Bring orange juice to boil in small saucepan over medium-high heat and simmer until reduced to about 1 Tbsp., about 6 minutes. Meanwhile, place spinach in large bowl, and set aside.
Whisk reduced orange juice, zest, ginger, vinegar, and honey together in small bowl. Whisk in vegetable and sesame oils and season with salt and pepper.
Toss shrimp, orange segments, and scallions,with 2 tablespoons dressing in bowl and season with salt and pepper. . Toss spinach with remaining dressing and season with salt and pepper. Divide spinach among 4 individual plates and top with shrimp and oranges. Serve.