Bulletin 75-04A: Cable Fire at Browns Ferry Nuclear Power Station
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
John G. Davis
Deputy Director for
Office of Inspection
Transmitted to Chairman Anders, 4/3/75, 9:55 a.m.
- 2 -
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
Assistant Directors, RL (6)
Assistant Directors, TR (4)
H. D. Thornburg, Chief, FSEB:IE
J. L. Crews, FSEB:IE
FADreher; GCGower; SEBryan; GHSmith; FSEB:IE
M. Meadows, Secretary, DDFO: IE
EDO Reading 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
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
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
g) Recognition that a fire, even one involving electrical equipment,
may, if of sufficient intensity require water as the ultimate
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
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, September 01, 2015