Information Notice No. 95-27: NRC Review of Nuclear Energy Institute, "Thermo-Lag 330-1 Combustibility Evaluation Methodology Plant Screening Guide"
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
May 31, 1995
NRC INFORMATION NOTICE 95-27: NRC REVIEW OF NUCLEAR ENERGY
INSTITUTE,
"THERMO-LAG 330-1 COMBUSTIBILITY
EVALUATION METHODOLOGY PLANT
SCREENING GUIDE"
Addressees
All holders of operating licenses or construction permits for
nuclear power plants.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this
information notice to inform addressees of the results of NRC
staff review of the Nuclear Energy Institute (NEI) "Thermo-Lag
330-1 Combustibility Evaluation Methodology Plant Screening
Guide." It is expected that recipients will review the
information for applicability to their facilities and consider
actions as appropriate. However, suggestions contained in this
information notice are not NRC requirements; therefore, no
specific action or written response is required.
Background
On December 15, 1992, NRC issued IN 92-82, "Results of Thermo-Lag
330-1 Combustibility Testing." On the basis of its review of
Thermo-Lag combustibility tests conducted by the National
Institute of Standards and Technology (NIST), the NRC staff
concluded that Thermo-Lag 330-1 is a combustible material. NRC
fire protection requirements (Section III.G, Appendix R to 10 CFR
50) preclude the use of combustible materials to
(1) enclose other combustibles, such as cables, between redundant
safe shutdown trains to eliminate the combustibles as a fire
hazard or (2) provide radiant energy heat shield protection for
shutdown components inside containments. These types of
applications are the principal NRC staff concerns with respect to
the combustibility of Thermo-Lag 330-1.
Discussion
On October 12, 1993, the Nuclear Management and Resources Council
(NUMARC), now NEI, submitted for information to the NRC its
"Thermo-Lag 330-1 Combustibility Evaluation Methodology Plant
Screening Guide" (Accession No. 9310210224). In that report, NEI
stated that Thermo-Lag 330-1 may not necessarily be considered a
combustible material from a generic standpoint and recommended a
performance-based approach, using fire modeling techniques, to
evaluate the combustibility hazards presented by Thermo-Lag 330-1
installations.
9505240424. IN 95-27
May 31, 1995
Page 2 of 2
The NRC staff, with technical assistance from NIST, reviewed the
Thermo-Lag combustibility evaluation methodology prepared by
NEI. The results of the staff review, which was based on
existing NRC requirements and guidance, are detailed in the
attached letter of March 13, 1995, to NEI (Accession No.
9503200111). In summary, the staff informed NEI that it will not
accept the use of the NEI methodology to justify the use of
Thermo-Lag materials, or other materials such as fire retardant
plywood or cable jackets, as noncombustible where noncombustible
materials are specified by NRC fire protection requirements.
Alternatives to the NEI guide are discussed in the March 13,
1995, letter. The Commission approved the letter to NEI in a
staff requirements memorandum of March 8, 1995 (Accession No.
9505090025).
Related Generic Communications
Generic Letter (GL) 83-33, "NRC Positions on Certain
Requirements of Appendix R," October 19, 1983.
GL 86-10, "Implementation of Fire Protection
Requirements," April 24, 1986.
GL 86-10, Supplement 1, "Fire Endurance Test Acceptance
Criteria for Fire Barriers Systems Used to Separate
Redundant Safe Shutdown Trains Within the Same Fire
Area," March 25, 1994.
This information notice requires no specific action or written
response. If you have any questions about the information in
this notice, please contact the technical contact listed below or
the appropriate Office of Nuclear Reactor Regulation (NRR)
project manager.
