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SNS Experimental Facilities Oak Ridge
Mercury Target Issues andDevelopment Program
Neutrino Factory and Muon Coll ider Collaboration
Targetry R&D Meeting
Dec. 16, 2000
Brookhaven National Laboratory
Tandem Library, Bldg 901A
John Haines
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SNS Experimental Facilities Oak Ridge
Outline
• Comparison Between SNS and Neutr ino Factory Target
Requirements
• Key Issues and R&D implemented to address them
– Removal of time-averaged power
– Handling pulsed beam loads
– Materials compatibility and irradiation damage
• Hg processing and storage of radioactive byproducts
• Comments on Safety Categorizat ion and R&D for Neutr ino
Factory and Muon Col l ider
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SNS Experimental Facilities Oak Ridge
SNS Mercury Target Requirements
• 2 MW average proton beam power
• 1 GeV protons
• Pulse duration ~ 0.5 µs
• 60 Hz rep rate
• Result ing target loads
– Energy deposition per pulse ~ 33 kJ
– Peak time-averaged current on target 0.25 A/m 2
– Peak time-averaged power flux on target vessel ~ 600 MW/m 3
– Peak time-averaged power flux from vessel to Hg ~ 1 MW/m2
– Peak energy deposition in Hg ~ 800 MW/m 3
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SNS Experimental Facilities Oak Ridge
Comparison of Heat Loads
Energy Density
(MJ/m3)
∆T (K)
SNS 13 7
Neutrino Factory @ 5 MW, 15 Hz
670 350
Single Pulse Loads in Hg
10-2
10-1
1
10
103
102
104
Neutrino Factory Hg Target w/ 2 MW Proton
Beam(time-averaged)
Volumetric Heating
Rate (MW/m3)
SNS Hg(time-averaged)
SNS Hg Vessel(time-averaged)
Fission Reactors
Proposed Fusion
Reactor First Wall
High performance copper magnets
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SNS Experimental Facilities Oak Ridge
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SNS Experimental Facilities Oak Ridge
• Power absorbed in Hg 1.2 MW
• Nominal Operating Pressure 0.3 MPa (45 psi)
• Flow Rate 340 kg/s
• V max ( In Window) 3.5 m/s
• Temperature
– Inlet to target 60ºC
– Exit from target 90ºC
• Total Hg Inventory 1.4 m 3 (20 tons)
• Pump Power 56 kW (75 HP)
SNS Hg Targetoperates at lowtemperature andpressure
Mercury Loop Flow Parameters @ 2 MW
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SNS Experimental Facilities Oak Ridge
Hg Process Loop
CollectionTank
PumpStorage Tank
Heat Exchanger
Target
Water Delay Tank
Gas Liquid
Separator
Process Bay Equipment
Plug
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SNS Experimental Facilities Oak Ridge
Key Issues for the SNS Mercury Target
• Steady state power handling
– Cooling of target/enclosure window - wettability
– Hot spots in Hg caused by recirculation around flow baffles
• Thermal Shock
– Pressure pulse loads on structural material
– Effects on bulk Hg flow
• Radiation damage to structural materials
• Compatibi l i ty between Hg and other target system materials
• Demonstration of key systems:
– Mercury loop operation
– Remote handling Some SNS Hg Target R&D Facilities,capabilities, and expertise might bedirectly applicable to neutrino factory
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SNS Experimental Facilities Oak Ridge
800 MeVProton Beam
Fiber-opticStrain gages
Fiber-opticPressure sensors
Mercury TargetVessel (316SS)
LANSCE-WNRHg Target Tests
MTHL
TTF
WTHL
Mercury Target Development
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SNS Experimental Facilities Oak Ridge
Mercury Process Cell at TTF
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SNS Experimental Facilities Oak Ridge
Materials R&D
• An aggressive materials R&D program has been developed for
Target Systems
§ Technical issues:
– Radiation induced embrittlement by p and n fluxes
– Effects of high He and H transmutation rates on properties
– Thermal gradient mass transfer in Hg
– Liquid metal embrittlement
– Interactions of radiation effects and compatibilityprocesses.
§ Facilities: LANSCE, SINQ, TIF, HFIR
§ Hg Loops and other test devices involving Hg have been builtat ORNL.
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SNS Experimental Facilities Oak Ridge
Test \ Item Energy Dose He H Hg Thick Stress Fatigue
SNS high high high high flow √ √ √
TIF3- Beam
low high high high
TIFp-Beam low low static* ?
