Information Notice No. 90-40: Results of NRC-Sponsored Testing of Motor-Operated Valves
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
June 5, 1990
Information Notice No. 90-40: RESULTS OF NRC-SPONSORED TESTING
OF MOTOR-OPERATED VALVES
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is intended to provide addressees with specific
information regarding the results of recent NRC-sponsored testing of
motor-operated valves (MOVs) which was discussed at a public meeting on
April 18, 1990. It is expected that recipients will review the information
for applicability to their facilities and consider actions, as appropriate,
to avoid problems with safety-related MOVs. However, suggestions contained
in this information notice do not constitute NRC requirements; therefore, no
specific action or written response is required.
Background:
The NRC Office of Nuclear Regulatory Research (RES) has been sponsoring an
MOV testing program in support of the resolution of Generic Safety Issue 87
(GI-87), "Failure of HPCI Steam Line Without Isolation." The initial scope
of GI-87 involved the evaluation of the capability of certain motor-operated
flexible wedge gate containment isolation valves to mitigate the loss of
reactor coolant inventory in the event of a pipe break outside of the
containment building at boiling-water-reactor (BWR) plants. The particular
MOVs involved in the GI-87 program were those in the turbine steam supply
lines for the high pressure coolant injection (HPCI) and reactor core
isolation cooling (RCIC) systems, and in the supply line to the reactor
water cleanup (RWCU) system.
The MOV research is applicable to the programs established by licensees in
response to Generic Letter 89-10, "Safety-Related Motor-Operated Valve
Testing and Surveillance." In that generic letter, the staff recommended
that licensees and construction permit holders establish a program to
provide for the testing, inspection, and maintenance of safety-related MOVs
and certain other MOVs in safety-related systems. The purpose of this
program is to provide assurance that the MOVs will function when subjected
to design-basis differential pressure and flow conditions. As part of the
generic letter program, the staff recommended that licensees and permit
holders test the MOVs
9005290270
.
IN 90-40
June 5, 1990
Page 2 of 5
within the program in situ under design-basis conditions, where practicable.
The schedule in the generic letter requested that the description of the MOV
program be available within about a year of issuance of the generic letter
and that the initial test program be completed in approximately five years.
As a followup to the initial program, the staff recommended that the MOV
switch settings and, thus, operability of the MOVs be reverified
periodically.
Although the generic letter has a five-year schedule for completing the
initial program, the staff indicated at the public workshops held to discuss
the generic letter that the NRC regulations require that licensees act to
resolve operability problems with specific MOVs when the problems are
identified. As part of its review of the research results, the staff will
consider the need to accelerate a portion or all of the Generic Letter 89-10
program for particular MOVs or systems.
In Generic Letter 89-10, the staff acknowledges that in situ testing of some
MOVs within the generic letter program under design-basis conditions will
not be practicable. At the generic letter workshops, the staff discussed
several possible alternatives if such testing is not practicable, as well as
potential problems and limitations associated with those alternatives. For
instances in which testing of an MOV in situ under design-basis conditions
is not practicable and the licensee cannot currently justify the use of an
alternative to design-basis testing in situ, the staff has recommended the
use of a "two-stage" approach: the licensee would set the MOV operating
switches by means of the best data available and then would work to obtain
applicable test data as soon as possible. The staff believes that
applicable test data can be obtained within the five-year schedule. For the
initial setting of the MOV switches under the two-stage approach, the test
results obtained through the NRC research may constitute some of the best
data available for the tested valves under a variety of fluid conditions.
Description of Circumstances:
The MOV testing program for GI-87 has been conducted in two phases by the
Idaho National Engineering Laboratory (INEL). Phase I was performed in 1988
at the Wyle Laboratory facility in Huntsville, Alabama. The most
significant tests in that phase consisted of opening and closing two 6-inch
flexible wedge gate valves (manufactured by Anchor/Darling and Velan) under
high differential pressure and high-temperature water conditions. The
valves in Phase I of the research program were considered typical of those
used for containment isolation in the supply line to the RWCU system. The
results of the tested valves were discussed at a public meeting on February
1, 1989, and are documented in NUREG/CR-5406, "BWR Reactor Water Cleanup
System Flexible Wedge Gate Isolation Valve Qualification and High Energy
Flow Interruption Test."
