Development of a Mechatronic system for underground sensor deployment Overview It is important to monitor the area beneath and around the Sellafield legacy ponds. Degradation of the concrete walls can lead to radioactive leaks into the surrounding environment with potentially long-reaching hazardous effects. The use of current borehole technology for monitoring radioactive leaks has limitations and therefore an autonomous underground system, capable of mapping the area directly beneath the Sellafield ponds has been suggested. Fig.1 shows a broad overview of the application. Technical Challenges Environment The developed device must be; • Tolerant to radiation doses. • Able to penetrate ground of varying densities. • Navigate obstacles autonomously. • Communicate with a surface base station. Obstacles/rocks Sellafield Legacy Pond Radioactive Contamination Radiation Tolerance Experiments Outputs of electronic components are rarely measured whilst being exposed to gamma radiation. A series of component test circuits were developed with an adaptable radiation tolerant test board. By connecting the circuits to LabVIEW, it is possible to monitor the output of a range of different components whilst being exposed to a Co-60 gamma source. Real-time data Figure 2 Example representation of radiation tolerance experimental set-up Experiment Results Voltage regulators, references and microcontrollers have been exposed to gamma radiation. • Output voltage of a voltage reference increases with higher dose. (Figure 3) • Voltage regulators show a drop in output voltage at an increased dose. This occurs at different rates for different currents. (Figure 4) • 18F4520 microcontroller’s memory degrades at 1000Gy. (Figure 5) Dose Average Output voltage 385Gy 770Gy 1.16kGy 1.54kGy 1.926kGy 2.3kGy 2.7kGy 3.01kGy 3.47kGy 3.85kGy 4.24kGy 4.62kGy 5kGy 4.95 4.96 4.97 4.98 4.99 4.99 5.00 5.01 5.02 5.03 5.04 5.04 5.05 Figure 3 Average output voltage of Fairchild LM336Z references at different doses Figure 1 Underground “mole” navigates the environment and searches for radiation leaks Robotic “mole” • It is important to try multiple mechanical options as underground materials vary significantly. • A collaboration of current control and burrowing techniques is required to design a device able to navigate, dig and propel itself whilst underground. • A novel technique for manoeuvrability must be created. Current underground systems travel in a single straight line or have very large turning circles. • Cheap, quick and easy prototypes can be made using 3D printers. Prototypes can be built using 3D printers Multiple options can be easily explored Ability to conduct tests on a small scale before expanding Figure 6 3D printed contrarotor screw for 11cm Figure 7 Screw propulsion technique developed by 3D printer for analysis Examples of a 3D-printed contra-rotor screw mechanism and screw propulsion Output Voltage with increasing dose 4.6 4.5 Output Voltage (V) 4.4 4.3 4.2 4.1 4 3.9 3.8 0 500 1000 1500 2000 2500 3000 Dose (Gy) Figure 4 Output voltage of Fairchild KA7805AETU with increasing dose 3500 4000 Line 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Address Opcode 0000 EFFF GOTO 0002 FFFF NOP 0004 FBEF NOP 0006 BFFF BTFSC 0008 BBFF BTFSC 000A FFBF NOP 000C FFFF NOP 000E FFEF NOP 0010 FFFB NOP 0012 FFFF NOP 0014 EBFF 0016 BFFF BTFSC 0018 EAFF 001A FFFF NOP 001C AFFF BTFSS Line Address Opcode 1 0000 AAAA BTFSS 2 0002 AAAA BTFSS 3 0004 AAAA BTFSS 4 0006 AAAA BTFSS 5 0008 AAAA BTFSS 6 000A AAAA BTFSS 7 000C AAAA BTFSS 8 000E AAAA BTFSS 9 0010 AAAA BTFSS 10 0012 AAAA BTFSS 11 0014 AAAA BTFSS 12 0016 AAAA BTFSS 13 0018 AAAA BTFSS 14 001A AAAA BTFSS 15 001C AAAA BTFSS Future Work Work still to be completed includes: • Design of additional burrowing mechanical prototypes based on results from the testing of current designs. • Testing of mechanical parts for suitability • Design a radiation tolerant voltage regulation circuit • Analysis of control and navigation systems • Create a main body for the device Figure 5 Microcontroller memory before dose and after 1000Gy For details contact: Matthew Nancekievill; Tel.: 07960449570 Control Systems School of Electrical and Electronic Engineering The University of Manchester E-Mail: [email protected] Supervisor: Barry Lennox; Tel.: 0161 306-4661; E-Mail: [email protected]