Although chemical sprays are effective for removing radioactive iodine, the suitability of a particular chemical solution for use in the reactor building spray system depends upon the solution’s stability and compatibility in the environment produced by LOCA. The suitability of alkaline sodium thiosulfate for use in the reactor building spray system as an iodine-removal agent has been the subject of an extensive research and development program by Babcock & Wilcox. The results of the program demonstrate the stability and compatibility of the sodium-thiosulfate spray solution.