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June 25-26, 2002 D&D Lessons Learned Workshop 1
Tritium Decontamination Techniques and Technology
C. A. Gentile, J. J. ParkerD&D Lessons Learned Workshop
June 25-26, 2002
PPPL
June 25-26, 2002 D&D Lessons Learned Workshop 2
Oxidative Chemistry Employed for Tritium Removal
1. H2O2 (hydrogen peroxide) liquid phase
2. O3 (ozone) gas phase
Technology Overview• Reduce tritium surface (and bulk) contamination on various
components and items
• Remove contamination by chemically reacting elemental T to tritium oxide (purge reaction effluent to TCS or stack)
• Control via implementation of specific concentrations, catalytic parameters, and/or process conditions
June 25-26, 2002 D&D Lessons Learned Workshop 3
Introduction
• Expendable items de-tritiated to activity levels at or slightly above background level
• Re-usable items de-tritiated to free release levels (< 1000dpm/100cm2, and for use in controlled areas)
• Oxidative Tritium Decontamination System (OTDS) capital cost and operation cost is relatively low, compared to other decontamination methods
June 25-26, 2002 D&D Lessons Learned Workshop 4
Background
• O3 and H2O2 decontamination processes both employ oxidative chemistry
• Process was implemented on contaminated RF Feedthrough components (copper, stainless steel)
• Post H2O2 process activity levels dropped significantly (< 1% initial activity)
• No discernable surface regrowth was noted after approximate 8 month hold time
June 25-26, 2002 D&D Lessons Learned Workshop 5
Background
Stainless Steel RF Feedthrough
Components
Copper Internal Conductor Component
June 25-26, 2002 D&D Lessons Learned Workshop 6
Background
June 25-26, 2002 D&D Lessons Learned Workshop 7
System Configurations
Oxidative Tritium Decontamination System
Rotary Stationary
June 25-26, 2002 D&D Lessons Learned Workshop 8
Rotary System Configuration
June 25-26, 2002 D&D Lessons Learned Workshop 9
Stationary System Configuration
June 25-26, 2002 D&D Lessons Learned Workshop 10
Piston-Cylinder Configuration
Vo = XCo = [O3] Vf = 0.5X
Cf = 2[O3]
uncompressed compressed
June 25-26, 2002 D&D Lessons Learned Workshop 11
Reaction Chemistry
June 25-26, 2002 D&D Lessons Learned Workshop 12
• Secondary reactions (promote additional release of hydrogen isotopes) • oxidation of carbon via ozone and/or diatomic oxygen to yield
CO2 (and CO)
• reaction of nitrogen (if present in system) with tritium to yield tritiated ammonia
• oxidative dissociation of polymer chains
Reaction Chemistry
June 25-26, 2002 D&D Lessons Learned Workshop 13
• Required duration of O3 exposure dependant upon:• concentration of pure O3 in feed
• residence time in reaction chamber
• These parameters are controlled via the following:• concentration of diatomic oxygen in gaseous supply to ozone
generator
• volumetric flow rate (output) of ozone generator
• volume of reaction chamber
Reaction Chemistry
June 25-26, 2002 D&D Lessons Learned Workshop 14
• Desiccation/drying of feed supply• Lowers relative humidity within reaction chamber, thus facilitating
evaporation of HTO (tritium oxide)
• Reduces possibility of formation of hydroxyl radicals, which can hinder the primary reaction mechanism
Desiccation/drying of feed supply yields shorter system run-time
Reaction Chemistry
June 25-26, 2002 D&D Lessons Learned Workshop 15
Decomposition of Excess Ozone Following Oxidation Process in OTDS
• HVAC ductwork, in most cases, is constructed of ferrous metal, which exhibits corrosion when exposed to strong oxidizing agents
• Ozone will degrade polymer-composite seals present in HVAC systems
• It is necessary to significantly reduce the release of ozone into these systems
June 25-26, 2002 D&D Lessons Learned Workshop 16
Decomposition of Excess Ozone Following Oxidation Process in OTDS
• Thermal Decomposition
• Activated Carbon Decomposition
• Hopcalite Catalyst Decomposition
June 25-26, 2002 D&D Lessons Learned Workshop 17
Thermal Decomposition
Ozone must be held at temperatures exceeding 300 degrees Celsius for an approximate 3 second duration for adequate conversion to occur
June 25-26, 2002 D&D Lessons Learned Workshop 18
Activated Carbon Decomposition
Design of activated carbon bed must allow for an approximate 3 second residence time for adequate conversion to occur
June 25-26, 2002 D&D Lessons Learned Workshop 19
Hopcalite Catalyst Decomposition
• MnO2 (manganese dioxide) based catalyst
• Not consumed during ozone decomposition
• Approximate 0.36-0.72 second residence time
• >99% conversion of up to 120000 ppm ozone
June 25-26, 2002 D&D Lessons Learned Workshop 20
Efficient Removal of HTO
• HTO formed via this reaction mechanism is not removed through chemical process
• Majority of HTO remains as condensate on material surfaces
• A physical process (i.e. evaporation) must be implemented to facilitate HTO removal
June 25-26, 2002 D&D Lessons Learned Workshop 21
Efficient Removal of HTO
June 25-26, 2002 D&D Lessons Learned Workshop 22
Results
June 25-26, 2002 D&D Lessons Learned Workshop 23
Results
