Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
April 3, 1989
TO: ALL HOLDERS OF LIGHT WATER REACTOR OPERATING LICENSES AND
CONSTRUCTION PERMITS
SUBJECT: GUIDANCE ON DEVELOPING ACCEPTABLE INSERVICE TESTING PROGRAMS
(GENERIC LETTER NO. 89-04)
BACKGROUND
Paragraph 50.55a(g) of 10 CFR Part 50, "Domestic Licensing of Production and
Utilization Facilities," requires that certain ASME Code Class 1, 2, and 3
pumps and valves be designed to enable inservice testing and that testing be
performed to assess operational readiness in accordance with the Section XI
requirements of the ASME Boiler and Pressure Vessel Code. The inservice
testing of ASME Code Class 1, 2, and 3 pumps and valves should be viewed as
one part of a broad effort to ensure operational readiness of equipment rather
than viewed in the narrow sense as compliance with 10 CFR 50.55a(g). The
intent of the testing is to detect degradation affecting operation and assess
whether adequate margins are maintained. While this letter has been written
to provide guidance reIative to meeting the requirements of 10 CFR 50.55a(g),
it is only one part of other ongoing industry and regulatory activities.
Recent efforts have been undertaken by the nuclear industry and NRC sponsored
research to provide information and techniques for enhanced assurance of
equipment operability. NRC staff concerns regarding equipment operability led
to the issuance of Bulletin 85-03, dated November 15, 1985, and Bulletin
85-03, Supplement 1, dated April 27, 1988. An expansion of the requirements
of this bulletin in the form of a generic letter is being considered by NRC.
In addition, NRC is considering rulemaking on IST to develop requirements to
address the inadequacies in the current scope and methods of testing per 10
CFR 50.55a(g).
Light Water Reactor (LWR) licensees have submitted to the NRC inservice
testing (IST) programs for pumps and valves pursuant to 10 CFR 50.55a(g). The
editions and addenda applicable to IST program intervals are outlined in 10
CFR 50.55a(g)(4). If the licensee believes that conformance with certain code
requirements is impractical, that conformance to the Code would cause
unreasonable hardship without a compensating increase in safety or that a
proposed alternative provides an acceptable level of quality and safety, 10
CFR 50.55a allows the licensee to request relief from the Code by notifying
the Commission and submitting infor-mation to support this determination.
Following the evaluation of this infor-mation, the Commission may grant relief
and may impose alternative requirements.
All IST programs contain requests for relief from various Code requirements.
In addition, the surveillance requirements of technical specification (T.S.)
4.0.5 for most plants state that this testing of pumps and valves must be
performed in accordance with ASME Section XI except where specific written
relief has been granted by the Commission. Because of the general nature of
the IST sections of the ASME Code which does not consider plant specific
designs and the resulting difficulty in complying with all the ASME Code
requirements, utilities frequently revise their programs as more experience
with IST is acquired. Programs at most plants are revised several times
during the
89033000105
. - 2 -
10 year interval between the program updates required by 10 CFR 50.55a. This
trend appears to be continuing even after the programs are updated at the end
of the first 10 year interval. The number of program revisions during these
10 year intervals resulted in the need for frequent review by the NRC of
licensee's proposed requests for relief from the ASME Section XI requirements
and required additional interaction by the NRC with utilities before a Safety
Evaluation Report (SER) could be issued.
Through reviews and inspections, the NRC staff has identified a number of
generic deficiencies that affect plant safety and have frequently appeared as
IST program-matic weaknesses. These programmatic weaknesses can be attributed
to a lack of understanding in the following areas: (1) Code testing
requirements, (2) technical specification requirements, and (3) acceptable
alternatives to Code requirements. In order to remedy these generic IST
deficiencies, to clarify the status of current programs with respect to
applicable T.S. and 10 CFR 50.55a requirements, and to alleviate the problem
with respect to review of program revisions, the NRC has established the
following guidance.
NRC GUIDANCE ON IST PROBLEMS AND IMPLEMENTATION OF IST PROGRAM/REVISIONS
A. Introduction
Together with the technical specification requirements, IST Programs are
intended to ensure the operational readiness of certain safety related pumps
and valves. The NRC staff has reviewed and has under review a number of
licensee IST programs and relief requests. Based on the review of these
programs, and on recent IST inspections, the staff has identified a number of
generic deficiencies that potentially affect plant safety. These weaknesses
adversely impact the basic objective of the ASME Code, Section XI, IST
requirements. Attachment 1 to this Generic Letter contains positions that
describe these deficiencies and explain certain ASME Code and T.S.
requirements and certain alternatives to the ASME Code that the staff
considers acceptable.
