Add the onion and scallions to the Dutch oven, and saute until soft and translucent, about 3-4 minutes. Add the garlic and ginger, stirring to combine, and cook for 2 minutes more. Add the carrots and celery, stir to combine, and season with salt and pepper to taste. Deglaze the Dutch oven with the rice wine vinegar, scraping up all the brown bits that have collected at the bottom of the pan. Add the brown sugar, stirring to coat. Add the soy sauce, mirin, and orange juice, stirring to combine. Return the short ribs to the Dutch oven, bring to a boil, reduce to a simmer, cover, and allow to cook until the meat is very tender, about 3 hours.