ML101020184 

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF NUCLEAR REACTOR REGULATION 

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS 

OFFICE OF NEW REACTORS 

WASHINGTON, DC 20555-0001 

 April 14, 2010 

NRC INFORMATION NOTICE 2010-09: IMPORTANCE OF UNDERSTANDING CIRCUIT 

BREAKER CONTROL POWER INDICATIONS 

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor issued 

under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, “Domestic Licensing of 

Production and Utilization Facilities,” except those who have permanently ceased operations 

and have certified that fuel has been permanently removed from the reactor vessel. 

All holders of or applicants for an early site permit, standard design certification, standard 

design approval, manufacturing license, or combined license issued under 10 CFR Part 52, 

“Licenses, Certifications, and Approvals for Nuclear Power Plants.” 

All holders of or applicants for a license for a fuel cycle facility issued pursuant to 

10 CFR Part 70, “Domestic Licensing of Special Nuclear Material.” 

All holders of or applicants for a certificate of compliance issued under 10 CFR Part 76, 

“Certification of Gaseous Diffusion Plants.” 

All holders of or applicants for a license for a uranium conversion facility issued pursuant to 

10 CFR Part 40, “Domestic Licensing of Source Material.” 

PURPOSE

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

addressees about circuit breaker control power indication issues that could result in degraded 

circuit breaker protection and control. 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 March 28, 2010, following an automatic reactor trip at H.B. Robinson Steam Electric Plant 

Unit 2, a non-safety related electrical circuit breaker did not automatically open to isolate an 

electrical fault because this breaker did not have control power to the trip circuit. The lack of 

control power was due to a faulty fuse assembly in the breaker’s control power circuit. The 

licensee’s corrective action program shows that the control power indicating lights on the front 
IN 2010-09 

Page 2 of 3 

panel of the breaker had not been illuminated for approximately one year. Additional 

information is available in Preliminary Notification of Event PNO-II-10-002 dated 

March 29, 2010, and can be found on the NRC’s public website in the Agencywide Documents 

Access and Management System (ADAMS) under Accession No. ML100880412. 

BACKGROUND 

The NRC previously issued two INs related to circuit breaker control power issues: 

(1) IN 1991-78, “Status Indication of Control Power for Circuit Breakers Used in SafetyRelated Applications,” November 28, 1991 (ADAMS Accession No. ML082380373). 

(2) IN 2007-34, “Operating Experience Regarding Electrical Circuit Breakers,” 

October 22, 2007 (ADAMS Accession No. ML072390061). 

The NRC issued IN 1991-78 to inform licensees of the importance of having control power for 

circuit breakers used in safety-related applications. This IN highlighted the importance of having 

control power indication for both safety-related and non-safety related applications. IN 2007-34 

highlighted the importance of identifying possible causes for breaker problems including the lack 

of control power indication. 

DISCUSSION

Industry operating experience shows similar control power fuse issues where the indicating 

lights were either dim or not illuminated. The loss or degradation of control power in circuit 

breakers can prevent the breaker from performing its design function of either opening or 

closing on demand. Although there is no regulatory requirement for the functionality of the nonsafety related breaker discussed in this IN, industry operating experience describes instances of 

technical specification required equipment being rendered inoperable due to similar circuit 

breaker control power issues. 

A recent review of breaker control power operating experience has determined that the following 

items are important to ensure proper breaker operation: 

• the verification of control power indication for both safety-related and non-safety related 

circuit breakers during walkdowns 

• the potential impact on safety-related equipment resulting from a loss of control power to 

non-safety related circuit breakers when they fail to open to isolate a fault 
IN 2010-09 

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 Office of Nuclear Reactor 

Regulation (NRR) project manager. 

/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 

/RA/ By John Tappert For/ 

Glenn Tracy, Director 

Division of Construction Inspection 

 and Operational Programs 

Office of New Reactors 

Technical Contacts: Jesse Robles, NRR Joseph Giantelli, NRR 

301-415-2940 301-415-0504 

E-mail: jesse.robles@nrc.gov E-mail: joseph.giantelli@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 2010-09 

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 Office of Nuclear Reactor 

Regulation (NRR) project manager. 

/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 

/RA/ By John Tappert For/ 

Glenn Tracy, Director 

Division of Construction Inspection 

 and Operational Programs 

Office of New Reactors 

Technical Contacts: Jesse Robles, NRR Joseph Giantelli, NRR 

301-415-2940 301-415-0504 

E-mail: jesse.robles@nrc.gov E-mail: joseph.giantelli@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: ML101020184 TAC ME3754 

OFFICE DIRS:IOEB DIRS:IOEB Tech Editor ABC:DIRS:IOEB D:NRR:DIRS BC:DE:EEB 

NAME JRobles JGiantelli KAKribbs EThomas FBrown GWilson 

DATE 04/14/10 04/14/10 04/12/10 e-mail 04/14/10 04/14/10 04/14/10 

OFFICE LA:PGCB:NRR PM:PGCB:NRR BC:PGCB:NRR D:NMSS:DFCSS D:DCIP:NRO D:DPR:NRR 

NAME CHawes DBeaulieu MMurphy DDorman GTracy TMcGinty 

OFFICE 04/14/10 04/14/10 04/14/10 04/14/10 04/14/10 04/14/10 

OFFICIAL RECORD COPY