United States Nuclear Regulatory Commission - Protecting People and the Environment

"Inaccuracy of Motor-Operated Valve Diagnotic Equipment" (Generic Letter 89-10, Supplement 5)

June 28, 1993




In Generic Letter (GL) 89-10 (June 28, 1989), "Safety-Related Motor-Operated
Valve Testing and Surveillance," the NRC staff requested holders of operating
licenses and construction permits for nuclear power plants to provide
additional assurance of the capability of safety-related motor-operated valves
(MOVs) and certain other MOVs in safety-related systems to perform their
intended functions 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 trending MOV problems.  The NRC staff issued
several supplements to GL 89-10 to clarify or modify its recommendations.

As an integral part of their GL 89-10 programs, most licensees are relying on
MOV diagnostic equipment to provide information on the thrust required to open
or close the valve as well as the thrust delivered by the motor actuator.  The
various types of MOV diagnostic equipment estimate stem thrust using different
parameters, such as spring pack displacement or strain in the stem, mounting
bolts, or yoke.  Because some licensees make decisions regarding the
operability of safety-related MOVs based on diagnostic equipment thrust
readings, the use of MOV diagnostic equipment can have a significant effect on
the safe operation of a nuclear power plant.


The NRC staff has recently become aware of new information on the accuracy of
MOV diagnostic equipment.  This new information raises a generic concern
regarding the reliability of the data provided by MOV diagnostic equipment. 
For example, the MOV Users Group (MUG) of nuclear power plant licensees on
February 3, 1992, released "Final Report - MUG Validation Testing as Performed
at Idaho National Engineering Laboratories" (Volume 1).  The MUG final report
indicates that the MOV diagnostic equipment that relied on spring pack
displacement to estimate stem thrust did not meet the accuracy claims of its
vendors.  In addition, the NRC staff has been informed of increased inaccuracy
of specific MOV diagnostic equipment that relies on valve yoke strain to
estimate stem thrust.


Generic Letter 89-10, Supp. 5      - 2 -                    June 28, 1993

On March 2, 1992, the NRC staff held a public meeting with representatives of
ITI-MOVATS to discuss the accuracy of the ITI-MOVATS thrust measuring device
(TMD) to estimate stem thrust on the basis of spring pack displacement.  At
this meeting, the representatives of ITI-MOVATS indicated that the results of 
their field validation program showed that the inaccuracy of the TMD may be
larger than licensees had assumed in some instances.  The ITI-MOVATS
representatives also discussed the results of their activities to resolve
concerns regarding the fact that the TMD is calibrated in the valve opening
direction, although it also is used to predict the thrust delivered by the
actuator in the valve closing direction.  ITI-MOVATS prepared Engineering
Report 5.2 (March 13, 1992) to provide guidance to its licensee customers for
evaluating the capability of an MOV to perform its safety function under
design-basis conditions in light of the increased inaccuracy of the TMD.  The
Nuclear Management and Resources Council (NUMARC) has developed guidelines for
licensees to use in evaluating individual MOVs that had been verified as
properly sized and set, using MOV diagnostic equipment manufactured by ITI-
MOVATS that relies on spring pack displacement to estimate stem thrust. 
Subject to comments provided to NUMARC on May 12, 1992, the NRC staff
considers the NUMARC guidelines to contain an acceptable approach for
addressing the uncertainty resulting from the use of the ITI-MOVATS TMD.

ABB-Impell manufactures MOV diagnostic equipment that relies on spring pack
displacement to estimate stem thrust.  Following the release of the MUG
report, Impell representatives stated that they would be working with their
licensee customers to develop new accuracy values.  The NRC staff has not
reviewed any guidance by Impell to address the new information on MOV
diagnostic equipment inaccuracy.

Liberty Technologies has manufactured MOV diagnostic equipment, referred to as
valve operation test and evaluation system (VOTES), that estimates the thrust
needed to open or close a valve on the basis of strain of the valve yoke.  The
VOTES equipment derives thrust from yoke strain that has been calibrated to
stem thrust using measured diametral strain of the valve stem and nominal
engineering material properties.  On October 2, 1992, Liberty Technologies
notified the NRC, in accordance with 10 CFR Part 21, that it had determined
that two new factors can affect the thrust values obtained with its VOTES
equipment.  Those factors involve (1) the possible use of improper stem
material constants and (2) the failure to account for a torque effect when the
equipment is calibrated by measuring strain of the threaded portion of a valve
stem.  In its October 2 submittal, Liberty Technologies provides guidance to
licensees for correcting the thrust data by hand calculations and states that
its new Software Version 2.3 will assist in performing the corrections.  The
staff has not evaluated guidance provided to licensees by Liberty Technologies
to address the increased inaccuracy of its MOV diagnostic equipment.

