis software (named KOVID). The manipulators BARVIS and WIM-2M have been designed

and developed by RTD-BARC, ULTVIS by Electronics Division-BARC and KOVID by M/s.

Lucid Software Ltd., Chennai. ULTVIS acts as interface between the other two components of the

system. It acquires data from all the 8 transducers as well as positional information of the probe

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holder while the manipulator is in motion and saves the C-scan data in a pre-defined data format

which is understood by the analysis software KOVID.

ULTVIS System Description

The ULTVIS system comprises of a) in-house developed 8-channel Ultrasonic Pulser Receiver

(UPR) [1], b) digitizer, c) GUI based control & C-Scan data acquisition software, d) potentiometer

and encoder interface for sensing the position of the probe holder. Fig. 1 shows different

components of ULTVIS and its interface with automated mechanical scanner.

Fig. 1: Ultrasonic Vessel Inspection System (ULTVIS) Components

8-channel Ultrasonic Pulser Receiver (UPR): Out of the 8 channels of UPR, five channels

have been configured in pulse-echo mode for 45°, -45°, 60°, -60° and 0° Normal Beam transducers

and remaining three channels in T/R mode for 70°, -70° and 0° Dual transducers. The 8 probes used

have different central frequencies in the range of 1 to 4MHz. Through software control, each pulser

channel can generate single negative pulse of variable width or burst of unipolar negative or bipolar

high voltage square wave signal of desired frequency for excitation of ultrasonic transducers. Each

receiver channel has independently controlled Programmable Gain Amplifier (PGA). Receiver

outputs are multiplexed using 8:1 multiplexer. Multiplexed echo signal is passed through a band

pass filter and additional gain is provided by using one more PGA before sending the RF signal out

for interfacing to data acquisition cards. The unit provides synchronized trigger output along with

the multiplexed echo signal for interface to data acquisition card. New features have been added in

the UPR, designed & developed earlier at ED-BARC, for application in ULTVIS.

C-Scan Data Acquisition Procedure: One of the important features of this system is that it

acquires C-scan data from all the eight probes while the manipulator is in continuous motion. All

the probes during this acquisition process can have independent acquisition parameters. After

system calibration, the user configures the area scan parameters (explained later in this paper)

before starting the C-scan data acquisition. Before starting the area scan for collection of C-scan

data, both the manipulator software and ULTVIS are synchronized with the help of handshake

PCI/USBRS232

RF Echo

Trigger

30m long

cables to

ultrasonic

transducers

Potentiometer and

Encoder Interface

Digitizer

Control & DAQ

Software on Host PC

Probe head

USB

Ultrasonic Pulser-Receiver

Automated

Mechanical

Scanner

USB

signals. The control & data acquisition software waits for the manipulator to reach the desired

location corresponding to the user defined step-size. As soon as it reaches the location within

programmed tolerance limits, the software issues command to UPR for generating trigger signals.

The UPR sequentially excites the selected probes after configuring each channel with user defined

parameters and also issues corresponding trigger commands to the digitizer. The digitizer stores the

A-scan data corresponding to all the selected channels. These data are now read by the software and

stored in the file. This procedure is continued for the whole area scan.

Technical Specifications

Ultrasonic Pulser Receiver:

No. of pulser-receiver channels : 1 to 8 (1 to 5 PE mode, 6 to 8 TR mode)

Pulse voltage : +/-35V to +/-250V (bipolar output)

-35V to -250V (unipolar output)

Pulse width : 125ns/250ns/500ns/Other (30-1000ns in steps of 1ns)

Pulse cycles : 1 – 20 complete cycles

Trigger source : Internal PRF (A-scan) or Auto (C-scan)

Channel firing : Sequential

Receiver gain : 20dB – 90dB user programmable

Receiver bandwidth : 25MHz

Receiver input protection : +/- 1kV

LPF : 4 settings

HPF : 4 settings

Output : RF (+/- 3.8V maximum)

Serial Communication : RS232

Power supply : 230VAC (12W approx.)

Dimensions : 19” x 6U x 320mm (D)

Digitizer:

Sampling rate : 50MSPS or more

Resolution : 8 bits

Input voltage range: 5Vpp or more

Input impedance : 50ohm/1Mohm

Bandwidth (3dB) : 50MHz min.

