Information Notice 2026-01, Degradation of Carbon Fiber Reinforced Polymer Composite Used for Piping Repair
| ML25251A088 | |
| Person / Time | |
|---|---|
| Issue date: | 01/09/2026 |
| From: | Philip Mckenna Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| IN-2026-01 | |
| Download: ML25251A088 (5) | |
ML25251A088 UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001
January 9, 2026
NRC INFORMATION NOTICE 2026-01: DEGRADATION OF CARBON FIBER REINFORCED
POLYMER COMPOSITE USED FOR PIPING
REPAIR
ADDRESSEES
All holders of an operating license or construction permit for a nuclear power reactor under
Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of
Production and Utilization Facilities, except those who have permanently ceased operations
and have certified that fuel has been permanently removed from the reactor vessel, and all
holders of a power reactor combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Plants.
All holders of or applicants for an early site permit, standard design certification, standard
design approval, manufacturing license, or combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees of the operating experience regarding the degradation of the carbon fiber reinforced
polymer (CFRP) composite that was installed for piping repair. It is expected that recipients will
review the information for applicability to their facilities and consider actions, as appropriate, to
avoid impacts to the operability of structures, systems, and components important to safety. INs
may not impose new requirements, and nothing in this IN should be interpreted to require
specific action.
DESCRIPTION OF CIRCUMSTANCES
In October 2021, at Arkansas Nuclear One, Unit 2, degradation was found in the CFRP
composite that was installed on the inner diameter of the circulating water return piping. The
purpose of the CFRP repair was to mitigate corrosion in the non-safety-related piping. In the
degraded condition, a portion of the CFRP composite was detached from the pipe and
entangled in a downstream screen, causing back pressure to build in the pipe. Some of the
material entangled in the screen was easily removed. However, one piece had to be broken
before removal.
Some sections of the topcoat were also found to be missing. In addition, the licensee found that
the CFRP composite was starting to delaminate at one of the terminal ends. The CFRP
composite for piping repair did not include a terminal-end compression ring. In CFRP composite
applications, the purpose of a terminal-end compression ring is to provide an extra layer of protection for damage to terminal ends by applying compressive forces between the composite
and the substrate (i.e., the base metal of the repaired piping).
DISCUSSION
A CFRP composite is composed of reinforcing carbon fibers saturated in a polymer matrix. In
piping repair using a CFRP composite to provide structural integrity or corrosion resistance, the
composite material is installed on site by wet lay-up and cure-in-place processes. The quality
and integrity of the CFRP repair depend on its material qualification, installation process, quality
control, verification testing for the installed composite, and inspections.
The specific piping associated with the operating experience presented above is
non-safety-related piping. However, when degradation of CFRP composites causes debonding
or delamination in non-safety-related piping, this may create a foreign material hazard with
potential impacts on the operability of safety-related systems and components that are relied
upon for plant safety.
Currently, there is no NRC staff-approved generic approach for CFRP repair in the American
Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code or code cases. The
NRC staff is working with ASME and industry stakeholders to develop a generically approved
approach for CFRP repair for ASME code class piping (e.g., development of a later version of
ASME Code Case N-871-1, Repair of Buried Class 2 and 3 Piping Using Carbon
Fiber-Reinforced Polymer Composite,Section XI, Division 1, to be included in Regulatory
Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1).
Within the past 10 years, the NRC staff received and approved licensees proposed alternatives
regarding the application of CFRP composite (also called CFRP repair system) for
safety-related piping. Of those approved, only one plant has installed the CFRP composite for
safety-related piping, and limited operating experience has not shown such degradation as
discussed above. This specific CFRP repair system (i.e., specific vendor, material, installation
process, etc.) has been also used in the piping systems of nonnuclear plants and municipal
water systems. In addition, this specific CFRP repair system has been used in nuclear plant
non-safety-related piping systems. The licensees operating experience evaluation of these
nonnuclear applications and nuclear plant non-safety-related applications further indicates that
there was no failure due to degradation associated with this specific CFRP repair system.
