Electrical Safety at the Holifield Radioactive Ion Beam Facility

1. Electrical Safety at the Holifield Radioactive Ion Beam Facility B. Alan Tatum SNS Electrical Safety Workshop June 2-3, 2004

2. Outline • Overview of the HRIBF • Specific Electrical Hazards at HRIBF • Hazard mitigation • Organizational structure • Inspection Processes • Training • Challenges

3. Mission • HRIBF is an accelerator-based National User Facility funded by DOE-NP to conduct nuclear structure and astrophysics research using short-lived, radioactive beam species produced primarily by the isotope separator on-line (ISOL) technique.

5. Existing FacilityPlan View

6. High PowerTarget Laboratory Plan View (rooms only)

7. High PowerTarget LaboratoryPlan View

8. Overview of Major Systems and Key Issues in ISOL Technology at HRIBF • Driver Accelerator • ORIC, a k=105 isochronous cyclotron • RIB Production (Injector) Platform • Presently a single, rather small injector • Target/Ion Sources • Kinetic Ejection Negative Ion Source (KENIS) for production of proton-rich beams such as 17F and 18F from Hafnium oxide (HfO2) target • Electron Beam Plasma (EBP) source for neutron-rich RIBs, pure Sn, etc…from Uranium Carbide (UC2) targets • Multi-sample sputter source for 7Be beams • Batch mode source for 56Ni • Post Accelerator • 25 MV tandem electrostatic accelerator w/ negative ion injection • Experimental Systems • Recoil Mass Spectrometer (nuclear structure) • Daresbury Recoil Separator (astrophysics) • Enge Spectrometer • General purpose end stations • Target and Ion Source Development and Testing Facilities • Low power On-line • Two off-line • High Power Target Laboratory (under construction)

9. Primary Hazards at HRIBF • Radiological • SF6 insulating gas • Compressed gases • High electric fields • High magnetic fields • RF • Confined spaces • Rotating Equipment • Chemical • Electrical

10. Ion Source Assembly Electrostatic Deflector RF Power Amplifier Tube RF Structure Coaxial Magnetic Channel Lower Magnetic Channel Beam Line to RIB Injector Magnet Structure Driver Accelerator: Oak Ridge Isochronous Cyclotron (ORIC)

11. ORIC Electrical Systems • High current power supplies to 90V and 6000 Adc • Motor-Generator sets (5000 hp synchronous motor with dual 1750 kVA generators 360V, 5000 A dc) • RF power amplifier system (20kV, 30A anode) • High voltage (5kV, 3A ion source, 80kV, 7.5mA deflector)

12. RIB Production (Injector) System Two interconnected platforms are biased at -300kV dc Target/ion source biased at 60kV dc relative to platform Procedure & training Redundant hardwired interlocks Mechanical shorting rod LOTO

13. RIB Injector Electrical Hazards • Electrostatic quadrupoles and electrostatic steerers, 5kV w/SHV connectors • Multiple high voltage ion source power supplies 5-300 kV dc • Ionization gauges • Dipole magnet, 385 Adc • Power supplies in tight spaces • Remotely coupled robotic handling system for activated target ion sources • Faraday cups, BPMs • Cesium charge exchange cell with ac heaters • EPICS/PLC-based control systems

14. Post Accelerator: 25 MV Tandem Electrostatic Accelerator • Largest in the World • NEC Pelletron charging chain design • Nominal max 25 MV terminal voltage (Has operated at higher voltages) • “Folded” Design • Considerably more internal ion optics than any other electrostatic accelerator • Beam energy is EI + VT (Q+1), for single stripping (EI=inject E, Q=charge state) • Maintenance access by a “central service platform” or by an “annular service platform” • Contained in an 80,000 ft3 Pressure vessel • Insulated with approx. 200,000 lbs SF6 gas ,

15. 25 MV Tandem

16. 25 MV Tandem • Electrical hazards are enclosed in the pressure vessel including generators • Controls and power supplies vulnerable to high voltage discharges • LO/TO required prior to pressure vessel entry Low Energy Acceleration Tube High Energy Acceleration Tube

17. Stable Ion Injector • Manufactured by NEC • Operates to -300kv • Houses multiple ion sources which produce stable ion beams for experiments and experimental setup • Low energy beam optics • Electrical safety devices • Enclosed in an interlocked cage • Rotating beacons • Grounding hooks

18. Experimental Systems

19. Mitigating Hazards: Organization • Electrical Safety Officer (1), member of the ORNL ESC • Electrical Engineers (4 +1 at ORELA) • Control system engineer (1) • Accelerator Operators (6) • Electricians (3) • Instrument Technicians (2) • Qualified Electrical Workers (numerous)

20. Mitigating Hazards: Inspection Processes • “Daily” assessments by electrical engineers who are involved in both operations and development • Quarterly self assessment program • Device mentors: in-house research staff responsible for experimental end-stations • End-station reviews • Experiment reviews • Work planning & JHE with crafts • Culture shift that blends expertise from facility operations and experimental systems • Culture in which the staff wants to “do the right thing” • Staff has taken ownership of safety

21. Training • Physics Division Electrical Safety • Electrical shock, burns, current effects • Common electrical devices • Flexible cords, extension cords, GFCIs, batteries • Electrical hazards specific to the facility • Accelerators, spectrometers, rf, power supplies, magnets, coils • High voltage safety • Safe work practices • PPE, wet areas, circuit breakers, insulated tools, conductive materials, fires, signs, barriers • Equipment • Grounding & bonding, flammable gases, clearances, interlocks • RIB Injector Electrical Safety • Platform and ion source voltages, LO/TO, special access situations • Qualified Electrical Worker • Exam and authorization required • Safety Flash Distribution

22. Challenges • Maintaining and updating aging equipment • Segregating systems for easier maintenance • How many levels of redundancy? • What do you trust to software/PLC systems? • Determination of qualified electrical workers • Appropriate PPE for Electricians and Instrument Technicians • Balancing safety with R&D. Pressures of delivering beam requires rapid recovery from failures. • Training visitors (experimentalists) in electrical safety