Ref.: PWR RM PI document, Rev.1 (Draft 8-10-09)

Attach. 3, “Significance Level 3 Event Examples”, ex. 3.9 and Attach. 4, “Significance Level 4 Event Examples”, ex. 4.6.

3.9          Unplanned Reactivity Change Caused by Equipment Problem or Personnel Error

                                Reactor Power Change > 0.5% RTP When >5% RTP

                                Reactivity Change > x pcm When < 5% RTP

4.9          Unplanned Reactivity Change Caused by Equipment Problem or Personnel Error

                                Reactor Power Change < 0.5% RTP When >5% RTP

                                Reactivity Change < x pcm When < 5% RTP

Are the above examples to be applied to “Design Runbacks”? Even though a plant runback was/is incorporated into a given plant’s control design, are these occurrences to be considered an “Unplanned Reactivity Change / Reactor Power Change”?

For example, at Oconee, a loss of the Operator Aid Computer (OAC) Core Thermal Power (CTP) Signal to the Integrated Control System (ICS) will cause the ICS to control the plant to a CTP calculated by the ICS, which typically results in a real power reduction, “by design”, of ~0.75% RTP. If this occurrence / scenario is considered to be “Unplanned”, then a “Significance Level 3 Event” appears to be required, even though the significance of such an Event pales in comparison to other Level 3 Event Examples. Is this what was / is intended for design runbacks?

Thanks in advance for your response,

T E (Gene) Sanders

ONS Rx Engineering

864.873.3377