United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-05: Fire in Annunciator Control Cabinets

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION
                             WASHINGTON, D.C.  20555

                                February 12, 1988


Information Notice No. 88-05:  FIRE IN ANNUNCIATOR CONTROL CABINETS 


Addressees: 

All holders of operating licenses or construction permits for nuclear power 
reactors. 

Purpose: 

This information notice is being provided to inform addressees of three oc-
currences of electrical fires in annunciator control panels supplied by 
Electro Devices, Inc.  It is expected that recipients will review the 
information for applicability to their facilities and consider actions, as 
appropriate, to avoid similar problems.  However, suggestions contained in 
this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required. 

Description of Circumstances: 

Recently, electrical fires have occurred in remote cabinets containing 
multiple circuit cards for the control of visual and audible annunciator 
functions in the main control rooms at three nuclear power plants.  The 
annunciator systems for the three plants were provided by Electro Devices, 
Inc. of St. Louis, Missouri. 

On January 28, 1988, while Beaver Valley 2 was in cold shutdown, all control 
room annunciator alarms were lost.  A small fire was detected in a remote an-
nunciator control cabinet, and it was immediately extinguished by the two 
operators who had been dispatched to investigate.  Plant parameters were 
available throughout the event from other control room instruments and the 
safety parameter display system.  Because of the sustained loss of the 
annunciators, the licensee declared an alert in accordance with the plant 
emergency plan.  Damaged solid state cards were removed, annunciator 
capability was restored,  and the alert was terminated.  The root cause of the 
fire is under investigation. 

On February 1, 1988, while Calvert Cliffs Unit 2 was operating at 100% power, 
an alert was declared because all control room annunciator alarms were lost.  
The complete loss of the annunciator system resulted from a fire in a remote 
control cabinet that provides audible and visual alarm functions for the main 
control room.  The operators were alerted to the fire by the actuation of the 
automatic fire protection system.  The visual indication function of all 
control room annunciator panels was out of service for 2 hours, and the 
audible function was not restored for two days.  The root cause of the fire is 
under investigation; however the licensee intends to review the adequacy of 
circuit protection 

8802110328 
.                                                            IN 88-05 
                                                            February 12, 1988 
                                                            Page 2 of 2 

(sub-fusing of branch circuits within the annunciator system) to determine if 
this contributed to the occurrence of the fire.  The unit remained at 100% 
power throughout the event. 

On February 8, 1988, while Rancho Seco was in cold shutdown, all control room 
annunciator alarms were lost because of a fire in a remote control cabinet 
that provides audible and visual control functions to the annunciator system.  
The fire is believed to have originated from a failed subcomponent on a solid 
state circuit card.  The root cause of the fire is under investigation. 

Although the NRC's investigation of these events is not yet complete, the 
following similarities among the events are noteworthy: 

.    The annunciator systems were provided by the same manufacturer. 

.    Common to each event was the licensee's lack of specific emergency 
     procedures to address complete loss of the annunciator system.

.    None of the licensees have provisions for monitoring ambient temperatures
     in the control cabinets.

.    In the events at Calvert Cliffs and Rancho Seco, the fire teams 
     experienced nausea and dizziness, apparently as a result of inadequate 
     oxygen in the area in which the fire occurred.  Licensees thus may wish 
     to review their procedures for fighting small fires in confined areas to 
     determine the adequacy of personnel protection and the need to specify 
     the use of breathing apparatus. 
     
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional
office. 




                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical Contact:  V. D. Thomas, NRR
                    (301) 492-0786

                    E. N. Fields, NRR
                    (301) 492-1173

Attachment:  List of Recently Issued NRC Information Notices
Page Last Reviewed/Updated Tuesday, November 12, 2013