A trial run of remote removal of the UCN target was performed using the shielded target cask (TTA0335) developed in 2020.  The work took place between Feb 9 - 17 under work permit C2021-02-09-1.

The procedure in work instruction Document-187117 R1 was followed. Draining and purging of the water system as well as venting of helium from the target crypt was performed by Tony Hessels.  The remainder of the procedure was carried out by Keith Ng, Maico Dalla Valle, and Isaac Earle.  A maximum field of 1.7mSv/hr was measured at 0.5m from the bare target;  This is higher than the approximate 500uSv/hr field that was expected, however dose incurred during the work was minimal (Isaac: 0.05mSv, Maico: 0.03mSv, Keith: 0.03mSv).

The cask aligned well to the target arm and no modifications to the cask or UCN hardware were required to carry out the procedure.  A few updates will be required to the work instruction document based on discoveries made during the procedure; notably: 

• Cask to be installed on the west side of where the water tubing connections for the crypt flange are located;  As a result the cask lid will be installed after the cask base (with target forearm inside) is removed from the rails
• Shims are not required under blocks TTA0550 and TTA0555 in order to clear the top of the cask (the concrete and steel supports for these blocks are higher than in the UCN area shielding model)
• In addition to the six 3/8"-16 bolts for the water manifold, two shoulders screws (one on each side of the manifold) must also be removed to allow the two halves to separate

The work instruction document will be updated to include the changes above, as well as other minor updates and extra figures. 

After testing, the target forearm was reinstalled and all connections re-made.  Leak checking of the water connections and crypt flange as well as testing of the target thermocouple signals is to be arranged by the UCN Group.  The cask has been stored on top of concrete shielding on the B2 level north-east of the UCN experimental area.

Various photos taken during the procedure are attached.