1. Cook pasta according to package directions, omitting salt and fat. Add peas and shrimp during last 2 minutes of cooking. Drain and rinse with cold water; drain.
2. Combine pasta mixture and radishes in a large bowl. Combine mayonnaise and remaining ingredients in a small bowl; stir well with a whisk. Pour over pasta mixture, tossing to coat. Cover and let stand 20 minutes. Serve at room temperature, or cover and chill until ready to serve.
Wine note: Sweet shrimp, peppery summer radishes, and the refreshing dill and buttermilk dressing all point to a wine with tangy acidity, fresh berry fruit, and a zip of citrus. The Fleur, Pinot Noir, Rosé (2009, Carneros, Calif.; $15)—with its shocking bright-red hue—is a hands-down crowd-pleaser and an excellent value.—Alexander Spacher