Information Notice No. 92-17: NRC Inspections of Programs Being Developed at Nuclear Power Plants in Response to Generic Letter 89-10
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
February 26, 1992
NRC INFORMATION NOTICE 92-17: NRC INSPECTIONS OF PROGRAMS BEING DEVELOPED
AT NUCLEAR POWER PLANTS IN RESPONSE TO
GENERIC LETTER 89-10
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 alert addressees to the general conclusions derived from the NRC
inspections of the programs being developed at nuclear power plants in
response to Generic Letter (GL) 89-10, "Safety-Related Motor-Operated Valve
Testing and Surveillance." 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.
Background
In GL 89-10 (June 28, 1989), the NRC staff requested that holders of nuclear
power plant operating licenses and construction permits ensure the
capability of motor-operated valves (MOVs) in safety-related systems by
reviewing MOV design bases, verifying MOV switch settings initially and
periodically, testing MOVs under design basis conditions where practicable,
improving evaluations of MOV failures and necessary corrective action, and
determining trends of MOV problems. The NRC staff requested that licensees
complete the GL 89-10 program by the end of the third refueling outage or 5
years from the issuance of the generic letter, whichever is later. On June
13, 1990, the NRC staff issued Supplement 1 to GL 89-10 to provide detailed
information on the results of public workshops held to discuss the generic
letter. On August 3, 1990, the NRC staff issued Supplement 2 to GL 89-10 to
allow licensees additional time to review and to incorporate the information
provided in Supplement 1 into their programs in response to the generic
letter. Upon reviewing the results of NRC-sponsored MOV tests, the NRC
staff issued Supplement 3 to GL 89-10 on October 25, 1990, which requested
licensees of boiling water reactor (BWR) nuclear plants to take action in
advance of the GL 89-10 schedule to resolve concerns about the capability of
MOVs used for containment isolation in the steam supply line of the high
pressure coolant injection and reactor core isolation cooling systems, in
the supply line of the reactor water cleanup system, and in other systems
directly connected to the reactor vessel. In
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Supplement 4 to GL 89-10, the NRC staff indicated that BWR licensees need
not address inadvertent MOV operation in their GL 89-10 programs. The NRC
staff is considering whether or not similar actions should be taken
regarding the need for licensees of pressurized-water reactor (PWR) nuclear
plants to address the inadvertent operation of MOVs in their programs to
respond to GL 89-10.
Description of Circumstances
The NRC staff has conducted inspections at more than 30 nuclear power plant
sites of programs being developed by licensees in response to GL 89-10. The
reports of those inspections are available in the NRC Public Document Room.
In performing the inspections, the NRC staff has followed Temporary
Instruction (TI) 2515/109 of January 14, 1991, "Inspection Requirements for
Generic Letter 89-10, Safety-Related Motor-Operated Valve Testing and Sur-
veillance." Part 1 of TI 2515/109 provides guidance for reviewing the
program being established by the licensee in response to GL 89-10, and Part
2 provides guidance for reviewing program implementation. The NRC has
focused these inspections on reviewing the GL 89-10 programs (Part 1 of TI
2515/109). The staff is issuing this information notice to provide the more
significant results of those NRC inspections.
In GL 89-10, the NRC staff requested that licensees prepare descriptions of
their programs established in response to GL 89-10 within 1 year after the
generic letter was issued or by the first refueling outage after December
28, 1989, whichever was later. The NRC staff's response to Question 44 in
Supplement 1 to GL 89-10 provided guidance on information expected in the
program descriptions. The NRC inspectors found some licensees to have
program descriptions that are thorough while other licensees did not.
Attachment 1 is a discussion of the inspection findings pertaining to the
recommendations of GL 89-10.
Related Generic Communications
In addition to NRC Generic Letter 89-10, "Safety-Related Motor-Operated
Valve Testing and Surveillance," and its supplements, the NRC has addressed
this and related topics in NRC Information Notices 89-88, "Recent
NRC-Sponsored Testing of Motor-Operated Valves;" 90-40, "Results of
NRC-Sponsored Testing of Motor-Operated Valves;" 90-72, "Testing of Parallel
Disc Gate Valves in Europe;" and 91-61, "Preliminary Results of Validation
Testing of Motor-Operated Valve Diagnostic Equipment."
