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Regional Basic Professional Training Course in Korea

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<strong>Regional</strong> <strong>Basic</strong> <strong>Professional</strong> <strong>Tra<strong>in</strong><strong>in</strong>g</strong> <strong>Course</strong> (BPTC) on Nuclear Safety<br />

nuclear safety enterprise is needed to protect. Sources of radionuclides <strong>in</strong>clude: the<br />

fission event, which produces about two fission fragments per fission; neutron absorption<br />

<strong>in</strong> structural materials, which produces various radioactive products such as cobalt‐60;<br />

and neutron absorption <strong>in</strong> fertile material (primarily U‐238), to produce transuranic<br />

elements, which are important to the long‐term radiation hazard from spent fuel.<br />

3.4.3.2. Removal of radionuclides<br />

Radionuclides are cont<strong>in</strong>uously removed by radioactive decay along decay cha<strong>in</strong>s that<br />

eventually lead to stable isotopes. Radionuclides may also absorb neutrons and be<br />

transmuted <strong>in</strong>to other elements. Xenon‐135 and samarium‐149 are particularly important<br />

<strong>in</strong> this regard. Thus, the radioactive material <strong>in</strong>ventory and decay paths will be different<br />

dur<strong>in</strong>g operation, with a high neutron population, from that after shutdown, with<br />

essentially no neutron population. This fact gives rise to such phenomena as “xenon<br />

transients” which are important <strong>in</strong> design of reactor control systems.<br />

3.4.3.3. Calculations<br />

While the calculations of the core radionuclide <strong>in</strong>ventory, both dur<strong>in</strong>g and after operation,<br />

are straightforward <strong>in</strong> pr<strong>in</strong>ciple, they require a very large amount of data <strong>in</strong>clud<strong>in</strong>g such<br />

<strong>in</strong>formation as: reactor operat<strong>in</strong>g history; neutron flux and energy spectrum; fission<br />

product yields, decay paths, and neutron cross‐sections for nuclides and reactors of<br />

importance; neutron, beta, alpha, and gamma decay data; and so forth. The ORIGEN2<br />

code is widely used to calculate the time dependent concentrations and source terms<br />

associated with a large number (about 1700) nuclides that are simultaneously generated<br />

or depleted by fission, neutron transmutation, radioactive decay, <strong>in</strong>put feed rates, and<br />

physical or chemical removal rates. Calculations done us<strong>in</strong>g ORIGEN2 can be applied to<br />

fuel irradiation <strong>in</strong> a reactor or to storage, transportation, or process<strong>in</strong>g of spent fuel<br />

elements.<br />

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