In addition to the generic deficiencies listed in Attachment 1, the staff has
concerns regarding the operability of motor operated valve actuators. These
concerns are addressed in Bulletin 85-03, dated November 15, 1985, Bulletin
85-03, Supplement 1, dated April 27, 1988, and Generic Issue II.E.6.1,
"In-Situ Testing of Valves."
B. Programs Currently Under NRC Review
For plants listed in Table 1, the NRC will be issuing an SER in the near
future. These plants need not respond with the confirmation letter discussed
below. After receipt of the SER, plants in this category should follow the
guidance in Part C of this generic letter. For other utilities not listed on
either Table 1 or 2, this letter constitutes the required approval for
implementation of IST program relief requests provided the utility reviews its
program and amends it as necessary to: (1) conform with the Code requirements
explained in Attachment 1, Positions 1, 3, 5, and 11; (2) conform with the
T.S. requirements explained in Attachment 1, Positions 4 and 8; and (3)
conform with the applicable Code requirement or the staff approved
alternatives in Attachment 1, Positions 1, 2, 6, 7, 9, and 10.
. - 3 -
Based on the staff's experience the positions contained in Attachment 1
can be implemented at all plants. However, should licensees be unable to
comply with one of these positions because of design considerations or
personnel hazard, as opposed to inconvenience, any alternative testing must
fulfill the basic test objective of detecting component degradation.
Alternative testing should be individually evaluated by the licensee and the
licensee's plant safety review committee (or equivalent). When evaluating
testing, licensees should address the following:
1. Maintenance history of the individual (specific) component,
2. Maintenance history of the related components in a similar
environment,
3. Component vendor records of degradation at other facilities, and
4. Records on degradation of the same or like component from other
utilities.
Licensees may utilize in-plant records, the NPRDS and other referenceable
sources to compile data to address the above four areas. A lack of service
experience or test results by itself is not sufficient to justify the
alternative test.
The alternative test is not considered acceptable unless the above data is
sufficient to justify its adequacy for detecting degradation and ensuring
continued operability. Justification for the alternative test should be
documented and retained in the IST program.
For plants not listed on either Table 1 or 2, currently submitted IST program
relief requests are hereby approved for licensees who have not received an SER
provided that they (1) review their most recently submitted IST programs and
implementation procedures against the positions delineated in Attachment 1 and
(2) within 6 months of the date of this letter confirm in writing their
conformance with the stated positions. In cases where conformance with the
stated positions would result in equipment modifications, the licensee should
provide in his confirmation letter a schedule for completing the required
modifications. All modifications must be completed within 18 months of the
date of the confirmatory letter, whichever occurs later. Changes to the IST
programs as a result of this generic letter, should be submitted to the NRC
along with the confirmation letter. Approval is granted provided the programs
are consistent with the positions taken in Attachment 1 or, for positions that
necessitate a plant modification, will be consistent with Attachment 1 on the
schedule noted above. Where a deviation needs to be taken from a specific
position in Attachment 1, the approval is granted provided the adequacy of the
proposed alternative testing for detecting degradation is justified as
discussed above.
C. Programs With Completed NRC Reviews
For the plants listed in Table 2 the staff has completed its review of the IST
program and issued an SER. These plants need not respond with the
confirmation letter discussed above. The status of the relief requests
approved in the SER is not affected by this letter. The relief requests that
were approved in the SER may continue to be implemented, and those that were
denied should be
. - 4 -
resolved in accordance with the guidance in the SER. The technical positions
found in Attachment 1 of this generic letter were used by the staff in reviews
of IST programs.
If licensees have modified or plan to modify their IST program beyond that
which was the basis for the staff's SER, the guidance in Part D below should
be used.
D. Program Updates/Revisions
If the licensees modify their IST program beyond that currently submitted to
the NRC, they should review the modifications against the positions found in
Attachment 1. For IST program changes for which specific positions are
provided in Attachment 1, licensees should follow the guidance in Section B
above. For IST program changes in areas not covered by Attachment 1, the
provisions of 10 CFR 50.55(a)g should be followed. The modified program
should comply with the disposition of relief requests in any applicable SER
based on a previously submitted IST program.
E. Implementing Procedures
IST programs contain basic information on the pumps and valves being tested,
the type of tests being performed, and the frequency of testing, but not the
procedures being followed. The positions in Attachment 1 primarily address
generic short-comings in IST programs. However, each of these positions, as
well as other areas of the ASME Code, are dependent upon the adequacy of the
implementing procedures. This letter provides guidance to be taken relative to
the positions in Attachment 1 to correct deficiencies in the IST programs.
