Using CompactRIO and LabVIEW to Develop a Control System for a Solid Target Transfer Mechanism for Radiopharmaceutical Production

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"Compared to the old solid target transfer system for the Cyclotron CS-30, the new system we created using CompactRIO and LabVIEW offers simpler hardware design and wiring, lower development cost, less development time, easier programming using the graphical approach, a better user interface, easier maintenance and troubleshooting, and expandability."

- Heranudin , Badan Tenaga Nuklir Nasional

The Challenge:
Replacing an old control system for the Cyclotron CS-30, a machine that produces thallium 201 for radiopharmacy use, with a new, expandable, easy-to-use and maintain control system that integrates with existing I/O.

The Solution:
Using the NI CompactRIO platform to provide the benefits of programmable logic controller (PLC)-like ruggedness and reliability with the flexibility of a PC and NI LabVIEW software to simplify development for our complex control system.

Author(s):
Heranudin - Badan Tenaga Nuklir Nasional

Introduction

Badan Tenaga Nuklir Nasional (BATAN) is the National Nuclear Energy Agency of Indonesia. The BATAN Center for Radioisotopes and Radiopharmaceuticals at the Science and Technology Centre in Serpong houses the Cyclotron CS-30. This machine is a charged particle accelerator used to produce radioisotopes and radiopharmaceuticals. It is mostly used in the medical field, for example: 18FDG for cancer diagnosis, 153Sm-EDTMP palliative therapy of bone cancer, 99Mo/99mTc generator diagnosis of nuclear medical therapy, 192Ir for brachytherapy, and thallium 201 (201Tl) to diagnose heart function abnormalities. We especially need a transfer system for thallium 201 because it is a solid target.

The Cyclotron CS-30 has an external solid target transfer system to transfer the target from the receiving station to the irradiation station. The transfer is performed using air pressure via a transfer tube that connects the receiving and irradiation station. The operator remotely controls the process from a separate control room. When this transfer control system was damaged, it halted thallium 201 production. The new control system needed to be easy to set up and maintain, integrate with existing I/O, and expandable.

Operating Principles of a Solid Target Transfer System

First, we place the solid target in a target holder. We then put it into the transfer tube at the receiving station and the sensor sends a signal to the control system that the target holder is in place and ready to send. The blower then produces pressurized air to push the target holder to the irradiation station. During the transfer process, detectors monitor the target’s location. When the target is close to reaching the irradiation station, the control system turns the blower off and activates the solenoid brake to stop the transfer. Then, a manipulator takes the target holder from the transfer tube, removes the solid target, and places it in an irradiation chamber.

When the target reaches the irradiation chamber, the control system activates the water cooling system and high-vacuum pump. When the high-vacuum condition is reached, the beamline valve opens and the irradiation process by the Cyclotron particle starts. Once completed, the control system closes the beamline valve and stops the water cooling system and the high-vacuum pump. We then take out the target, place it in the target holder, and move it back to the transfer tube. A sensor signals the control system that the target holder is ready. The blower then activates to move the target back to the receiving station. Once there, a pharmacist processes the target into a radio nucleus, which is then further processed into the radiopharmaceuticals needed in biomedical applications.

Developing a Hardware Control System at the Solid Target Transfer System

The previous control system was based on an old technology using a button control and lamp indicator. To build the new system, we used the NI CompactRIO hardware platform, an NI PPC-2015 panel PC, and NI Developer Suite. We chose CompactRIO because it is rugged and reliable like a PLC, but has the flexibility and power of a PC. We chose the PPC-2015 for its dual features as an operator interface and main controller. With these choices, we made a simpler mobile design to save time during installation. It is also expandable for future needs.

A solid target transfer system has several inputs and outputs. We use a 10-channel NI 9201 C Series analog input module to capture signals from the vacuum thermocouple and cold-cathode vacuum sensor; two 32-channel NI 9425 modules to acquire the digital input from a limit switch, pressure switch, and flow switch; and two 32-channel NI 9476 modules to control via relay the AC/DC motors, solenoids, valve, and vacuum diffusion pump.

We added these five modules to the 8-slot NI cRIO-9114 chassis. The remaining three slots are for future system expansion. We chose a cRIO-9014 as the controller for this chassis, which we connected to the PPC-2015 through Ethernet. Using this panel PC saves a lot of time and cost because separate lamp indicators and input buttons are no longer needed.

Developing the Software Control System

The Cyclotron CS-30 facility has several rooms: a cyclotron vault, three irradiation rooms, a power supply room, a cooler system room, and a control room. The latter is where the new solid target transfer system is located to centralize the operation. The solid target transfer system has three operation modes:

- Mode 1: Automatic
- Mode 2: Major States
- Mode 3: Micro States

Modes 1 and 2 are actually a collection of several states in Mode 3. Hence, Modes 1 and 2 do not require much interaction with the operator, whereas Mode 3 does. However, Mode 3 offers debugging and tracking. The state diagram for these modes (Figure 1) shows the sequential states of each mode. Daily operation is done in Mode 2 because it does not require much intervention but still allows the operator to see its states, which are as follows:

- Send: target is transferred from receiving station to irradiation station
- Place: target is moved from irradiation station to irradiation room
- Arm: water coolant and vacuum pump are activated
- Run: beamline valve is opened and irradiation starts
- Disarm: water coolant and vacuum pump are deactivated
- Replace: target is moved from irradiation room to irradiation station
- Return: target is transferred from receiving station to irradiation station

In general, the control system software follows the state diagram displayed in Figure 1 along with the I/O of each state. It is divided in two parts: field-programmable gate array (FPGA) programming on CompactRIO, and LabVIEW on the panel PC. I/O signal processing is done by the FPGA, whereas the state diagram is implemented in LabVIEW on the panel PC. The LabVIEW graphical programming environment makes it much easier to implement the state diagram. This saves a lot of time in making, integrating, and debugging the code. It was also easy to design a GUI in LabVIEW.

Testing the New Solid Target Transfer System

We first performed the test on each state in Mode 3. The test for Modes 2 and 1 followed. Then, we integrated the new control system with the Cyclotron control system for deployment test. After passing all tests, the system was finally ready for daily operation (see Figure 2).

Conclusion

Compared to the old solid target transfer system for the Cyclotron CS-30, the new system we created using CompactRIO and LabVIEW offers simpler hardware design and wiring, lower development cost, less development time, easier programming using the graphical approach, a better user interface, easier maintenance and troubleshooting, and expandability.

Author Information:
Heranudin
Badan Tenaga Nuklir Nasional
Gd. 11, PRR-Batan, Kawasan Puspiptek Serpong, Tangerang
Indonesia
Fax: +62 21 756 3141
broedyne@yahoo.com

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