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Regional Basic Professional Training Course in Korea

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S<strong>in</strong>gle failure criterion<br />

❙ 239 ❙<br />

4. DESIGN OF NUCLEAR REACTORS<br />

The s<strong>in</strong>gle failure criterion shall be applied to each safety group <strong>in</strong>corporated <strong>in</strong> the plant<br />

design.<br />

Spurious action shall be considered as one mode of failure when apply<strong>in</strong>g the concept to<br />

a safety group or system.<br />

Compliance with the criterion shall be considered to have been achieved when each<br />

safety group has been shown to perform its safety function under the follow<strong>in</strong>g<br />

conditions:<br />

Any potentially harmful consequences of the PIE for the safety group are assumed<br />

to occur; and<br />

The worst permissible configuration of safety systems perform<strong>in</strong>g the necessary<br />

safety function is assumed, with account taken of ma<strong>in</strong>tenance, test<strong>in</strong>g, <strong>in</strong>spection<br />

and repair, and allowable equipment outage times.<br />

Non‐compliance with the s<strong>in</strong>gle failure criterion shall be exceptional, and shall be clearly<br />

justified <strong>in</strong> the safety analysis.<br />

In the s<strong>in</strong>gle failure analysis, it may not be necessary to assume the failure of a passive<br />

component designed, manufactured, <strong>in</strong>spected and ma<strong>in</strong>ta<strong>in</strong>ed <strong>in</strong> service to an extremely<br />

high quality, provided that it rema<strong>in</strong>s unaffected by the PIE.<br />

Fail‐safe design<br />

The pr<strong>in</strong>ciple of fail‐safe design shall be considered and <strong>in</strong>corporated <strong>in</strong>to the design of<br />

systems and components important to safety for the plant as appropriate: if a system or<br />

component fails, plant systems shall be designed to pass <strong>in</strong>to a safe state with no

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