Phase II of the MOV test program was performed in 1989 at the Kraftwerk
Union facility in the Federal Republic of Germany. This phase consisted of
opening and closing three 6-inch flexible wedge gate valves (Anchor/Darling,
Velan, and Walworth) and three 10-inch flexible wedge gate valves
(Anchor/Darling, Powell, and Velan) against normal and blowdown
(design-basis) flow conditions. The Phase II 6-inch and 10-inch valves were
considered typical of those used for containment isolation in the supply
line to the RWCU system and the turbine
.
IN 90-40
June 5, 1990
Page 3 of 5
steam supply line of the HPCI systems, respectively. On December 26, 1989,
the NRC staff issued Information Notice 89-88, "Recent NRC-Sponsored Testing
of Motor-Operated Valves," which alerted addressees to the tests and
provided some preliminary results. On April 18, 1990, the NRC staff held a
public meeting to discuss the results of Phase II of the MOV testing
program. The test data are available in printed form in the NRC Public
Document Room (Accession No. 9005170l54). Magnetic tapes of the test data
are available through the INEL Office of Technology Transfer.
The overall objectives of the MOV test program included the determination of
the force required to close the tested valves under various operating and
design-basis fluid conditions through the measurement of stem thrust. Other
program objectives were the determination of opening thrust requirements for
the tested valves under different fluid conditions; evaluation of valve
closure force components (such as disc friction and packing drag);
measurement of the effects of temperature, pressure, and valve design on
valve opening and closing loads; and evaluation of the valve thrust equation
commonly used in the industry.
The tests for each MOV included cold leakage, cold and hot cycling, opening
and closing under normal flow, closure under design-basis, and partial
opening and closing under high differential pressure and flow conditions.
Although the tested valves were intended to be typical of those used for
containment isolation in the HPCI and RWCU systems of BWR plants, the
results of the tests should be considered in terms of their applicability to
all MOVs in nuclear power plants. A detailed analysis of the test data
should be available in July 1990. Nevertheless, the NRC staff has begun to
develop conclusions from the test data as a result of its review of the data
and the discussions at the April 18, 1990, public meeting. Several
preliminary conclusions are discussed below:
1. Regardless of fluid conditions (i.e., steam, slightly subcooled water,
or cold water), the tested valves required more thrust for opening and
closing under various differential pressure and flow conditions than
would have been predicted from standard industry calculations and
typical friction factors. Thus, a potential exists for the
underestimation of thrust requirements for valves in applications, and
under fluid conditions, other than those of the valves involved in the
NRC research. For the conduct of the tests, the motor operators for
the valves were sized, and the torque switches were set, in an effort
to ensure that each valve would fully stroke without regard to the
thrust requirements predicted by the commonly used valve thrust
equation. (Despite this effort, one valve failed to close completely
during a blowdown test.) To provide an indication of the accuracy of
the valve thrust equation, the thrust predicted by that equation for
valve friction factors of both 0.3 and 0.5 was calculated during each
test. Table 1 provides a summary of the blowdown tests and the minimum
required thrust to close the tested valves. The table also indicates
whether the valve thrust equation would have bounded the thrust
requirement if valve friction factors of 0.3 or 0.5 had been used.
.
IN 90-40
June 5, 1990
Page 4 of 5
2. Some of the tested valves sustained considerable internal damage during
the blowdown tests. The occurrence of internal damage can cause the
thrust required to operate a valve to exceed the thrust requirements
predicted by the valve thrust equation. Such valves were referred to
as "unpredictable" in the test program and included the 6-inch
Anchor/Darling valve and the 10-inch Anchor/Darling, Powell, and Velan
valves. In some instances, this increase in required thrust can be
considerable and might exceed the capability of the motor or operator.
Thrust requirements to close unpredictable valves under design-basis
loads cannot be accurately determined without testing the valves
(either individually or as prototypes) under those conditions.
3. The research program revealed that the testing of a valve under static
or low flow conditions cannot always be used to accurately predict the
behavior of the valve under design-basis conditions by extrapolation.
For example, the valves that were damaged during blowdown tests
operated normally under less severe flow tests. Thus, low-flow tests
might not identify a valve that requires significantly more thrust than
predicted by the valve thrust equation (i.e., a valve that is
unpredictable).
