ML12038A235

Email from M. King, NRR to R. Bernardo, NRR North Anna Rx Trip - from Ioeb Clearinghouse Screening Summary for Friday, September 09, 2011

ML12038A235
Person / Time
Site:	North Anna
Issue date:	09/12/2011
From:	Mark King Office of Nuclear Reactor Regulation
To:	Robert Bernardo Office of Nuclear Reactor Regulation
References
FOIA/PA-2011-0357
Download: ML12038A235 (1)

Text

King, Mark From: King, Mark Sent: Monday, September 12, 2011 6:57 AM To: Bernardo, Robert

Subject:

RE:North Anna Rx Trip --- from IOEB Clearinghouse Screening Summary for Friday, September 09, 2011 RE: 4) NORTH ANNA 1 &.2 Trip - Dominion noted that the cause of the negative rate trip (first annunciator out) is still being investigatedc.tAt this point, it appears that the grippers for several of the control rods de-energized and dropped. RCCAs into the core leading to the negative rate trip. They have confirmed that the flux was decreasing on all four power range channels, but do not have the root cause completed. By their post trip analysis, the trip due to negative flux rate occurred at 13:51:11, followed by the loss of off site power at 13:51:12. Transformers 1-EP-MT-1A, 2-EP-MT-1A, 1 B, 1C, all RSSTs, 1-EP-S.ST-1C and switchyard transformer #2tripped due to sudden pressure relay actuations (Loss of off site power). Thus, the negative flux rate trip occurred BEFORE the loss of off site power. Pass to the TRG Leads for AFW. ECCS. Electrical Power, EDGs, Emergency Preparedness, Flooding/Missiles, Spent Fuel Handling., Structural and to NRO.

Assigned to Bob Bernardo.

Bob, Did they say ifthey had a normal full scram- i.e., basically all rod bottom lights coming on at the same time. Or was there a few rods dropping first (due to the earthquake shaking causing several dropped rods) causing the "negative rate trip" ---followed by the dropping the rest of the rods into the core. - Do you know I have you heard?

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V uutside oT zcope K

If you know let me know. Just curious.

Thanks, Mark From: Bernardo, Robert Sent: Friday, September 09, 2011 2:13 PM

Subject:

IOEB Clearinghouse Screening Summary for Friday, September 09, 2011 S

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