Transcript 10_Tritium_Line-Breaks.PPT
Line Breaks
Steve Raftopoulos
D&D Lessons Learned Workshop June 25-26, 2002
PPPL
What is a Line Break?
• At PPPL, a
line break
is any operation that breaks into the nuclear boundary.
• The
nuclear boundary
is defined as the combined systems that provide primary containment of tritium.
• Since the nuclear boundary was being continually changed during the D&D project, documentation that had been relied upon for years, was no longer current.
• Extra diligence during the planning and engineering phases was critical to ensure that proper
(SAFE)
actions were taken.
June 25-26, 2002 D&D Lessons Learned Workshop
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Types of Line Breaks
• • • • •
Heavily contaminated pumpable spaces.
Heavily contaminated non-pumpable spaced Lightly contaminated pumpable and non-pumpable spaces.
Line breaks involving oils.
Line breaks involving particulates.
June 25-26, 2002 D&D Lessons Learned Workshop
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Elephant Trunk System
• • • • Extension of the building HVAC.
Provides 3”, 6” or 12” diameter, flexible hose that draws air (and airborne contaminants) away from worker breathing zone.
Effluents pass through HEPA filters before being released to stack.
Stack monitors measure tritium being released, actions taken as necessary.
June 25-26, 2002 D&D Lessons Learned Workshop
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Tritium Bubbler
• • • •
Relies on exchange of HTO with H 2 O for ~ a 10:1 reduction in airborne HTO tritium levels.
Refrigerant dryer at output end “wrings out” tritiated water vapor from exhaust stream, releasing ~40 o dew point air.
Output can be directed to stack or to the Gas Holding Tanks (GHT), depending on tritium concentration.
Has been used as the long-term cleanup system on the TFTR neutral beam boxes.
June 25-26, 2002 D&D Lessons Learned Workshop
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Oil Change Carts
• • • • • • Used to remove and/or refill the oil from our vacuum pumps.
Uses kegs to collect or feed oil from/to pump.
Pressure or vacuum is used as the motive force. Mechanical equipment (and associated headaches) are eliminated.
Pumps must be fitted with a means of connecting
PPPL has installed “quick disconnect” fitting on all the vacuum pump sumps.
Separate carts are available for hydrocarbon and fluorinated oils.
June 25-26, 2002 D&D Lessons Learned Workshop
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Pump/Purge Carts
• • • • • Used to transfer tritium from various systems to the Torus Cleanup System (TCS).
Incorporate a calibrated volume that’s used for assaying and calculating total tritium.
Incorporate vacuum pump(s) for moving the gasses.
Two versions were available:
– One design with a vane pump capable of evacuating to 10 -3 torr. This was used during TFTR operations to restore vacuum to operational levels.
– Second design with a bellows pump
(Oil Free)
that was used on highly contaminated systems and during D&D.
Must have service ports on the systems to be able to connect the carts.
June 25-26, 2002 D&D Lessons Learned Workshop
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Heavily Contaminated Pumpable Spaces
• Pump/Purge method • •
Typical system
– Vacuum systems – Tritium handing systems (Tritium Storage & Delivery System [TSDS], Tritium Purification System [TPS]) – Anything that can hold a good vacuum and has some type of access/service port.
Methodology
– Isolate the line break volume – Using pump/purge cart, repeatedly evacuate and backfill the volume. Evacuation does not have to be to “high vacuum” standards. Effluents directed to the GHT or TCS (via tritiated vent).
– Backfill is with room air. The moisture in the air does the work, therefore the humid New Jersey air is very effective.
– Elephant trunk ventilation set up for worker protection.
– Tritium concentration measured. Concentration x Volume = total tritium, and is used in the decision making process.
– Line break(s) performed. Caps & blank flanges are available to seal openings ASAP
June 25-26, 2002 D&D Lessons Learned Workshop
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Heavily Contaminated Non-Pumpable Spaces
• • • Flow Purge method
Typical system
– – – Tritium levels too large to allow purging to stack via HVAC.
Very large volume systems (vacuum vessel, TFTR vacuum roughing/backing lines, etc.) – – Tritium handing systems (TCS, waste gas systems) Anything that cannot hold a good vacuum.
