Information Notice No. 89-81: Inadequate Control of Temporary Modifications to Safety-Related Systems
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 6, 1989
Information Notice No. 89-81: INADEQUATE CONTROL OF TEMPORARY
MODIFICATIONS TO SAFETY-RELATED SYSTEMS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is intended to alert addressees to potential
problems resulting from inadequate control of temporary modifications to
safety-related systems in operating nuclear plants. 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 do not constitute NRC
requirements; therefore, no specific action or written response is required.
Description of Circumstances:
Several NRC design inspections of modifications to safety systems have
revealed instances in which the licensee's control of temporary
modifications to safety-related systems was inadequate. Specifically, these
inspections revealed that temporary modifications were not properly tracked,
were not documented in a timely fashion, and were not given a timely
technical review. The following findings from four inspections illustrate
these concerns.
Zion Nuclear Power Station, Unit 1 (50-295/88-03)
The inspection team reviewed the licensee's "Temporary Alteration Program"
for the installation of temporary modifications to the safety systems. This
program had the following weaknesses.
1. The program allowed immediate installation of a temporary modification
without a safety evaluation as required by 10 CFR 50.59. In accordance
with the procedural guidelines, detailed technical analysis was not
required for a temporary modification that was installed for less than
30 days. In addition, the program allowed the time frame for
performing the technical review to be extended to 60 days if the
temporary modifications were installed for use beyond 30 days. Thus,
the modification could remain technically unreviewed for 60 days, and
if the modification
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was cancelled within 30 days, it might never be analyzed. Because an
assessment of the individual and synergistic effects of 30-day modifi-
cations on the plant's safety systems was not performed, there was no
way of determining whether the safety of the plant had been compromised
by operating the systems with temporary modifications.
2. The program did not provide an effective system for tracking the
temporary modifications. As a result, many temporary modifications
remained installed for a long time without being analyzed.
3. The program did not provide any directive for timely marking of the
control room copies of the controlled set of drawings to reflect a
modified configuration of the system after the temporary modification
had been installed. Control room drawings that do not correctly
reflect the as-built plant configuration could impair the capability of
plant operators to troubleshoot problems and to operate the plant
safely.
Sequoyah Nuclear Plant, Units 1 and 2 (50-327/86-27 and 50-328/86-27)
Temporary modifications at the Sequoyah plant were performed through the
Temporary Alteration Control Form (TACF) program and associated
administrative procedures. The procedures addressed requirements for
generation of follow-up documentation, such as design change requests
(DCRs), which include a required detailed technical evaluation and also an
evaluation to determine the possible existence of an unreviewed safety
question. The inspection team reviewed the TACF program and a sample of the
temporary modifications installed through the TACF program. This program
had the following weaknesses.
1. The TACF program did not require a DCR to be issued for a temporary
modification that was expected to be removed within 60 days of
installation. Therefore, such modifications were not given the
detailed technical evalu-ation required by the DCR process. Such a
modification could remain unreviewed for 60 days, and if the
modification was cancelled within 60 days, it might never be analyzed.
Because an assessment of the individual and synergistic effects of
60-day modifications on the plant's safety systems was not performed,
there was no way of determining whether the safety of the plant had
been compromised by operating the systems with temporary modifications.
2. The TACF program was routinely used to make permanent changes in the
plant. The decision to use this temporary modification program for
installation of permanent modifications was made at the discretion of
station personnel without adequate guidance. Sometimes the decision
was based on merely whether the Engineering Department would be able to
provide a modification package in a timely fashion. This approach
resulted in many installations of permanent modifications without
appropriate engineering evaluations.
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3. The TACF program did not have an effective system for tracking
temporary modifications. This weakness resulted in installation of
many permanent changes in plant safety systems without the proper
safety evaluation and associated documentation. The program lacked
instructions for updating controlled copies of the control room
drawings in a timely manner to reflect installed temporary
modifications. These weaknesses resulted in many errors in the control
room drawings.
Enrico Fermi Atomic Power Plant, Unit 2 (50-341/89-200)
The inspection team reviewed the licensee's "Temporary Modification Program"
and a sample of the temporary modifications in detail. One modification was
installed during 1987 to silence a "high drywell temperature" alarm that was
triggered by steam leaking from a valve in the drywell area. The design
temperature of the drywell was 135 F but the actual ambient temperature was
about 200 F because of the steam leak. Since the leak could not be fixed
while at power, the temporary modification raised the alarm setpoint to
silence the alarm. The review of this modification revealed that the
licensee's evaluation was inadequate. The effects of higher drywell ambient
temperatures on various design attributes, including environmental
qualification of equipment in the vicinity, density compensation for the
filled instrument sensing lines of the reactor instrumentation passing
through the higher temperature area, and higher voltage drop in the cables
and wires as a result of higher ambient temperatures, were not evaluated.
Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (50-317/89-200 and
50-318/89-200)
The inspection team reviewed the licensee's "Temporary Modification Control"
procedure and a sample of the temporary modifications in detail. The team
found that the licensee's temporary modification program failed to ensure
the proper review of all modifications by the Plant Review Committee before
their installation into the plant, and that the program was not under
sufficient management oversight to minimize the number of temporary
modifications installed. The licensee's procedure permitted the shift
supervisor to install any temporary modification for up to 24 hours without
a technical review or a safety evaluation. Although the licensee's
technical specifications required that the Plant Review Committee review all
proposed changes or modifications to plant systems or equipment affecting
nuclear safety, the licensee's procedure allowed the installation of
temporary modifications for up to 14 days with interim approval from two SRO
licensed individuals, one of whom must be a shift supervisor. The temporary
modification tracking system was not being kept up to date.
Discussion:
It is important for licensees to evaluate the temporary modifications to
safety-related systems before implementing these modifications. The
evaluation includes
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verification that the modification will not have an adverse effect on the
plant's systems, equipment, or safety. Although licensees have generally
met the NRC requirements in 10 CFR 50.59, some licensees have not exercised
an adequate level of control for the activities associated with the
temporary modifications to safety-related systems, as illustrated in the
above-identified deficiencies.
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 contacts listed below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: E. V. Imbro, NRR
(301) 492-0954
S. V. Athavale, NRR
(301) 492-0974
J. R. Ball, NRR
(301) 492-0962
Attachment: List of Recently Issued NRC Information Notices
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Page Last Reviewed/Updated Friday, May 22, 2015