Storage length : 128k samples or more

No. of channels : 1

Trigger : Self or External

Trigger threshold : Adjustable

Trigger Modes : Edge, Positive and Negative

Coupling : AC/DC

Acquisition : Single shot or Sequence

Scanner Interface:

Two types of manipulators have been designed by RTD-BARC, one for upper shell region

named WIM-2M and other for core belt region named BARVIS. BARVIS employs three

potentiometers for indicating its position while the WIM-2M position is obtained from one encoder

(vertical motion by fuelling grappler) and one potentiometer (horizontal motion by pneumatic

motor).

Potentiometer: 10 turn potentiometer mounted at motor shaft provides 0 – 10V analog signal for

position information

Encoder: A 200 ppr incremental encoder with programmable counter is used. Counter displays

pulse count as well as facilitates transfer data to remote terminal through its RS485 serial interface

Handshaking: Communication between BARVIS and ULTVIS is established through digital I/O

of respective DAQ. Two handshake signals are mainly used during C-scan operation: BARVIS

generates READY signal once it attains initial position for the scan and ULTVIS generates START

trigger pulse for the scan to BARVIS.

Control and C-scan Data Acquisition Software:

Dedicated GUI based interactive software has been developed with following main features,

suitable for this application:

Data acquisition : Sequential from 8-channels

UPR Control : Using RS232 connection with predefined command format

Averaging : upto 256 in A-scan

Display : on line A-scan and B-scan

Display modes : RF, Rectified (Full wave/ negative or positive half wave)

Gates : For calibration of probes

Measurements : Peak/ Flank based

Scanner interface : Potentiometer and encoder interface for BARVIS and WIM-2M scanners.

A-scan display and system calibration

Fig. 2 Shows the screen print of the A-scan panel of ULTVIS for selection of various active

channels, online A-scan display, setting of UT parameters for the UPR, calibration of probes by

carrying out measurements on A-scan using ‘Gates‘ etc. Various UPR parameters which can be set

by the user include acquisition range, sound velocity, probe angle, probe delay, no. of cycles in

excitation, type of excitation (spike or square wave), pulse width, receiver gain etc.

Fig. 2: A-scan Panel of ULTVIS

C-scan data acquisition

Fig. 3 Shows the C-scan data acquisition panel. After calibrating all the probes/ channels in the A-

scan panel the user comes to this panel. This panel facilitates the user to select the probe holder

type. Two types of probe holders are used: horizontal and vertical. Depending on the selection, the

type of scanning is configured either as meander or comb. For horizontal scanning meander type

scan is used and for vertical scanning comb type scan is used. Depending upon the type of

manipulator used for scanning (BARVIS or WIM-2M) there are three potentiometer and one

encoder interfaces to chose from for defining the major axis and index axis for acquiring the

position of the manipulator. Before starting the C-scan data acquisition the user needs to select the

start & end coordinates of the manipulator as well as step size on main and index axes for which

data is to be acquired. For operator convenience the file name for the C-scan data is automatically

generated comprising of weld identification, probe holder, , start & end coordinates, date and time

of scanning e.g. L21_BH(128_1200)(203_900)_09-30-2014_13-07-28.csn. While acquiring the C-

scan data the current location of the manipulator as well the scanned region are displayed on the

screen.

Fig. 3: C-scan Panel of ULTVIS

B-scan display of acquired data

Fig. 4 shows the B-scan display panel. Here the user can open the B-scan image from the acquired

C-scan data by selecting ‘B-Scan’ option from main panel. User can select the index axis location

and view the corresponding B-scan on the screen. The displayed image contains B-scans

corresponding to all the selected probes side by side. The image is displayed in pseudo colours

using predefined colour palette.

Fig. 4: B-scan Panel of ULTVIS

ULTVIS-KOVID Interface

The ULTVIS software stores the C-scan data in a pre-defined data file format which is passed on to

KOVID designers. The pre-defined data file format includes header information (probe holder,

probe, area scan, UPR, digitizer parameters) and A-scan raw data with corresponding position at

each location of probe holder. The files thus saved can be opened in the KOVID environment and

can be analyzed for flaw detection, sizing, report generation, merging of C-scan data etc. The PCs

used by ULTVIS and KOVID are connected using a hub, thereby instantly transferring the data

files after completion of each area scan.

