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Regional Basic Professional Training Course in Korea

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❙ 897 ❙<br />

16. In‐Plant Accident Management<br />

Emergency events can be divided <strong>in</strong>to two classes. There are events where an accurate<br />

diagnosis can be made. It is highly desirable to provide mitigat<strong>in</strong>g guidance which is<br />

selected and sequenced to strategically address that symptom set s<strong>in</strong>ce these types of<br />

events have been well analyzed and understood (e.g. LOCA, SGTR). There are other<br />

events where the operator are unable to identify a unique symptom set for the<br />

disturbance. This may be due to errors <strong>in</strong> symptom assessment by the operators, multiple<br />

and simultaneous failures <strong>in</strong> the plant, the occurrence of an heretofore unanalyzed event,<br />

or <strong>in</strong>strumentation failures which distort the symptom picture.<br />

Emergency procedure guidel<strong>in</strong>es must provide guidance for both classes of emergencies.<br />

Thus EPGs written to treat specific symptoms are called Optimal Recovery Guidel<strong>in</strong>es.<br />

The EPG which provide guidance for undiagnosed events for which a reactor trip is<br />

required is called the Functional Recovery Guidel<strong>in</strong>e. Fig. 16.2.2 illustrated the system of<br />

EPGs.<br />

Standard Post Trip Actions evaluate the status of each safety functions and provide<br />

immediate actions which can be quickly and easily performed to improve the status of<br />

safety functions <strong>in</strong> jeopardy. Dur<strong>in</strong>g and follow<strong>in</strong>g the SPTAs, diagnostic actions are<br />

performed to determ<strong>in</strong>e the symptom set correspond<strong>in</strong>g to the type of event <strong>in</strong> progress.<br />

Depend<strong>in</strong>g on the operators’ ability to diagnose, they will then select either an ORG or<br />

the FRG.<br />

Each ORG conta<strong>in</strong>s a section which requires the operator to confirm the diagnosis and<br />

cont<strong>in</strong>ually review the status of safety functions by use of the Safety Function Status<br />

Check. If the diagnosis is not confirmed or if the safety function acceptance criteria are<br />

not met, the operators then evaluate the need to implement another ORG or the FRG.<br />

Thus, if the symptoms are not responsible to treatment as anticipated or if the core is not<br />

be<strong>in</strong>g adequately cooled, the ORG may be exited and the FRG implemented.

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