IDS-NF Mercury System Overview

1. IDS-NF Mercury System Overview Van Graves IDS-NF 5th Plenary Meeting April 9, 2010

2. Background • MERIT demonstrated Hg jet target is feasible for Neutrino Factory • Goal now is to further develop the conceptual design for Reference Design Report • ORNL investigating mercury system design to identify operational or functional issues NF Mercury System Concept

3. General Target Concept w/Downstream Drain Neutrino Factory Study 2 Target Concept SC-5 SC-2 SC-3 SC-4 Window SC-1 Nozzle Tube Mercury Drains Mercury Pool Proton Beam Water-cooled Tungsten Shield Mercury Jet Iron Plug Splash Mitigator Resistive Magnets ORNL/VG Mar2009

4. SC-3 SC-2 SC-1 Nozzle Tube Proton Beam (67 mrad) Mercury Pool Iron Plug Mercury Jet (100 mrad) Water-cooled Tungsten Shield Splash Mitigator Resistive Magnets Cryostat Upstream End

5. Front View • Includes slope for Hg drainage downstream • Mechanical issues between nozzle and beam • Splash mitigation scheme incorporated • Relatively thin beam stop (Hg depth)

6. SC-5 Window Overflow Drain Valved Drain Tungsten Shielding Cryostat Downstream End • Window becomes a liquid barrier • Mercury pool serves as additional SC shielding • Cryostat becomes trapped by mercury nozzle and drain piping

7. Front Drain Views • Investigated possibility of having the Hg drain from the nozzle end of the cryostat

8. Front Drain Cross Section View • Mercury Chamber extends forward under resistive magnets • Allows the mercury exiting the vessel to flow out the front of the cryostat • Puts beam window in middle of cryostat Beam Window Tungsten Shield Mercury Drain

9. Flow Loop Review • 1 cm dia nozzle, 20 m/s jet requires 1.57 liter/sec mercury flow (94.2 liter/min, 24.9 gpm). • MERIT experiment showed that a pump discharge pressure of ~40 bar gauge required to produce the desired jet. • Reference: SNS nominal flow 1440 liter/min (380 gpm), 7 bar gauge pump discharge pressure, ~1400 liters total Hg inventory • Basic flow scheme Pump → Nozzle → Jet/Beam Dump → Heat Exchanger → Pump

10. Overflow Mercury Drain Mercury Pump Beam Dump Gravity Drain Flow Control Valve Heat Exchanger Storage Tank Hg Flow • Minimize pressure drops through piping by increasing diameter • 2" nozzle supply piping transitioning to 1 cm nozzle • Actual NF Hg inventory may reach SNS volumes • ~500 liters in the half-length beam dump shown

11. Heat Removal • From Study 2, the mercury jet/pool receive < 10% of beam energy; 50-60% goes into WC shielding (~2.4MW for 4MW beam) • Currently assumed to be WC spheres cooled by water • Much larger heat exchanger needed to cool shielding • Considering that both W and WC must be water-cooled, their effective densities will approach that of Hg. • Consequently, IF a Hg target is selected, the infrastructure will be in place to support use of Hg as a solenoid shield. • Would probably be a separate loop due to vastly different flow/pressure requirements, but could share a storage tank Beam Window Tungsten Shield Mercury Drain

12. Decay Channel Cryostats Main Cryostat (Target Region) Core Vessel Mercury Process Hot Cell NF Target Building Development Work • Using Study 2 concept as a starting point • Goal is to produce RDR Target Facility concept with cost estimate

13. Potential Future Mercury Work • Systems Engineering • Mercury loop refinement and design for remote maintenance • Target/beam dump remote maintenance • Beam window remote replacement • Cryostat/magnet design integrated with mercury jet and beam dump • Facility development • Hardware studies • Continuous jet flow loop • Nozzle studies, beam dump experiments • Tungsten shielding • Thermal / hydraulic studies

14. Implications of Using a Mercury Target • http://www.hep.princeton.edu/~mcdonald/mumu/target/graves/graves_121708.pdf

15. SNS Target Building Layout Instrument Ports (9 ea) Proton Beam Instrument Ports (9 ea) Target Service Bay (Hot Cell) Target

16. SNS Target Support Utilities Carbon Filters Tritium Removal LLLW Water Cooling Loop Primary & Secondary Confinement Exhaust

17. SNS Mercury Related Facilities Mercury-based target systems require extensive support facilities. • Mercury Containment • Leaks assumed inside Hg pump room • Leaks in core vessel area routed back into hot cell • Mercury vapors condense and leave activated beads on surfaces unrelated to maintenance operations • Hot Cell / Remote Handling • Complex, expensive systems required to maintain mercury equipment and magnet systems • Ventilation / Filtration • Hg vapors must be removed from cell exhaust & process off-gas prior to HEPA filtration

18. SNS Mercury Related Facilities Cont’d • Waste Handling • In US, mercury treatment and disposal governed by the Resource Conservation and Recovery Act (RCRA) (hazardous waste) • Radioactive mercury imposes additional requirements • In the US, this type of waste is called “mixed waste”. • Disposal options are VERY limited. • Water Cooling System • Process mercury cooled with secondary water system • Hands-on maintenance after beam-off • Mercury Target Safety Considerations • Accident & hazard analyses required to ensure protection of workers / public / environment • Operational Considerations • Maintenance of Hg systems complex, long downtimes expected • Maintenance of remote tooling is significant operational cost

19. Summary • Work continues towards development of mercury-jet-based target system for Neutrino Factory • Several engineering challenges remain in the design of a mercury nozzle / beam dump • SNS experience highlights the realities and challenges of using a mercury target