United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9411280210

                                              NTD-NRC-94-4344

Westinghouse         Energy Systems           Box 355
Electric Corporation                          Pittsburgh, Pennsylvania
                                              15230-0355


                                              November 15, 1994

U.S. Nuclear Regulatory Commission
Attn:  Document Control Desk
Washington, DC  20555


Subject:   Closeout of an Interim Report of an Evaluation of a
           Deviation or Failure to Comply Pursuant to 10CFR21.21(a)(2)

Reference:      (1)  ET-NRC-94-4303, Interim Report of an Evaluation of
                     a Deviation or Failure to Comply Pursuant to
                     10CFR21.21(a)(2), dated September 19, 1994


The attached information is provided as a closeout to Interim Report
94-012.  Preliminary information was previously provided per Reference
1 pursuant to the requirements of 10CFR Part 21 to submit an Interim
Report on issues that will not be completed within 60 days from the
discovery of the deviation or failure to comply.

A closeout to Interim Report 94-012 is enclosed for the following
Potential Issue under Westinghouse evaluation:

1.    Reactor Coolant Pump (RCP) Support Column Tilt

If you have any questions regarding this matter, please contact Mr. H.
A. Sepp of my staff at 412/374-5282, or myself.

Sincerely,


N. J. Liparulo, Manager
Nuclear Safety Regulatory and Licensing Activities

Attachment


Westinghouse Electric Corporation
Energy Systems
P.O. Box 355
Pittsburgh, PA  15230-0355
                                              Interim Report No. 94-012
                                              Date: 11/16/94

SUBJECT:

      Closeout to an Interim Report of an Evaluation of a Deviation or
      Failure to Comply Pursuant to 10CFR21.21(a)(2).

TITLE:

      Reactor Coolant Pump (RCP) Support Column Tilt

BASIC COMPONENT SUPPLIED BY:

      Westinghouse Electric Corporation

NATURE OF DEVIATION:

      As provided in the original issue of Interim Report 94-012,
      Westinghouse identified a potential issue related to certain
      reactor coolant pump (RCP) support columns that may be tilted
      beyond design parameters.  Specifically, certain three and four
      loop plants have a loop piping layout in which the crossover leg
      piping interferes with the front inside support column of the
      RCP.  The other columns on the RCP are oriented to be vertical in
      the normal full power condition.  This condition was recognized
      by the support designer and changes were made to the column
      layout to accommodate the interference between the column and the
      crossover leg.  The change consists of moving the base of the one
      RCP column toward the reactor pressure vessel approximately 6-12
      inches so that the tilted column no longer interferes with the
      crossover leg piping.  The required tilt is from approximately 2
      to 5 degrees depending on the column length and amount of
      movement.  This condition was apparently reconciled during the
      design phase and was not considered a significant issue.  The
      actual change in the value of the vertical stiffness is small,
      but there is an impact on the thermal expansion of the system. 
      There are tolerances in the RCP columns that would potentially
      absorb some of the vertical movement associated with the column
      rotation.

SAFETY ASSESSMENT

      Analyses have been performed to evaluate the impact of the RCP
      column tilt on the plant with the most severe tilt.  A plant with
      a column tilt associated with a 12 inch movement of the column
      base from the front inside pump column was chosen for this
      evaluation.

      The additional loadings associated with column tilt originate
      from the use of a support stiffness that has been rotated from
      vertical by a few degrees.  This rotated stiffness at one of the
      three column locations acts to restrain and rotate the RCP.  For
      a loop piping system thermal expansion


      of approximately 1.8 inches, the vertical displacement associated
      with the rotation of an RCP column will vary from about 10 mils
      for a nearly vertical column to about 1.30 mils for an upper
      bound tilted column.  This difference in displacements at the
      three RCP columns is what causes a rotation in the pump not
      previously accounted for.  This source of additional loading
      varies from plant to plant based on the primary equipment support
      design.  There are plants with pin-ended columns that will not
      have this type of additional loading.  There are a number of
      plants that have support details not of Westinghouse design. 
      Many of the Westinghouse designed supports have a tilt that is
      approximately half of that analyzed as a part of this evaluation.

      When this enhancement was made to the thermal analysis, different
      system loadings resulted.  The bending moment at the RCP outlet
      nozzle for the example plant increased by more than 100%.  The
      RCP column loads also changed.  The tilted column went from a
      compression load to a tension load.  The change in column loading
      met applicable Code allowable limits.  The loop Leak-Before-Break
      (LBB) evaluation was of particular concern for system load
      changes.  The LBB evaluation is performed with the goal of
      achieving certain margins.  The new loadings were reviewed for
      all 12 weld locations in the primary loop for the example plant,
      and acceptable margins were maintained.

      The loop evaluation performed for the example plant, for column
      tilt loads, met acceptable stress levels.  The column tilt for
      the example plant is approximately twice (12 inches versus 6 or
      6.5 inches) that of most other plants.  It has been determined
      that due to the overwhelming plant specific nature of both RCS
      loops and the RCP column design, the example plant configuration
      is not generic nor necessarily enveloping, but is representative
      of a typical Westinghouse configuration.  Every plant affected by
      the RCP column tilt issue has a plant-specific loop analysis that
      has a unique set of margins.  Because loadings local to the RCP
      can be quite different due to the inclusion of column tilt, those
      plants that have small margins in this area may require
      additional analysis.  As mentioned, there are conservative
      margins that are part of the licensing basis associated with LBB. 
      Even in the event that LBB licensing margins are not satisfied,
      previous experience in the use of the margins associated with LBB
      lead to the conclusion that the LBB design basis continues to
      apply.

      A review of the increased loadings on our example plant yielded
      acceptable results in all areas reviewed.  For the example plant
      evaluation, there were significant margins available in the areas
      where loadings increased.  If specific modeling techniques are
      the cause of lower margins, additional analysis may reduce some
      of the potential conservatism that led to the low margins. 
      Westinghouse has determined that there is no RCS pressure
      boundary integrity concern due to the RCP column tilt issue, and
      as such, this issue is not reportable pursuant to 10 CFR part 21.

DATE OF DISCOVERY OF DEVIATION:

      July 20, 1994

CORRECTIVE ACTIONS TO DATE:

      Westinghouse has completed an extensive evaluation of this issue. 
      It has been determined that the RCP Column Tilt issue does not
      pose a challenge to the reactor coolant system pressure boundary
      and therefore, a substantial safety hazard does not exist. 
      Westinghouse has published a Nuclear Safety Advisory letter to
      communicate this information to affected utilities.


EVALUATION COMPLETION SCHEDULE DATE

      Complete


                     N. J. Liparulo, Manager
                     Nuclear Safety Regulatory and Licensing Activities



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