/s/'d by BKGrimes
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor
Regulation
Technical contact: Pat Madden, NRR
(301) 415-2854
Attachments:
1. Letter of March 13, 1995, from C. McCracken, NRC,
to A. Marion, NEI, and its enclosures
2. List of Recently Issued NRC Information Notices
UNITED STATES Attachment 1
NUCLEAR REGULATORY COMMISSION IN 95-27
WASHINGTON, D.C. 20555-0001 May 31,1995
March 13, 1995
Mr. Alex Marion, Manager
Technical Division
Nuclear Energy Institute
1776 "I" Street, N.W., Suite 300
Washington, DC 20006-3706
SUBJECT: THERMO-LAG 330-1 COMBUSTIBILITY EVALUATION
METHODOLOGY PLANT SCREENING GUIDE
Dear Mr. Marion:
The Nuclear Regulatory Commission (NRC) staff has reviewed the
"Thermo-Lag 330-1 Combustibility Evaluation Methodology Plant
Screening Guide" that the Nuclear Management Resources Council,
now the Nuclear Energy Institute (NEI), submitted to the NRC by
letter dated October 12, 1993. The NEI guide provides a
performance-based approach, using fire modeling techniques, for
evaluating the combustibility hazards presented by Thermo-
Lag 330-1 installations.
In a Staff Requirements Memorandum (SRM) of June 27, 1994,
"Options for Resolving the Thermo-Lag Fire Barrier Issue," the
Commission approved the NRC staff recommendation to return plants
to compliance with existing NRC requirements and explained its
position with respect to the use of performance-based approaches
to resolve Thermo-Lag issues (see enclosed SRM). The staff found
that the NEI guide contains bases (interpretations) regarding
material combustibility and the use of combustible materials in
nuclear power plants that are not consistent with established
staff positions. The NRC staff responses to the NEI bases are
provided in Enclosure 2.
On the basis of its combustibility tests and review, the staff
concluded that Thermo-Lag 330-1 fire barrier material has
combustible characteristics similar to those of other nuclear
power plant combustible materials, such as fire-retardant plywood
and cable jackets. The staff also concluded that the NEI method
does not provide a level of fire safety equivalent to that
specified by existing NRC fire protection regulations and
guidelines. Therefore, the staff will not accept the use of the
NEI guide to justify the use of Thermo-Lag materials where
noncombustible materials are specified by NRC fire protection
requirements or to assess the combustibility hazards presented by
Thermo-Lag materials.
As an alternative to the NEI guide, the staff recommends that
licensees reevaluate their use of Thermo-Lag as radiant energy
heat shields inside the containment or as an enclosure to create
a 20-foot combustible-free zone between redundant trains and seek
other solutions. Examples of possible solutions include the
following: (1) reanalyze post-fire safe shutdown circuits inside
containment and their separation to determine if the
.A. Marion -2-
Thermo-Lag radiant energy shields are needed, (2) replace Thermo-
Lag barriers installed inside the containment with noncombustible
barrier materials, (3) replace Thermo-Lag barriers used to create
combustible-free zones with noncombustible barrier materials, (4)
reroute cables or relocate other protected components, or (5)
request plant-specific exemptions where technically justified.
For other Thermo-Lag applications, licensees, if they have not
already done so, should address the presence of the combustible
Thermo-Lag materials in the fire hazards analyses in accordance
with existing NRC fire protection guidance.
The NRC staff will inform the licensees of the results of its
review of the NEI methodology. If you have any questions, please
contact Mr. Steven West at 301-415-1220.
Sincerely,
ORIGINAL SIGNED BY
Conrad E. McCracken, Chief
Plant Systems Branch
Division of Systems Safety and
Analysis
Office of Nuclear Reactor
Regulation
Enclosures: As stated
. UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
June 27, 1994
MEMORANDUM TO: James M. Taylor
Executive Director for Operations
FROM: John C. Hoyle, Acting Secretary /s/
SUBJECT: SECY-94-127 - OPTIONS FOR RESOLVING THE
THERMO-LAG FIRE BARRIER ISSUES
The Commission (with all Commissioners agreeing) has approved the
continued use of Option 1, which requires compliance with
existing NRC requirements and permits plant-specific exemptions
where justified. The Commission does not intend to limit the
staff's consideration of requests for exemptions currently
permitted by regulations.
