Do you know how you were exposed to radiation? X-rays, medical dye injections or treatments, live by power plants? Do you live in an area that may be affected by depleted uranium?
Cysteine (as in your supplement) protects against some damage from radiation by neutralizing the free radicals it produces.
Here are other things that can help with that....
Baking Soda and Dead Sea Salt baths, use 1 lb. of each and soak for 20-30 minutes. (what radiation workers use, easy and cheap)
Bentonite Clay baths or ingest. Clay is negatively charged and binds with positively charged particles.
Chlorella, spirulina or the best seaweed for radiation is Laminaria Japonica usually marketed under the brand name Modifilan.