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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 />

needs to be assumed to be gaseous. The distribution of iod<strong>in</strong>e <strong>in</strong>to gas and aerosol<br />

portions has to be justified.<br />

If filters are placed <strong>in</strong> the ventilation systems, the retention factors of the filters need to be<br />

selected conservatively.<br />

The time of failure of fuel rods and the number of failed rods have to be selected<br />

conservatively, tak<strong>in</strong>g <strong>in</strong>to account the results of analyses related to plant behavior. The<br />

number of fuel rods hav<strong>in</strong>g failed dur<strong>in</strong>g a LOCA can be obta<strong>in</strong>ed from the relevant<br />

analysis. However, a conservative assumption of 100% fuel failures for LB‐LOCAs is<br />

often prescribed by national requirements.<br />

The amount of radioactivity released from the failed rods also has to be chosen<br />

conservatively. A certa<strong>in</strong> share of the radioactive substances released from failed rods to<br />

the primary coolant enters the conta<strong>in</strong>ment atmosphere directly. The air–steam and liquid<br />

volume distribution pattern needs to be justified.<br />

An additional release of radioactive substances from the failed rods has to be assumed<br />

later when cool<strong>in</strong>g water enters the rods and carries fission products out from the fuel.<br />

This share of radioactive substances, which <strong>in</strong>itially ends up <strong>in</strong> the water, needs to be<br />

justified by experiments, or the assumptions have to be conservative.<br />

Assumptions on the transport of radioactive substances with<strong>in</strong> the conta<strong>in</strong>ment can be<br />

based on experiments if the results are applicable to the situation <strong>in</strong> question.<br />

Alternatively, a conservative model may be used which gives a slower normal release of<br />

radioactive substances from the gaseous volume of the conta<strong>in</strong>ment.<br />

If air is discharged from the conta<strong>in</strong>ment dur<strong>in</strong>g normal plant operation, the mix<strong>in</strong>g of<br />

radioactive substances with the discharged air needs to be estimated conservatively. The<br />

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