In a large saucepan, saute the onion, celery and green pepper in butter until tender. Stir in flour until blended; gradually add broth. Bring to a boil; cook and stir for 2 minutes or until thickened., Reduce heat to low. Add the cream, corned beef, sauerkraut, salt and pepper; heat through (do not boil). Stir in cheese until melted.