United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 75-04A: Cable Fire at Browns Ferry Nuclear Power Station



BL75004A 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 

                                APR 3 1975 

J. P. O'Reilly, Director, Region I 
N. C. Moseley, Director, Region II 
J. G. Keppler, Director, Region III 
E. M. Howard, Director, Region IV 
R. H. Engelken, Director, Region V 

IE BULLETIN NO. - 75-04A 
CABLE FIRE AT BROWNS FERRY NUCLEAR PLANT 

The subject Bulletin should be dispatched for action to all power reactor 
facilities with operating license by close of business on April 3, 1975. 

The Bulletin should also be dispatched for information to all other power 
reactor facilities with operating license or construction permit. 

The text of the Bulletin and draft letters to licensees are enclosed for 
this purpose. 


                                   John G. Davis 
                                   Deputy Director for 
                                     Field Operations 
                                   Office of Inspection 
                                     and Enforcement 

Enclosures: 
As stated 

Transmitted to Chairman Anders, 4/3/75, 9:55 a.m. 
.

                                 - 2 - 

Distribution: 

D. F. Knuth, IE 
J. G. Davis, DDFO:IE 
L. I. Cobb, A/D, IE (3) 
H. H. Brown, D, ISP 
D. Thompson, AD, IP, OOE:IE 
B. H. Grier, AD, CO:IE 
C. W. Kuhlman, AD, REMP:IE 
Director, NRR 
Director, RL 
Director, TR 
Assistant Directors, RL (6) 
Assistant Directors, TR (4) 
Director, OOE:IE 
H. D. Thornburg, Chief, FSEB:IE 
J. L. Crews, FSEB:IE 
FADreher; GCGower; SEBryan; GHSmith; FSEB:IE 
M. Meadows, Secretary, DDFO: IE 
Central Files 
EDO Reading Files 
IE Files 
IE Reading Files 
DDFO:IE Reading Files
IE Bulletin No. 75-04A 

.

CABLE FIRE AT BROWNS FERRY NUCLEAR PLANT 

The following material supplements and modifies IE Bulletin 75-04. 

DESCRIPTION OF CIRCUMSTANCES 

Additional, though still preliminary, information has become available 
related to the fire which occurred at the Browns Ferry Site on March 22, 
1975. The fire started in the cable spreading room at a cable penetration 
through the wall between the cable spreading room and the reactor building 
for Unit 1. A slight differential pressure is maintained (by design) across 
this wall, with the higher pressure being on the cable spreading room side. 
The penetration seal originally present had been breached to install 
additional cables required by a design modification. Site personnel were 
resealing the penetration after cable installation and were checking the 
airflow through a temporary seal with a candle flame prior to installing the
permanent sealing material. The temporary sealing material was highly 
combustible, and caught fire. Efforts were made by the workers to extinguish
the fire at its origin, but they apparently did not recognize that the fire,
under the influence of the draft through the penetration, was spreading on 
the reactor building side of the wall. The extent of the fire in the cable 
spreading room was limited to a few feet from the penetration; however, the 
presence of the fire on the other side of the wall from the point of 
ignition was not recognized until significant damage to cables related to 
the control of Units 1 and 2 had occurred. 

Although control circuits for many of the systems which could be used for 
Unit 1 were ultimately disabled by the fire, the station operating personnel
were able to institute alternative measures by which the primary system 
could be depressurized and adequate cooling water supplied to the reactor 
vessel. Unit 1 was shut down manually and cooled using remote manual relief 
valve operation and condensate booster pump, and control rod drive system 
pumps. Unit 2 was shut down and cooled for the first hour by the RCIC. After
depressurization, Unit 2 was placed in the RHR shutdown cooling mode with 
makeup water available from the condensate booster pump and control rod 
drive system pump. 

ADDITIONAL ACTIONS TO BE TAKEN BY LICENSEES 

1.   Because the occurrence appears to have resulted from modifications 
     being made to an operating unit, all power reactors with operating 
     licenses should address the actions requested in Bulletin 75-04 as well 
     as the actions described below. 
     
2.   Review your policies and procedures relating to construction or c 
     maintenance and modification work to assure that activities which might
     affect the safety of a unit in operation, including the 
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IE Bulletin No. 75-04A            -2-                       Date: 4/3/75 

     ability to shut down and cool the unit are properly controlled. Your 
     review should consider particularly your policy on deferring 
     construction, maintenance or modification work on a unit until a 
     shutdown period except for emergency maintenance vital to continued 
     safe operation or safe shutdown of the unit. 

3.   Review your policies and procedures to assure that for construction or 
     modification and maintenance activities during plant operation, 
     particular attention is given to the following areas: 

     a)   The degree of safety significance of affected and nearby cabling 
          and piping. 

     b)   The use and control of combustible materials. 

     c)   The use and control of equipment that may be an ignition source. 

     d)   The assignment of personnel, knowledgeable of plant arrangement 
          and plant operations, whose sole temporary responsibility is 
          monitoring the safe performance of construction or maintenance and 
          modification work, including attention to otherwise unattended 
          areas adjacent to the work areas. 

     e)   Provision of installed or portable equipment to provide the 
          monitoring personnel with prompt communication with the  operating
          staff in the control room. 

     f)   Provision of adequate fire prevention and fire suppression 
          equipment, installed or portable, for the following locations: 

          (1)  Areas where work is being performed. 

          (2)  Areas where occurrence of a fire has high safety 
               significance, even though the probability of occurrence is 
               relatively small. 

     g)   Recognition that a fire, even one involving electrical equipment, 
          may, if of sufficient intensity require water as the ultimate 
          suppression medium. 

4.   Review your emergency procedures to assure that consideration for 
     alternate methods for accomplishing an orderly plant shutdown and 
     cooldown are provided in case of loss of normal and preferred 
     alternative shutdown and cooldown systems for any reason (e.g. a fire).
     In this connection, assure that the minimum 

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IE Bulletin No. 75-04A             -3-                      Date: 4/3/75 

     information necessary to assist the operators in such shutdown actions,
     the minimum protection system actions required (e.g. scram) and the 
     spectrum of alternative paths available to the operators to supply, 
     cooling water and remove decay heat dependent on plant conditions are 
     included in your emergency procedures. 

5.   Report to this office, in writing, within 20 days of the date of this 
     Bulletin, your schedule for review in each of the above areas. 

6.   Upon completion of your reviews, provide this office with the results 
     of these reviews and the schedule for accomplishment of any revisions 
     to your policies and procedures, and any proposed changes to the 
     facility, and the date by which the changes are scheduled to be 
     completed. If this latter date is more than 30 days after the date of 
     the initial report, provide a monthly summary report detailing your 
     progress in the review and/or proposed procedure or facility 
     modifications. Reports requested by Bulletin 75-04 may be incorporated 
     with the initial response to this Bulletin. 
Page Last Reviewed/Updated Tuesday, July 23, 2013