The implementing procedures for these positions should likewise be reviewed
and amended to address any deficiencies related to implementation of these
positions.
F. Inspection and Enforcement
The NRC may conduct inspections to determine licensee conformance with the
provisions of the approval granted by this letter. Enforcement action against
licensees may result in cases where the program and procedures are not in
confor-mance with 10 CFR 50.55a(g), as explained in this guidance. The areas
covered in Attachment 1 will be the focus of future IST inspections. Aspects
of the IST programs not addressed by Attachment 1 may also be inspected.
IST PROGRAM APPROVAL
This generic letter approves currently submitted IST program relief requests
for licensees who have not received an SER provided that they (1) review their
most recently submitted IST programs and implementation procedures against the
positions delineated in Attachment 1 and (2) within 6 months of the date of
this letter confirm in writing their conformance with the stated positions.
Since the IST program reviews for licensees listed on Table 1 are nearly
complete, they will receive relief request approvals by separate
correspondence.
By addressing the technical areas identified in Attachment 1, the staff has
concluded that certain significant deficiencies in the IST programs and in IST
relief requests will be corrected. Other deficiencies related to assurance of
. - 5 -
the operational readiness of pumps and valves have been or will be the subject
of regulatory actions such as generic letters and rulemaking. Provided the
provisions of this letter are followed, the staff has determined that relief
is granted to follow the alternative testing delineated in positions 1, 2, 6,
7, 9, and 10, pursuant to 10 CFR 50.55a(g)(6)(i), is authorized by law, and
will not endanger life or property or the common defense and security and is
otherwise in the public interest. In making this determination the staff has
considered the impracticality of performing the required testing considering
the burden if the requirements were imposed.
This request is covered by Office of Management and Budget Clearance Number
3150-0011 which expires December 31, 1989. The estimated average burden hours
is 700 man-hours per owner response, including assessment of the new recom-
mendations, searching data sources, gathering and analyzing the data, and
preparing the required letters. These estimated average burden hours pertain
only to these identified response-related matters and do not include the time
for actual implementation of the requested actions. Comments on the accuracy
of this estimate and suggestions to reduce the burden may be directed to the
Office of Management and Budget, Room 3208, New Executive Office Building,
Washington, D.C. 20503, and the U.S. Nuclear Regulatory Commission, Records
and Reports Management Branch, Office of Administration and Resources Manage-
ment, Washington, D.C. 20555.
Sincerely,
Steven A. Varga, Acting
Associate Director for Projects
Office of Nuclear Reactor Regulation
Enclosures:
Tables 1 and 2
w/Attachment 1
.
TABLE 1
PLANTS WITH SERs TO BE ISSUED IN NEAR FUTURE
Beaver Valley 1 Peach Bottom 2&3
Braidwood 1&2 Rancho Seco
Brunswick River Bend
Calvert Cliffs 1&2 Robinson 2
Clinton Seabrook 1
Comanche Peak SONGS 2&3
D.C. Cook 1&2 St. Lucie 2
Farley 1&2 Summer
Ft. Calhoun Surry 1&2
Hatch 1&2 Vogtle 1
Hope Creek Waterford 3
Kewaunee Wolf Creek
Limerick 1&2 WNP 2
McGuire 1&2 Zion 1&2
Millstone 2
Nine Mile Point 1
Nine Mile Point 2
.
TABLE 2
PLANTS WITH CURRENT IST PROGRAMS REVIEWED
AND SER ISSUED
Browns Ferry 1,2&3
Byron 1&2
Davis Besse 1
Diablo Canyon 1&2
Calloway
Fermi 2
Millstone 3
Palo Verde 1,2&3
Prairie Island 1&2
Sequoyah 1&2
Shearon Harris
South Texas 1&2
TMI 1
Vogtle 2
.
ATTACHMENT 1
POTENTIAL GENERIC DEFICIENCIES RELATED TO
IST PROGRAMS AND PROCEDURES
1. Full Flow Testing of Check Valves
Section XI of the ASME Code requires check valves to be exercised to the
positions in which they perform their safety functions. A check valve's
full-stroke to the open position may be verified by passing the maximum
required accident condition flow through the valve. This is considered
by the staff as an acceptable full-stroke. Any flow rate less than this
will be considered a partial-stroke exercise. A valid full-stroke
exercise by flow requires that the flow through the valve be known.
Knowledge of only the total flow through multiple parallel lines does not
provide verification of flow rates through the individual valves and is
not a valid full-stroke exercise.
