long period of operation is about 0.2 TBq (5 Ci) per watt of power. Thus, the core of a 1000 MW(e) power reactor, say 3500 MW(t), would contain 7∙108 TBq (1.75∙1010 Ci), a very large quantity. From the point of view of safety, the characteristics of the radionuclides that are of most concern are: Chemical volatility, because volatility promotes release in accidents; A strong chemical affinity for the human body, because such nuclides are easily taken up and remain in the body; A high energy decay, because of the need to shield against such radiation; and/or A relatively long half-life, because of the persistence of contamination from such a nuclide. Thus, some of the radionuclides of particular interest include the gases, strontium-90, iodine-131, and caesium-137. Uncontrolled release of radioactive materials must be prevented or mitigated by confinement as as possible to their point of origin or their intended location. This is achieved by physical barriers that enclose radioactive materials. Confinement as a applies to those barriers that are in direct contact or very close to the radioactive material. In principle, these barriers must be passive. In a typical pressurized or boiling water reactor confinement is provided by: The fuel matrix (sintered uranium dioxide) which can retain solid fission products; The zirconium cladding of the fuel rods which retains fission gases and volatile fission products as long as its integrity is preserved; The reactor coolant pressure boundary (reactor pressure vessel, primary piping, steam generator tubes, pressurizer, reactor coolant pumps) which retains fission products that may have leaked through the cladding and dissolved activation products. In the spent fuel pit confinement is provided by: The fuel matrix; The zirconium cladding of the fuel rods; The spent fuel pit stainless steel cladding and the filtered cooling system. In the radioactive waste storage and repository confinement is provided by the: Waste form (usually it is solidified in some way); Container. Questions
long period of operation is about 0.2 TBq (5 Ci) per watt of power. Thus, the core of a 1000 MW(e) power reactor, say 3500 MW(t), would contain 7∙108 TBq (1.75∙1010 Ci), a very large quantity. From the point of view of safety, the characteristics of the radionuclides that are of most concern are: Chemical volatility, because volatility promotes release in accidents; A strong chemical affinity for the human body, because such nuclides are easily taken up and remain in the body; A high energy decay, because of the need to shield against such radiation; and/or A relatively long half-life, because of the persistence of contamination from such a nuclide. Thus, some of the radionuclides of particular interest include the gases, strontium-90, iodine-131, and caesium-137. Uncontrolled release of radioactive materials must be prevented or mitigated by confinement as as possible to their point of origin or their intended location. This is achieved by physical barriers that enclose radioactive materials. Confinement as a applies to those barriers that are in direct contact or very close to the radioactive material. In principle, these barriers must be passive. In a typical pressurized or boiling water reactor confinement is provided by: The fuel matrix (sintered uranium dioxide) which can retain solid fission products; The zirconium cladding of the fuel rods which retains fission gases and volatile fission products as long as its integrity is preserved; The reactor coolant pressure boundary (reactor pressure vessel, primary piping, steam generator tubes, pressurizer, reactor coolant pumps) which retains fission products that may have leaked through the cladding and dissolved activation products. In the spent fuel pit confinement is provided by: The fuel matrix; The zirconium cladding of the fuel rods; The spent fuel pit stainless steel cladding and the filtered cooling system. In the radioactive waste storage and repository confinement is provided by the: Waste form (usually it is solidified in some way); Container. Questions
Module03%20Basic%20principles%20of%20nuclear%20safety.docx