1. Cook rice in water with salt according to package directions. 2. Cool. 3. Combine mayonnaise, onion, mustard, and salt. Stir into rice. 4. Cover and throughly chill. 5. Stir in cucumber and radishes just before serving. Measurements and timing are designed only for Uncle Ben's Fast Cooking Rice Pilaf, Original Rice Pilaf, Fast Cooking Spanish Rice, Long Grain & Wild Rice Blend, and Converted Brand Rice