The Commission (with the Chairman and Commissioners Remick and de
Planque agreeing) requests that the staff, in consultation with
industry, consider possible new exemptions to Appendix R based on
state-of-the-art fire protection methodology and technology and
proceed to evaluate the feasibility of developing new guidance
for rating fire barriers on the basis of representative plant
fire hazards as described in Option 2. The responsibility for
developing the technical basis for any new exemptions should rest
with the licensees.
Commissioner Rogers disapproved proceeding with Option 2. In
particular, he felt the staff should not proceed with the
development of a Regulatory Guide in support of this option.
However, he did not object to the staff's initiating a research
project to investigate the feasibility of either developing
standard fire curves or using realistic fire loads. This
information would be applicable to a performance-based approach
to a fire protection rule.
The Chairman and Commissioner Rogers approved the staff
recommendation not to proceed with the development of a
performance-based approach to resolve the Thermo-Lag issue as
described in Option 3. They believe that the performance based
approach should be applied to support development of the fire
protection rule. Commissioner Remick and Commissioner de Planque
had no objection to pursuing Option 3 if the responsibility and
initiative came from industry.
The Commission (with all Commissioners agreeing) has approved the
staff recommendation to proceed as planned with the development
of a performance-based fire protection rule. This should be
pursued by the staff as part of its continuing program for
regulatory improvement and/or once a request for rulemaking is
received. The Commission felt that the new rule should not be
considered a means to resolve the Thermo-Lag issues.
cc: The Chairman
Commissioner Rogers
Commissioner Remick
Commissioner de Planque
OGC
OCA
OIG
Office Directors, Regions, ACRS, ACNW, ASLBP (via E-Mail)
Response by the Office of Nuclear Reactor Regulation
Plant Systems Branch
To Nuclear Energy Institute Interpretations
of Material Combustibility
Section 3.2, "Licensing Bases," of the "Thermo-Lag 330-1
Combustibility Evaluation Methodology Plant Screening Guide" that
Nuclear Energy Institute (NEI) submitted to the NRC by letter
dated October 12, 1993, provides NEI's bases for assessing
material combustibility. The following are the NRC staff
responses to the NEI bases.
1.0 Appendix R
1.1 NEI Basis
Appendix R does not provide a definition for combustibility. In
[Information Notice] 92-82, the NRC uses ASTM E136 as a test of
combustibility but there is no regulatory basis for the use of
this standard's criteria.
1.2 NRC Response
Appendix R does not address all aspects of nuclear power plant
fire protection programs. As stated in 10 CFR 50.48, each
operating nuclear power plant must have a fire protection plan
that satisfies GDC 3. Basic fire protection guidance is provided
in a number of NRC documents. Branch Technical Position (BTP)
APCSB 9.5-1 and its Appendix A was the basic fire protection
guidance used by the NRC staff to review the fire protection
programs of operating reactors at the time Appendix R was
promulgated. BTP APCSB 9.5-1 defined noncombustible materials as
"materials, no part of which will ignite and burn when subjected
to fire." This definition was also used in Regulatory Guide
1.120. For plants licensed after January 1, 1979, the staff used
Standard Review Plan (SRP) 9.5.1 to review nuclear power plant
fire protection programs. This guidance defined noncombustible
material as "[a] material which in the form in which it is used
and under the conditions anticipated, will not ignite, burn,
support combustion, or release flammable vapors when subjected to
fire or heat." The SRP definition was derived from National Fire
Protection Association (NFPA) Standard 220, "Standard on Types of
Building Construction." NFPA 220, which is referenced in the
SRP, defines noncombustible material as "[a] material which in
the form in which it is used and under the conditions
anticipated, will not ignite, burn, support combustion, or
release flammable vapors when subjected to fire or heat.
Materials which are reported as passing ASTM E136 � shall be
considered noncombustible materials." On this basis, the NRC
staff used the test methods specified in ASTM E136, an industry
consensus test standard, to assess Thermo-Lag combustibility. As
reported in Information Notice 92-82, the NRC staff concluded
that Thermo-lag 330-1 is combustible as defined in the
aforementioned NRC fire protection guidelines.
