Long-lived fission products

The inventory of long-lived fission products is far less than an LWR because of the short exposure of the fuel to minimize Pu-240 production. But the health effects from an accident are comparable because it primarily results from short lived radionuclides. 

The solvent extraction of pertechnetate with cyclohexanone has proved to be an efficient and selective method which can be applied to the separation of Tc from long-lived fission products in the bum-up analysis . The recovery of technetium from the fission products is about 93 %. 

In general, the radioactive half-life increases down the chain of fission products, but some long-lived fission products, for example 90Sr, have short-lived daughters. 

TABLE 14. Radioactivity of long-lived fission products, Bq... 

Nuclear reactors and reprocessing plants are constructed and operated in such a way that the radioactive inventory is confined to shielded places. Only limited amounts of radionuclides are allowed to enter the environment. The amounts of T and produced in nuclear reactors vary with the reactor type, between about 10 and 10 Bq of T and about lO Bq of per GWg per year. Tritium is released as HTO and about one-third of the is in the form of " C02. Under normal operating conditions, very small amounts of fission products and radioelements are set free from nuclear reactors and reprocessing plants. In this context, the actinides and long-lived fission products, such as °Sr, Tc, I, and Cs, are of greatest importance. 

Neutron transmutation of long-lived radioactive minor actinides by the fission process—which entails producing energy and simultaneously turning them into shorter-lived nuclides—is being intensely analyzed in the technical community. Also being proposed is the neutron transmutation of selected long-lived fission products. 

Haug, H. 0., "Production, Disposal, and Relative Toxicity of Long-Lived Fission Products and Actinides in the Radioactive Wastes from Nuclear Fuel Cycles," (in German), KFK-2022, translated as 0RNL-tr-it302, Oak Ridge National Laboratory,... 

Previous discussion indicated that for both spent fuel and reprocessed waste, the chief sources of radioactivity for the first 10 to 100 y are the fission products °Sr and Cs. For later times out to 10 y, isotopes of Am, Pu, and Np are successively the dominant contributors to radioactivity. Assuming, as is likely, that corrosion failure of metal-waste packages in a geologic repository will not be significant before 10 to lO y, both Sr and - Cs with 30 y half-lives, will have decayed to insignificance. The actinides and long-lived fission products and Tc remain important at later times (cf. Krauskopf 1988). The U.S. program assumes that 1, Tc, and the actinides and... 

Hanford in the first decade of operation (B5). As a result of their pile accident, the Chalk River plant disposed of over a million gallons of liquid waste containing 104 curies of long-lived fission products to the ground (M3). At Oak Ridge, thousands of curies of fission products have been disposed of in open waste pits (S2). The specific experiences at these locations, however, cannot be applied to other locations without field and laboratory evaluation of local problems. 

In addition to fissionable isotopes ( U, or plutonium) and fertile isotopes ( U or thorium), spent fuel from a reactor contains a large number of fission product isotopes, in which all elements of the periodic table from zinc to gadolinium are represented. Some of these fission product isotopes are short-lived and decay rapidly, but a dozen or more need to be considered when designing processes for separation of reactor products. The most important neutron-absorbing and long-lived fission products in irradiated uranium are listed in Table 1.4. 

To predict the decay-heat rate from fission products after cooling times of several years, additional corrections must be made for absorption of neutrons in long-lived fission products, particularly the absorption of neutrons in stable Cs to form 2.05-year Cs. Computer codes such as ORIGEN [B2] and CINDER [El] are particularly useful for this purpose. 

N — atoms of long-lived fission product present after cooling for a time Tr = irradiation time, s Tc = cooling time, s... 

Neutron Absorption by Long-lived Fission Products... 

Table 8.3 Long-lived fission products from lOOOMWe power reactors...

Radioactive waste is any waste material—gas, liquid, or solid—whose radioactivity exceeds certain limits. These limits have been established by governments or by local authorities, guided by the recommendations of the International Commission on Radiation Protection (ICRP). The ICRP recommendations define the maximum permissible concentration (MPC) for each individual radionuclide and for mixtures of radionuclides in water or air. The U.S. regulation defines such limiting concentration as the radioactivity concentration limit (C), which is the terminology used in this text, Values of C for selected actinides and long-lived fission products in water or air are given in App. D. 

Since stable isotope dilution depends on the mass spectrometric determination of isotope ratios, the method is generally restricted to elements which have at least two stable isotopes. However, in the case of mono isotopic cesium, the long-lived fission product Cs136 or Cs137 can be used as a tracer for the analysis of this element. In all, some 68 elements can be... 

The terminology "Maximum Expected" reflects the expectation that the actual primary circuit activity will always be less than that criteria throughout the life of the plant for the following reasons. First and foremost, the fuel and core are designed so the best estimate of the core releases are less than these "Maximum Expected" criteria. Secondly, the long-lived fission products, such as 30-year Cs-137, build up slowly in the primary circuit throughout the 40-year plant lifetime. Finally, the core release rates... 

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