Patent Number: 052456420
Section: claims

1. A method for controlling Co-60 radiation recontamination on the surfaces of structures providing a coolant water circuit of a boiling water nuclear fission reactor following decontamination, consisting essentially of: adding a solution of at least one iron compound selected from the group consisting of ferrous oxalate, ferric citrate, and freshly prepared Fe(OH).sub.3, Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4 to coolant water of a water cooled nuclear fission reactor in amounts sufficient to maintain an iron concentration in the coolant water circulating through the coolant water circuit of the water cooled nuclear fission reactor at about 200 parts per billion.  adding a solution of at least one iron compound selected from the group consisting of ferrous oxalate, ferric citrate, and freshly prepared Fe(OH).sub.3, Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4 to coolant water of a water cooled nuclear fission reactor in amounts sufficient to maintain an iron concentration in the coolant water circulating through the coolant water circuit at about 200 parts per billion, and maintaining a dissolved oxygen content in the coolant water circulating through the coolant wataer circuit of the water cooled nuclear fission reactor at about 200 to about 400 parts per billion.  adding a solution of at least one iron compound selected from the group consisting of ferrous oxalate, ferric citrate, and freshly prepared Fe(OH).sub.3, Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4 to coolant water of a water cooled nuclear fission reactor in amounts sufficient to maintain an iron concentration in the coolant water circulating through the coolant water circuit at about 200 parts per billion, maintaining the coolant water circulating through the coolant water circuit at a temperature of at least about 230.degree. C., and continuing said pH adjustment, iron solution addition and temperature maintenance for a period of at least about 500 hours. 2. The method for controlling Co-60 radiation recontamination on the surface of structures providing a coolant water circuit of a boiling water nuclear fission reactor of claim 1, comprising maintaining the coolant water circulating through the coolant water circuit at a temperature of at least about 230.degree. C. 3. A method for controlling Co-60 radiation contamination on the surfaces of structures providing a coolant water circuit of a boiling water nuclear fission reactor, consisting essentially of the steps of: 4. The method for controlling Co-60 radiation recontamination on the surface of structures providing a coolant water circuit of a boiling water nuclear fission reactor of claim 3, comprising maintaining the coolant water circulating through the coolant water circuit at a temperature of at least about 230.degree. C. 5. The method for controlling Co-b 60 radiation recontamination on the surface of structures providing a coolant water circuit of a boiling water nuclear fission reactor of claim 3, comprising maintaining the induced pH and iron concentration condition of the circulating coolant water for a period of at least about 500 hours. 6. The method for controlling Co-60 radiation recontamination on the surface of structures providing a coolant water circuit of a boiling water nuclear fission reactor of claim 3, comprising applying the pH adjustment and iron concentration while the nuclear reactor is shut down, and continuing the treatment during subsequent fission operation of the water cooled nuclear reactor while maintaining an iron concentration in the circulating coolant water at about 50 to about 100 parts per billion. 7. A method for controlling Co-60 radiation contamination on the surfaces of structures providing a coolant water circuit of a boiling water nuclear fission reactor, consisting essentially of the steps of: 8. The method for controlling Co-60 radiation contamination on the surface of structures providing a coolant water circuit of a boiling water nuclear fission reactor of claim 7, comprising applying the pH adjustment, iron solution addition and temperature maintenance while the nuclear reactor fuel core is shut down, and continuing the said treatment steps during subsequent fission operation of the fuel core of the water cooled nuclear reactor while maintaining a lower iron concentration in the circulating coolant water of about 50 to about 100 parts per billion.