Recent fusion reactor conceptual designs include pressurized water as the coolant for the first wall and blanket. To determine design adequacy, the consequences of a pressurized water cooling tube failure within the blanket have been analyzed using the time-dependent computer code ATHENA. The ATHENA code, being developed by EG&G Idaho, Inc., simulates safety related transients in fusion blankets, first walls, and other reactor systems. The analysis showed that some blanket design modifications must be made to ensure module integrity following an internal cooling tube break.