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					        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

                                                                    1
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
                                                             2
Helge Ravn/CERN   ENG, Target & Collector Meeting 09/07/03
                     Why a mercury-jet target
•   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




                                                             4
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
By a trivial distillation of target
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
                                                              5
Helge Ravn/CERN    ENG, Target & Collector Meeting 09/07/03
      Prospective medical radionuclides obtained
              from distillation of the Hg




                                                             6
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
•   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
                                                                                 7
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.




                                                             9
Helge Ravn/CERN   ENG, Target & Collector Meeting 09/07/03
         Toxicological properties of mercury




                                                             10
Helge Ravn/CERN   ENG, Target & Collector Meeting 09/07/03
         Sources of Hg release to the
                environment Consumer products
  Industrial/Process sources of Hg                            containing Hg
 •Chlorine alkali electrolysis                       •Batteries (most uses now banned)
 •Tanning and Dyeing                                 •Paint (most uses now banned)
 •Textile Production                                 •Barometers And Manometers
 •Pulp& paper production                             • Thermometers
 •Portland cement production                         •Catalysts And Pigments
 •Waste incineration                                 •Mercury containing switches
 •Coal heated power plants                           •Dental Amalgams
 •Steel Industry- coke production                    •Fungicides/Preservatives (most uses
 •Lime manufacturing                                 now banned)
 •Primary copper smelting                            •Laboratory Reagents
 •Crematories                                        •Medicines
 •Sulfuric acids obtained from smelting              •Cosmetics
 operations                                          •Fluorescent lamps and Mercury
 •Plastic materials & resin manufacturing            Vapor Lamps (~25mg/m)
 •Copper foil production                             •Metal Plating
 •Hot mix asphalt batch plants                       •Photography
 •Gold mining                                        •Solder
                                                                                  11
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                             • Iron and steel sectors
possible emission rates, the                          • Cement industry
OECD considers estimates of                           • Coal-burning for power
global emissions are extremely                         generation and industrial
difficult to make.                                      uses

  Global anthropogenic                                •Municipal and hospital
  emissions of mercury to                               waste incinerators
  air were estimated at 3,560 tonnes                  • Gold mining and refining
  in 1983, and to water and soil at                   • Thermometers
  4,600-8,300 tonnes,                                 • Dental amalgam.


                                                                              13
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
global emissions are extremely       • Biological formation of
                                       elemental mercury (or possibly
difficult to make.                     dimethylmercury) from
                                                        methylmercury
  Global OECD estimates of                            • Volatilisation from soil
  natural emissions of mercury to                     • Seismic activities such as
  air, water and land range from                        earthquakes
  2,500-15,000 tonnes/year.                           • 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




                                                             15
Helge Ravn/CERN   ENG, Target & Collector Meeting 09/07/03
          European chlorine-alkali plants using the mercury
                        process (July 1998)




                                                              16
Helge Ravn/CERN   ENG, Target & Collector Meeting 09/07/03
         The chlorine-alkali mercury-cell process




                                                             17
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




                                                                                  18
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.                                                        19
Helge Ravn/CERN      ENG, Target & Collector Meeting 09/07/03
                               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