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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 />

the fuel pellet is limited to the fuel fusion temperature. This results <strong>in</strong> the<br />

consideration of a design limit on the power density equal to 590W/cm.<br />

The extreme value of the trip setpo<strong>in</strong>ts is calculated from limits def<strong>in</strong>ed above. The<br />

validity of this value is then checked from two po<strong>in</strong>ts of view:<br />

The existence of a sufficient work<strong>in</strong>g marg<strong>in</strong>, given the various uncerta<strong>in</strong>ties<br />

(calibration, uncerta<strong>in</strong>ties about the various parts of the channels etc.). This marg<strong>in</strong><br />

must be such that there is no automatic shutdown dur<strong>in</strong>g category 1 transients;<br />

The study of core behavior <strong>in</strong> transient operat<strong>in</strong>g conditions: category 2, 3 and 4<br />

accidents. This study results <strong>in</strong> design<strong>in</strong>g protection channel characteristics other<br />

than the trip set po<strong>in</strong>ts (lead‐delay systems, channel response time), and check<strong>in</strong>g<br />

that the criteria relat<strong>in</strong>g to accident acceptable consequences are respected.<br />

The area of protection aga<strong>in</strong>st l<strong>in</strong>ear excess power is designed us<strong>in</strong>g the 590W/cm<br />

criteria, i.e. a maximum power of 118% of the rated power (maximum setpo<strong>in</strong>t selected<br />

for accident studies).<br />

The setpo<strong>in</strong>t displayed on the site is obta<strong>in</strong>ed by tak<strong>in</strong>g <strong>in</strong>to account the follow<strong>in</strong>g<br />

uncerta<strong>in</strong>ties:<br />

Calibration uncerta<strong>in</strong>ty: The neutron flux chamber measurement <strong>in</strong>formation be<strong>in</strong>g<br />

compared with the power achieved from the daily thermal balances, the calibration<br />

uncerta<strong>in</strong>ty corresponds to the precision of this measurement, i.e. 2% of rated<br />

power.<br />

Neutron channel permissible global shift: The neutron channels are adjusted when<br />

their <strong>in</strong>dication deviates 2% from the rated power of the daily thermal balance<br />

results.<br />

Effect of power distribution on the total current of the chambers outside the core:<br />

❙ 638 ❙

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