LANSCE high high high high √
SINQ high high high high √
HFIR low high high √
TC Loop flow √
LMETensile static √ √
LMEFatigue static √ √
* Low flow rate upgrade may be possible√√ Typical for SNS? Possible relevance to SNS
Materials Qualification Tests
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SNS Experimental Facilities Oak Ridge
Hg processing and handling ofradioactive byproducts
• Mercury lasts the entire 40 year l i fetime of SNS with no
changeout required
– “Burn-up” over 40 years is only ~ 0.1%
§ Most conversion is from one Hg isotope to another
§ Tritium production rate ~ 8 kCi/year
• No fi ltering required; trit ium released from Hg to absorptionsystem
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SNS Experimental Facilities Oak Ridge
Safety Issues for SNS Hg Target
• SNS Target Region is a a Hazard Category 2 Nuclear Facil i ty
– Inventory of certain radionuclides (primarily mercury isotopes)exceed thresholds
• Mercury releases that exceed the site boundary l imits are onlypossible if the mercury is at elevated temperature
• Safety Class Systems required to avoid elevated temperatures
– Target Protection System used to trip the proton beam forabnormal loop conditions (high temperature or low flow)
– Safety Class fire protection
§ Combustion Control program
§ 2 hour fire wall
§ fire suppression system
• Additional Safety Signif icant Equipment needed to protectworkers
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SNS Experimental Facilities Oak Ridge
Hazard Category 2 Indices for SNS Hg Target
HC Indices - 1999 (EOL after 30-y continuous operation @ 2 MW)
0.01
0.10
1.00
10.00
HG203
HG197
GD148
HG194
HF172
HG195
I125
HG193
AU195
AU188
W17
5
W17
4I1
24
HF171
OS183M
LU168
Dominant Nuclides
Inve
nto
ry/T
hre
sho
ld
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SNS Experimental Facilities Oak Ridge
DOE Safety Documentation RequirementsDiffer for Nuclear and Accelerator Facilities
• Accelerator Facilities: DOE Order 420.2 and related guidance
– Preliminary Safety Assessment Document (PSAD) required for designstage
– Independent review required
– Approval authority with project management
– Includes facilities integrally connected to accelerator
– DOE approval of the Accelerator Safety Envelope required prior tocommissioning and/or operations.
• Nuclear Facilities: DOE Order 420.1, 10 CFR 830, DOE Standards3009, 1027, 1019-24, and others
– Preliminary Safety Analysis Report (PSAR) required for nuclear facilities… per DOE-STD-1027 this includes the SNS target and related facilities
– Approval required before construction begins
– DOE reviews and approves the PSAR
– Approval of final SAR (FSAR) required for operation & commissioning
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SNS Experimental Facilities Oak Ridge
Nuclear boundary in red
Neutron instruments,balance of building,
defined as
part of the accelerator facility
Ring-to-targettransport tunnel
Target Building
The Nuclear Facility Includes a Portion ofthe Target Building (1)
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SNS Experimental Facilities Oak Ridge
Section through target, monolith and neutron beam lines
The Nuclear Facility Includes a Portion ofthe Target Building (4)
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SNS Experimental Facilities Oak Ridge
PSAR Process Takes Signif icant Time & Resources,
and Must Be Completed Prior to Construction
Activity Time
Preparation by SNS andcontractor
June – December 1999
DOE Review January/February 2000
Approval (stipulated completion ofchemical consequence analysis)
February 2000
Chemical hazard and fireaccident analysis
May – August 2000
DOE Review of Chem/fireanalysis
October 2000 (ongoing, approvalexpected soon)
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SNS Experimental Facilities Oak Ridge
Chemical Consequences Are More Limitingthan Radiological
• WORKER, accident l imit:
– Toxicity limit for infrequent accidents is 10 mg/m3 for 0.5-hours(IDLH -- “immediately dangerous to life and health”)
– Rad dose due to 10 mg/m 3 for 0.5-hours (long lived Hg isotopes) =4 rem (within 10 CFR 835 annual limit)
• PUBLIC: accident l imit does not exist (SNS plans to propose 2mg/m 3 for “ERPG-2” l imit)
– Toxicity “limit” is 2 mg/m 3 for 1-hour exposure (proposed ERPG-2)
– Rad dose due to 2 mg/m 3 for 1-hour = 1.6 rem [DOE’s “evaluationguideline” (max limit) is 25-rem for public exposure to infrequentaccidents]
• Bottom line: For accidents, the toxicity consideration is morelimiting by factor of approximately 10.
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SNS Experimental Facilities Oak Ridge
The Emergency Response PlanningGuideline (ERPG) Values
• The Emergency Response Planning Guideline-2 (ERPG-2) value is themaximum airborne concentration below which it is believed that nearly allindividuals could be exposed for up to 1 hr without experiencing or developingirreversible or other serious health effects or symptoms which could impair anindividual's ability to take protective action.
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SNS Experimental Facilities Oak Ridge
Comments on Using a Hg Target forNeutrino Factory
• Must carefully define requirements, and a Hg target conceptual designthat meets these requirements
– Until this is done, efforts are likely to flounder and could be irrelevant inthe end
– Derive feasibility issues
– Define R&D program that addresses critical feasibility issues
• Feasibility issues:
– Hg jet formation and stability, especially in high B field, will be critical issue
– How to re-establish jet before next beam pulse
– Likely that others will result from conceptual design process
• Using mercury could significantly complicate the Environmental ImpactStatement and Safety Analysis
– Neutrino factory/muon collider will likely be a Nuclear Facility
• SNS facilities, capabilities, and expertise are available for the NeutrinoFactory and Muon Collider Collaboration