Soak the meat in cold water for 1 hour, making sure it is completly submerged. Change to clean water a few times. If the meat is frozen, add an additional hour to the soaking time.
Bring 8 cups of water to boil and add the ribs. Boil for 5 minutes without the lid. When time is up, discard the boiled water and wash the meat throughly in cold water.
Into a big stock pot, add 13 cups of water, meat, radish, ginger, garlic, onion and scallion. Bring to boil. Boil on high with lid for 30 min.
Bring the heat to med/low and simmer for 40 min or until the meat is tender.
Discard ginger, garlic, onion and scallion. Take away scum as needed and remove fat from soup.
Add soy sauce, salt and pepper. Stir and simmer 2-3 min and turn off heat. (If you prefer, you can also add soaked sweet potato noodles at this point) Adjust the salt level to your liking.
Sprinkle with pepper and chopped scallions when serving.