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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 />

<strong>in</strong> the control room and elsewhere, and requirements for operator action <strong>in</strong> case abnormal<br />

conditions are encountered. Abnormal conditions may <strong>in</strong>clude violation of limits on<br />

process variables or operability requirements. Requirements for restart of the plant after a<br />

normal or forced shutdown may be <strong>in</strong>cluded. All conditions encountered <strong>in</strong> normal<br />

operation, especially <strong>in</strong>clud<strong>in</strong>g shutdown and start‐up, must be considered <strong>in</strong> establish<strong>in</strong>g<br />

m<strong>in</strong>imum equipment operability requirements.<br />

10.3.2. IAEA guidance on limits and conditions<br />

10.3.2.1. Reactivity control<br />

Negative reactivity requirements<br />

The m<strong>in</strong>imum negative reactivity available <strong>in</strong> the reactivity control devices shall be such<br />

that the degree of subcriticality assumed <strong>in</strong> the safety report can be reached immediately<br />

after shutdown from any operational state and relevant accident conditions. To ma<strong>in</strong>ta<strong>in</strong><br />

the specified degree of subcriticality for an <strong>in</strong>def<strong>in</strong>ite period of time after shutdown,<br />

additional means, as provided <strong>in</strong> the design, may be used, such as the use of borated<br />

water, or other poisons where the compensation for temperature, xenon or other transient<br />

reactivity effects cannot be achieved by normal reactivity control devices.<br />

The required negative reactivity shall be specified <strong>in</strong> terms of the <strong>in</strong>formation available to<br />

the reactor operator such as control rod positions, liquid poison concentration or neutron<br />

multiplication factors.<br />

Reactivity coefficients<br />

Where the safety report <strong>in</strong>dicates the need, limits shall be stated for the reactivity<br />

coefficients for different reactor conditions to ensure that the assumptions used <strong>in</strong> the<br />

accident and transient analyses rema<strong>in</strong> valid through each fuell<strong>in</strong>g cycle.<br />

❙ 640 ❙

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