The APTW front end was moved into the hot cell, on the lift table, following procedures outlined in Document-244862.

The mock-up frame was transferred from the east turntable to the west turntable above the front end. The east turntable is covered with the aluminum plate. During covering we accidentally broke the o-ring for the turntable plate flange. The new o-ring seal should be made ~1" longer in circumference to avoid difficulties with seating in the o-ring groove.

When we attempted to move the front-end with the manipulator, we noticed that the front end tended to carry on sliding down the slope of the hot cell (see TRI-DN-23-20 / Document-238536). The manipulators were subsequently unable to arrest the front end, likely because they cannot apply a load towards the CG of the front end. Therefore, for heavy-duty jigs in the hot cell it is advisable to avoid using wheels/rollers that allow the heavy assemblies to move freely on the lift table.

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UPDATE Nov 21, 2024

• FE attachment related tests completed:
  • replacement of shim plates
  • mock-up alignment of FE with shield plug (adjustment made in person, hot cell operator instruct and give direction with remote camera views
• Difficulties encountered:
  • keeping track of which hole/screws are seen by the cameras during alignment was difficult for the operator
  • shim plate awkward to handle if not familiar
  • incompatible coupling screw and nut threads (M24 course vs fine threads) prevent completion of coupling and uncoupling tests
  • 'loose' service tray requires separate alignment check when raising the FE with the lift table
• Lessons learned:
  • shim plate replacement easier if FE is semi-attached (screw lifts FE, leaving small gap for shim plate to be inserted)
  • need a cover plate to prevent dropping shim plate and associated screws
  • rotation clearance of FE checked, will clear
  • need to also check service tray alignment when raising
  • magnetic cameras would be beneficial for this operation
• Follow up items:
  • crane-based positioning of FE for replacement to be tested after concrete pours/hand-testing/when APTW is exchanged for AETE.
  • future design of protective covering when performing shim plate removal
  • optionally implement magnetic camera array to check hole alignment by looking directly at the holes

At end of shift, mock up and FE was separated, markings made on floor to specify where FE needs to be to couple.

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UPDATE Nov 25, 2024

Replacement nuts arrived (M24x3) for the coupling screws. Tests were completed to try and couple/uncouple the front end to the cart/mock up.

• For taking the FE on/off the cart the cart should be able to rotate with the FE so that we can secure the coupling screws.
• For dropping the FE off from the shield plug, we should make use of the alignment features (cup and cones), once screws are undone and the FE rests on the cones on the cart, it should be secured.
• If markings on floor is made to assist with alignment, we need to do two sets; one for unloaded cart, one for loaded cart, this is because the lift table will tilt differently when there is a load.
• The threads on the coupling screws are fine threaded in the real case, there is a slight concern with cross-threading when turning them onto the nuts remotely (from above).
• Existing camera views sufficient to check for clearance between coupling plates and FE structures.
• To allow the FE to guide freely into the alignment features (cup/cone), it may be a good idea to still use the air skates, but supplement it with structural 'stopping' features to keep it from rolling off the table.

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UPDATE Nov 26, 2024

We returned the front-end to the cart to allow the shield-plug mock up to be rotated by the target hall crane (turntable still not functioning as of this date).

During this operation we noticed that the front end did not fully return to the alignment cones on the cart (see images), somehow the contact pad screws made contact first, and so the two-faced alignment cone did not come into contact.

For the real support frame we should use a minimal number of contact points. Also,more clearance at the coupling screws between the cart to the front end should be added.

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UPDATE Nov 27, 2024

We rotated the mock-up frame manually to have the HTV side face the hot cell window. During which the o-ring fell and we decided to cut it for convenience, this should be replaced with an equivalent o-ring but made ~1" longer in circumference.

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UPDATE Nov 28, 2024

Today we attempted to re-couple the front end to the mock up frame in the orientation where the HTV faces the hot cell window. The misalignment between the FE on the cart to the mock-up frame is worse in this orientation than in the previous (90 CCW facing down). There was approximately a 1" gap difference between the opposite ended screws. Factors contributing to the misalignment include uneven seating of the FE onto the bosch frame and uneven 'brake' engagement on the bosch frame wheels. During the attachment process the the screws had to be tightened very unevenly, with the HTV side being tightened far more than the extraction electrode side.

Additionally, the service tray shifted significantly from handling in the previous days and it was difficult to align the locating pins/cylinders. This further complicated the coupling process, in the future the service tray attachment should be made a separate operation to the process of coupling the  FE to the shield plug.

Under these conditions, during tightening, the inner screw at the HTV-side somehow jammed against the nut and the nut conversely jammed into the bracket. Subsequently, that screw could not be tightened further and required great difficulty to be removed, even after removing the bracket. In the aftermath, the nut bracket became forced apart (see picture) and the threads on the screw deformed beyond use. This is a critical failure mode for this coupling system. Note that the screw was hand started onto the nuts on the brackets prior to fully tightening the screws.

We believe the factors contributing to this failure include:

1. bracket gap being too large and allows the nut to wedge itself during tightening,
2. screw threads not being hardened/of proper grade,
3. tightening the screws too unevenly and sharply (too large turns per-screw when bringing the FE up, 1/2-1 turn) / allowing some screws being slack,
4. high misalignment (pitch and roll) between the FE plate and the mock-up frame,
5. the brackets not being able to accommodate the observed misalignment,
6. hole for screw is ~short and creates possibility for jamming when there is misalignment (pitch and roll),
7. aligning the service tray locating features while aligning the screw holes for the FE coupling was difficult,
8. possibly the extra lead in (chamfer) on the coupling screws is excessive and a non-standard design, which may cause problems starting the nut, likely a standard chamfer on the end of a standard screw would be sufficient for this operation

In the real operation, the long length of the screw will help prevent this failure from happening but some things to keep in mind/improve on would be:

1. bracket re-design to use standard wrench/nut gaps to avoid nut jamming
2. use hardened threads
3. try to see if no-lead in/chamfer/using standard screw profiles is sufficient
4. re-design the coupling system to not require a nut at the bottom and avoid cross-threading/thread jamming in the hot cell (move threads and nuts all above the FE assembly)
5. extra: the screw should not be fine threaded in the real case to avoid cross threading
6. minimize misalignment when trying to couple in the future (rotate turntable to minimum misalignment orientation)
7. tighten the screws more incrementally to have them go together evenly, don't allow screws to be fully slack if possible to prevent jamming
8. fully remove the service tray and attach only after the FE is attached

Of the above recommendations we strongly recommend re-designing the nut bracket - even when coupling was smooth (without misalignment) the nuts made a visible dent onto the bracket at the highest point (see image). A smaller gap (standard wrench gap) would prevent such a mark from forming.

We replaced the deformed screw with a standard (off the shelf) one to keep the FE secure to the mock-up.

We also noted after completing coupling that the extraction electrode, farthest out screw had damaged threads (see image).

It is recommended to perform repeated coupling/decoupling operations in the hot cell after some process/design changes are made/implemented to work out any possible failure modes with this operation.