However, the operating experience related to the CFRP composite degradation in the
non-safety-related piping and the CFRP repair approach, which maintained the integrity of
piping repair, suggests that the following approaches are important to ensure the integrity of
CFRP repair systems:
Adequate materials (e.g., carbon fiber fabric and epoxy resin) are selected based on the
material qualification tests for tensile strength, tensile elastic modulus, bond strength, and glass transition temperature to ensure that the design criteria are met.
A proper installation process is conducted with quality control using in-process
inspections to ensure that qualified materials are used in the installation; the surface of
the substrate (host piping) is properly prepared and clean; the substrate pipe has a
proper thickness at the terminal end regions; the carbon fiber fabric is properly saturated with the polymer resin; and the installation temperature is monitored and controlled to
achieve the specified cure condition, degree of cure, and glass transition temperature.
Verification testing is performed by using witness panels or samples, which are prepared
at the installation and represent the installation process, to confirm that the properties of
the installed CFRP composite (e.g., tensile strength and modulus, degree of cure and
glass transition temperature) meet the design criteria.
Preservice and in-service inspections are conducted to ensure that the installed CFRP
composite does not have defects (e.g., matrix cracking, delamination, blisters, and wear)
that may affect the integrity of the CFRP repair, and the CFRP composite continues to
be free of degradation during the service.
Technical personnel involved in the CFRP repair installation have sufficient training and
qualification to adequately conduct the installation processes, including in-process and
quality control inspections.
Although this IN does not require specific actions of licensees, the approaches discussed above
can help to ensure that the CFRP repair maintains its structural integrity and performs its
intended functions.
Recently, the NRC staff used the agencys probabilistic risk assessment (PRA) software and
plant-specific Standardized Plant Analysis Risk models to evaluate the potential impact of CFRP
failures on plant systems and components. This risk analysis was conducted for sites where the
NRC staff has received and approved the proposed alternatives involving the application of
CFRP composite for safety-related piping. Analysts examined plant drawings, system
descriptions, and abnormal operating procedures for each plant to understand how specific
plant design specifications could mitigate potential failures.
The following insights were identified based on the NRCs review of the issue:
Verification testing, using witness panels to confirm that the margin between the cure
temperature and the glass transition temperature is sufficient, would reduce uncertainty
in the risk analysis.
Licensees that analyze the effects of potential failures of CFRP on downstream
components and systems, and how operators and systems would respond to such
failures, can identify vulnerabilities before installation.
CONTACT
S
Please direct any questions about this matter to the technical contacts listed below.
/RA/
Philip McKenna, Acting Director
Division of Reactor Oversight
Office of Nuclear Reactor Regulation
Technical Contacts: Ali Rezai, NRR
301-415-1328
301-415-8054 e-mail: Ali.Rezai@nrc.gov
e-mail: Ching.Ng@nrc.gov
301-415-2045 e-mail: Seung.Min@nrc.gov SUBJECT: NRC INFORMATION NOTICE 2026-01, DEGRADATION OF CARBON FIBER
REINFORCED POLYMER COMPOSITE USED FOR PIPING REPAIR
DATE: JANUARY 9, 2026
ADAMS Accession No.: ML25251A088 EPID No.: L-2025-GEN-0002
OFFICE
NRR/DNRL/NPHP
NRR/DNRL/NPHP
NRR/DRA/APOB
NRR/DNRL/NPHP
OCIO
NAME
SMin
ARezai
CNg
MMitchell
KBenney
DATE
9/19/2025
9/16/2025
9/17/2025
9/19/2025
12/18/2025 OFFICE
NRR/DRO/IOEB
NRR/DRA
NRR/DRO/IOEB
NAME
JPeralta
GSpaulding
RPascarelli
BBenney
DATE
12/16/2025
12/30/2025
9/19/2025
1/5/2026
12/30/25 OFFICE
NRR/DRO/
NAME
PMcKenna
DATE
12/30/25
1/9/2026