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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 l.jpg

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


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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


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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


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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


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Background

Stainless Steel RF Feedthrough Components

Copper Internal Conductor Component

D&D Lessons Learned Workshop


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Background

D&D Lessons Learned Workshop


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System Configurations

Oxidative Tritium Decontamination System

Rotary Stationary

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Rotary System Configuration

D&D Lessons Learned Workshop


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Stationary System Configuration

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Piston-Cylinder Configuration

Vo = X

Co = [O3]

Vf = 0.5X

Cf = 2[O3]

uncompressed compressed

D&D Lessons Learned Workshop


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Reaction Chemistry

D&D Lessons Learned Workshop


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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


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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


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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


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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


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Decomposition of Excess Ozone Following Oxidation Process in OTDS

  • Thermal Decomposition

  • Activated Carbon Decomposition

  • Hopcalite Catalyst Decomposition

D&D Lessons Learned Workshop


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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


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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


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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


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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

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Efficient Removal of HTO

D&D Lessons Learned Workshop


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Results

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Results

D&D Lessons Learned Workshop


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