CAPE CANAVERAL, Fla. — American astronaut Sunita Williams has now spent more time in space than any other woman, setting the record yesterday as she and a crew mate upgraded the international space station’s cooling system.

Ms. Williams broke the previous female spacewalking record of more than 21 hours when she and Michael Lopez-Alegria completed the second of what could be a precedent-setting three spacewalks in nine days.

The new record is 22 hours and 27 minutes.

During the spacewalk, which lasted more than seven hours, small amounts of toxic ammonia leaked from a fluid line. The liquid ammonia, which freezes into flakes when it hits the vacuum of space, did not appear to touch either astronaut. Mission Control told them to continue their task of hooking up ammonia fluid lines from a temporary cooling system to a permanent one.

Once they were back in the space station’s airlock, Mission Control made the astronauts test for contamination. The test was negative.

A tiny bit of ammonia also leaked during Mr. Lopez-Alegria’s and Ms. Williams’s first spacewalk Wednesday. Mission Control ordered them to take precautions since ammonia could cause respiratory problems for the three-person crew if enough of it got into the space station.

“They look like pinpoints,” Mr. Lopez-Alegria said of the flakes yesterday. “They don’t look like what we saw the other day, but they are coming out with some velocity.”

Mr. Lopez-Alegria and Ms. Williams hooked up the permanent cooling system, covered an obsolete radiator that was retracted by remote control from the ground, and stowed a fluid line that was connected to an ammonia reservoir.

They then moved on to other jobs ahead of schedule: removing a sun shade, photographing a solar array that will be retracted during space shuttle Atlantis’s mission next month, and making electrical connections for a new system that will allow power from the station to be shared with a docked shuttle.

Mr. Lopez-Alegria originally was supposed to jettison the sun shade, but NASA engineers instead had him fold it up and stow it away inside the space station.

The third spacewalk is set for Thursday, marking the first time three spacewalks will have been conducted in such a short period at the space station without a shuttle docked to it. Mr. Lopez-Alegria planned to conduct a fourth spacewalk with Russian flight engineer Mikhail Tyurin on February 22.

After yesterday’s spacewalk, Mr. Lopez-Alegria moved up to third on the list of the most time spacewalking.

He is expected to surpass Jerry Ross’s American record of more than 58 hours over nine spacewalks by the end of the month. Russian cosmonaut Anatoly Solovyov has more than 77 1/2 hours over 16 spacewalks.