# Presentation: 537063

## Tritium Retention in Vessel Tiles & Oil

- Charles A. Gentile
**D&D Lessons Learned Workshop**
**June 25-26, 2002**
**PPPL**

## Acknowledgement of Others                                 Working on these Issues:

- P. LaMarche
- G. Gettelfinger
- S. Langish
- R. Parsells

- J. Parker
- S. Raftopoulos
- K. Rule
- R. Feder

## Introduction to TFTR, Tritium History

- Scale Model Testing
- Decontamination
- Results
- Summary/Conclusion

## Tokamak Fusion Test Reactor

## T fueling by neutral beam injection (NBI)

- Small amount by direct gas puffing
- T captured on NB enclosure cryopanels
- Batch processed to holding tanks
- D/T mixture with trace hydrocarbon
- Early stages of TFTR Ops scrap gas oxidized and shipped offsite for reprocessing
- Total T processed through facility - 99g

## Carbon tiles - Major location of T inventory

**6000 Ci “tenaciously bound” in torus**

- Approximately 1 ton of carbon tiles
- Codeposited Layer
- Plasma generated Carbon/Tritium coating
- Most tritium inventory in codeposited layer
- Carbon dust and debris
- Highly contaminated
- Smearable hazard to personnel
- Low total inventory
- Stainless Steel vessel wall
- Modest inventory
- Low outgassing rates at room temperature

## Cut up TFTR vacuum boundary while:

- Minimizing worker exposure to T-contaminated and activated materials
- Leave internal components inside TFTR
- Remove tiles from cut lines
- Minimizing amounts of  T or T-contaminated material released to the environment
- Minimizing waste
- Waste disposal cost is a significant fraction of D&D cost

## Mock-up of TFTR VV conditions in a Type-A waste container

- Eight tiles placed in container
- About 10Ci of tritium in tiles
- Three lifts (about 10 gallons each) loaded in container on successive days
- Passive measurements taken after each lift
- Core samples of cured concrete measured for T

## Slide 10

## Slide 11

## Great deal of moisture was released as the concrete cured

- T monitors gave false high signal (moisture and foam agent) during curing time
- Once concrete cures, smearable contamination was low

## 		Sample			Tritium (μCi/gm)

- 		_Sample_			_Tritium (__μCi/gm)_
- 		2001-1262			0.0178
- 		2001-1263			0.1342
- 		2001-1724			0.0201
- 		2001-1725			0.0226
- 		2001-1726			0.0353
- 		2001-1727			0.0231

## Level of tritium in concrete

- DAC ≈ 40.9 g/m3 (estimate)
- Very difficult to suspend 41 g/m3 and greatly exceeds the TLV for silica (0.005 mg/m3)
- Miniscule hazard from tritium in the dust!
- Conclusion from empirical data
- Low level of tritium to be released in concrete fill
- Concrete dust will have very low level of T

## Strategy to contain T while concrete filling and segmenting vessel:

- Concrete/Foam Filling of the vacuum vessel (VV)
- Displaced air passed though bubblers to reduce T release
- Detritiation factor ≈10X
- Possible to go directly to stack via E-trunks
- Segmentation of the VV using Diamond Wire Cutting (DWC)
- Dry process - no large volumes of cutting fluid or gas
- Containment of particulates generated by the DWC during the segmentation process

## Slide 16

## Diamond Wire Cutting

## Concrete pour on three separate days in  Summer 2001

- Vessel segmentation commenced in Summer 2001
- Completed Spring 2002
- No whole body doses detected for this task
- Tritium released is modest over plant chronic release (CY 2001 totals)
- HTO:  191Ci vs 115Ci/yr chronic rate prior to pour
- HT:   39Ci vs 10Ci/yr chronic rate prior to pour

## Activity in Stack During D&D Task

## Full face supplied air respirators worn in enclosures

- Reduces/eliminates facial skin exposure
- Facial skin exposure is only credible internal exposure risk
- Full anti-contamination protective clothing worn in enclosures and cutting lay-down area
- Minimal T exposure to workers. No whole body uptakes from activated components

## Slide 21

## Sector Disassembly

**Sector Disassembly**

## Worker Inside DWC Enclosure

**Worker Inside DWC Enclosure**

## Sector Removal

**Sector Removal**

## 2 types of oil used for TFTR

- Krytox
- Hydrocarbon
- Both types of oil found to have great affinity for “collecting” tritium
- Personnel exposure to oil is hazardous
- Oil easily sticks to and passes through skin
- High specific activity of tritium in oil – makes it extremely hazardous

## Oil removed from primary (nuclear) pumping system measured to levels of 200μCi/g

- Approximately 2-3 g of oil (due to high specific weight) per drop
- A single drop of tritiated oil exposed to skin would lead to an uptake of approximately 30 mRem