Full flow testing of a check valve as described above may be impractical
to perform for certain valves. It may be possible to qualify other
techniques to confirm that the valve is exercised to the position
required to perform its safety function. To substantiate the
acceptability of any alternative technique for meeting the ASME Code
requirements, licensees must as a minimum address and document the
following items in the IST program:
1. The impracticality of performing a full flow test,
2. A description of the alternative technique used and a summary of the
procedures being followed,
3. A description of the method and results of the program to qualify
the alternative technique for meeting the ASME Code,
4. A description of the instrumentation used and the maintenance and
calibration of the instrumentation,
5. A description of the basis used to verify that the baseline data has
been generated when the valve is known to be in good working order,
such as recent inspection and maintenance of the valve internals,
and
6. A description of the basis for the acceptance criteria for the
alternative testing and a description of corrective actions to be
taken if the acceptance criteria are not met.
An acceptable alternative to this full-stroke exercising requirement is
stated in position 2 below.
. - 2 -
2. Alternative to Full Flow Testing of Check Valves.
The most common method to full-stroke exercise a check valve open (where
disk position is not observable) is to pass the maximum required accident
flow through the valve. However, for some check valves, licensees cannot
practically establish or verify sufficient flow to full-stroke exercise
the valves open. Some examples of such valves are, in PWRs, the contain-
ment spray header check valves and combined LPSI and safety injection
accumulator header check valves and, in BWRs, the HPCI or RCIC check
valves in the pump suction from the suppression pool. In most commercial
facili-ties, establishing design accident flow through these valves for
testing cou1d result in damage to major plant equipment.
The NRC staff position is that valve disassembly and inspection can be
used as a positive means of determining that a valve's disk will full-
stroke exercise open or of verifying closure capability, as permitted by
IWV-3522. If possible, partial valve stroking quarterly or during cold
shutdowns, or after reassembly must be performed.
The staff has established the following positions regarding testing check
valves by disassembly:
a. During valve testing by disassembly, the valve internals should be
visually inspected for worn or corroded parts, and the valve disk
should be manually exercised.
b. Due to the scope of this testing, the personnel hazards involved and
system operating restrictions, valve disassembly and inspection may
be performed during reactor refueling outages. Since this fre-quency
differs from the Code required frequency, this deviation must be
specifically noted in the IST program.
c. Where the licensee determines that it is burdensome to disassemble
and inspect all applicable valves each refueling outage, a sample
disassembly and inspection plan for groups of identical valves in
similar applications may be employed. The NRC guidelines for this
plan are explained below:
The sample disassembly and inspection program involves grouping
similar valves and testing one valve in each group during each
refueling outage. The sampling technique requires that each
valve in the group be the same design (manufacturer, size, model
number, and materials of construction) and have the same service
conditions including valve orientation. Additionally, at each
disassembly the licensee must verify that the disassembled valve
is capable of full-stroking and that the internals of the valve
are structurally sound (no loose or corroded parts). Also, if
the disassembly is to verify the full-stroke capability of the
valve, the disk should be manually exercised.
. - 3 -
A different valve of each group is required to be disassembled,
inspected, and manually full-stroke exercised at each successive
refueling outage, until the entire group has been tested. If the
disassembled valve is not capable of being full-stroke exercised
or there is binding or failure of valve internals, the remaining
valves in that group must also be disassembled, inspected, and
manually full-stroke exercised during the same outage. Once this
is completed, the sequence of disassembly must be repeated unless
extension of the interval can be justified.
Extending the valve sample disassembly and inspection interval from disas-
sembly of one valve in the group every refueling outage or expanding the
group size would increase the time between testing of any particular
valve in the group. With four valves in a group and an 18-month reactor
cycle, each valve would be disassembled and inspected every six years.
If the fuel cycle is increased to 24 months, each valve in a four-valve
sample group would be disassembled and inspected only once every 8 years.
Extension of the valve disassembly/inspection interval from that allowed
by the Code (quarterly or cold shutdown frequency) to longer than once
every 6 years is a substantial change which may not be justified by the
valve failure rate data for all valve groupings. When disassembly/
inspection data for a valve group show a greater than 25% failure rate,
the licensee should determine whether the group size should be decreased
or whether more valves from the group should be disassembled during every
refueling outage.
Extension of the valve disassembly/inspection interval to one valve every
other refueling outage or expansion of the group size above four valves
should only be considered in cases of extreme hardship where the
extension is supported by actual in-plant data from previous testing. In
order to support extension of the valve disassembly/inspection intervals
to longer than once every 6 years, licensees should develop the following
information:
a. Disassemble and inspect each valve in the valve grouping and document
in detail the condition of each valve and the valve's capability to
be full-stroked.
b. A review of industry experience, for example, as documented in
NPRDS, regarding the same type of valve used in similar service.
c. A review of the installation of each valve addressing the "EPRI
Applications Guidelines for Check Valves in Nuclear Power Plants"
for problematic locations.
