United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-106, Supplement 2: Feedwater Line Break

                                                            SSINS No.:  6835 
                                                            In 86-106 
                                                            Supplement 2 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                            WASHINGTON, DC 20555

                               March 18, 1987

Information Notice No. 86-106, SUPPLEMENT 2:   FEEDWATER LINE BREAK 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit. 

Purpose: 

Information Notice No. 86-106 provided general information to addressees 
about the catastrophic failure of feedwater ping that occurred on December 
9, 1986, at Unit 2 of the Surry Power Station and resulted in four 
fatalities. Supplement 1 to that notice provided information about thinning 
of piping walls which was the cause of the failure of feedwater piping. This 
supplement provides addressees with information about potentially generic 
systems interaction problems that were caused by release of large quantities 
of feedwater. Recipients are expected to review the information provided for 
applicability to their facilities and consider actions, if appropriate, to 
preclude the occurrence of similar problems. However, suggestions contained 
in this information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required. 

Discussion: 

On December 9, 1986, both units at the Surry Power Station were operating at
full power when an 18-inch suction line to a main feedwater pump in Unit 2 
failed catastrophically releasing, in the turbine building, large quantities
of hot feedwater which flashed to steam. Condensed steam saturated a 
security card reader in the turbine building basement approximately 50 feet 
from the failed pipe and shorted out the card reader system for the entire 
plant. As a result, key cards would not open doors controlled by the 
security system. Controlled-access doors to the control room were blocked 
open to provide access for operating, emergency, and management personnel. 
Security personnel were posted at the doors and permitted entry of essential 
personnel based on personal recognition. Twenty minutes after the failure, 
the card reader system was functioning normally. 

Water also entered a fire protection control panel through an open conduit 
and shorted circuits in the panel. This resulted in the discharge of 62 
water sprinkler heads in the fire suppression system within minutes of 
failure of the feedwater piping. Actuation of the sprinkler heads did 
provide cooling of the atmosphere in the turbine building but added to the 
quantity of water in the 

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                                                  IN 86-106, Supplement 2 
                                                  March 18, 1987  
                                                  Page 2 of 3 

turbine building basement. Water from the sprinklers outside the Unit 2 
cable tray room apparently flowed under the door into the cable tray room, 
leaked around foam fire seals in floor penetrations, and dripped into the 
control room. The control room serves Units 1 and 2 and is located beneath 
the cable tray rooms for these units. 

A carbon dioxide fire suppression system is provided for the cable tray 
rooms. Water from sprinkler heads located directly over and adjacent to 
control panels for this system and water from the failed feedwater pipe 
entered the control panels through the ends of several open conduits. Within 
a few minutes after failure of the feedwater pipe, shorting of fire 
protection control circuits caused the contents of the main carbon dioxide 
storage tank to be emptied into the cable tray rooms leaving the station 
without carbon dioxide in the event of fire. Carbon dioxide, which is 
heavier than air, entered the control room via stairwells and 
controlled-access doors which were blocked open. Personnel on the Unit 2 
side of the control room complained of shortness of breath, dizziness, and 
nausea. 

A halon fire suppression system is provided for the emergency switchgear 
rooms for Units 1 and 2. These rooms are located below the control room. The
halon system was actuated in the same way that the carbon dioxide system was
actuated. Halon leaked into the Unit 1 computer room through floor 
penetrations and from the computer room into the Unit 1 side of the control 
room. Halon haze was reported but did not hamper the performance of 
operators. 

An operator who was in the stairwell behind the control room when the card 
readers failed experienced difficulty in breathing. Because of locked doors,
he could not exit through the control room or a switchgear room which 
contained halon. The other means of egress was through a cable tray room 
which contained carbon dioxide. An operator in the control room heard him 
knocking and admitted him. 

The security communications system includes radio repeaters that improve the 
clarity of reception of low-power hand-held radios used in the plant. A 
radio repeater, located in the Unit 1 cable tray room and approximately 5 
feet from a carbon dioxide nozzle, was covered with a thick layer of ice as 
a result of cooling from the discharge of carbon dioxide. The performance of 
the radio repeater was temporarily degraded and may have resulted in the 
need for personnel using hand-held radios to move to other locations in 
order to communicate effectively. 

The licensee intends to seal and shield control cabinets and conduits for 
the carbon dioxide and halon fire suppression systems from water sources, as
necessary, to prevent inadvertent actuation of these systems. Penetrations 
connecting the computer and emergency switchgear rooms have been sealed, as 
necessary, to prevent leakage of halon into the control room. Additional 
actions to preclude system interactions may be warranted. 

Additional information about the Surry accident and system interactions can 
be found in NRC Inspection Reports 50-280/86-42 and 50-281/86-42 dated 
February 10, 1987, and in Licensee Event Report 86-020-01 in Docket 50-281 
dated January 14, 1987. 

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                                                  IN 86-106, Supplement 2 
                                                  March 18, 1987  
                                                  Page 3 of 3 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate NRC regional office or this 
office. 




                                   Edward L. Jordan, Director
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Roger Woodruff, IE 
                    (301) 492-7205 

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