Patent Number: 047298553
Section: summary

BACKGROUND OF THE INVENTION As nuclear reactors are operated, metal surfaces gradually corrode, and become coated with highly radioactive deposits. In order to operate the reactor properly and to perform maintenance on it, it is necessary to remove these radioactive deposits. This is generally accomplished by the use of chemical decontamination processes. In these processes, aqueous solutions containing chelants and organic acids are passed over the metal surfaces to solubilize and remove the compounds that form the deposits. While these processes are effective in decontaminating the metal surfaces, the chelants used in the processes end up as part of the radioactive process waste and must be disposed of as radioactive waste. Unfortunately, most burial sites for radioactive waste have maximum levels on the chelants and organic acids which are permissible in the waste. As a result, either the waste must be specially disposed of at increased cost or the chelants and organic acids must be removed from the waste before it is sent to the burial site. SUMMARY OF THE INVENTION We have discovered that the condensation product of hydrazine, or a derivative thereof, with a polycarboxylic acid, acts as a chelant for metal ions and will effectively decontaminate radioactive deposits on metal surfaces. An aqueous solution of this condensation product is circulated between the deposit on the metal surface and a cationic ion exchange resin, where the chelated metal ions are deposited. The ion exchange resin can be preloaded with the hydrazine portion of the condensation reaction product to prevent the deposition of that portion onto the column in preference to the metal ions. We have found that the decontamination solution of this invention, when exhausted, can be oxidized to form nitrogen, carbon dioxide, and water, so that the resulting waste contains neither chelants nor organic acids, and can be deposited at nuclear waste burial sites.