There are certain interactions while inspecting a ruin where instead of trying your luck and getting injured if it doesn't work, you can use the personal shield to auto pass that prompt and it will be consumed. It works like the salvage kit or critter repellant, it shows up directly in the dialog choice box automatically.
Some crew members have a general interaction with tech items that yields resources or other items or so, so I guess this is where the melting it down comes from.