1. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 1 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

2. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 2 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

3. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 3 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  t = 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

4. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 4 Windowless liquid metal-jet target inside a pion focusing horn

5. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 5 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 194 Hg in equilibrium with its daughter product 194 Au. Their radiation will be screened by self absorption in the Hg. Today the 60 cm 3 ISOLDE Pb-target is distilled at a rate of ~30 g/h or 3cm 3 /h

6. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 6 Prospective medical radionuclides obtained from distillation of the Hg

7. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 7 The SNS and JSNS Hg targets are in an advanced stage of construction or planning Power absorbed in Hg-jet1 MW Operating pressure100 Bar Flow rate2 t/m Jet speed30 m/s Jet diameter10 mm Temperature - Inlet to target30° C - Exit from target100° C Total Hg inventory<10 t Pump power50 kW SNS target station Pion target data

8. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 8 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

9. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 9 Chemical properties of mercury 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. HgHgCH 3 Methylmercury

10. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 10 Toxicological properties of mercury

11. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 11 Sources of Hg release to the environment 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 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 Industrial/Process sources of Hg Consumer products containing Hg

12. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 12 Mercury production and consumption in 1996

13. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 13 Iron and steel sectors Cement industry Coal-burning for power generation and industrial uses Municipal and hospital waste incinerators Gold mining and refining Thermometers Dental amalgam. Due to the complexity of identifying anthropogenic sources and possible emission rates, the OECD considers estimates of global emissions are extremely difficult to make. Anthropogenic emissions of mercury 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,

14. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 14 Natural mercury emission Degassing from geological mineral deposits Emissions from volcanic activities Photo reduction of divalent mercury in natural waters Biological formation of elemental mercury (or possibly dimethylmercury) from methylmercury Volatilisation from soil Seismic activities such as earthquakes Geothermal sources – including the oceanic crust – related to submarine volcanoes. Due to the complexity of identifying anthropogenic sources and possible emission rates, the OECD considers estimates of global emissions are extremely difficult to make. Global OECD estimates of natural emissions of mercury to air, water and land range from 2,500-15,000 tonnes/year.

15. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 15 Concentration of Hg in the food chain

16. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 16 European chlorine-alkali plants using the mercury process (July 1998)

17. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 17 The chlorine-alkali mercury-cell process

18. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 18 Mercury process chlorine plant Typical Hg inventory 100 - 400 t All factories in Europe 12000 t

19. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 19 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. Mercury process chlorine plant phase out

20. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 20 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

21. Helge Ravn/CERN ENG, Target & Collector Meeting 09/07/03 21 The chlorine-alkali mercury-cell process