# Presentation: 108001

## 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
- 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

## 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

## 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

## Background

- Stainless Steel RF                                Feedthrough Components

- Copper Internal                         Conductor Component

## Background

## Oxidative Tritium Decontamination System

**Rotary ****	****	****        Stationary**

## Rotary System Configuration

## Stationary System Configuration

## Piston-Cylinder Configuration

**Piston-Cylinder Configuration**

**V****o**** = X**
**C****o**** = [O****3****]**

**V****f**** = 0.5X**
**C****f**** = 2[O****3****]**

- uncompressed                    compressed

## Reaction Chemistry

**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

**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

**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*

**Reaction Chemistry**

## 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

## Thermal Decomposition

**Decomposition of Excess Ozone                          Following Oxidation Process in OTDS**

- Activated Carbon Decomposition
- Hopcalite Catalyst Decomposition

## Thermal Decomposition

**Thermal Decomposition**

- 	Ozone must be held at temperatures exceeding 300 degrees Celsius for an approximate 3 second duration for adequate conversion to occur

## Activated Carbon Decomposition

**Activated Carbon Decomposition**

- 	Design of activated carbon bed must allow for an approximate 3 second residence time for adequate conversion to occur

## 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

## HTO formed via this reaction mechanism is not removed through chemical process 

- 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

## Efficient Removal of HTO

**Efficient Removal of HTO**

## Results

**Results**

## Results

**Results**