What is 1-131 treatment?

I have a multi-nodular goiter, my right side has nodules of 3.4, 2.8x2.9 and 1.6, my left side has 4.5 & 2.3 on the Isthmus a 1.2 nodular. These are mostly all solid, I have had 2 biopsies, both negative. Over the past 6 months the nodules grew quite a bit in size. A month ago I went to one of the best Endo's in Denver and he took a number of blood test and urine tests. My THS is around .7, and my thyroglobulin  was elevated. I have never had any thyroid problems, my weight is normal, I sleep well, seem to have plenty of energy, The Dr. in Denver put me on Levothyroxine 75MCG, and I am to see him again in January to see if there is any change in the size of the nodules.
I hope to avoid surgery and I would like to know what is the 1-131 treatment? I have noticed some discomfort in my throat from the goiter, this seems to vary from day to day.
It has been helpful to educate myself my reading the entries from various people and I thank you for any advice.