Consistent with the intent of this guideline and the way BWRs are implementing it, this would be a SL3. The fact that the power reduction is automatic and by design is immaterial. The unplanned part is the loss of the initiating parameter, OAC in this case. If something causes an power change, the event is a SL3/SL4 depending on greater or less than 0.5%.
The PWR REs really need a peer group like the BWRs' RCRC group to help each other with these kinds of questions. I have been hoping that either the PWROG or INPO would step up and form a group with that intent. Unfortunately that does not look like it will happen anytime soon. Does anyone else have an idea of how to accomplish this idea?
Tom Tomlinson RETAQS
-----Original Message----- From: pwrrm@retaqs.com [mailto:pwrrm@retaqs.com] On Behalf Of pwrrm-request@retaqs.com Sent: Tuesday, January 26, 2010 12:00 PM To: pwrrm@retaqs.com Subject: PWRRM Digest, Vol 34, Issue 12
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Today's Topics:
1. PWR RM PI Significance Level for "Designed Runbacks" (Sanders, Gene Jr)
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Message: 1 Date: Mon, 25 Jan 2010 14:49:17 -0500 From: "Sanders, Gene Jr" Gene.Sanders@duke-energy.com Subject: [Pwrrm] PWR RM PI Significance Level for "Designed Runbacks" To: "pwrrm@retaqs.com" pwrrm@retaqs.com Message-ID: <22A8474FC8468A439A927EF628FED52B159F2D349F@IMCLUSEXCP55.nam.ent.duke-energy .com> Content-Type: text/plain; charset="us-ascii"
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