Cobalt neutron activation products

The major neutron activation product is cobalt-60 with a reasonably long half-life (5.3 years). It emits high-energy beta particles and gamma rays appropriate for radiographic, irradiation, and isotopic power applications. It is an ideal product because naturally occurring cobalt is uniquely mono-isotopic cobalt-59 as well as a relatively stable metal. 

A number of artificial radionuclides are produced as a result of activation during nuclear weapons tests, operation of reprocessing plants and reactors in nuclear power stations, and in nuclear studies. Modem radioanalytical techniques have enabled activation products such as Na, Cr, " Mn, Fe, °Co, Ni Zn, °Ag, and " Sb to be detected in the environment [28,29]. Stainless steel containing iron, nickel, and cobalt is an important material in nuclear power reactors and is used to constmct nuclear test devices or their supporting stmctures [30,31]. During neutron activation of the stable isotopes of cobalt, radioactive isotope °Co (J = 5.27 years) is produced. It is a beta emitter and decays into °Ni, with energy niax of... 

Radionuclides classified as activation products are created in nuclear reactors and other nuclear devices by the reactions of neutrons with fuel and construction materials. Activation products include the isotopes of the transuranic elements and radioisotopes of hydrogen, carbon, caesium, cobalt, iron, manganese, zinc, and a host of other radionuclides, all of which should be recognised and considered in determining the environmental pathways to human exposure. 

The concentrations of the corrosion product radionuclides in the reactor water depend on the same parameters as those that control the behavior of the total corrosion products and, in addition, on the intensity of neutron activation. As a consequence, the concentrations of radioisotopes may vary considerably from plant to plant and also within a plant. According to the observations reported by Anstine et al. (1984), the concentrations of Co and Co, the two most prevalent radioisotopes, do vary, but not as greatly as the iron concentrations. In the BWR plants examined in this context, the majority of Co and Co in the reactor water appeared in the dissolved state. On the average, the concentrations of dissolved Co increased for the first 3 to 5 fuel cycles and then leveled off to values on the order of 7 kBq/1, whereas the dissolved Co already reached its steady-state level in the same range of concentrations during the first fuel cycle. These differences in the time behavior of both cobalt isotopes probably are to be attributed to their different halflives. The concentrations of particulate Co and Co, on the other... 

The irradiation of steels in a neutron flux results in activation of alloying elements and impurities and the packaging of steels must take account of the inventory of activation products. The key issue for OCR steel is heat production and radiation dose due to the activation products cobalt-60, iron-55 and nickel-63. Generally for normal steels the dominant activation product for heat and dose is Co-60 but it is important to understand the chemical composition of steels used inside a reactor as special grades or alloys may introduce unusual radionuclides which could be important contributors to heat, dose and other aspects of package performance such as post-closure risk. 

The anthropogenic sources of radioactivity in the environment include the testing of nuclear weapons and radioactive material handling, especially in nuclear power plants. In the explosion of atomic bombs or in nuclear reactors, a complex mixture of different radionucHdes is produced, namely uranium plutonium Pu, caesium Cs (half-Hfe of 30 years), strontium Sr (half-life of 28 years), cobalt Co (half-Hfe of 5.3 years), caesium Cs (half-Hfe of 2 years), ruthenium Ru (half-Hfe of 1 year) and iodine 1 (half-Hfe of 8 days). A number of other radionucHdes result from an atomic explosion by coUision of neutrons with the atoms of elements that are contained in the casing of the non-explosive parts of the atomic bomb. For example, these activation products include zinc Zn (half-Hfe of 245 days). 

There would be even more cobalt-60 available when Chalk River s NRU came on line. It was estimated that NRU s isotope-production capacity would be seven times that of NRX. Because of its greater neutron flux, it would also be able to produce higher-specific-activity cobalt-60. Lessons learned from isotope production in NRX were taken into account when NRU was designed. Cobalt was employed as an absorbent element in two control rods that extended vertically through the... 

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