3. Back Flow Testing of Check Valves.
Section XI requires that Category C check valves (valves that are self
actuated in response to a system characteristic) performing a safety
function in the closed position to prevent reversed flow be tested in a
manner that proves that the disk travels to the seat promptly on
cessation or reversal of flow. In addition, for category A/C check
valves (valves that
. - 4 -
have a specified leak rate limit and are self actuated in response to a
system characteristic), seat leakage must be limited to a specific
maximum amount in the closed position for fulfillment of their function.
Verifica-tion that a Category C valve is in the closed position can be
done by vis-ual observation, by an electrical signal initiated by a
position-indicating device, by observation of appropriate pressure
indication in the system, by leak testing, or by other positive means.
Examples of ASME Code Class check valves that perform a safety function
in the closed position that are frequently not back flow tested are:
a. main feedwater header check valves
b. pump discharge check valves on parallel pumps
c. keep full check valves
d. check valves in steam supply lines to turbine driven AFW pumps
e. main steam non-return valves
f. CVCS volume control tank outlet check valves
4. Pressure Isolation Valves
a. General
Pressure isolation valves (PIVs) are defined as two normally closed
valves in series that isolate the reactor coolant system (RCS) from
an attached low pressure system. PIVs are located at all RCS low
pressure system interfaces. The 10 CFR 50.2 contains the definition
of the RCPB. PIVs are within the reactor coolant pressure boundary
(RCPB).
The following summary is based upon the staff's review of responses
to Generic Letter 87-06, Periodic Verification of Leak Tight
Integrity of Pressure Isolation Valves. All plants licensed since
1979 have a full list of PIVs in the plant Technical Specifications
(TS) along with leak test requirements and limiting conditions for
operation (LCOs). The plants licensed prior to 1979 fall into
several categories. Some pre-1979 plants have a full list of PIVs
along with leak test requirements and LCOs in the plant TS. Some
pre-1979 plants have only Event V PIVs (see below) in the plant TS.
Some pre-1979 plants have no TS requirements regarding PIVs.
All PIVs listed in plant TS should be listed in the IST program as
Category A or A/C valves. The TS requirements should be referenced
in the IST program.
b. Event V PIVs
Event V PIVs are defined as two check valves in series at a low
pressure/RCS interface whose failure may result in a LOCA that by-
passes containment. Event V refers to the scenario described for
this event in the WASH-1400 study.
. - 5 -
On April 20, 1981, the NRC issued an Order to 32 PWRs and 2 BWRs
which required that these licensees conduct leak rate testing of
their PIVs, based on plant-specific NRC supplied lists of PIVs, and
required licensees to modify their TS accordingly. These orders are
known as the "Event V Orders" and the valves listed therein are the
"Event V" PIVs. The Event V PIVs are a subset of PIVs.
Based upon the results of recent inspections, it has been determined
that the following implementation problem still exists with respect
to testing of PIVs. The staff has determined that in some cases the
procedures are inadequate to assure that these valves are
individually leak tested and evaluated against the leakage limits
specified in the TS; in other cases, the procedures were adequate
but were not being followed. Specifically, some check valves were
tested in series as opposed to individually and some check valves
were not tested when required.
Licensees should review their testing procedures to ensure the Event
V PIVs are individually leak rate tested.
5. Limiting Values of Full-Stroke Times for Power Operated Valves
The Code intent with respect to measuring the full-stroke times of power
operated valves is to verify operability and to detect valve degradation.
Measurement of full stroke times for air operating valves fulfills this
intent. However, reviews of operating experience have identified several
problems with motor operated valves (MOVs) including limitations with
stroke time as a measure of operational readiness of the MOV. As a
result, the industry has made extensive efforts to improve the knowledge
and under-standing of operational characteristics of motor operated
valves. This effort has been conducted by industry groups (NUMARC, INPO,
NMAC, EPRI), individual licensees, equipment vendors, and national
standards groups.
We believe the information and knowledge developed by these groups should
be reviewed and utilized. Some of the information publicly available
includes an INPO white paper titled, "Motor-Operated Valve Performance
Update," issued October 4, 1988. This document identifies MOV problem
areas and provides the key elements for a comprehensive MOV program.
