Brittain, 25, made 10 AHL appearances with Springfield last season, posting a record of 4-5-0 with a 2.42 goals-against average and a .905 save percentage.
In 42 career AHL games with Springfield, Portland and San Antonio, Brittain is 16-17-4 with a 2.53 GAA, a .912 save percentage and one shutout. He made his AHL debut with the Rampage on Mar. 25, 2015.
Originally a fourth-round draft choice by Florida in 2010, Brittain played four seasons at the University of Denver.
Atkinson, 24, collected 10 goals and 40 assists in 66 games with Atlanta (ECHL) last season, ranking fourth in the league among rookie defensemen in scoring. He also made his AHL debut, appearing in two games with the Chicago Wolves.
The native of Spruce Grove, Alta., played four seasons at the University of Alaska-Fairbanks.