GL 91-18, "Information to Licensees Regarding Two NRC Inspection Manual
Sections on Resolution of Degraded and Nonconforming Conditions and
Operability," contains information on guidance provided to NRC inspectors in
the area of operability of safety-related components.  If an MOV is determined
to be inoperable, the licensee will be expected to satisfy the requirements of
the NRC regulations and plant technical specifications.

Generic Letter 89-10, Supp. 5       - 3 -                   June 28, 1993


1.    On the basis of the new information on MOV diagnostic equipment
      inaccuracy discussed in this letter, licensees are requested to
      reexamine their MOV programs and to identify measures taken or planned
      to account for uncertainties in properly setting valve operating thrust
      to ensure operability.  Licensees should not limit their evaluation to
      only the specific examples of increased inaccuracy of MOV diagnostic
      equipment provided in the Discussion section of this GL supplement, but
      should consider any information reasonably available to them.  

2.    Licensees are requested to evaluate the schedule necessary (a) to
      consider the new information on MOV diagnostic equipment inaccuracy and
      (b) to respond to that information.


Pursuant to section 182a of the Atomic Energy Act of 1954, as amended,
10 CFR 50.54(f) and 10 CFR 2.204, each addressee is required to submit a
written response providing the information described below.  The response
shall be addressed to the U.S. Nuclear Regulatory Commission, ATTN:  Document
Control Desk, Washington, DC 20555, under oath or affirmation.  A copy shall
also be submitted to the appropriate regional administrator.  This generic
letter supplement requires information that will enable the NRC to verify
whether the licensee is evaluating new information on the accuracy of MOV
diagnostic equipment.  This information will enable the Commission to
determine whether or not any license should be modified, suspended or revoked.

(1)   Within 90 days of receipt of this letter, all licensees are required to
      notify the NRC staff of the diagnostic equipment used to confirm the
      proper size, or to establish settings, for MOVs within the scope of
      GL 89-10.

(2)   Within 90 days of receipt of this letter, licensees are required to
      report whether they have taken actions or plan to take actions
      (including schedule and summary of actions taken or planned) to address
      the information on the accuracy of MOV diagnostic equipment.


The NRC staff has determined that the actions requested in this generic letter
supplement are necessary to provide confidence that nuclear power facilities
are in compliance with their safety analyses and Criterion XI, "Test Control,"
of Appendix B to 10 CFR Part 50, which requires that test procedures include
provisions for ensuring that adequate test instrumentation is available. 
Therefore, the NRC staff has determined that this generic letter supplement is
exempt from the requirements for preparation of a backfit analysis under 
10 CFR 50.109(a)(4)(i).

Generic Letter 89-10, Supp. 5       - 4 -                   June 28, 1993

The NRC published a proposed version of this generic letter supplement for
public comment in the Federal Register on July 8, 1992.  The NRC staff 
response to each public comment received on the proposed generic letter
supplement is being placed in the NRC Public Document Room.  The accession
number for this document is 9306010155.


This generic letter contains information collection requirements that are
subject to the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.). 
These requirements were approved by the Office of Management and Budget,
approval number 3150-0011.

The public reporting burden for this collection of information is estimated to
average 150 hours per licensee response, including the time for reviewing
instructions, searching existing data sources, gathering and maintaining the
data needed, and completing and reviewing the collection of information.  Send
comments regarding this burden estimate or any other aspect of this collection
of information, including suggestions for further reducing this burden, to the
Information and Records Management Branch (MNBB-7714), U.S. Nuclear Regulatory
Commission, Washington, D.C., 20555; and to the Desk Officer, Office of
Information and Regulatory Affairs, NEOB-3019, (3150-0011), Office of
Management and Budget, Washington, D.C., 20503.

Compliance with the following request for information is purely voluntary. 
The information would assist the NRC in evaluating the cost of complying with
this generic letter supplement:

(1)   the licensee's time and costs to perform requested inspections,
      corrective actions, and associated testing;

(2)   the licensee's time and costs to prepare the requested reports and

(3)   the additional short-term costs incurred as a result of the inspection
      findings, such as the costs of the corrective actions or the costs of
      down time; and

(4)   an estimate of the additional long-term costs that will be incurred in
      the future as a result of implementing commitments such as the estimated
      costs of conducting future inspections or increased maintenance.

Generic Letter 89-10, Supp. 5       - 5 -                   June 28, 1993

If you have any questions about this matter, please contact the contacts
listed below or the appropriate Office of Nuclear Reactor Regulation project


                                    Orig /s/'d by JGPartlow

                                    James G. Partlow
                                    Associate Director for Projects
                                    Office of Nuclear Reactor Regulation

List of Recently Issued NRC Generic Letters

Technical contact:  Thomas G. Scarbrough
                    (301) 504-2794

Lead Project Manager:  Anthony T. Gody, Jr.
                       (301) 504-1387

Page Last Reviewed/Updated Friday, June 28, 2013