Enclosure 2
2.0 Thermo-Lag Combustibility
2.1 NEI Basis
With respect to the noncombustible radiant energy shield, BTP
CMEB 9.5-1 and BTP APCSB 9.5-1 essentially have the same
definition of combustible:
Combustible Material - material that does not meet the
definition of noncombustible.
Noncombustible Material - A material which in the form
in which it is used and under the conditions
anticipated, will not ignite, burn, support combustion,
or release flammable vapors when subjected to fire or
heat.
The important part of [the SRP] definition is "in the form in
which it is used and under the conditions anticipated." If the
physical geometry of the room (area) and the combustible loading
(including combustible material geometry) is such that Thermo-Lag
will not be ignited under the conditions anticipated then
Thermo-Lag can be considered non-combustible.
2.2 NRC Response
The intent of the SRP definition is to focus material
combustibility evaluations on the form in which the material is
used and the conditions anticipated. For example, steel plate,
when subjected to ASTM E136 test, would not ignite, burn, support
combustion, or release flammable vapors. However, steel wool
would ignite and burn.
The results of the NEI tests, ASTM E1321, "Lateral Ignition and
Flame Travel Test," and ASTM E1354, "Cone Calorimeter Test" are
used to determine specific combustion characteristics of a
material. The NEI tests determined the ignition temperature and
the heat release rates of Thermo-Lag 330-1. These combustible
characteristics are similar to those of other nuclear power plant
combustible materials, such as fire-retardant plywood and cable
jackets. Therefore, the staff expects that when exposed to a
postulated fire using the fire loadings, potential heat release
rates of the known combustibles, and predicted fire severities of
representative nuclear power plant areas, Thermo-Lag 330-1
material would release flammable vapors, ignite, and burn. In
fact, it is by burning that Thermo-Lag provides its fire
resistive capabilities.
3.0 Generic Letter 86-10
3.1 NEI Bases
With respect to intervening combustibles, Generic Letter (GL) 86-
10 provides the following guidance:
For fire protection, "no intervening combustible" means
that there is no significant quantity of in-situ
materials which will ignite and burn located between redundant
shutdown system. The amount of such combustibles that has
significance is a judgmental decision.
Generic Letter 86-10 provides further guidance when discussing
factors to consider when dealing with negligible combustibles.
In Section 3.6.1 of GL 86-10 the NRC provides the following
response as an allowable justification:
"The likely fire propagation direction of burning
intervening combustibles in relation to the location of
the vulnerable shutdown division should be considered."
Therefore, if a material such as Thermo-Lag will neither ignite
nor propagate a fire (self extinguishes) between the two paths of
safe shutdown equipment separated by the "20-ft separation" then
the material can be considered a negligible quantity of
intervening combustible and the requirements of Appendix "R" or a
plant's specific license are satisfied.
3.2 NRC Response
In GL 86-10, the NRC staff also stated that if more than a
negligible quantity of combustible materials (such as isolated
cable runs) exists between redundant shutdown divisions, an
exemption request should be filed. Moreover, the NRC stated that
the regulation is focused on the absence of in-situ exposed
combustibles and that there is no specific definition of no
intervening combustible. In GL 86-10, the NRC staff identified
cables in cable trays which are either open or fully enclosed and
cables coated with a fire retardant material as intervening
combustibles. On these bases, the staff concluded that
Thermo-Lag 330-1 material located between redundant safe shutdown
divisions should be considered an intervening combustible
material. Whether or not the amount of Thermo-Lag has
significance, could be determined by a licensee using the
guidance of GL 86-10 (and cited in the NEI guide). If the
licensee determines that the amount of Thermo-Lag has
significance, it could use guidance of GL 86-10 (and cited in the
NEI guide) to evaluate the technical merits of an exemption
request.
Page Last Reviewed/Updated Tuesday, March 09, 2021