– Systems without access/service port.
Must have connectivity with the TCS
Methodology
– Isolate the line break volume.
– Establish valve lineup to TCS or the GHT. Connecting piping may have to be installed. Effluents directed to GHT.
– – Open system and establish flow to the GHT. Purge until tritium concentrations are lowered enough to allow either: Line breaks to commence or to allow switchover to stack purge.
– Elephant trunk ventilation set up at line break point(s) for worker protection.
– Line break(s) performed. Caps & blank flanges are available to seal openings ASAP.
June 25-26, 2002 D&D Lessons Learned Workshop
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Lightly Contaminated Pumpable and Non-Pumpable Spaces
• • Flow Purge method
Typical system
– Tritium levels low enough to allow purging to stack via HVAC.
– Very large volume systems (TFTR, TFTR vacuum roughing/backing lines, etc.) – Systems that were heavily contaminated, but have undergone tritium reduction and are now at low levels.
•
Methodology
– Isolate the line break volume.
– If necessary, establish valve lineup to allow flow purge through the entire system. May have to remove flanges from “dead legs”.
– – – Open system and establish flow to the Elephant Trunk. Purge until tritium concentrations are lowered enough to allow line breaks to commence.
Elephant trunk ventilation set up at line break point(s) for worker protection.
– Line break(s) performed. Caps & blank flanges are available to seal openings ASAP.
June 25-26, 2002 D&D Lessons Learned Workshop
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Line Breaks Involving Oils
• • Typical systems: – Vacuum pumps – Vacuum piping Methodology: – Remove oil from pumps using the oil change cart.
– Drill holes into large diameter piping and inspect with boroscope. – Set up ventilated enclosure around line break point(s).
– Ensure that oil absorbing media (pads, petroset, rags) are available.
– Ensure that caps or blank flanges are available for immediate use after line break.
– Perform line break(s), solidify oils, foam fill piping, cap open ends.
June 25-26, 2002 D&D Lessons Learned Workshop
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Line Breaks Involving Particulates
• •
Typical systems
: – Molecular sieve beds.
– Graphite lined vacuum vessel (DWC process).
– In-vessel entry.
Methodology:
– Protect the workers!!! The appropriate PPE is selected. PPE has ranged from Tyvek suits/half face respirators, to double PCs/supplied air breathing systems.
– If possible, stabilize the particulates. This was done using foam for the pump ducts, and with concrete for the vacuum vessel.
– Use of filtration systems. We used a closed loop, industrial filtration system during TFTR DWC to capture the particulates generated during the segmentation process.
– If proper precautions are taken, these become routine line breaks.
June 25-26, 2002 D&D Lessons Learned Workshop
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Examples of Lines Breaks with Combined Hazards
•TFTR vacuum pumping duct. Dust, from graphite tiles, was major concern.
•Technicians filled duct with expanding foam, stabilizing the airborne contaminants.
•Roughing/backing lines up against the test cell basement ceiling. Oil from the vacuum system pumps was a major concern. •Holes were drilled in strategic locations. Boroscope inspections were performed. •Elephant trunk drew air through pipes from the opposite (far) end. •Technicians were prepared to deal with oil, even though we did not find any during inspections.
June 25-26, 2002 D&D Lessons Learned Workshop
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“Snatch and Cap” Line Breaks
• • • • • Term given to line breaks involving component removal from the TFTR Vacuum Vessel.
Vacuum Vessel was put into purge mode by connecting an elephant trunk to a 12” port. Whenever a flange is removed, air flows into that opening.
Aluminum blank flanges were used (inexpensively fabricated via water jet cutter) to replace the conflat and custom TFTR port covers.
Gore-Tex rope-gasket material was used to make seals.
Once the Vacuum Vessel was in purge mode, several ports could be replaced in one day’s effort.
June 25-26, 2002 D&D Lessons Learned Workshop
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Conclusion/Lessons Learned
• Line breaks can be
successfully and safely
accomplished with the proper system in place.
• At PPPL this system includes: – Engineered hardware; – Trained, skilled personnel; – Strict adherence to PPPL and DOE procedures and protocol.
June 25-26, 2002 D&D Lessons Learned Workshop
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