Supporting deep underground astrophysics research through high-precision F-gas engineering and closed-loop recovery
1. Context
The LUNA-MV (Laboratory for Underground Nuclear Astrophysics – Mega Volt) project, developed at the INFN National Laboratories of Gran Sasso, involves the installation of a 3.5 MV electrostatic accelerator in a deep underground environment to study nuclear reactions of astrophysical interest. To ensure the electrical insulation of this high-voltage generator, the accelerator relies on large quantities of pressurized SF6 gas. It was therefore necessary to engineer a dedicated system for the comprehensive management of the gas during all operational and maintenance phases of the facility.
2. Objective
Design, supply, and install a complete SF6 gas management system for the LUNA-MV accelerator, delivering a solution capable of ensuring:
- deep vacuum evacuation of the accelerator vessel prior to filling operations;
- controlled transfer and precision loading of the SF6 gas;
- full recovery of the gas during scheduled maintenance activities;
- filtration and purification of the gas to enable its safe reuse;
- secure storage in dedicated cylinder racks;
- continuous monitoring of gas quality parameters.
3. Challenge
- Complex Underground Infrastructure: The plant had to operate within a highly complex, deep underground scientific infrastructure, managing large volumes of SF6 while maintaining strict purity and reliability parameters.
- Environmental & Leakage Control: A critical focus was placed on minimizing gas losses, protecting the quality of the insulating fluid, and guaranteeing its complete recovery during scheduled accelerator shutdowns.
- Confined Space Logistics: Ensuring seamless operation, storage, and maintenance capabilities within the restrictive spatial and logistical constraints of a deep underground laboratory.
4. Solution
Synecom developed an integrated gas management system capable of executing the full lifecycle of the insulating fluid. The solution included:
- Pre-Filling Vacuum System: A system allowing the complete evacuation of air and nitrogen from the accelerator vessel down to pressures below 1 mbar absolute, ensuring the conditions needed to maintain high SF6 purity.
- Integrated Processing Cycle: A complete plant capable of executing filling, recovery, liquefaction, and transfer of the gas into dedicated storage units.
- High-Efficiency Filtration Unit: A multi-stage treatment unit designed to maintain the insulating performance of the SF6 by removing moisture via molecular sieves, absorbing decomposition products, and eliminating solid particulates.
- Continuous Quality Monitoring: Integration of a multi-functional analysis system for real-time tracking of gas purity, moisture content (dew point), and SO₂ concentration.
5. Sustainable Engineering Contribution
The project applied circular economy principles to a highly sensitive scientific environment:
- Closed-Loop Reuse: Designed to minimize emissions and preserve the chemical-physical characteristics of the gas, allowing for its continuous reuse.
- Preventative Diagnostics: Real-time monitoring allows operators to quickly verify the state of the gas and schedule preventative maintenance, extending the fluid’s lifecycle.
- Emission Elimination: Total recovery of the gas during maintenance ensures zero venting into the atmosphere, fully complying with strict F-gas environmental regulations.
6. Implementation
Beyond engineering and design, Synecom directly managed the supply, installation, and commissioning of the entire system at the Gran Sasso National Laboratories. Activities included the integration of:
- the gas recovery and treatment plant;
- the advanced multi-stage filtration unit;
- customized secure storage systems;
- precision connection lines to the accelerator vessel;
- all associated measurement and control instrumentation.
7. Quality & Environmental Control
Quality assurance and environmental protection were embedded into the system’s core architecture:
- Continuous Analyzer: Automated, real-time tracking of the primary SF6 qualitative parameters to monitor for potential decomposition processes.
- Ultra-Low Moisture Processing: The filtration system guarantees extremely low moisture levels, keeping the gas strictly within the specifications required for high-voltage equipment.
- Strict Compliance: The entire infrastructure was validated to ensure full adherence to technical regulations applicable to fluorinated gases and high-voltage equipment.
8. Results
- Deep Vacuum Achieved: Successful evacuation of the accelerator vessel to < 1 mbar absolute prior to filling.
- Secure Gas Handling: Delivered a safe, efficient, and highly automated management framework for the SF6 used in the LUNA-MV accelerator.
- Emission Reduction: Ensured the complete recovery and reuse of the gas during maintenance windows, drastically reducing atmospheric emissions.
- Operational Reliability: Maintained high-quality insulating gas, thereby guaranteeing the long-term reliability of the accelerator.
9. Strategic Value
The LUNA-MV project represents a prime example of Synecom’s expertise in insulating gas management for advanced scientific infrastructures. The developed solution successfully combined ultra-high-performance research requirements with environmental sustainability, operational safety, and the long-term preservation of SF6 characteristics, even within the logistical constraints of a deep underground laboratory.
The images shown below have all been sourced from: Luna – LNGS