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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
the technical contact 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 contact: Thomas G. Scarbrough, NRR
(301) 504-2794
Attachments:
1. Inspection Findings Pertaining to the Recommendations Contained In
Generic Letter 89-10
2. List of Recently Issued NRC Information Notices
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Attachment 1
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INSPECTION FINDINGS PERTAINING
TO THE RECOMMENDATIONS CONTAINED IN GENERIC LETTER 89-10
Administration
Some licensees have not ensured adequate management oversight and direction
for the motor-operated valve (MOV) program. One licensee had contracted an
internal audit that revealed problems with the MOV program similar to those
found subsequently during the NRC inspection, but the licensee had not taken
action to correct the deficiencies. The safety significance of the MOV
program and the extensive resources needed to develop and implement the
program make it imperative that licensee's management closely monitor its
staff's activities.
Scope
In issuing Generic Letter (GL) 89-10, the NRC staff intended that the scope
include all safety-related MOVs and other MOVs in safety-related systems.
In Supplement 1 to GL 89-10, the NRC staff limited the scope of GL 89-10 to
safety-related MOVs and other MOVs that are position-changeable in safety-
related piping systems, as well as safety-related MOVs that might be in non-
safety-related piping systems. The NRC staff's response to Questions 3-13
in Supplement 1 to GL 89-10 provided further guidance on the scope of
GL 89-10. For example, in the NRC staff's response to Question 4 in
Supplement 1, the staff defined "position-changeable" as any MOV in a
safety-related piping system that is not blocked from inadvertent operation
from the control room. In Supplement 4 to GL 89-10, the NRC staff indicated
that licensees for boiling water reactor (BWR) plants need not address
inadvertent MOV operation in their GL 89-10 programs. The NRC staff is
considering whether or not similar actions should be taken regarding the
need for the licensees of pressurized-water reactor (PWR) plants to address
inadvertent MOV operation in their programs to respond to GL 89-10.
The NRC inspectors found most licensees to be establishing the scope of
their GL 89-10 programs consistent with the recommendations of the generic
letter. However, some licensees needed to improve the documentation of
their justification for excluding particular MOVs from the GL 89-10 program.
Design-Basis Reviews
In recommended action "a" of GL 89-10, the NRC staff requested the licensees
to review and document the design basis for operating each MOV within the
generic letter program to determine the maximum differential pressure and
flow (and other factors) expected for both normal operations and abnormal
conditions. The NRC staff's response to Questions 14 to 18 and 36 in
Supplement 1 to GL 89-10 provides guidance on performing design-basis
reviews under GL 89-10.
Many licensees are appropriately reviewing plant documentation such as the
final safety analysis report and the technical specifications as part of
their design-basis reviews. However, some licensees had failed to identify
worst-case conditions for various design-basis scenarios. Some licensees
have
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assumed nominal reactor pressure for differential pressure across MOVs in
lines directly connected to the reactor vessel without evaluating whether
this differential pressure bounds the worst-case MOV design-basis
differential pressure. At certain facilities, the licensee found errors in
the previous design basis determinations for many MOVs that would have
affected the capability of the MOVs to perform their safety function if
called upon under design-basis conditions.
Some licensees focused on differential pressure and had not adequately ad-
dressed other design-basis parameters such as flow, fluid temperature,
ambient temperature, and the effects of seismic and dynamic events.
Although differential pressure is the primary design-basis parameter used to
predict the thrust requirements in the industry's equations, the other
design-basis parameters are needed to ensure that the test results
demonstrate that the MOV would operate under design-basis conditions. Some
licensees have not ensured that generic studies of design-basis differential
pressure apply to specific plants.
MOV Sizing and Switch Settings
In recommended action "b" of GL 89-10, the NRC staff requested licensees to
review and revise, as necessary, the methods for selecting and setting all
MOV switches. The NRC staff's response to Questions 19-21 in Supplement 1
to GL 89-10 provides guidance on selecting and setting MOV switches.