Speed of C-scan Data Acquisition

ULTVIS can acquire A-scan data from all the 8 transducers in less than 100ms time. Assuming that

the data is acquired at every 2mm of probe holder position, this corresponds to manipulator speed of

more than 20mm/second.

Assuming manipulator speed of 10mm/second, total time to acquire an area scan of 80mm x

500mm at step size of 2mm along major axis and 5mm along index axis shall be about 13.5minutes.

Advantages of using ULTVIS

ULTVIS interfaces with two axes of mechanical scanner and acquires C-scan data automatically.

Also C-scan data file format has been communicated to the designers of the analysis software. The

analysis software provides unified views in the object plane, thereby helping analyst to differentiate

the actual flaws from the artefacts as well as sizing of the flaws by spending much less time. Thus

ULTVIS helps reduce the data acquisition & analysis times drastically.

Qualification Trials of ULTVIS

Performance Demonstration of ULTVIS on RPV Calibration Block: The RPV calibration

block (Fig. 5) is 130mm thick with 6mm thick austenitic stainless steel cladding. The cladding is

intentionally left un-machined to simulate the actual condition that exists in RPV. The calibration

block has 6mm diameter side drilled holes (SDH) at a depth of 32mm (T/4) and 96mm (3T/4) as

well as surface and sub-surface notches of 9mm, 12.5mm and 19mm depth. These SDHs and

notches are used as reference standards. The

performance of ULTVIS has been checked

on this calibration block using the angle and

normal beam probes which will be used for

RPV inspection. All the reference defects in

the calibration block were detected reliably

using ULTVIS with an acceptable SNR and

sufficient reserve of gain and other

parameters of UPR. Fig. 6 shows the A-scan

signals of 6mm SDH at T/4 and 3T/4 using

2MHz, 60° angle beam probe.

Fig. 6: A-scan signal of 6mm SDH using 2MHz, 60° angle beam probe at a) T/4 depth b) 3T/4

depth

Mock-up Trails using ULTVIS: ULTVIS has been successfully tested in the mock-up facility

at TAPS 1&2 using an integrated RPV inspection system comprising of BARVIS manipulator,

ULTVIS and KOVID analysis software. C-scan data, corresponding to horizontal and vertical area

scans, were acquired using ULTVIS. The acquired C-scan data were analyzed using KOVID. Fig. 7

shows screen shot of C-scan images obtained for 45°, 60° and UCC probes using KOVID analysis

software.

Fig. 5: UT Calibration Block for RPV Inspection

a) b)

Fig. 7: Screen shot of C-scan images obtained for 45°, 60° and UCC probes using KOVID

analysis software

Conclusion

An Ultrasonic Vessel Inspection System (ULTVIS) has been designed and developed at Electronics

Division-BARC for Reactor Pressure Vessel (RPV) inspection of TAPS-1&2, Tarapur. It acquires

C-scan data from 8 ultrasonic transducers while the probe holder moves continuously. It saves the

data and each probe holder position in a predefined file format. This file can be opened and

analyzed by KOVID analysis software developed specifically for RPV inspection by M/s. Lucid,

Chennai. The ULTVIS has been tested successfully along with BARVIS manipulator using a test

setup at TAPS-1&2. The test data have been analyzed successfully using KOVID.

Acknowledgements

Authors are thankful to the team of manipulator designers from RTD-BARC (Shri MP Kulkarni and

Shri Jitpal Singh), TAPS-1&2 QA team (Shri AP Kulkarni, Shri NK Roy, Shri J. Akhtar, Shri BJ

Mishra, Shri Chetan Mali) for providing tremendous support during qualification trials of ULTVIS

at TAPS-1&2. Authors are also thankful to Dr. TS Ananthakrishnan, Head, ED-BARC, Shri RJ

Patel, Head, RTD-BARC and Shri NS Gulavani, Superintendent (QA), TAPS for their

encouragement and guidance.

References

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