United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 92-46: Thermo-Lag Fire Barrier Material Special Review Team Final Report Findings, Current Fire Endurance Tests, and Ampacity Calculation Errors

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

                              June 23, 1992


NRC INFORMATION NOTICE 92-46:  THERMO-LAG FIRE BARRIER MATERIAL SPECIAL
                               REVIEW TEAM FINAL REPORT FINDINGS, CURRENT 
                               FIRE ENDURANCE TESTS, AND AMPACITY                                      CALCULATION ERRORS


Addressees

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

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to inform addressees of (1) the findings of the NRC's Thermo-Lag
Special Review Team, (2) current Thermo-Lag 330 fire resistance testing
being conducted by Texas Utilities (TU) and Thermal Science, Inc. (TSI),
and (3) errors found in the calculation of cable ampacity derating factors
for Thermo-Lag fire resistive barriers.  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 required. 


Discussion

FINAL REPORT BY THE SPECIAL REVIEW TEAM FOR THE REVIEW OF THERMO-LAG FIRE
BARRIER PERFORMANCE

The NRC has been reviewing the qualification of Thermo-Lag 330-1 fire
barrier systems.  The NRC previously issued two information notices on
these fire barrier systems: (1) Information Notice 91-47, "Failure of
Thermo-Lag Fire Barrier Material to Pass Fire Endurance Test," August 6,
1991, and (2) Information Notice 91-79, "Deficiencies in the Procedures
for Installing Thermo-Lag Fire Barrier Materials,"  December 6, 1991.

On February 12, 1992, the NRC's Special Review Team for the review of
Thermo-Lag fire barrier performance met with the Nuclear Utilities
Management and Resources Council (NUMARC) to discuss the coordination of
the industry's response to Thermo-Lag fire endurance, installation, and
ampacity concerns.  During the meeting, the staff provided NUMARC a
proposed draft generic letter on the Thermo-Lag fire barrier issue for
review and comment.  The draft generic letter was included in the meeting
minutes which were placed in the Public Document Room as an enclosure to
a February 24, 1992, letter to NUMARC.  In a letter of March 3, 1992,
NUMARC commented on the proposed draft generic

9206150492.

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letter and committed to coordinate the industry's efforts associated with
the issues involving Thermo-Lag.  In addition, NUMARC requested that the
NRC make available any additional information on the qualification of
these barriers.  

In response to this request, the NRC provided NUMARC the "Final Report-
Special Review Team for the Review of Thermo-Lag Fire Barrier
Performance," of April 21, 1992, (Attachment 1).  The final report
concluded that some licensees have not adequately reviewed and evaluated
the fire endurance and ampacity test results for applicability to the
Thermo-Lag fire barrier systems installed in their facilities.  In
addition, the final report stated that some facilities have used
inadequate installation procedures to construct Thermo-Lag fire barriers
on electrical raceways and equipment.  

CURRENT THERMO-LAG 330-1 FIRE BARRIER ENVELOPE TESTING

As a result of the concerns in Information Notices 91-47 and 91-79, TU
instituted a fire endurance testing program to qualify the Thermo-Lag fire
barrier protective system specifically for its Comanche Peak Steam
Electric Station.  This testing was conducted during the weeks of June 15
and 22, 1992.  The NRC witnessed the preparation of test specimens and the
actual testing of the TU electric test articles.

The tests consist of a series of 1-hour fire endurance tests on a variety
of cable tray and conduit "mock-ups".  The "mock-ups" were designed to
duplicate actual plant configurations.  TU installed the fire barriers
using stock material and actual plant procedures and personnel.  

The first actual tests occurred on June 17, 1992.  Three-quarter-inch, and
one-inch and five-inch conduit configurations were tested.  All tests
passed American Nuclear Insurers criteria, in that electrical cable
continuity was not lost.  However, several temperature readings were above
specifications for the 3/4-inch and 1-inch conduit tests, and for a
junction box that was common to all the conduits.  Additionally,
subsequent investigation of the cabling revealed evidence of charring and
blistering.  NRC standards require that the protected components be free
of fire damage.

Preliminary information from the second test of a 12-inch cable tray
configuration on June 18, 1992, showed satisfactory results.  Thermocouple
temperatures on the protected cables were less than 325 �F.  

The third test was conducted on June 19, 1992.  This article was a wide 
(30-inch) ladder back cable tray configuration.  At 17 minutes into the
test, the Thermo-Lag panel on the bottom of the test article began to sag
and the stainless steel banding was carrying the load of the panel.  At
18 minutes, the joint at the interface between the tray support and the
tray showed signs of weakening and separation.  Internal temperatures
within areas of this cable tray assembly exceeded 325 �F at 25 minutes. 
The joint fully separated in 41 minutes resulting in cable circuit
integrity failure and fire damage to the cables.
.

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TU has established roving fire watches for Unit 1, in accordance with its
Fire Protection Manual.  The roving fire watches cover plant areas where
Thermo-Lag fire barrier configurations, similar to those which failed, are
used to provide a fire endurance barrier for safe-shutdown equipment.

TSI is also instituting a fire endurance testing program.  This program
includes testing a new installation technique required for cable trays
installed with gap widths greater than 0.030 inches.  The new seam joining
technique requires that either (1) stainless steel tie wires be placed
through the stress skin at specified intervals or (2) stress skin and a
layer of Thermo-Lag trowel grade material be placed over the entire seam
length and banded in place.  Preliminary results of a June 9, 1992, test
using the new seam joining technique (on seams without wide gaps) on a 36-
inch cable tray system and a 3/4-inch conduit assembly were considered
successful by the vendor and testing laboratory.   

The NRC will provide additional information on these fire endurance
testing programs as it becomes available.

AMPACITY DERATING CALCULATION ERROR

In April 1992, the Washington Public Power Supply System, the licensee for
Washington Nuclear Project, Unit 2, found a mathematical error in the
calculation of the ampacity derating factor for the Thermo-Lag fire
barrier enclosure of cable trays in Industrial Testing Laboratories (ITL)
Incorporated Test Report ITL-82-5-355C.  The error occurred when ITL
adjusted the test current to baseline temperatures of 40 �C ambient and
90 �C cable.  This adjustment is required when tests are performed at
different ambient and cable temperatures. ITL used the correct equation
for adjusting to temperature parameters that differ from the Insulated
Cable Engineers Association (ICEA) publication P-46-426: I- = I X MF
(where "I" is at 40 �C ambient and 90 �C cable temperature, and "I-" is
at other ambient and cable temperature conditions).  However, in
calculating "I," ITL multiplied "I-" by "MF" instead of dividing.  The NRC
determined that the ampacity derating factor will change from 18 to 
33 percent when the mathematical error is corrected.  While reviewing
other ITL test reports, the NRC staff found similar errors in other
calculations performed by ITL in the adjustment equation for ambient and
cable temperature conditions.  The NRC also noted that the baseline
currents obtained from the test vary widely (up to 32 percent) from those
published in the ICEA publication P-54-440.  
.

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




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


Technical contacts:  Ralph Architzel, NRR
                     (301) 504-2804

                     Patrick Madden, NRR
                     (301) 504-2854

Attachments:
1.  "Final Report - Special Review Team for the Review of Thermo-Lag Fire
      Barrier Performance," April 21, 1992
2.  List of Recently Issued NRC Information Notices

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Page Last Reviewed/Updated Tuesday, November 12, 2013