The North Hot Cell shielding window gaskets have been changed and the window has been filled with new oil.  Although there was no noticeable oil leaks before starting the job, the gaskets had not been changed since initial installation approximately 15 years ago, so they were done now as part of construction of the new  cell.  The work took place between January 26 – Feb 8, 2017 following the attached PDF “Full procedure for NHC shielding window gasket change” which references “Gasket change procedure from Hot Cell Services” (also attached).

To drain the window a 1/2”polyethylene hose was attached to the drain line using  a Swagelok fitting and routed into a 55 gallon drum.  A vent valve on the expansion tank was opened to allow air to enter  the window.  It took approximately 5 hours to drain the window using this method.  Approximately 50 US gallons were drained from the window, agreeing with the amount specified on Hot Cell Services drawing #96173-100 (attached).

After draining, the window was purged with helium then pressurized to approximately 13” WC with helium.  A pressure drop of 0.6” WC was observed over a 2 hour period.  While pressurized, a Varian G8601-60001 leak detector was  used to sniff for helium around the perimeter of the gaskets on both the hot and cold  sides – no helium leaks detected.  A small leak was found on the pressure gauge used to monitor helium pressure.

The cold side cover panel assembly was  then removed  following the HCS procedure.  From HCS Drawing #96173-100, the weight  of the cold side glass cover panel was estimated to be  approximately 50lbs.  The guide  pins used were McMaster-Carr PN# 93460A385.  The trim frame could be easily removed, however the glass panel was stuck to the window housing.  A putty knife and isopropyl alcohol were used to cut through the gasket to separate the window from the housing.  The alcohol did not damage the paint of the housing – acetone was also tested on a small area and did not cause damage  to the paint.  Two suction cup handles were used to transport the glass panel, and it was easily lifted by two people.  Various methods were attempted to remove old gasket material and gasket adhesive  from the trim frame and housing surfaces – the most successful was using a razor blade scraper to remove the majority of the material, followed by an acetone wipe to remove the remainder of the stuck-on gasket adhesive.  The panel was reinstalled with new gaskets following the attached  procedures - no issues encountered.  After torqueing the trim frame bolts the window was leak checked as before.  A drop of 0.8” WC was observed over two hours, and no helium could be detected around  the perimeter of the new cold side gasket.

The hot side cover panel assembly was changed using the same method as for the cold side.  The glass panel was estimated to be 150lbs.  A small amount of oil (< 0.5 L) remained behind the hot side glass panel after draining which spilled out after removal of the glass. Four suction cup handles were used, and four people were required to remove and reinstall the panel.  After installation the leak check was repeated with a drop of 0.3” WC observed over two hours, and no helium detectable around the perimeter of the hot side gasket.

The replacement gaskets were ordered from Hot Cell Services under PO# 3033973 matching the material and sizes specified on  HCS drawing #96173-100.

The window was filled with Drakeol 10B LT MIN OIL NF, Product  code: PEN1550-00-C-DR, PO #3034657.  The window was filled by lifting the drum onto the walkway leading  to the target hall entrance, and siphoning the oil out of the drum with a 1/2” polyethylene tube connected to the drain fitting, and an air vent open on the expansion tank.  Oil was added until the expansion tank was approximately 80% full.

After filling was complete, the cold side housing was repainted using Macropoxy 646 epoxy paint, 4019 Flint Gray.  When the inside of the NHC is next accessible the hot side trim frame bolts will be re-painted to protect the bare metal exposed from removing and reinstalling them.

Note that a quote for $74,313 ($56,823 USD) (PDF attached) was received from Hot Cell Services for them to do this job.  We were able to  successfully complete this ourselves with approximately $4500 required for the gaskets, $200 for other materials, and roughly 8 FTE days of work.