Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor

American Journal of Mechanical Engineering and Automation 2018; 5(4): 99-109 http://www.openscienceonline.com/journal/ajmea ISSN: 2381-6198 (Print); ISSN: 2381-6201 (Online) Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor Nafiz Imtiaz, Mahidul Haque Prodhan *, Faisal Rahman, Hossain Sahadath, Khorshed Ahmad Kabir Department of Nuclear Engineering, University of Dhaka, Dhaka, Bangladesh Email address * Corresponding author To cite this article Nafiz Imtiaz, Mahidul Haque Prodhan, Faisal Rahman, Hossain Sahadath, Khorshed Ahmad Kabir. Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor. American Journal of Mechanical Engineering and Automation. Vol. 5, No. 4, 2018, pp. 99-109. Received: August 4, 2018; Accepted: August 21, 2018; Published: September 29, 2018 Abstract The TRIGA Mark-II Research Reactor of Bangladesh Atomic Energy Commission (BAEC) is the only nuclear reactor of Bangladesh. Presently power level variation of this reactor is done by manual movement control of the control rods by the operator, which is a manual and time consuming process. Here, according to the input by the operators to make the reactor critical at a definite power, the system would automatically move the control rods to positions (upper or lower) to attain the desired power level. Microcontroller based simple electronic circuit is used to control reactor power level. The target of this research is to design a simulation based system for TRIGA Mark-II Research Reactor of BAEC to vary the power level by automatic movement control of the control rods. By controlling the control rod positions reactor power level can be controlled easily. A separate power measurement system measures reactor power levels which would compensate the power level variation due to reactor poisoning. The overall system seems to be more safe, reliable, efficient and cost effective than the old manual system. Considering all this aspects, this design could be effective for the developing countries like Bangladesh. In this project only simulation is done by Proteus software, which is perfectly succeeded. In future this project can be implemented in hardware. Keywords Nuclear Research Reactor, Arduino Uno, Arduino Mega, Control Rod, Temperature Sensor, Banking Mode, Non-banking Mode, Proteus Software 1. Introduction The government of Bangladesh has taken a great endeavor to build its first nuclear power plant in the country. Although Bangladesh is an embarking country in nuclear power, it already has an operational research reactor, which is called TRIGA Mark-II, operated by Bangladesh Atomic Energy Commission (BAEC). It is a tank type research reactor and is used for training, research and isotope production. It was designed and constructed by General Atomics of USA [1]. In the BAEC research reactor, the reactivity control is done by 6 control rods of Boron Carbide (B 4 C). The control rods are positioned at different locations of D-Ring of the reactor core. The reactor Instrumentation & Control (I&C) system manages all control rod movements taking into account the choice of operating mode and interlocks [2-3]. It also includes the instrumentation for monitoring reactor parameters during all operational states and for recording all variables of reactor operation. The control rod mechanism is very important in reactor operation meaning to control reactivity or neutron production in the reactor. Among the six (6) control rods of TRIGA Mark-II, one is air follower controlled by pneumatic drive mechanism and five are fuel follower controlled by electromagnetic drive mechanism. Currently, the TRIGA Mark-II Reactor can be operated in two modes of operation: MANUAL and AUTOMATIC mode. In MANUAL mode operation, for the power/specific flux, reactor operators need to adjust the control rod position by pressing buttons on a console. Each of these control rods can be controlled up or down at a time. To reduce the floatation in the manual mode the reactor operator had to

