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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 />

accident conditions and to assure that mitigation is available if an accident should occur.<br />

The LCOs should restrict operation of the plant such that all plant parameters are with<strong>in</strong><br />

the safety design basis. Thus, if a postulated <strong>in</strong>itiat<strong>in</strong>g event were to occur, the control<br />

and safety systems could function as designed to prevent excessive radioactive release.<br />

The LCOs are based on the whole safety assessment of the plant, both determ<strong>in</strong>istic and<br />

probabilistic, <strong>in</strong>clud<strong>in</strong>g not only the analysis of plant performance, but also issues such as<br />

surveillance and test<strong>in</strong>g requirements for safety systems, allowable system outage times,<br />

etc. In recent years, the use of probabilistic safety assessment (PSA) <strong>in</strong>sights <strong>in</strong><br />

evaluat<strong>in</strong>g surveillance, test<strong>in</strong>g, and ma<strong>in</strong>tenance requirements for plant systems has<br />

<strong>in</strong>creased significantly. This so‐called “risk based ma<strong>in</strong>tenance” is one of the most<br />

practical applications of PSA <strong>in</strong> plant operations.<br />

10.1.2.2. Scope of LCOs<br />

LCOs shall consider all aspects of plant operation that bear on safety, <strong>in</strong>clud<strong>in</strong>g not only<br />

the process related aspects such as power level, pressure, temperature, flow, and the like,<br />

but also equipment status, personnel status, the existence of potential external threats, etc.<br />

LCOs may be classified as:<br />

Safety limits: limits to process variables with<strong>in</strong> which the plant operation is safe;<br />

Safety system sett<strong>in</strong>gs: limits on safety system sett<strong>in</strong>gs that will assure activation of<br />

safety systems <strong>in</strong> time to prevent a safety limit from be<strong>in</strong>g exceeded, should a<br />

postulated <strong>in</strong>itiat<strong>in</strong>g event (PIE) occur;<br />

Limits and conditions for normal operation <strong>in</strong>cludes limits on normal process<br />

variables, as well as requirements for m<strong>in</strong>imum staff<strong>in</strong>g, m<strong>in</strong>imum operable<br />

equipment, and allowable outage times for systems and equipment;<br />

Surveillance requirements: requirements for periodic checks, tests, calibrations, and<br />

<strong>in</strong>spections of equipment, components, and processes to establish operability,<br />

❙ 628 ❙

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