Information Notice 2007-15, Effects of Ethernet-based, Non-Safety Related Controls on the Safe and Continued Operation of Nuclear Power Stations

Effects of Ethernet-based, Non-Safety Related Controls on the Safe and Continued Operation of Nuclear Power Stations

ML071010303
Person / Time
Issue date:	04/17/2007
Revision:	0
From:	Case M J NRC/NRR/ADRA/DPR
To:
References
IN-07-015
Download: ML071010303 (4)

April 17, 2007

NRC INFORMATION NOTICE: 2007-15:EFFECTS OF ETHERNET-BASED, NON-SAFETYRELATED CONTROLS ON THE SAFE AND CONTINUED OPERATION OF NUCLEAR POWER STATIONS

ADDRESSEES

All holders of operating licenses for nuclear power reactors, except those who havepermanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alertlicensees about recent operating experience related to the effects of potential interactions and unanticipated failures of ethernet connected non-safety equipment on the safety and performance capability of nuclear power station NRC expects that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problem However, suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is required.DESCRIPTION OF CIRCUMSTANCESOn August 19, 2006, operators at Browns Ferry, Unit 3, manually scrammed the unit following aloss of both the 3A and 3B reactor recirculation pump Plant procedures following the loss of recirculation flow required the manual scra Immediate loss of the recirculation flow placed the plant in a high power, low flow condition where core thermal hydraulic stability problems may exist at boiling-water reactors (BWRs). Generally, intentional operation in this condition, of high power and low flow, is not permitte Although some BWRs are authorized for single loop operation, sudden loss of even one pump could present the plant with the same stability problems and could result in the reactor protection system initiating a shutdown of the plan The initial investigation into the dual pump trip found that the recirculation pump variablefrequency drive (VFD) controllers were nonresponsiv The operators cycled the control poweroff and on, reset the controllers, and restarted the VFD The licensee also determined that the Unit 3 condensate demineralizer controller had failed simultaneously with the Unit 3 VFD controller The condensate demineralizer primary controller is a dual redundant programmable logic control (PLC) system connected to the ethernet-based plant integrated computer system(ICS) networ The VFD controllers are also connected to this same plant ML071010303 IN 2007-15