Spray 4-quart saucepan or Dutch oven with cooking spray. Heat over medium-high heat until hot. Add celery; cook and stir 1 1/2 to 2 minutes or until crisp-tender. Add frozen chicken breasts, broth and water. Heat to boiling. Reduce heat; cover and simmer 10 to 12 minutes, stirring occasionally, until juice of chicken is clear when center of thickest part is cut. Remove chicken from saucepan; cool slightly. Cut into bite-size pieces.