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Tritium Decontamination Techniques and Technology

Tritium Decontamination Techniques and Technology. C. A. Gentile, J. J. Parker D&D Lessons Learned Workshop June 25-26, 2002 PPPL. Oxidative Chemistry Employed for Tritium Removal. H2O2 (hydrogen peroxide) liquid phase O3 (ozone) gas phase Technology Overview

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Tritium Decontamination Techniques and Technology

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  1. Tritium Decontamination Techniques and Technology C. A. Gentile, J. J. Parker D&D Lessons Learned Workshop June 25-26, 2002 PPPL D&D Lessons Learned Workshop

  2. Oxidative Chemistry Employed for Tritium Removal • H2O2 (hydrogen peroxide) liquid phase • 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 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 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 D&D Lessons Learned Workshop

  5. Background Stainless Steel RF Feedthrough Components Copper Internal Conductor Component D&D Lessons Learned Workshop

  6. Background D&D Lessons Learned Workshop

  7. System Configurations Oxidative Tritium Decontamination System Rotary Stationary D&D Lessons Learned Workshop

  8. Rotary System Configuration D&D Lessons Learned Workshop

  9. Stationary System Configuration D&D Lessons Learned Workshop

  10. Piston-Cylinder Configuration Vo = X Co = [O3] Vf = 0.5X Cf = 2[O3] uncompressed compressed D&D Lessons Learned Workshop

  11. Reaction Chemistry D&D Lessons Learned Workshop

  12. Reaction Chemistry • 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 D&D Lessons Learned Workshop

  13. Reaction Chemistry • 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 D&D Lessons Learned Workshop

  14. Reaction Chemistry • 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 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 D&D Lessons Learned Workshop

  16. Decomposition of Excess Ozone Following Oxidation Process in OTDS • Thermal Decomposition • Activated Carbon Decomposition • Hopcalite Catalyst Decomposition 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 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 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 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 D&D Lessons Learned Workshop

  21. Efficient Removal of HTO D&D Lessons Learned Workshop

  22. Results D&D Lessons Learned Workshop

  23. Results D&D Lessons Learned Workshop

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