Another document is the "Technical Repair Guidelines for the Limitorque
Model SMB-000 Valve Actuator," issued by the Nuclear Maintenance Applica-
tion Center (NMAC) in January 1989. This guide addresses several areas
such as setting torque and limit switches, preventive maintenance,
actuator failure modes, failure analysis to determine root cause and
corrective action, and preoperational and post-maintenance testing.
NRC staff concerns regarding MOV operability led to the issuance of
Bulletin 85-03 and Bulletin 85-03, Supplement 1. Expansion of this
bulletin in the form of a generic letter is being considered by the NRC.
. - 6 -
In spite of the limitations of stroke time testing of MOVs, IWV-3413(a)
of the ASME Code requires that the licensee specify the limiting value
of full-stroke time of each power operated valve. The corrective actions
of IWV-3417(b) must be followed when these limiting values are exceeded.
The Code does not provide any requirements or guidelines for establishing
these limits nor does it identify the relationship that should exist
between these limits and any limits identified for the relevant valves in
the plant TS or safety analysis.
The purpose of the limiting value of full-stroke time is to establish a
value for taking corrective action on a degraded valve before the valve
reaches the point where there is a high probability of failure to perform
its safety function if called upon. The NRC has, therefore, established
the guidelines described below regarding limiting values of full-stroke
time for power operated valves.
The limiting value of full-stroke time should be based on the valve
reference or average stroke time of a valve when it is known to be
in good condition and operating properly. The limiting value should
be a reasonable deviation from this reference stroke time based on
the valve size, valve type, and actuator type. The deviation should
not be so restrictive that it results in a valve being declared
inoperable due to reasonable stroke time variations. However, the
deviation used to establish the limit should be such that corrective
action would be taken for a valve that may not perform its intended
function.
When the TS or safety analysis limit for a valve is less than the value
established using the above guidelines, the TS or safety analysis limit
should be used as the limiting value of full-stroke time.
When the TS or safety analysis limit for a valve is greater than
the value established using the above guidelines, the limiting value
of full-stroke time should be based on the above guidelines instead of
the TS or safety analysis limit.
6. Stroke Time Measurements for Rapid-Acting Valves
The Code requires the following for power operated valves with stroke
times 10 seconds or less: (a) Limiting values of full-stroke times shall
be specified [IWV-3413(a)], (b) Valve stroke times shall be measured to
(at least) the nearest second [IWV-3413(b)] and (c) If the stroke time
increases by 50% or more from the previous test, then the test frequency
shall be increased to once each month until corrective action is taken
[IWV-3417(a)]. Paragraph IWV-3417(b) specifies corrective actions that
must be taken.
With reference to (c) above, measuring changes in stroke times from a
reference value as opposed to measuring changes from the previous test
is an acceptable (and possibly better) alternative to the staff.
However, since this is different from the Code requirement, this
deviation should be documented in the IST program.
. - 7 -
Most plants have many power operated valves that are capable of stroking
in 2 seconds or less such as small solenoid operated valves. Licensees
encounter difficulty in applying the Code 50% increase of stroke time
corrective action requirements for these valves. The purpose of this
requirement is to detect and evaluate degradation of a valve. For valves
with stroke times in this range, much of the difference in stroke times
from test to test comes from inconsistencies in the operator or timing
device used to gather the data. These differences are compounded by
rounding the results as allowed by the Code. Thus, the results may not
be representative of actual valve degradation.
The following discussion illustrates the problem that may exist when
complying with the Code requirements for many of these rapid-acting
valves:
A valve may have a stroke time of 1.49 seconds during one test and a
stroke time during the following test of 1.51 seconds. If stroke
times are rounded to the nearest second as allowed by the Code, the
difference between these tests would exceed the 50% criteria and
would require an increased frequency of testing until corrective
action is taken. This can result from a stroke time difference of
0.02 seconds, which is usually not indicative of significant valve
degradation.
Power operated valves with normal stroke times of 2 seconds or less are
referred to by the staff as "rapid-acting valves." Relief may be granted
from the requirements of Section XI, Paragraph IWV-3417(a) for these
valves provided the licensee assigns a maximum limiting value of
full-stroke time of 2 seconds to these valves and, upon exceeding this
limit, declares the valve inoperable and takes corrective action in
accordance with IWV-3417(b).
An acceptable alternative to the Code stroke timing requirements is the
above stated rapid-acting valve position. Since this represents a devi-
ation from the Code requirements, it should be specifically documented in
the IST program.
7. Testing Individual Control Rod Scram Valves in Boiling Water Reactors
(BWRs)
BWRs are equipped with bottom-entry hydraulically driven control rod
drive mechanisms with high-pressure water providing the hydraulic power.
