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Regional Basic Professional Training Course in Korea

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❙ 917 ❙<br />

16. In‐Plant Accident Management<br />

impact result<strong>in</strong>g <strong>in</strong> public exposure of the order of the prescribed limits or significant<br />

damage to a reactor core/radiological barriers or the fatal exposure of a worker) or higher.<br />

On the INES scale, Chernobyl is situated at the maximum level whereas the TMI‐2<br />

accident which led to a (partial) core meltdown, is ranked as level five ("accident with off<br />

‐site risk").<br />

≫ Conta<strong>in</strong>ment Source term [5]:<br />

The source term corresponds denotes the radioactive material composition and<br />

magnitude, as well as the chemical and physical properties of the material with<strong>in</strong> the<br />

conta<strong>in</strong>ment that are available for leakage from the reactor to the environment.<br />

≫ Radiological consequences [6]:<br />

This relates to the impact of the fission products on the environment, especially<br />

tak<strong>in</strong>g <strong>in</strong>to account the different means of exposure (radiation, <strong>in</strong>halation, <strong>in</strong>gestion,<br />

deposit) and weather conditions.<br />

≫ The corium [6]:<br />

The mixture of the molten core and structure materials is formed at very high<br />

temperature (~3000 K).<br />

16.4.3. Progression of severe accidents<br />

A severe accident (except for reactivity accident) is ma<strong>in</strong>ly characterized by lengthy<br />

water depletion of the core, caus<strong>in</strong>g it to degrade and, <strong>in</strong> particular, the release of a large

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