Abstract
This paper describes a system, which is installed at Nuclear Fuel Complex, Hyderabad. The system was designed by EEC, Mumbai with the technical and other assistance provided by NFC Engineers having long experience in running different types of ultrasonic systems available at NFC.

It is a tube rotation fixed probe type of system designed for fully automatic operation at high speed using immersion technique for ultrasonic flaw detection and dimensional measurement of precision Zirconium alloy seamless tubes used in fuel bundles for nuclear reactors. The System was fabricated at EEC, Mumbai and installed, conunissioned/tested at NFC, Hyderabad. Such a system has been developed indigenously for the first time for commercial application.

The system detects artificial notches of the order of 0.04 mm depth in 14 mm dia x 0.4 mm wall thickness tubes at a linear speed of 2 mtrs/minute. The technical parameters like sensitivity, repeatability etc. compare well with the system made by established manufacturers internationally. However, the speed of testing is lower than that obtained in multiple probe rotation system which are made by select international manufacturers.

This high performance system uses specially developed system components. The system integrates measurement for wall thickness and diameter along with flaw detection 'm a single run. P. C. is used for tracking the tube and recording the test data A range of customized test reports are generated. The system includes strip chart recorder, true to location automatic marking and programmable sorting in 3 categories.

Introduction-
The equipment was designed keeping in mind high test speed, repeatability of test results, maximum sensitivity and precision in measurement. The performance parameters made it necessary that the system was constructed with precision components. It made it necessary to build features not found on general test systems.

Test mechanics-
The mechanical construction is built on a rigid &ame. On the frame are mounted a series of adjustable driven and idler rollers. The drive to the rollers is given by a timing belt and pulley system placed on the central drive shaft mounted on special bearing placed within the machine frame. Pinch rollers add stability to the rotation and the necessary friction to helically rotate and move the tube forward. The kick in system is a soft loading type with a circular rotary set of holders.

The test table consist of immersion tank and unique tube entry and exit arrangement through a pneumatically operated barrier which retains the water inside the tank during the tube movement. A set of multi axis precision manipulators hold the test probe, precisely over the required spot.

Loading and unloading racks are provided. The fully automatic operation results in sorting of tubes in acceptable and non acceptable categories.

Water conditioning-
Water to be used should be free of air bubbles and suspended particles. A series of filters are used to clean the suspended particles. Water is heated and stabilized to remove entrapped air bubbles. A main conditioning tank stores the water which is continuously circulated through the system. Excess water draining from the immersion tank is collected and re-circulated.

Instrumentation -
The system uses four nos. of specially developed Ultrasonic instrumentation model ESM3 in parallel mode. This equipment has a large, CRT display with a LCD display of set parameters. The equipments microprocessor is fast enough for the test task.

A single channel Ultrasonic I-figh Precision Wall Thickness gauge model WTM3 was developed for this test system. It has a resolution of 0.001nun and is able to read tubes with very thin walls, 0.3mm and above. The diameter measurement is done by a high speed laser device which is capable of measuring during tube movement.

The system uses a P.C. based data management system which has a custom built software. A series of reports are possible to be prepared, stored and printed. The software is flexible giving the operator the choice of selecting the test parameters. The P.C. has also special hardware and software to track the tube movement and co-ordinate the information for the PLC to perform various test mechanics operations including the markers.

The system uses a PLC based automation. Since the system em be run in fully auto mode an elaborate automation components like infrared light barriers, proximity sensors, reed switches etc. have been built in.

A 6 channel digital strip chart recorder is incorporated to record the proportional values of signals from flaws and measured values of diameter and wall thickness variations. Audio & Visual alarms are provided to alert the. Operator during defects or out of range in measured values.

Test configuration-
4 Nos. 10 MHz, line focus probes are provided for flaw detection in clockwise, anticlockwise, forward and reverse directions.
1 No. 17MHz line focus probe is used for wall thickness measurement.
O.D. is measured over the entire rotating surface.

Photos -
1. System Photographs.
2. Sample Report Printouts.

Key words : Tube rotation fixed probe system, immersion technique, flaw detection, artificial notches, sensitivity, repeatability, multiple probe rotation system, system components, automatic programmable sorting.

TEST RESULTS
1. Tube details : Zr-4 fuel tubes
OD: 15.215 ± 0.065 mm
Wall: 0.381 + 0.076 mm - 0.00
Length: 2 - 6 M.
2. Reference standard used :
Flaw : 38 microns and 50 microns deep, 60° V-shaped notches on inside and
outside surface in longitudinal and transverse direction
OD : 15.202 and 15.330 mm
Wall : 0.391 and 0.457 mm
3. Probe: Line focussed 1 0 MHz for flaws
Line focussed 20 MHz for wall measurement

4. Test speed : 2 meters per minute
5. Recording on calibration chart:
L1 - OD and ID notch
L2 - OD and ID notch
T1 - ID and OD notch
T2 - ID and OD notch
OD channel - 15.202 and 15.330 mm
Wall - 0.381 and 0.457 mm

Another chart of actual tube is also given.