[en] The Sodium Loop Safety Facility (SLSF) is a doubly-contained, closed sodium loop designed to test full length fast breeder reactor (FBR) fuel pins under simulated hypothetical fast reactor accident conditions. The W-1 experiment has two distinct and separate objectives. The primary objective is to evaluate fuel pin heat release characteristics during loss-of-piping integrity (LOPI) accident flow and power conditions. The Clinch River Breeder Reactor (CRBR) conditions during this accident are being used as representative of FBR's. A progression of four LOPI tests will be conducted to collect data at different fuel pin conditions. These four tests will be performed on fuel pins with (a) fresh, unrestructured fuel, (b) fresh, restructured fuel, (c) irradiated, uncracked fuel (after steady-state irradiation), and (d) irradiated, cracked fuel (after shutdown and startup). The second objective of the W-1 experiment is to determine stable boiling and recovery limits (boiling window) as a function of fuel pin power