Information Notice No. 94-26: Personnel Hazards and Other Problems from Smoldering Fire-Retardant Material in the Drywell of a Boiling-Water Reactor


March 28, 1994

                               SMOLDERING FIRE-RETARDANT MATERIAL IN THE
                               DRYWELL OF A BOILING-WATER REACTOR


All holders of operating licenses or construction permits for nuclear power


The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert licensees to the potential for large amounts of thick, acrid
smoke to be produced from smoldering fire-retardant plastic sheeting.  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 are not
NRC requirements; therefore, no specific action or written response is

Description of Circumstances

On December 28, 1993, a fire occurred in the drywell of the Shoreham Nuclear
Power Station (Shoreham).  Shoreham, a boiling-water reactor with a Mark II
containment, is currently undergoing decommissioning.  The fire was caused by
hot slag that fell from the 137-foot elevation of the drywell where workers
were cutting a biological shield wall stabilizer support with an oxyacetylene
torch.  The hot slag dropped through an opening in the biological shield wall
onto paper toweling and a coil of hemp rope at the 102-foot elevation, setting
them on fire.  The burning rope subsequently dropped to the 78-foot level and
landed just below a temporary water collection system in the annulus space
between the lower portion of the reactor pressure vessel support pedestal and
the shield wall.  The collection system was constructed of rope and
fire-retardant plastic sheeting (Herculite and Griffolyn) and had been
installed to collect the runoff of potentially radioactive water expected from
cutting the shield wall.  The burning rope made the plastic sheeting smolder,
giving off a large quantity of thick, acrid smoke.  Because of the smoke, it
was difficult for personnel in the area to breathe and to see in which
direction to go to leave the drywell.

Workers in the area saw the smoke and alerted the control room to a suspected
fire.  The control room operators activated the plant fire brigade which
entered the drywell wearing self-contained breathing apparatus.  However, the
fire brigade was unable to locate the source of the smoke because the dense

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smoke blocked their vision.  To help locate the source, the fire brigade asked
the control room to place the reactor building normal ventilation system on
standby.  This action was not effective and the fire brigade leader informed
the control room that the fire brigade could not find the source of the smoke.
The control room operators called the local off-site fire department to help
find and suppress the fire.

The plant fire brigade made sure that all personnel had been evacuated from
the area and again searched for the source of the smoke.  The local fire
department entered the drywell to search for the fire and found some burnt
paper toweling and charred rope.  About this time, the smoke in the drywell
began to clear, apparently because the combustible material feeding the fire
had been consumed.  No flames were observed during the event.  The plant fire
brigade checked the area for ignition sources and found none.  The licensee
suspended work inside the drywell and continued to investigate.  The licensee
determined that the smoke had come from an approximately 5.5-square-meter
[60-square-foot] section of the plastic sheeting that made up the collection

The licensee determined that the fire had not harmed station equipment or
affected nuclear safety.  However, 11 personnel reported to the first aid
station suffering from smoke inhalation.  The licensee found the following
weaknesses in industrial safety practices:

Openings in the biological shield wall had not been covered to prevent
hot slag from passing through.

Fire protection measures were not adequately understood or were not
adequately specified in the fire permit.

The fire permit did not clearly assign responsibility to check the area
for combustible materials before cutting the structural support.

Workers were not required to look for day-to-day changes in the work
area, such as the presence of combustibles in vulnerable locations.


The plastic sheeting materials involved in this event are commonly used at
many nuclear power stations.  Although these materials are fire-retardant,
they are capable of generating large amounts of smoke when involved in or
exposed to a fire condition.  The total amount of material that was burned or
smoldered at Shoreham was small; however the smoke from the smoldering plastic
created significant hazards for personnel in the drywell and made it
impossible for the fire brigade to locate the source of the smoke.  Because of
the smoke, personnel in the drywell were unable to see in which direction to
go to exit the drywell or to avoid the fire.  Several of the plant personnel
suffered smoke inhalation.
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The Material Safety data Sheets for the Herculite and Griffolyn sheeting state
that those materials produce hydrogen chloride gas when burned and that
self-contained breathing apparatus should be worn when attempting to
extinguish fires involving these materials.  In addition to the hazard of
smoke inhalation, there is a potential for toxic side-effects from these
fires. Because these and similar plastic materials are routinely used at
nuclear facilities for contamination control, welding flash shields, and other
purposes, it is important to recognize that, if these materials are exposed to
or are involved in a fire, they generate a large quantity of smoke that
creates hazards for plant workers and may adversely affect plant operations or
fire-fighting efforts.  These problems are exacerbated in confined spaces or
in areas with limited ventilation.

This information notice requires no specific action or written response.  If
you have any questions about this matter, please contact one of the technical
contacts listed below or the appropriate Office of Nuclear Reactor Regulation
(NRR) project manager.

                      original signed by

Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation

Technical contacts:  R. L. Nimitz, RI
                     (215) 337-5267

                     F. L. Bower III, RI
                     (215) 337-5328

                     P. M. Madden, NRR
                     (301) 504-2854

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