100 Nafiz Imtiaz et al.: Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor make adjustments to get the right power for every moment in the operation of the reactor. In the operation of AUTOMATIC mode, the system can only adjust one control rod while the other control rods will remain at their current positions. Adjustment of the control rod reactivity depends on the value of five permanent control rods, either to be increased to increase the reactivity or otherwise. The system will take power readings when taking into account the position of all the control rods. Then, the system will provide signals to the control rods one by one, which will make adjustments and change its position, other five control rods will remain at their current position. This is a very slow process. Aging, analog based technology, slow response and instability also put the reactor safety under question [4-5]. To solve this problem, the authors have developed an automated controller system. It has been developed to control the movement of the control rods by using microcontroller based circuitry, displacement and temperature sensors and stepper motors. The simulation program for reactor power has been developed using high speed computer and Proteus software. The whole components have been integrated to produce one automated controller system [6]. The microcontroller can run and guide the movement of six control rods simultaneously. Simultaneous movement for the six control rods means that each control rod will move in the position set by the program with a fast response rate. This developed system is based on the calibration data of control rod position for different power levels. Routine test or calibration is done in every reactor after definite time and the calibration data is saved carefully. From the calibration data we can easily find out the control rods position for a particular power level at which the operators want to make the reactor critical [7-8]. After every calibration the project related programming codes that contains the control rod position should be modified. Reprogramming an Arduino is a very easy and low time consuming process so it will not create much trouble for the operator [9]. Therefore, the developed automated controller system will ensure highly responsive, accurate, reliable and safe operation of the reactor [10]. 2. Methods and Circuit Analysis Total system consists of different subsystems. They are: Master Control Portion, Control Rod Position Detection and Control Circuit, Stepper Motor Driver Circuit & Continuous Power Monitoring Circuit. 2.1. Master Control System The master Control system controls all the activities of this control system. The heart of this control system is Arduino Mega Boards which consists of Atmel ATmega 325 microprocessor. Figure 1. Master Control System. In Master Controller unit three Arduino Mega boards are used, which is shown in Figure 1. One Arduino Mega board works like main controller (shown in Figure 2) which takes input from keypad and sends data to other two Arduino Mega boards. This two Arduino Mega board control three slave Arduino Uno boards each. This three Arduino Mega is called Master Controller as a whole. Figure 2. Master Controller Circuit. 2.1.1. Keypad Interfacing with Arduino Mega This portion is used to take input command to make reactor critical at a definite power level defined by the operator. The operator simply types a password through the 3x4 keypad. For a defined password a particular power required input is send to the Arduino Mega-1. Then Arduino mega send necessary commands to control rod control circuit to supervise stepper motor movement to make reactor critical at operator defined power level. Keypad Interfacing with Arduino Mega-1 is shown in Figure 3. Figure 3. Keypad Interfacing with Arduino Mega-1.

American Journal of Mechanical Engineering and Automation 2018; 5(4): 99-109 101 2.1.2. LCD Display Interfacing with Arduino Mega This portion is used to display necessary information regarding this project. Mainly initialization and the desired power level at which the reactor will be critical are shown in the display. Here 20X4 alphanumeric LCD display is used. LCD Display interfacing with Arduino Mega-1 is shown in Figure 4. Figure 4. LCD Display interfacing with Arduino Mega-1. 2.1.3. Master Slave Circuit Here Arduino Mega 2&3 are used as a master and Arduino Uno s is used as slave which get commands from the master. This system is called master slave because here unidirectional data flow is occurred. Command only flows from the master to slave, which is shown in Figure 5. Here master receive operator required power level input from the keypad through a secret password. After receiving the keypad input, the Arduino Mega shows the desired power to the LCD display. Now Arduino Mega generates a digital output according to the desired input power level. This digital output is sent to the different slaves. According to the slave input which is actually controls the rod position: different control rod position is obtained as a digital data stream by the master and controls the movement of stepper motor driver circuit to make a reactor critical at a desired power level. Figure 5. Master Slave Circuit. 2.2. Control Rod Position Detection and Control Circuit This portion is designed to detect the control rod position and take the control rod position at the desired level to obtain desired power level directed by the operator, which is shown in Figure 6. 2.2.1. Sensor Interfacing With Arduino Uno In this portion control rod position related data is collected. The authors can detect control rod position at different levels of control rod such as 0, 25, 50, 75 percent position of control rod. But it is not possible that the control rod position will be within the definite positions that can be sensed by this project. So we assume that the control rod is at a random position. Now the authors have programmed Arduino Uno to command stepper motor control circuit to turn the stepper motor in the anti-clockwise direction. The control rod is connected to the shaft of stepper motor. So control rod will be inserted to the core and the control rod position will decrease. When the control rod reaches to our predefined positions like 0, 25, 50, 75 percent positions then we detect it by the sensor. For different position detection, individual sensors are used. Most obviously after reaching the position stepper motor stopped automatically. Here, touch sensor is used. 2.2.2. Stepper Motor Driver Circuit Interfacing with Arduino Uno In this portion according to the detected control rod position, the operator defined power level can be obtained by the movement of control rod. This is done by the program inserted in the Arduino Uno Board. For a defined power level and for a detected control rod position, there is a particular Figure 6. Control rod position detection and control circuit. stepper motor input given by the Arduino Uno to make the reactor critical at the operator defined power level. Here calibration data is used to define the control rod position for different power level. 2.3. Stepper Motor Driver Circuit Figure 7 shows the Stepper Motor Driver Circuit. This circuit is used normally for efficient operation of stepper motor by the commands given by Arduino Uno Board. Here dual H-Bridge is used to control the movement of stepper motor. Here bipolar stepper motor is used. Figure 7. Stepper Motor Driver Circuit. 2.4. Power Monitoring and Poison Effect Compensation Circuit This circuit, shown in figure 8, is used for monitoring reactor power. Here IC LM35 is used as a temperature sensor which collects the temperature information from the reactor core. Otherwise the authors can collect the power related data from the console directly which is the most accurate way. Now the Arduino Mega processes the temperature info according to the code. If sensor is used, then two (2)