Each control rod is operated by a hydraulic control unit (HCU), which
consists of valves and an accumulator. The HCU is supplied charging and
cooling water from the control rod drive pumps, and the control rod
operating cylinder exhausts to the scram discharge volume. Various
valves in the control rod drive system perform an active function in
scramming the control rods to rapidly shut down the reactor.
The NRC has determined that those ASME Code Class valves that must change
position to provide the scram function should be included in the IST
program and be tested in accordance with the requirements of Section XI
except where relief has been granted in a previously issued Safety
Evaluation Report or as discussed below.
. - 8 -
The control rod drive system valves that perform an active safety
function in scramming the reactor are the scram discharge volume vent and
drain valves, the scram inlet and outlet valves, the scram discharge
header check valves, the charging water header check valves, and the
cooling water header check valves. With the exception of the scram
discharge volume vent and drain valves, exercising the other valves
quarterly during power operations could result in the rapid insertion of
one or more control rods more frequently than desired.
Licensees should test these control rod drive system valves at the
Code-specified frequency if they can be practically tested at that
frequency.
However, for those control rod drive system valves where testing could
result in the rapid insertion of one or more control rods, the rod scram
test frequency identified in the facility TS may be used as the valve
testing frequency to minimize rapid reactivity transients and wear of the
control rod drive mechanisms. This alternate test frequency should be
clearly stated and documented in the IST program.
Industry experience has shown that normal control rod motion may verify
the cooling water header check valve moving to its safety function
position. This can be demonstrated because rod motion may not occur if
this check valve were to fail in the open position. If this test method
is used at the Code required frequency, the licensee should clearly
explain in the IST program that this is how these valves are being
verified to close quarterly.
Closure verification of the charging water header check valves requires
that the control rod drive pumps be stopped to depressurize the charging
water header. This test should not be performed during power operation
because stopping the pumps results in loss of cooling water to all
control rod drive mechanisms and seal damage could result. Additionally,
this test cannot be performed during each cold shutdown because the
control rod drive pumps supply seal water to the reactor recirculation
pumps and one of the recirculation pumps is usually kept running.
Therefore, the HCU accumulator pressure decay test as identified in the
facility TS may be used as the charging water header check valve
alternate testing frequency for the reasons stated above. If this test
is not addressed in the licensee's TS this closure verification should be
performed at least during each refueling outage, and this alternate test
frequency should be specifically documented in the IST program.
The scram inlet and outlet valves are power operated valves that
full-stroke in milliseconds and are not equipped with indication for both
positions, therefore, measuring their full-stroke time as required by the
Code may be impractical. Verifying that the associated control rod meets
the scram insertion time limits
. - 9 -
defined in the plant TS can be an acceptable alternate method of
detecting degradation of these valves. Also, trending the stroke times
of these valves may be impractical and unnecessary since they are
indirectly stroke timed and no meaningful correlation between the scram
time and valve stroke time may be obtained, and furthermore, conservative
limits are placed on the control rod scram insertion times. If the above
test is used to verify the operability of scram inlet and outlet valves,
it should be specifically documented in the IST program.
8. Starting Point for Time Period in TS ACTION Statements
ASME Section XI, IWP-3220, states "All test data shall be analyzed within
96 hours after completion of a test." IWP-3230(c) states, in part, "If
the deviations fall within the 'Required Action Range' of Table
IWP-3100-2, the pump shall be declared inoperative,...."
In many cases pumps or valves covered by ASME, Section XI, Subsections
IWP and IWV, are also in systems covered by TS and, if declared
inoperable, would result in the plant entering an ACTION statement.
These ACTION statements generally have a time period after which, if the
equipment is still inoperable, the plant is required to undergo some
specific action such as commence plant shutdown.
The potential exists for a conflict between the aforementioned data
analysis interval versus the TS ACTION statement time period. Section
XI, IWP-6000 requires the reference values, limits, and acceptance
criteria to be included in the test plans or records of tests. With this
information available, the shift individual(s) responsible for conducting
the test (i.e., shift supervisor, reactor operator) should be able to
make a timely determination as to whether or not the data meets the
requirements.
When the data is determined to be within the Required Action Range of
Table IWP-3100-2 the pump is inoperable and the TS ACTION statement time
starts. The provisions in IWP-3230(d) to recalibrate the instruments
involved and rerun the test to show the pump is still capable of
fulfilling its function are an alternative to replacement or repair, not
an additional action that can be taken before declaring the pump
inoperable.
The above position, which has been stated in terms of pump testing, is
equally valid for valve testing.
In summary, it is the staff's position that as soon as the data is recog-
nized as being within the Required Action Range for pumps or exceeding
the limiting value of full-stroke time for valves, the associated
component must be declared inoperable and the TS ACTION time must be
started.