4. During opening of the valves, the maximum required thrust did not
always occur at unseating. Rather, in certain instances, it occurred
much later during the valve stroke. At nuclear plants, the staff has
found that torque switches for MOVs are sometimes bypassed only during
the initial portion of the opening stroke on the assumption that the
thrust required to unseat the valve would be the maximum thrust for the
full stroke. Thus, the research results raise a concern that the
torque switches in some MOVs at nuclear plants might not be bypassed
for a sufficient period of time during the opening stroke.
5. For certain tests, the valve was closed from a partially open position.
This partial stroking of the valve failed to predict the thrust
requirements and to identify nonpredictable performance that were found
during closure of the valve from a full open position. For example,
during certain blowdown tests, valve damage began to occur before the
valve was half closed. The accumulated damage over the full stroke
influences the thrust required to close the valve.
6. The research program revealed that measurements of torque, thrust, and
motor operating data were needed to completely characterize MOV
performance. For example, the measurement of torque or thrust alone
cannot identify problems in the conversion of torque to thrust (i.e.,
abnormally large stem factors). Such problems can cause the thrust
measured at normal or static conditions to be misleading as compared to
the thrust that actually would be available under design-basis
conditions. The measurement of motor operating characteristics allows
the adequacy of the motor to be determined.
7. The research program revealed that reliable information can be obtained
from diagnostic analysis of MOVs only when operating data are collected
by trained personnel using accurate and calibrated equipment. The MOV
data must then be evaluated by individuals experienced in the
performance of MOV diagnostic analysis.
.
IN 90-40
June 5, 1990
Page 5 of 5
The staff is continuing its review of the results of the MOV research. From
this review, the staff may prepare additional information notices that
discuss the staff's conclusions regarding the research. If an immediate
safety problem is identified, the staff will initiate regulatory action to
ensure the MOVs will perform their safety functions.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of 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: Thomas G. Scarbrough, NRR
(301) 492-0916
Richard J. Kiessel, NRR
(301) 492-1154
Attachments:
1. Table 1 - GI-87 Research Results for Blowdown Tests
2. List of Recently Issued NRC Information Notices
.
Attachment 1
IN 90-40
June 5, 1990
Page 1 of 1
TABLE 1
GI-87 RESEARCH RESULTS FOR BLOWDOWN TESTS
Manufacturer D/P (psi) T (F) Fluid Required NOTES
Thrust (lbs)
SIX-INCH VALVES
Anchor/Darling 990 524 Hot water 20,000 (1)(2)
(Phase 1)
Anchor/Darling 900 520 Hot water >23,000 (1)(2)(3)
(Phase 2)
Velan (Phase 1) 990 524 Hot water 15,000 (4)
Velan (Phase 2) 950 520 Hot water 14,000 (2)
1040 550 Steam 14,000 (4)
750 <100 Cold water 13,000 (2)
600 540 Hot water 9,000 (2)
1000 470 Hot water 14,000 (2)
1300 520 Hot water 16,000 (4)
Walworth 920 520 Hot water 9,000 (4)(5)(6)
1100 550 Hot water 12,000 (4)(5)(6)
1300 570 Hot water 15,000 (4)(5)(6)
TEN-INCH VALVES
Anchor/Darling 750 510 Steam 29,000 (1)(2)
Powell 800 525 Steam 28,000 (1)(4)
1040 550 Steam 29,000 (1)(4)
Velan 990 550 Steam 33,000 (1)(2)
1400 590 Steam 40,000 (1)(2)
1100 560 Steam 36,000 (1)(2)
NOTES:
1. Valve damage during stroke could result in higher thrust requirements
than predicted by the valve thrust equation. (These valves are
referred to as "unpredictable").
2. The valve thrust equation with valve friction factors of either 0.3 or
0.5 did not bound the required thrust in the blowdown test.
3. The torque switch tripped before full valve closure.
4. The valve thrust equation with a valve friction factor of 0.3 did not
bound the required thrust in the blowdown test, but the equation did
bound the required thrust if a valve friction factor of 0.5 was used.
5. This valve had a removable guide which deformed during the blowdown
test.
6. In determining whether the MOV can accommodate the required thrust to
close the valve, the weak link among the motor, operator, and valve
must be identified. For the Walworth valve, this is especially
important because stems with relatively small diameters are typically
used in these valves.
.ENDEND
Page Last Reviewed/Updated Tuesday, March 09, 2021