At the No. 2 White Liquor Clarifier Tank, two employees were working on a mixer on top of a large tank to replace the gear box that rotates the mixer. The employees removed five of the eight bolts from the flange when the flange fractured through the bolt holes of the three remaining bolts causing the unit to rotate about 10 degrees (6"). The gear housing struck one of the employees on the right leg and fractured his femur.