Transcript ISOLDE highlights

Safety issues in relation to use
of mercury in industry and in
liquid-metal high-power targets
H. L Ravn CERN
http://hlr.home.cern.ch/hlr/files/Hg safety.ppt
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Overview
•Why a mercury-jet target
•Reduction of spallation product inventory and a source of
prospective medical radio-nuclides obtained from distillation
of the Hg
•The SNS and JSNS Hg targets are in an advanced stage of
construction or planning
•Chemical properties of mercury
•Toxicological properties of mercury
•Sources of Hg release to the environment
•Mercury production and consumption
•Concentration of Hg in the human food chain
•The chlorine-alkali mercury-cell process
•Conclusion
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Why a mercury-jet target
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High pion and neutron yield (high Z)
High source brightness (high density)
Flowing liquid metals have excellent power handling capabilities and have the capability
to go to the highest power densities
No water radiolysis
No target material fatigue limit caused by the radiation damage
No build up of dusty and pyroforic material
Liquid at ambient temperature (no liquid-to-solid phase change issues)
Minimal waste stream (compared to solid alternatives since the Hg is reused)
Most of the spallation products can be removed from the Hg by distillation
Passive removal of decay heating
No confinement tubing or beam windows with lifetime limits caused by the radiation
damage
Alternative molten lead-bismuth (PbBi) alloy mp. 125° C
Higher Dt = higher power handling capability
More corrosive than Hg causing lifetime problems for the plumbing and containment
This will be tested in a 1 MW MEGAPIE PbBi target is under construction at PSI
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Windowless liquid metal-jet target
inside a pion focusing horn
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
The molten-lithium neutron source for
a 7 MW d-beam as model for the Hg
target
By a trivial distillation of
the Hg in the bypass
loop most of the nuclear
reaction can be removed
from the target and
concentrated into a
disposal friendly solid
form. The only
radioactivity left in the
Hg will be the long-lived
194Hg in equilibrium with
its daughter product
194Au. Their radiation will
be screened by self
absorption in the Hg.
Today the 60 cm3 ISOLDE Pb-target
is distilled at a rate of ~30 g/h or 3cm3/h
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Prospective medical radionuclides obtained
from distillation of the Hg
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
The SNS and JSNS Hg targets are in
an advanced stage of construction or
planning
SNS target station
Pion target data
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Power absorbed in Hg-jet 1 MW
Operating pressure
100
Bar
Flow rate
2 t/m
Jet speed
30 m/s
Jet diameter
10 mm
Temperature
- Inlet to target
30° C
- Exit from target
100° C
Total Hg inventory
<10 t
Pump power
50 kW
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Mercury belongs to the zink group #12
of the periodical system
•Used by man since 1500 BC
•Mercury is a marketable commodity not a hazardous waste
•It has numerous beneficial use that provide value to our society
and will not be replaced in any foreseeable future
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Chemical properties of mercury
Hg
HgCH3 Methylmercury
HgS is the most insoluble Hg
compound and the best disposal
way i. E. the Brookhaven sulphur
polymeric disposal method that
solidifies the liquid waste Hg.
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Toxicological properties of mercury
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Sources of Hg release to the
environment Consumer products
Industrial/Process sources of Hg
•Chlorine alkali electrolysis
•Tanning and Dyeing
•Textile Production
•Pulp& paper production
•Portland cement production
•Waste incineration
•Coal heated power plants
•Steel Industry- coke production
•Lime manufacturing
•Primary copper smelting
•Crematories
•Sulfuric acids obtained from smelting
operations
•Plastic materials & resin manufacturing
•Copper foil production
•Hot mix asphalt batch plants
•Gold mining
containing Hg
•Batteries (most uses now banned)
•Paint (most uses now banned)
•Barometers And Manometers
• Thermometers
•Catalysts And Pigments
•Mercury containing switches
•Dental Amalgams
•Fungicides/Preservatives (most uses
now banned)
•Laboratory Reagents
•Medicines
•Cosmetics
•Fluorescent lamps and Mercury
Vapor Lamps (~25mg/m)
•Metal Plating
•Photography
•Solder
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Mercury production and consumption in
1996
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Anthropogenic emissions of mercury
Due to the complexity of identifying
anthropogenic sources and
possible emission rates, the
OECD considers estimates of
global emissions are extremely
difficult to make.
• Iron and steel sectors
• Cement industry
• Coal-burning for power
generation and industrial
uses
Global anthropogenic
emissions of mercury to
air were estimated at 3,560 tonnes
in 1983, and to water and soil at
4,600-8,300 tonnes,
•Municipal and hospital
waste incinerators
• Gold mining and refining
• Thermometers
• Dental amalgam.
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Natural mercury emission
• Degassing from geological
Due to the complexity of identifying
mineral deposits
anthropogenic sources and
• Emissions from volcanic
activities
possible emission rates, the
• Photo reduction of divalent
OECD considers estimates of
mercury in natural waters
• Biological formation of
global emissions are extremely
elemental mercury (or possibly
difficult to make.
dimethylmercury) from
Global OECD estimates of
natural emissions of mercury to
air, water and land range from
2,500-15,000 tonnes/year.
methylmercury
• Volatilisation from soil
• Seismic activities such as
earthquakes
• Geothermal sources – including
the oceanic crust – related to
submarine volcanoes.
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Concentration of Hg in the food chain
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
European chlorine-alkali plants using the mercury
process (July 1998)
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
The chlorine-alkali mercury-cell process
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Mercury process chlorine plant
Typical Hg inventory 100 - 400 t
All factories in Europe 12000 t
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
Mercury process chlorine plant
phase out
Although chlorine-alkali plants are only
responsible for ~5% of the
anthropogenic mercury emissions in the
atmosphere, chlorine producers in
Western Europe have agreed not to
build any new mercury processing
plants and comply with a total phase
out of the mercury process by
2010.This decision was less for safety
reasons than for economical reasons
since the factories are at the end of their
economic lives and less energy
consuming alternatives are now
available. A major safety problem of
what to do with the 12000 t surplus Hg
now on the market will instead be
created.
Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
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Conclusion
•The mercury inventory in the pion target is compared
to the industrial uses insignificant
•In the target Hg will be completely enclosed
•Leak detecting will be orders of magnitude more sensitive than in industry
due to the presence of short-lived Hg isotopes
•Significant release to the environment can be made highly unlikely
•There is no large and continuous Hg-containing effluents as in the
industrial processes and from spent consumer goods
•Safe handling and monitoring methods of Hg exists
•Handling of Hg needs specially trained people like for
radioactivity
•Disposal methods for elementary Hg are well understood and published
•They are very similar to the ones used for for radioactivity disposal
•No safety reason not to use Hg for accelerator target purposes
•The use of Hg is justified and we should actively join the already
considerable R&D efforts of the SNS and JSNS on such targets
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03
The chlorine-alkali mercury-cell
process
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Helge Ravn/CERN
ENG, Target & Collector Meeting 09/07/03