. - 10 -
9. Pump Testing using Minimum-flow Return Line With or Without Flow
Measuring Devices
An inservice pump test requires that the pump parameters shown in Table
IWP-3100-1 be measured and evaluated to determine pump condition and
detect degradation. Pump differential pressure and flow rate are two
parameters that are measured and evaluated together to determine pump
hydraulic performance.
Certain safety-related systems are designed such that the minimum-flow
return lines are the only flow paths that can be utilized for quarterly
pump testing. Furthermore, some of these systems, do not have any flow
path that can be utilized for pump testing during any plant operating
mode except the minimum-flow return lines. In these cases, pumping
through the path designed for fulfilling the intended system safety
function could result in damage to plant equipment. Minimum-flow lines
are not designed for pump testing purposes and few have installed flow
measuring devices.
In cases where flow can only be established through a non-instrumented
minimum-flow path during quarterly pump testing and a path exists at cold
shutdowns or refueling outages to perform a test of the pump under full
or substantial flow conditions, the staff has determined that the
increased interval is an acceptable alternative to the Code requirements
provided that pump differential pressure, flow rate, and bearing
vibration measurements are taken during this testing and that quarterly
testing also measuring at least pump differential pressure and vibration
is continued. Data from both of these testing frequencies should be
trended as required by IWP-6000. Since the above position is a deviation
from the Code required testing, it should be documented in the IST
program.
In cases where only the minimum-flow return line is available for pump
testing, regardless of the test interval, the staff's position is that
flow instrumentation which meets the requirements of IWP-4110 and 4120
must be installed in the mini-flow return line. Installation of this
instrumentation is necessary to provide flow rate measurements during
pump testing so this data can be evaluated with the measured pump differ-
ential pressure to monitor for pump hydraulic degradation.
NRC Bulletin 88-04, dated May 5, 1988, advised licensees of the potential
for pump damage while running pumps in the minimum-flow condition. The
above guidelines for meeting the Code or performing alternative testing
is not intended to supersede the thrust of this Bulletin. Licensees
should ensure that if pumps are tested in the low flow condition, the
flow is sufficient to prevent damage to the pump.
. - 11 -
10. Containment Isolation Valve Testing
All containment isolation valves (CIVs) that are included in the Appendix
J, program should be included in the ISI program as Category A or A/C
valves. The staff has determined that the leak test procedures and
requirements for containment isolation valves specified in 10 CFR 50,
Appendix J are equivalent to the requirements of IWV-3421 through 3425.
However, the licensee must comply with the Analysis of Leakage Rates and
Corrective Action requirements of Paragraph IWV-3426 and 3427(a).
IWV-3427(b) specifies additional requirements on increased test
frequencies for valve sizes of six inches and larger and repairs or
replacement over the requirements of IWV-3427(a). Based on input from
many utilities and staff review of testing data at some plants, the
usefulness of IWV-3427(b) does not justify the burden of complying with
this requirement. Since this position represents a deviation from the
Code requirements, it should be documented in the IST program.
11. IST Program Scope
The 10 CFR 50.55a requires that inservice testing be performed on certain
ASME Code Class 1, 2, and 3 pumps and valves. Section XI Subsections
IWP-1100 and IWV-1100 defines the scope of pumps and valves to be tested
in terms of plant shutdowns and accident mitigation. The plant's FSAR
(or equivalent) provides definitions of the necessary equipment to meet
these functions. The staff has noted during past IST program reviews and
inspections that licensees do not always include the necessary equipment
in their IST programs. Licensees should review their IST programs to
ensure adequate scope. Examples that are frequently erroneously omitted
from IST programs are:
a. BWR scram system valves,
b. control room chilled water system pumps and valves,
c. accumulator motor operated isolation valves, or accumulator
vent valves,
d. auxiliary pressurizer spray system valves,
e. boric acid transfer pumps,
f. valves in emergency boration flow path,
g. control valves that have a required fail-safe position,
h. valves in mini-flow lines.
It should be recognized that the above examples of pumps and valves do
not meet the IWP/and IWV scope statement requirements for all plants.
The intent of 10 CFR 50 Appendix A, GDC-1, and Appendix B, Criterion XI,
is that all components, such as pumps and valves, necessary for safe
operation are to be tested to demonstrate that they will perform
satisfactorily in service. Therefore, while 10 CFR 50.55a delineates the
testing requirements for ASME Code Class 1, 2, and 3 pumps and valves,
the testing of pumps and valves is not to be limited to only those
covered by 10 CFR 50.55a.