102 Nafiz Imtiaz et al.: Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor temperatures are recorded per minute and calculate slope values, Slope = (Y 2 -Y 1 )/(X 2 -X 1 ) Here, Y 1 is the Initial temperature, Y 2 is the final temperature after 1 minute.(x 2 -X 1 ) is the time difference between the temperature measurements here it is 3 minute. Reactor Power in KW= Slope *60*100 /3.752 Due to poison effect, the authors can t achieve the desired power so after measuring power Master Controller Arduino Mega compensated the power fluctuation according to the coding by moving stepper motor either in clockwise or anticlockwise direction to attain desired power level. Figure 8. Continuous Power Monitoring Circuit. 2.5. Overall Circuit Description and Feature With Diagram This section describes the basic principles and features of this developed system with diagram. For simplicity overall circuit can be understandable by using only one stepper motor. 2.5.1. Simple Circuit Figure 9. Block diagram of Simple circuit with two arduino mega and one motor. Figure 10. Simple circuit with two arduino mega and one motor.

American Journal of Mechanical Engineering and Automation 2018; 5(4): 99-109 103 After turning the system on, the LCD display shows Enter Password. Then the authorized operator needs to give the password according to his power demand at which the reactor should be critical. Now Arduino Mega got the input related data from the keyboard which is the input for this board. Then according to the code written in Arduino Mega driver, the output digital port is enabled and it contains some digital data. The data is transferred to the slaves connected to the Arduino Mega. Now the stepper motor started to rotate anti-clockwise which means the control rod has been inserted at a defined rate until it triggers a control rod detection switch. When a control rod detection switch is triggered, the stepper motor stops running. According to the power requirement this Arduino Uno, which is a slave in this project, gets its input from the master Arduino Mega as a stream of digital data. After that the Arduino Uno internally calculates the number of rotation required in stepper motor to make the reactor critical at operator defined power level. Arduino Uno does the calculations according to the codes written on its board. These codes can be easily modified according to the calibration data or operator demand. The Arduino Uno gives commands to stepper motor control circuit to rotate stepper motor for a calculated number of turns to make the reactor critical at operator defined power level. When the desired rotation of stepper motor has been completed, pin A5 of each Arduino Uno goes high. If all uno pins are high then Power measurement wouldstart by the master controller Arduino Mega which consists of a temperature sensor. If the calculated power is lower or upper than target value duo to reactor poisoning then Arduino Uno commands stepper motor to rotate clockwise or anticlockwise direction unit the power level reaches to desired level. 2.5.2. Complete Circuit Figure 11. Block diagram of complete circuit. Figure 12. Complete circuit.

