Sodium Thiosulfate Spray System for Radioiodine Removal

Radioiodine constitutes a radiological hazard to the public in the event of a loss-of-coolant accident (LOCA). The potential thyroid dose is normally the most restrictive factor in the siting requirements of nuclear power plants. When analysis of the LOCA shows that the thyroid dose limits are exceeded, an engineered safeguard system must be installed to reduce the dose to the allowable limits. At present, there are two ways to remove iodine from the containment atmosphere: filter-absorber systems and containment spray systems. The advantages of the spray system are (a) the removal rate for radioiodine is faster, resulting in lower thyroid site doses, (b) an existing system could be modified, and (c) the cost of the system is less.