ok IŽll try to explain
You have to clear Wraith, White Mousse and Orthros hunting mission
Then youŽll have the Sluice Gate Key, which you get from the reward of White Mousse hunting mission, and youŽll be able to control the panel
Go to the central control section and light off all panels.....
Then you have to:
light on No. 11 Area Panel,
light on No. 4 Area Panel,
light off No. 11 Area Panel,
light on No. 3 Area Panel,
light off No. 4 Area Panel
Now you have to go around South in this same area and youŽll find the shiny object on the ground, which is the Dull Fragment

Hope this helps you