1. Cook pasta according to package directions, omitting salt and fat; drain.
2. Combine juice, mustard, and garlic in a small bowl, stirring well with a whisk. Gradually add oil, stirring constantly with a whisk. Stir in salt and pepper.
3. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add shrimp to pan; cook for 2 minutes or until done. Stir in spinach, cannellini beans, red onion, and 2 tablespoons capers; toss to combine. Add the pasta and juice mixture to shrimp mixture; toss.