104 Nafiz Imtiaz et al.: Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor In this system the authors control six control rod movements to make a reactor critical at different power levels. When power on the project then the LCD display shows initialization information and then Enter Password. Then the authorized operator needs to give the password according to his power demand at which the reactor should be critical. Now Arduino Mega-1 got the input related data from the keypad which is the input for this board. Now according to the code written in Arduino Mega drivers six output digital ports are enabled and they contain some digital data. The data is transferred to the six slaves (Six Arduino Uno) connected to the Arduino Mega 2&3. Now the six stepper motors connected to the six Arduino Uno s by six stepper motor control circuit, starts to rotate anti-clockwise that means the control rods are inserted at a used defined rate until it triggers a control rod detection switch individually for six control rods. When a particular control rod detection switch among six units is triggered then the respective stepper motor stops running. Now according to the power requirement, the six Arduino Uno s, which are slaves in this project, get their inputs from the master Arduino Mega as a stream of digital data. Now the Arduino Uno s internally calculate the number of rotation required in stepper motors to make the reactor critical at operator defined power level. The calculation that Arduino Uno s do are according to the codes that are written on their boards which can be easily modified according to the calibration data or operator demand. Now the six Arduino Uno s give commands to respective stepper motor control circuits to rotate stepper motor for a calculated number of turns to make reactor critical at operator defined power level. When the desired rotation of stepper motor completed then pin 12 of each Arduino Uno goes high. If all Uno pins are high then through an AND Gate +5V goes to master controller Arduino Mega and power measurement is started by master controller Arduino Mega which consists of a temperature sensor. If the calculated power is lower or higher than target value due to reactor poisoning then Arduino Uno commands stepper motor to rotate clockwise or anticlockwise direction unit the power level reaches to desired level. 3. Result Analysis In this research work, the system can be simulated for different kinds of input conditions. But for testing the accuracy and performance of this system, the authors are demonstrating only one desired power level input because performance will be same for all the inputs. For Example, if anyone needs to make reactor critical at 50 KW then the operator should start the system. After starting, the display will show enter password. Then if the operator presses 1234 on the keypad, the display shows initial reactivity and target reactor power. As for Arduino-1 (controller Arduino) Port A & Port K is designed for output. For an input of 1234, Arduino-1 sends digital 8 bit digital data (00000011) to output ports. This is shown below in Figure 13. Figure 13. Keypad input impact. Arduino-1 output ports are connected to Arduino-2 and Arduino-3 input port. For Arduino-2 and Arduino-3 port K is allocated as input port. So Arduino-1 output digital data (00000011) is send to Arduino-2 and Arduino-3.

American Journal of Mechanical Engineering and Automation 2018; 5(4): 99-109 105 Figure 14. Master controller functionality. For simplicity here only Arduino-2 is shown on the below figure for easy interpretation. Figure 15. Interfacing between Arduino-1 and 2. Arduino-2 is the master Arduino which controls the slave Arduino Uno. For an input of 00000011 in port-k of Arduino-2, it activates Port-A, Port-C, Port-F and Port-L of Arduino-2 which are configured as output ports. Inside the program we coded that for an input of 00000011 in Arduino2 it will send 00000111 to all its output ports. In Arduino-2

106 Nafiz Imtiaz et al.: Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor and Arduino-3 output ports, there are three slave Arduino Uno sare connected individually (total 6 slave Arduino Uno are used here). For simplicity, here we are only showing one slave Arduino Uno is connected to port C of Master Arduino- 2. So 00000111 digital binary data stream is sent to Slave Arduino Uno. Port-D is used as output port in Slave Arduino Uno. This is shown in Figure 16. Figure 16. Interfacing between Arduino-2 and Arduino Uno. 8, 9, 10 & 11 pins of Slave Arduino Uno is connected to Stepper motor controller. Through this pins Arduino Uno send data to Stepper motor controller to control stepper Motor. After having the input stepper motor started to rotate Anti-clockwise direction. This is shown in Figure 17. Figure 17. Stepper motor control.

American Journal of Mechanical Engineering and Automation 2018; 5(4): 99-109 Now, there are 2 Control rod position switches which are connected to pin number 12 and 13. These switches are used to send Arduino Uno about control rod current position related data. After getting the position related information and desired output power level related data (here 50 KW for this example), it is written in the code that the stepper motor 107 is rotated for 10 full turn. And after 10 seconds we found out that those 10 full rotations are completed by stepper motor and come to a standstill. Now for power measurement testing (for simplicity weare showing here Arduino Uno, as coding is similar for Arduino Mega), we initially set current reactor core temperature to 58 C. Figure 18. Starting temperature setup at 58 C to 61 C. So currently reactor generates 1561 KW power. But our target power is 1600 KW so the stepper motor rotates 1 rotation in anticlockwise direction. For any kind of emergency or wrong operation or if anyone want to change the power level during operation then he has to push the RESET BUTTON. RESET BUTTON is shown in the previous picture. The system will be reset after pressing this button, which is shown in Figure 19. Figure 19. Reset Button functionality test.

