ML083080368

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF NUCLEAR REACTOR REGULATION 

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS 

WASHINGTON, DC 20555-0001 

March 11, 2009 

NRC INFORMATION NOTICE 2009-03: SOLID STATE PROTECTION SYSTEM CARD 

FAILURE RESULTS IN SPURIOUS SAFETY 

INJECTION ACTUATION AND REACTOR TRIP 

ADDRESSEES 

All holders of operating licenses for nuclear power reactors, except those who have 

permanently ceased operations and who have certified that fuel has been permanently removed 

from the reactor vessel, as well as licensees and certificate holders of nuclear fuel cycle 

facilities. 

PURPOSE 

The Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform 

addressees of an event at North Anna Power Station, Unit 2, involving a solid state protection 

system (SSPS) card failure that resulted in a spurious actuation of the “B” train safety injection 

(SI) and a reactor trip. The NRC expects that recipients will review the information for 

applicability to their facilities and consider actions, as appropriate, to avoid similar problems. 

Suggestions contained in this IN are not NRC requirements; therefore, no specific action or 

written response is required. 

DESCRIPTION OF CIRCUMSTANCES 

On June 29, 2007, North Anna Power Station, Unit 2, experienced a spurious actuation of the 

“B” train SI caused by a Zener diode failure on a “B” train SSPS card. The spurious SI caused 

main feedwater system isolation, a turbine trip, and a reactor trip, along with emergency core 

cooling system water flow into the reactor coolant system (RCS). Because of the nature of the 

failure, the licensee could not reset from the control room the actuation signal for some “B” train 

SI equipment, which resulted in overfilling the pressurizer and multiple actuations of a 

pressurizer power-operated relief valve (PORV) to limit RCS pressure. RCS inventory from the 

PORV discharged to the pressurizer relief tank (PRT), rupturing one of the PRT rupture disks, 

which allowed RCS water to reach the containment basement. 

Plant personnel successfully defeated the malfunctioning SI logic train and terminated the SI. 

The licensee reset and deenergized the malfunctioning “B” train SI logic by placing the SSPS 

into TEST, locally delatching some relays, and deenergizing the circuit by pulling fuses. 

Procedures did not address manually resetting the partial SI in the presence of the SSPS card 

failure. The SSPS card failure was mitigated by securing and resetting the SI signal using 

operator knowledge and the information in several different procedures that were not specifically 

developed to address the inability to reset a SI signal. 
IN 2009-03 

Page 2 of 3 

The licensee determined that the most probable cause of the diode failure on the “B” train SSPS 

card was either age-related degradation or a random failure. The diode failed as a short circuit 

actuating certain “B” train master relays and resulting in the invalid actuation of the “B” train SI. 

This same failure also prevented “B” train SI from being reset from the control room, which 

required operations and maintenance staff to take local actions. A contributing cause of the 

failure was that the licensee had not implemented a program to detect and correct age-related 

degradation of the SSPS cards. 

Licensee corrective actions for this event included (1) establishing a preventive maintenance 

program to remove, test, and repair these cards, along with cards in other sensitive systems, at 

periodic intervals, (2) developing an abnormal operating procedure to reset SI locally, and (3) 

implementing life-cycle management for SSPS cards. 

Additional information is available in the document “North Anna Power Station – NRC Special 

Inspection Report 05000339/2007009,” dated August 27, 2007, which can be found on the 

NRC’s public Web site in the Agencywide Documents Access and Management System 

(ADAMS), under Accession No. ML072410359. See also North Anna Power Station, Unit 2, 

Licensee Event Report 50-339/2007-003-00, dated August 27, 2007 (ADAMS Accession 

No. ML072480671). 

DISCUSSION 

The SSPS card failure at North Anna resulted in a complicated reactor trip response that 

required manual actions outside the control room to secure SI flow and restore other equipment 

that actuated from the signal. This event revealed the lack of procedure guidance to reset the 

SI after SSPS card failure, which was an obstacle to mitigating the event. Power reactor 

licensees rely on circuit cards such as SSPS cards being operable in systems as specified in 

technical specifications. Industry operating experience shows that circuit cards are susceptible 

to age-related component failures. Power reactor licensees can address this by establishing 

periodic preventive maintenance of circuit cards. Similarly, licensees and certificate holders of 

fuel cycle facilities are required to perform inspection, testing, calibration, and maintenance of 

certain systems and components as delineated in applicable sections of Title 10 of the Code of 

Federal Regulations, Parts 70 and 76. 
IN 2009-03 

Page 3 of 3 

CONTACT 

This IN requires no specific action or written response. Please direct any questions about this 

matter to the technical contacts listed below or the appropriate project manager in the Office of 

Nuclear Reactor Regulation (NRR). 

/RA/ /RA/ 

Timothy J. McGinty, Director Daniel H. Dorman, Director 

Division of Policy and Rulemaking Division of Fuel Cycle Safety and Safeguards 

Office of Nuclear Reactor Regulation Office of Nuclear Material Safety and Safeguards 

Technical Contacts: Jim Dodson, Region II Subinoy Mazumdar, NRR 

404-562-4655 301-415-2904 

e-mail: Jim.Dodson@nrc.gov e-mail: Subinoy.Mazumdar@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, 

http://www.nrc.gov, under Electronic Reading Room/Document Collections. 
IN 2009-03 

Page 3 of 3 

CONTACT 

This IN requires no specific action or written response. Please direct any questions about this 

matter to the technical contacts listed below or the appropriate project manager in the Office of 

Nuclear Reactor Regulation (NRR). 

/RA/ /RA/ 

Timothy J. McGinty, Director Daniel H. Dorman, Director 

Division of Policy and Rulemaking Division of Fuel Cycle Safety and Safeguards 

Office of Nuclear Reactor Regulation Office of Nuclear Material Safety and Safeguards 

Technical Contacts: Jim Dodson, Region II Subinoy Mazumdar, NRR 

404-562-4655 301-415-2904 

e-mail: Jim.Dodson@nrc.gov e-mail: Subinoy.Mazumdar@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, 

http://www.nrc.gov, under Electronic Reading Room/Document Collections. 

ADAMS Accession Number: ML083080368 

OFFICE R2:BC:RPB5 TECH EDITOR EICB:DE BC:EICB:DE 

NAME JDodson e-mail HSpencer SMazumdar WKemper 

DATE 10/30/2008 11/10/2008 01/29/2009 1/29/2009 

OFFICE D:DE BC:RER2 D:FCSS 

NAME PHiland RAuluck DDorman 

DATE 1/29/2009 11/05/2008 03/02/2009 

OFFICE PGCB:DPR PGCB:DPR BC:PGCB:DPR D:DPR 

NAME DBeaulieu CHawes MMurphy TMcGinty 

DATE 2/3/2009 2/17/2009 2/18/2009 03/11/2009 

OFFICIAL RECORD COPY