The recommendations of GL 89-10 for selecting and setting MOV switches apply
to switches for torque, torque bypass, limit, and thermal overload. The
licensees are using various methods to determine the proper size of MOVs and
their appropriate torque switch settings. Some licensees have increased the
valve factors assumed in the industry's equations used to predict the thrust
required to operate the valves to reflect experience throughout the industry
and at their specific plant. However, other licensees continue to use old
guidance from valve vendors and manufacturers in estimating the thrust
requirements that may be found inadequate during design-basis tests.
The NRC inspectors found that licensees for various facilities had not done
the following when establishing methods to size MOVs and set their switches:
(1) Provide justification for assumptions regarding stem friction
coefficients and changes in stem friction over the lubrication interval
(2) Consider effects that can reduce the thrust delivered by the motor
operator under high differential pressure and flow conditions in
relation to the thrust delivered under no-load conditions
(3) Consider the effects of ambient temperature on motor output and thermal
overload sizing
(4) Demonstrate applicability of industry's databases in predicting thrust
requirements
(5) Consider inertia in establishing the maximum settings for torque
switches
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(6) Demonstrate applicability of contractors' studies of actuator
capability
(7) Demonstrate applicability of generic motor curves for specific motors
(8) Provide justification for removing conservatisms (such as the
application factor) from the industry's standard sizing calculations
(9) Consider torque switch repeatability
(10) Consider uncertainties regarding the accuracy of MOV diagnostic
equipment.
Some licensees have had problems in performing MOV sizing and switch setting
calculations because of (1) incorrect spring packs installed in MOVs,
(2) incorrect MOV data on the motor or actuator nameplates and in the
procurement documents from the vendor, and (3) spring packs with different
performance characteristics from different manufacturers, but with the same
part number.
One licensee determined that the MOV sizing and switch setting activities to
establish motor operator capability had not adequately addressed the effect
of those activities on other MOV safety functions. These activities had
hindered the ability of the clutch of certain MOVs to be released to enable
the MOV to be manually operated in the event of an evacuation of the control
room.
Many licensees are updating their degraded voltage studies to ensure that
the worst-case minimum voltage available at the motor has been determined
for each MOV. Some licensees had not ensured that their assumptions of
minimum voltage available at the MOVs were consistent with their licensing
commitments in safety analyses. Some licensees did not justify the
assumptions for the starting point for the degraded voltage calculations,
current used to calculate cable losses, losses caused by the resistance of
thermal overload devices in the circuit, or the effects on MOV stroke time
under degraded voltage conditions. Of particular significance, the
inspectors found one licensee to be assuming an excessively small
locked-rotor power factor (0.2) in the motor for use in the calculation of
voltage drop from the motor control center to the MOV. The licensee's
selection of this power factor was based on guidance in an Institute of
Electrical and Electronics Engineers' standard that was not applicable to
the size of motors typically used to operate valves in nuclear power plants.
The assumption of an excessively small power factor causes an
underestimation of the cable voltage drop and may result in the
overestimation of MOV capability under design-basis conditions.
Licensees are improving their documentation of current and required MOV
switch settings, but some weaknesses remain. For example, one licensee had
simplified its control over changes to torque switch settings to expedite
the process but, in so doing, caused the concern that the quality assurance
department may not participate adequately in accepting those changes. Some
of the weakness in documenting torque switch settings appears to result from
the difficulty in reading the switches. Some licensees have raised torque
switch settings for MOVs above the manufacturer's maximum specified value
without performing an adequate safety analysis in accordance with the
requirements of 10 CFR 50.59.
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Design-Basis Differential Pressure and Flow Testing
In recommended action "c" of GL 89-10, the NRC staff requested licensees to
test MOVs within the generic letter program in situ under their design-basis
differential pressure and flow conditions. The NRC staff allows alternate
methods to be used to demonstrate the capability of the MOV if testing in
situ under those conditions is not practicable. The NRC staff suggested
that the licensees follow a two-stage approach for a situation in which
design-basis testing in situ is not practicable and the licensees could not
justify an alternate method of demonstrating MOV capability. In performing
the two-stage approach, a licensee would evaluate the capability of the MOV
using the best data available and then would obtain applicable test data
within the schedule of the generic letter. The NRC staff's response to
Questions 22-32 and 37 in Supplement 1 to GL 89-10 provides guidance on
design-basis testing and the two-stage approach.
