United States Nuclear Regulatory Commission - Protecting People and the Environment

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
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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 
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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.

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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.  
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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
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                                                            Attachment 1 
                                                            IN 90-40 
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                                                            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
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