A chemical decontamination process for solid waste treatment

The decontamination of actual radioactivity metal parts by nitric plus hydrofluoric acid solution have been investigated. The results have been compared with those of other decontamination reagents. And results of extensive laboratory test using radioactive Pressurized Water Reactor (PWR) primary loop system specimens have been reported. This is a two step process. Specimens sampled are pretreated with nitric acid and permanganate (NP), then decontaminated by nitric plus hydrofluoric acid. The decontamination efficiency mainly depends on the mixed acid concentration (1-2v% HNO3 +0.1-1v% HF) and temperature (RT - 80degC). It is also related to decontamination time and items to be decontaminated. The decontamination efficiency (Deff) is more than 90% at 60degC and more than 96% at 80degC. Using 2v% HNO3 plus 25-1v% HF solution decontaminates surfaces, a high decontamination factor (DF) is also obtained (in excess of 2000) in 1h on PWR large samples. The corrosion rate has been measured by the weight loss of the stainless steel specimens, and evaluated inhibition efficiency of inhibitor selected for reducing corrosivity. The treatment of the secondary waste is also described briefly. (author)