CAPE CANAVERAL, Fla. -

Laboratories in the U.S. portion of the International Space Station are running at full power again after a pair of spacewalks to repair a partially failed cooling system.

Teams in Houston worked through Christmas Day to activate a new coolant pump installed during the second spacewalk on Tuesday, and to integrate it with equipment that transfers heat generated inside the outpost to giant radiators outside.

That allowed normal operations to resume in the U.S. Destiny and Japanese Kibo labs and two connecting modules. Only the European Space Agency’s Columbus lab hasn't yet been fully powered back up.

“Everything is working perfectly now,” NASA TV commentator Kelly Humphries reported. “Cooling Loop A is looking great.”

Loop “A” is one of two running outside the station. The Dec. 11 failure of a valve in an ammonia pump module that regulated the loop’s temperature caused it to get too cold.

That created a risk that water from the internal cooling system could freeze and expand, potentially cracking heat exchangers and allowing highly toxic ammonia inside the six-person crew’s living area.

Non-essential systems inside were shut down for about two weeks, while the station operated with only one of its cooling loops and more vulnerable to a second failure.

NASA astronauts Rick Mastracchio and Mike Hopkins performed spacewalks on Saturday and Tuesday to remove the faulty pump and install one of three available spares.

They rested on Christmas Day while the ground teams restored the second cooling loop without incident.

On Friday, Russian cosmonauts Oleg Kotov and Sergey Ryazanskiy will head outside for the year’s 11th and final ISS spacewalk, a planned seven-hour excursion to update experiments and install cameras.