Information Notice 2009-03, Solid State Protection System Card Failure Results in Spurious Safety Injection and Reactor Trip
| ML083080368 | |
| Person / Time | |
|---|---|
| Issue date: | 03/11/2009 |
| From: | Dan Dorman, Mcginty T NRC/NMSS/FCSS, Division of Policy and Rulemaking |
| To: | |
| C HAWES | |
| References | |
| IN-09-03 | |
| Download: ML083080368 (4) | |
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. 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
NRCs 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.
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.
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