Fire Watch, by Connie Willis

Fire Watch was first published in Isaac Asimov's Science Fiction Magazine, in Feb 1982, and won the 1982 Nebula and 1983 Hugo awards for best novelette:

http://www.infinityplus.co.uk/stories/firewatch.htm

Ten years later, she expanded the story of Kivrin's practicum, here only alluded to, into the novel The Doomsday Book, which also won both the Hugo and the Nebula Awards.