Ultrasonic Data Acquisition and Analysis System for the Reactor Vessel Inspection Robot Guided by LASER

Jong Po Lee, Chul Hoon Park and Byong Guk Um,
Research Institute, Korea Advanced Inspection Technology, Inc. (KAITEC)
Jae Hee Kim
Korea Atomic Energy Research Institute (KAERI)
Contact

ABSTRACT

The key component of a nuclear power plant is a reactor pressure vessel. Its integrity of a pressurized water reactor is remotely examined from inside. There are two types of reactor inspection systems. One is a tri-pod (fixed) type and the other is a robot (mobile) type. The former is heavier and bulkier than the latter. Hence, RPV inspection tools of robot type have been recently developed, because it is not only easy to handle but also speedy to complete the inspection. In addition, its position accuracy is much improved. KAITEC and KAERI has developed an ultrasonic data acquisition and analysis system as well as an underwater mobile robotic system for reactor vessel inspection. The mobile robot is guided by a laser beam emitted from a laser positioner. This Robot is extraordinary light and it is very easy to handle.

Keywords : Ultrasonic Test, RPV, Acquisition system, Analysis system, Inspection.

1. Introduction

A reactor pressure vessel (RPV) of a pressurized light water reactor (PWR) is periodically examined to confirm its integrity by using remote controlled ultrasonic systems. The systems consist of a mechanical device manipulating ultrasonic transducers and data acquisition & analysis system. As far as manipulators are concerned, there are two types of robots. One is a fixed type (typically tri-pod) and the other is a mobile type (typically turtle). The former systems were frequently used for RPV inspection many years ago, while the latter type of systems have been developed and applied to the field inspection recently. Each type has its own advantages and disadvantages. A fixed type is usually heavy and difficult to install and disassemble, but positioning accuracy is good. A mobile type is very light and easy to handle, but difficult in path tracking control. Table 1 shows the comparisons among various RPV inspection tools and systems.[1-7]

As shown in the Table 1, the Korea Atomic Energy Research Institute (KAERI) has developed a new mobile type of Robot, named by RIROB (Reactor Inspection Robot) which is guided and pointed by Laser positioner and Korea Advanced Inspection Technology, Inc. (KAITEC) has developed an ultrasonic data acquisition and analysis system which were interfaced with the RIROB. This paper introduces the development of RIROB and UT data acquisition & analysis system.[11-14]

Type	Manufacturer	Country	Manipulators(Robot)	UT DAS
Fixed Type manipulator	Rolls-Royce	UK	MMM (Main Mast Manipulator )	Micro Pulse 2
	SwRI	USA	PaR (Programmed and Remote)	EDAS
	Westinghouse	USA	Reactor Vessel ISI Tool /SUPREEM	UDRPS-2
	Inter Control	France	In-service Inspection Machine	RTEA O/S
	KWU	Germany	ZMM4	DEA 5
	ABB TRC	Sweden	PWR Mast Manipulator	I/MX UX
	Tecnatom	Spain	PaR (Programmed and Remote)	SUMIAD
Mobile Robot Type	Framatome Tech	USA	URSULA	ACCUSONEX
	Mitsubishi	Japan	Advanced UT Machine	EDAS
	KAERI &KAITEC	Korea	RIROB	KIUS
Table 1: Comparisons among various types of manipulators for RPV inspection

2. Reactor Inspection Robot (RIROB)

In order to replace a conventional fixed type of a manipulator which is heavy, bulky and time consuming to install and disassemble, a new RIROB was developed. The RIROB is magnetic wheel mounted and moves by a laser beam. This laser beam positioner is located on the bridge and the RIROB has the positioner sensitive detector to move and generate position information. If scan information is given by main computer, then laser beam guides the robot according to the scan pattern. The robot has 5 degrees of freedom of motion.

As a RIROB controller, main processor is Intel 8097BH and DC servomotor drivers are used. External communication is made by RS 422 and program language is C & assembler. Sensor interface is wheel encoder and small sized 4-layer control board is used. Photograph 1 shows the RIROB.

Photo 1: Reactor Inspection Robot(RIROB).

Photo 2: Laser Positioner.

3. Laser Beam Positioner(LAPOS) and Main Control Station(MCS)

Laser beam pointer is made from diode laser of which wave length is 630 nm. Two axis pan-tilt device is used and its resolution is 0.02deg per step. The locations and positioning of RIROB is performed by a laser beam detector attached to the RIROB. In order to avoid laser beam deflection, hemi-spherical plastic cap covers the laser beam positioner.

The RIROB can be also controlled by a mouse or a joystick. The functions of main control computer are to execute inspection planning and generate reports. Camera images and graphics are also displayed. Photograph 2 shows the Laser Positioner.

4. Ultrasonic Data Acquisition and Analysis System for RIROB

Pentium III 800 MHz PC was used for an ultrasonic data acquisition & analysis system. Lynx Operating System was employed for real time, multi-tasking, and multi-users. Ultrasonic data information is shared between UT data acquisition computer and UT data analysis computer connected by LAN using TCP/IP protocol.[8, 9, 10]

Fig 1: A new mobile type of RPV inspection system.
Fig 2: Display of UT signal analysis.

The Main Control Station (MCS) controls LAPOS and RIROB. For the movement of RIROB's LAPOS generate the position trigger pulse which is the differential voltage signal. By that trigger pulse, the UT system takes one frame of UT data.

These thing are well depicted in Fig 1. And additional communication protocol (DLE sequence) is used between MCS and UT systems to share the exam plan.

The software consists of "UT Calibration", "Exam", "UT Analysis", "Trend Analysis", and "System Utilities". In the calibration menu, all the information necessary to the ultrasonic transducers is included. This will be done per each channel. In the analysis menu, scan information is given including scan axis and index axis. While examination is going on, self-monitoring which diagnoses the status of system is being carried out. UT analysis is simultaneously being performed during examination. A-, B-, C-, and D-scan are displayed by computer processing. Fig. 2 shows one example of UT signal analysis.

5. Concluding Remarks

A new mobile type of reactor pressure vessel inspection system was developed. This system consists of reactor inspection robot (RIROB), laser positioner (LAPOS), main control station (MCS) and ultrasonic data acquisition and analysis system (KIUS). This is very light, compact, and easy to handle and maintain. It is expected to make inspection time shorten. The functions and capabilities will be verified through UT performance demonstration.

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