NASA is in the process of planning for a Friday spacewalk to replace a failed pump in one of the ISS’s cooling systems. The pump failed over the weekend with what appears to be an electrical short between the motor and its controller.
The loss of one of the two coolant loops has forced the Station to power down some systems and reroute others. NASA states that the crew is in no danger.
The Space Station uses ammonia as a coolant that makes the repair more difficult as that the astronauts must watch not to contaminate there suits when venting the coolant lines.