108 Nafiz Imtiaz et al.: Simulation of Automated Controller System for Controlling TRIGA Mark -II Research Reactor This system was just a simple way to demonstrate. As both banking &Non-banking mode is supported, we have tested the whole system for different power level value and compare these values with our coded values. The test results are given below: Table 1. The test results of Banking Mode and Non-Banking Mode. Power Level 50KW 50KW 100KW 100KW 250KW 500KW 1MW 1MW Mode of Operation Banking Non-Banking Banking Non-Banking Banking Non-Banking Banking Non-Banking According to Coding & Measured Value Number of Turns of Stepper Motor CR-1 CR-2 CR-3 CR-4 CR-5 CR-6 Coding 8 8 8 8 8 8 Measured 8 8 8 8 8 8 Coding 8 5 5 10 8 8 Measured 8 5 5 10 8 8 Coding 16 16 16 16 16 16 Measured 16 16 16 16 16 16 Coding 24 22 20 18 16 14 Measured 24 22 20 18 16 14 Coding 40 40 40 40 40 40 Measured 40 40 40 40 40 40 Coding 88 84 80 66 60 50 Measured 88 84 80 66 60 50 Coding 160 160 160 160 160 160 Measured 160 160 160 160 160 160 Coding 188 180 160 152 145 130 Measured 188 180 160 152 145 130 So, by simulating the overall circuit we can say that this system ensures the following characteristics: A simple, least complex circuitry, logic and coding based project, inherently safe, no change for total control rod withdrawal, very low cost design related to similar projects, easy controlling system, Reliable system design, highly secure, password protected design, high accuracy of stepper motor ensures precise power control, Simple Fault finding based system. 4. Conclusion The number of steps of stepper motor for all input was found perfectly. For all the inputs, the clockwise & anti clockwise movements of the stepper motor was found satisfactory. Overall the performance of this project was quite impressive and efficient. In the present work we have shown the feasibility of automatic control of the power output of a research reactor. However, the demonstration of the fact that the control system actually works is based on simulation using a software name proteus. Implementation of this system in an actual reactor will require a lot of further work. First a prototype has to be built with hardwire and tested industrially by companies like Siemens, Areva, Westinghouse, Toshiba etc. After the approval of nuclear regulatory authorities this system may then be implemented in an actual reactor. References [1] General Atomics. TRIGA MARK-II. Nuclear research reactors. [Online]. Available: http://www.gaesi.com/triga/index.php [2] M. M. Islam, M. M. Haque, S. M. A. ISLAM, J. I. Khandaker, Calculation of Control Rod Worth of TRIGA MARK II Reactor Using Evaluated Nuclear Data Library JEFF-3.1.2, IOSR Journal of Applied Physics (IOSR-JAP), vol. 9, no. 4, 2017, pp. 67 72. [3] P. K. Bhowmik, S. K. Dhar, and S. Chakraborty, Operation and Control of TRIGA Nuclear Research Reactor with PLC, International Journal of Information and Electronics Engineering, Vol. 3, No. 6, November 2013, pp. 553-557. [4] Reactor Operation and Maintenance Unit (ROMU), TRIGA MARK-II Reactor Manual, Bangladesh Atomic Energy Commission (BAEC), Bangladesh, Revised 2009. [5] Islam, M. S., Haque, M. M., Salam, M. A., Rahman, M. M., Khandokar, M. R. I., Sardar, M. A., Saha, P. K., Haque, A., Malek Sonar, M. A., Uddin, M. M., Hossain, S. M. S., & Zulquarnain, M. A. (2004), Operation experience with the 3 MW TRIGA Mark-II research reactor of Bangladesh, 2nd world TRIGA users conference, conference volume, (p. 207), Austria: Atomic Institute of the Austrian Universities. http://www.iaea.org/inis/collection/nclcollectionstore/_publ ic/38/039/38039499.pdf [6] R. Harisudhan, M. Ganesh Kumar, A. Udhaya Prakash, P. Sathya, Stepper Motor Control using ARDUINO ATMEGA - 328 Micro-Controller, IJSRD - International Journal for Scientific Research & Development Vol. 2, Issue 12, 2015 ISSN (online): 2321-0613 [7] G. Žerovnik, L. Snoj, A. Trkov, L. Barbot, D. Fourmentel and J. F. Villard, "Measurements of Thermal Power at the TRIGA Mark II Reactor in Ljubljana Using Multiple Detectors," in IEEE Transactions on Nuclear Science, vol. 61, no. 5, pp. 2527-2531, Oct. 2014. doi: 10.1109/TNS.2014.2356014 [8] Son N. A., Hoa N. D., Nguyen, T. T., Tuan, T. Q. and Raul, O. C. (2017) Control Rod Calibration and Worth Calculation for Optimized Power Reactor 1000 (OPR-1000) Using Core Simulator OPR1000. World Journal of Nuclear Science and Technology, 7, 15-23. http://dx.doi.org/10.4236/wjnst.2017.71002.

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