Many licensees have committed to test MOVs within the scope of their GL
89-10 program under design-basis conditions, where practicable. Some
licensees have indicated that most MOVs can be tested at or near
design-basis conditions. Other licensees (primarily those of BWR plants)
estimate that a much smaller percentage of MOVs can be tested at or near
design-basis conditions. These licensees have not thoroughly evaluated the
ability to conduct MOV tests under design-basis or maximum achievable
conditions.
Licensees who have begun differential pressure and flow testing have found
some MOVs to require more thrust to operate than predicted by the industry's
standard equation with typical valve factors (such as 0.3 for flexible wedge
gate valves) assumed in the past. For example, the Alabama Power Company,
the licensee of the Joseph M. Farley Nuclear Plant, found less than half of
the 55 flexible wedge gate valves tested under differential pressure and
flow conditions to have their thrust requirements bounded by the industry's
standard equation with a 0.3 valve factor. The industry's test results
confirm the conclusions of NRC-sponsored MOV research that the industry's
past methods of determining the size of MOVs and setting their torque
switches were inadequate for some MOVs.
The NRC staff has found weaknesses in the licensees' procedures for
conducting the differential pressure and flow tests, the acceptance criteria
for the tests in evaluating the capability of the MOV to perform its safety
function under design-basis conditions, and the process for incorporating
the test results into the methodology used by the licensee in predicting MOV
thrust requirements. The NRC regulations and the plant's technical
specifications (TS) establish requirements for licensees' actions and
reporting when safety-related equipment is determined to be, or has been,
unable to perform its safety functions. Some licensees did not appear aware
of their obligations to address MOV operability following testing performed
under their programs established in response to GL 89-10. For example, some
licensees have not been evaluating the results of MOV tests to verify the
capability of the tested MOVs to perform their safety functions under
design-basis conditions and to evaluate the adequacy of their methodology to
size and set other MOVs. Some licensees appeared to discard test data as
suspect without careful evaluation. The NRC
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staff has also found a lack of coordination among licensees in disseminating
and using MOV test data. For example, some licensees are not considering
tests conducted by other licensees which might reflect on the adequacy of
their assumptions in predicting thrust requirements.
For MOVs that cannot be tested under design-basis differential pressure and
flow conditions, the NRC inspectors have found that some licensees are not
following their commitments to the two-stage approach (discussed in
Supplement 1 to GL 89-10) to test those MOVs at the maximum differential
pressure and flow achievable. If the test pressure and flow are near to the
design-basis conditions, the licensee may be able to justify extrapolating
from the test results to demonstrate the capability of the MOV to perform
its safety function under design-basis conditions. Where the MOV cannot be
tested near design-basis conditions, the licensee can use the results of the
test at maximum achievable conditions to help confirm valve factor
assumptions in its sizing and switch setting methodology and to set the MOV
using the best available data. The licensee may also find TS actions and
reporting requirements that take effect as a result of tests of MOVs at less
than full design-basis differential pressure and flow conditions if those
tests reveal that the MOVs could not perform their safety functions under
design-basis conditions.
Testing MOVs at maximum achievable conditions is especially helpful in
establishing a plant-specific database if the licensee estimates that only a
small percentage of MOVs can be tested at or near design-basis conditions.
Some licensees who, in their initial response to GL 89-10, committed to
implement the recommendations of GL 89-10 to test MOVs where practicable
have indicated an interest in grouping certain MOVs to reduce the amount of
testing (although testing of those MOVs would be practicable). Item l. of
GL 89-10 states that licensees shall submit any changes to scheduled
commitments, and that revised schedules or alternative actions may be
implemented without NRC approval with justification retained on site.
In their initial responses to GL 89-10, some licensees stated that they
would attempt to group MOVs to limit the extent of design-basis testing.
The preliminary results of design-basis tests at several plants (for
example, Catawba, Farley, Oconee and Surry) indicated that apparently
identical MOVs performed significantly different under high differential
pressure and flow conditions. This could cause difficulty in grouping MOVs
in such a manner that a small sample of MOV tests can be used to demonstrate
that all MOVs can perform their safety functions under design-basis
conditions.
