Capsule irradiations are being performed on fast reactor fuel pins in a sodium environment under loss-of-cooling conditions to determine the consequences of a fuel-pin failure. Special emphasis is given to the extent of possible fuel-sodium interactions (FSI) and the relocation of the fuel. The fuel pins were neither preirradiated nor prepressurized. So far no evidence has been found for a violent FSI on fuel ejection and sodium re-entry. Nevertheless, most probably a moderate FSI resulted from some fuel particles dropping into liquid sodium. These experiments indicate that considerable clad melting can occur before the fuel stack disintegrates. In addition, considerable fuel relocation can occur, which can ultimately lead to failure of the sodium containment.