Heat oil in a large saucepan over medium heat. Add the onion, celery and carrot; cook and stir vegetables until they begin to soften, approximately 2 to 3 minutes. Add rice and cook, stirring until rice is evenly coated in oil, 1 to 2 minutes. Stir in tomatoes, chicken stock, salt and pepper. Bring to the boil. Reduce heat, cover and simmer for 15 minutes.
Rinse the scallops, and if large cut scallops in half. Stir the scallops into soup and cover. Continue to simmer until the rice is tender and the scallops are opaque, approximately 5 to 10 minutes.
Season to taste with salt and pepper. Stir in the basil and serve.