1. Marsupial Miniature Robotic Crawler System
for Camera and Sensor Deployment in Nuclear Waste Double Shell Tank Refractory Air Slots
Presented by Colin Dobell, President & CEO, Inuktun ASNT Annual Conference, — Salt Lake City, UT

2. Agenda Background Challenges & Risks Conclusion Questions
Getting to the Air Slots through Annulus
Maneuvering Inside Air Slots / Spalled Material
Negotiating Bends, Slot Type Transitions
Integration of Onboard Sensors
System Recovery
Conclusion
Questions

3. Background — Hanford, 1940s…
How to protect from irradiated/chemically contaminated fuel rods?
No traditional disposal methods: underground storage tanks
Integrity problems with single shell tanks: leaks (groundwater contamination risk)
The Hanford Site contains underground storage tanks that contain 204 million liters (54 million gallons) of hazardous and radioactive waste—enough to fill nearly 2,800 railroad tanker cars.*
There were 177 tanks built at the Hanford Site between 1943 and 1985.*
*Source:

4. Background — Hanford (DOE), 1940s…
Newer “Double shell” tanks, reinforced concrete base
Despite advantages, nature of stored waste mandates regular tank inspections
Current inspection practices (mostly) effective for assessing overall integrity of tank walls
Challenge = tank floor
Cannot be emptied; inspection equipment cannot be used internally
No in-situ or empty-tank inspection
BUT: Tanks supported by concrete foundation w/ refractory air slots
Accessible by very small remote robotic system w/ Integrated video cameras & Nondestructive Testing (NDT) tools

5. Challenge # 1 - Getting to the Air Slots
Only access to annulus space is through risers in tank dome
10 risers available (6 x 6”, 2 x 12”, 2 x 24” diameter) 
No deployment via pole (accesses only air slots directly below risers)
Riser-mounted manipulator arm prohibitively complex, expensive…
Option – attach to the inner wall and drive to the air slots
30’
75’

6. 1 Solution: Marsupial Approach
One Robot Carries Another
‘Motherbot’ based on off-the-shelf Versatrax 100 MicroMag™ crawler
Customized to carry smaller inspection crawler + special mechanism for positioning, cable handling
Deployed through 12” & 24” risers, maneuvered from inner tank wall (best location)

7. 1 Deployment & Positioning
System fits through 12 and 24 inch risers
Simple pole to get vehicle through the riser and onto the inner tank wall
Deployment “Arm”
Articulating arm to carry & position inspection crawler
Cable sheave to manage umbilical cable for inspection crawler
Mounted on loose joint
Ensure center of gravity always below magnetic vehicle
Reduce likelihood of separation from tank wall

8. 1 Travelling on the Inner Tank Wall
Positioned on inside wall, Motherbot can be driven to desired location by joystick or computer control
Travelling long horizontal distances away from riser  issues w/ cable weight & handling
BUT: Using all 12” & 24” risers total horizontal travel = < 30 feet
(75’ diameter, 90° riser separation)

9. 1 Inspection Crawler Deployment
Position inspection crawler system directly above target air slot entry point using video cameras
Onboard Motherbot
Onboard inspection crawler
PTZ deployed through neighboring riser
By manipulating angle of deployment arm: inspection crawler at ideal entry angle
With the arm and Motherbot parked in place, inspection crawler drivable independently

10. Challenge # 2 - Maneuvering Inside Air Slots
Size & shape of air slots (≥ 1” across, rectangular/trapezoidal) makes moving, positioning remote system within challenging
Two track system using new Inuktun miniature crawler modules:
Picotrac™ — based on larger Minitrac™ & Microtrac™
Fully sealed, modular, independently operated
Approx 1” square x 7” long: tracks maneuver in all but smallest air slots

11. (Only Type 1 is contemplated)
2 Typical Air Slot Configuration
AZ Tank Farm
AY Tank Farm
(Only Type 1 is contemplated)

12. 2 Spalled Material
Over time, pieces of concrete, and possibly other material, loosen and fall to bottom of air slots
Material reduces effective size of slot
Difficult to achieve traction, accurately position NDT sensors
Operating inside w/ spalled material prohibits complete inspection
BUT: Cleaning module attached to Motherbot instead of deployment arm

13. 2 Spalled Material Removal
Cleaning operation - prior to deployment of inspection crawler
Mechanism w/ brush tool outfitted to same Motherbot for accessing air slots
Onboard cable drive w/ two Microtrac™ modules used to force miniature push cable into slots
On retrieval, brush system pulls loose material out of air slot into annulus space
End effector orientation remotely adjusted to push cable through specific bends
Multiple passes required if debris excessive

14. Challenge # 3 – Negotiating Bends and Transitions
In-line system steerable through bends between slot types (except AY tanks, two total)
NDT Probe Mount
Front Picotrac™
Rear Picotrac™
Linear Actuator
Front Camera
Mid Camera

15. Challenge # 4 - Integration of Onboard Sensors
System size limits amount and type of technology on crawler
Umbilical cable:
Fiber optics for high speed data transfer (real-time video & NDT)
Small, lightweight (inspection crawler = limited pulling power)
Low friction cable jacket material (Nylon, Polyethylene)
Multiple video cameras and NDT tool (unspecified) deployable against tank underside
Wide angle camera lens with digital pan/tilt/zoom
Laser profiling “ring” to quantify shape, externally visible flaws in tank bottom

16. Challenge # 5 - System Recovery
During normal operation, deployment & retrieval straightforward:
Motherbot inserted onto internal annulus wall through riser
Motherbot positions inspection crawler at entry to air slot
Inspection crawler drives into air slot, performs inspection
Inspection crawler drives back onto Motherbot deployment arm, parks
Motherbot returns to top of annulus, is retrieved through riser
Risk of stuck vehicle best minimized via operating procedure
BUT: Design of system components simplifies retrieval, especially in emergencies:
Umbilical cables for both crawler units incorporate aramid fiber strength member (systems retrieved by simply pulling on cable)
Mechanical linkages designed, tested for safety under emergency retrieval conditions
Worst case scenario:
Small crawler vehicle fails inspecting innermost portion of air slots
Keeping the Motherbot positioned at entry to air slot, retrieve the system by pulling on umbilical from above tank, while cable sheave in position

17. Conclusion
Combination of existing, newly developed remote systems & components can provide reliable access into refractory air slots underneath subterranean double shell tanks
No suitable commercially available solution: unique entry limitations and extremely confined spaces
Inuktun marsupial system truly modular (IM3 Standards):
Builds on prior engineering efforts & established design techniques
Allows addition of NDT tools, cameras, sensors & end effectors
Satisfies immediate inspection requirements
Meets virtually any future remote inspection, tooling needs

18. Marsupial Miniature Robotic Crawler System
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19. Marsupial Miniature Robotic Crawler System
for Camera and Sensor Deployment in Nuclear Waste Double Shell Tank Refractory Air Slots
Presented by Colin Dobell, President & CEO, Inuktun ASNT Annual Conference, — Salt Lake City, UT