The motor operators for most gate valves are set to close on torque to
provide adequate leakage control. Licensees are attempting to develop a
method to ensure that MOVs closed using the limit switch meet the requisite
leakage limitations in safety analyses without causing an MOV overstress
condition.
Periodic Verification of MOV Capability
In recommended action "d" of GL 89-10, the NRC staff requested that
licensees prepare or revise procedures to ensure that adequate MOV switch
settings are
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determined and maintained throughout the life of the plant. In paragraph
"j" of GL 89-10, the NRC staff recommended that the surveillance interval be
based on (1) the safety importance and (2) the maintenance and performance
history of the MOV, but that the interval not exceed 5 years or 3 refueling
outages, whichever is later. Further, the staff stated that the capability
of the MOV should be verified if the MOV is replaced, modified, or
overhauled to an extent that the existing test results do not represent the
MOV. The NRC staff's response to Questions 33-35 and 38 in Supplement 1 to
GL 89-10 provides guidance on periodically verifying MOV switches and
performing tests after completing maintenance.
The recommendation of GL 89-10 for verifying periodically the adequacy of
MOV switch settings includes torque, torque bypass, limit, and thermal
overloads. Many licensees have stated that they will attempt to use tests
of MOVs with diagnostic equipment under zero differential pressure and flow
conditions (static conditions) to demonstrate the adequacy of torque switch
settings and the continued capability of MOVs to perform their safety
functions under design-basis conditions. However, to date, none of those
licensees have provided justification for applying the results of tests
conducted under static conditions to demonstrate design-basis capability.
These licensees appear to be waiting on yet to be developed generic
justification for static or low differential pressure and flow testing.
At least one licensee indicated an intent to clean and lubricate the valve
stem before performing periodic verification testing. This would be
inconsistent with demonstrating that the MOV had been set adequately and was
capable of performing its function at the end of the test interval.
In GL 89-10, the NRC staff stated that testing at design-basis conditions
need not be repeated unless the MOV is replaced, modified, or overhauled to
the extent that the licensee considers that the existing test results are
not representative of the MOV in its modified configuration. Many licensees
are improving their methods to demonstrate that the MOVs are capable of
performing their safety functions under design-basis conditions following
maintenance.
MOV Failures, Corrective Actions, and Trending
In recommended action "h" of GL 89-10, the NRC staff requested that
licensees analyze or justify each MOV failure and corrective action. The
staff also requested that the documentation include the results and history
of each as-found deteriorated condition, malfunction, test, inspection,
analysis, repair, or alteration. The staff noted that the licensee must
retain and report all documentation in accordance with the plant's
requirements. The staff also suggested that the material be examined every
2 years or after each refueling outage after the program is implemented as
part of the monitoring and feedback effort to establish trends of MOV
operability. These trends could provide the basis on which the licensee can
revise the testing frequency established to verify periodically that the MOV
has adequate capability. The NRC staff indicated that the system should be
well-structured and should track, capture, and share history data on
individual components. The NRC staff's response to Questions 39 and 40 in
Supplement 1 to GL 89-10 provides guidance on identifying trends of MOV
problems.
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The NRC inspectors have found some licensees to have weaknesses in
evaluating MOV failures and deficiencies (such as the operability effects of
spring pack relaxation). Some licensees have not been thorough in
performing root cause analyses of MOV problems. Most licensees are
attempting to improve their methods for identifying trends in MOV problems.
Schedule
In GL 89-10, the NRC staff requested that, by June 28, 1994, or by the third
refueling outage after December 28, 1989, whichever is later, licensees com-
plete all design-basis reviews, analyses, verifications, tests, and
inspections that were initiated in order to satisfy the actions recommended
in the generic letter. The NRC staff's response to Question 41 in
Supplement 1 to GL 89-10 provides guidance on the schedule for implementing
these actions specified in GL 89-10.
Some licensees have not made adequate progress for resolving the MOV issue
for their facilities within the recommended schedule of GL 89-10. The
findings of licensees as they begin to initiate their programs in response
to GL 89-10 and the results of the NRC inspections of GL 89-10 programs
reinforce the importance of promptly resolving this safety-significant
issue. The NRC staff has accepted limited extensions of the GL 89-10
schedule for particular licensees who have provided justification.
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