Liquid Lithium Argonne

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Engineering and safety issues of lithiumtargets and film strippers

3rd High-Power Targetry Workshop

September 10 - 14, 2007

Bad Zurzach, Switzerland

Claude B. Reed, Jerry A. Nolen, and Yoicihi Momozaki


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Presentation Overview

Liquid Metal Systems for High Power Accelerators

Targets

Thin Film Strippers Beam Dumps

Technical Issues

Engineering

Thermalhydraulics Liquid metal pumps

Alkali Metal Safety Issues

Control of impurities

Alkali metal handling

Fire protection

Waste treatment & disposal


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AEBL Liquid Metal Systems

AEBL Targets

for heavy-ion beams on low-

Z targets

for light-ion beams on high-(Z) targets

AEBL Thin Film Strippers

within the driver linac increases ion beam charge

state

AEBL Liquid Metal Beam Dumps

end of the production area low melting point

low vapor pressure

Liquid lithium stripper

Liquid lithium targetLiquid tin beam dump

Color code:

Black = existing facili ty

Blue+ green = AEBLbaseline

Red = Low-cost upg rade


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RIA Windowless Li Target

heavy-ion beams on

a low-Z (Li) target

Beam energy: 400 MeV/u

Beam power: 400 kW

Beam diameter: 1 mm

Target thickness: 1.5 g/cm2


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Windowless Target- Experimental Layout, Setup, and Instrumentation (contd)

Beamline

Loop in heat shieldVacuum system

Gate valve

Heater wiring

Windowless Liquid Li Target Loop

Splash

Shield


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The Choice of Liquid Lithium

Low Z (=3)---good from nuclear considerations

Large working temp range T ~ 1160 C

High boiling point (1342oC)

Low melting point (181oC)

Low vapor pressure (10-7 Pa at 200oC)---only Ga and Sn lower Lowest pumping power required because:

Lowest density (511 kg/m3)---easiest liquid metal to pump

High heat capacity ( 4.4x 103 J/kg-K)---highest of liquid metals

Low viscosity (5.4 x 10-4 Pa-s)

Low Prandtl No. ~0.05 excellent heat transfer

Applications

Heat Transfer fluid to cool solid targets with light-ion beams

Functions as combined coolant and target for high-power heavy-ion

beams


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Liquid Metal Engineering Issues

Materials of construction

Mechanical joint designs

Sealing materials

Secondary containment

Heating system design

Wetting of EM pumps & flowmeters


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Material Compatibil ity with Liquid Lithium

Liquid lithium dissolves most materials including:

Metals Cu, Ag, Au, Ni

Can not use Cu gaskets Lost 41% of gasket mass in less than 4 hours

of operation causing major vacuum leak

Ceramics, glasses

Concrete

Organics

Liquid lithium systems can be fabricated from

Stainless steel

Fe, Ta, Mo, Nb, Be


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Mechanical Joint Designs

Metal-to-metal seals are necessary for

liquid alkali metals

1. Grayloc flanges w/17-4 PH SS

seal rings2. Conflat flanges w/soft iron

gaskets

3. Hollow SS o-rings w/high polish

surface finish

4. Cajon flanges w/SS gaskets

Suitable for both pressure & high

vacuum


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Containment Objectives

Prevent water from contacting any lithium in the system.

Prevent air from contacting hot, molten lithium.

Fabricate containment from proper materials.

Secondary containment is essential.

Ideal:

sealed containment, enclosing primary vessel, with inert gas backfill,

maintained at a temperature below the melting point of lithium.

Minimum:

containment of any liquid lithium spills and splashes, with a negative

pressure air flow through a aerosol removal system.


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Secondary Containment

Necessary to minimize consequences of

alkali metal leak

ANL/MSU Li/Be target

2-part containment

Beamline vacuum system

SS containment cover


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Target & Stripper Heater Systems

Multiple-zone control system to

minimize hot spots

Ceramic band heaters provide

easy installation


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ANL/MSU DC EM pump foradjustable thickness target

DC EM pump for AEBL

Windowless target

EM Pumps


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Lithium Reactivity

Lithium is the least reactive of all alkali metals.

Nonetheless, liquid lithium is still very reactive.

The most violent reactions of liquid lithium occur with:

Water

Water vapor

Organics

Fluorocarbons

Lithium reacts slowly with oxygen and nitrogen.

H2 is evolved from water and many organic reactions with Li.

H2 is explosive in concentrations between 4% and 74.2% in air.

Li3N violently decomposes on contact with moisture.


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Lithium Fires

Potential for fire exists only when lithium is molten at a temperature greater

than 400oC in dry air.

Fire has been reported to occur at temperatures as low as 200oC in very

moist air.

Potential for fire suggests that a fire/safety watch be present when opening

a lithium filled system for experimental modification, maintenance or any

task requiring Li exposure to air or water.

Graphite and powdered carbon (Lith-X) are the most popular effective

extinguishing agents.


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Additional Operational Safety Considerations

Properly trained personnel.

Continuously monitor experimental systems when Li is flowing.

Heater coverage should approach 100% to eliminate cold spots.

Slowly increase pump current when establishing flow.

Place TCs at suspected cold spots in addition to heater controls/monitors.

Heat system reservoirs prior to internal passages to eliminate expansion

problems (~1.5% volume expansion upon melting).

Add lithium to cold system if possible.

Solid Li tends to stick to hot surfaces.


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Decontamination and Cleaning

Use gloves and eye protection.

Clean components in a hood or ventilated glove box like enclosure.

H2O is easiest and simplest cleaning agent.

Limit quantity of reactive Li to about 10 g per event.

Use approximately 500 ml of H2O per gram of Li to be reacted.

Completely disassemble components Water will not penetrate cracks and

crevices to react Li.

Water will be very basic. Treat appropriately before disposal.


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Conclusions

Liquid Metal Systems for High Power Accelerators

Targets---Look very promising, 20kW beam on target in 9/03

LiLiT (SARAF Li Target)

Thin Film Strippers---development underway Beam Dumps---currently evaluating feasibility

Technical Issues

Engineering---well understood

Stripper film thickness---currently measuring

Liquid metal pumps ---10-20 atm. pump required for Li stripper

Thermalhydraulics---bubble formation & boiling---Momozaki talk

Alkali Metal Safety Issues

Control of impurities---standard cold & hot trap technology

Alkali metal handling---well understood

Fire protection---well understood

Waste treatment & disposal---well understood

Liquid Lithium Argonne

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