United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9711030183



                                   ABB



                                   October 30, 1997

                                   LD-97-031



Document Control Desk

U.S. Nuclear Regulatory Commission

Washington, DC 20555



Subject:  Report Pursuant to 10 CFR 21 Regarding Incorrect Nut And Washer

          Plate Material for ECCS Suction Strainer Bolted Connections



Gentlemen:



The purpose of this letter is to notify the Nuclear Regulatory Commission

of a defect pursuant to 10 CFR 21, "Reporting of Defects and

Noncompliance." The identified "defect" is the use of incorrect material

in the fabrication of nut plates and washer plates for Peach Bottom Unit

3 Emergency Core Cooling System (ECCS) suction strainer bolted

connections.



The nut plates and washer plates were fabricated from incorrect material

and delivered to the Peach Bottom Unit 3 site.  US Tool and Die Company

fabricated the parts as a subvendor to ABB-CE.  During receipt inspection

by Philadelphia Electric Company (PECO), it was determined that the nut

plates and washer plates were fabricated with SA-240, Type 304 material

instead of the specified 17-4 PH material, SA-564, SA-693, or SA-705,

Grade 630 in H1150 condition per ASME Code Section III, Class 1,

Subsection NF, 1989 Edition, no addenda.  These parts are used as part of

the bolted connection when two or more strainer modules are joined

together to form a strainer train.  High strength bolts are threaded into

the nut plates and torqued to a level that results in a bolt preload that

exceeds required operational bolt loads.  This assures that the strainer

train remains continuous for all loading cases, and that no unacceptable

gaps develop between strainer modules.  The SA-240, Type 304 material has

lower yield and tensile properties than the specified material.



These nut and washer plates were never installed, and replacement parts

have been provided which have the required material properties.  This is

the first application of this design and, therefore, no previous

applications exist.



              ABB Combustion Engineering Nuclear Operations



Combustion Engineering,  P.O.  Box 500           Telephone (203) 688-1911

Inc.                     1000 Prospect Hill Road  Fax (203) 285-9512

                         Windsor, Connecticut

                         06095-0500



                                                                LD-97-031

                                                                   Page 2



An evaluation was performed to determine the potential conditions that

might have existed if this material discrepancy had not been discovered

and the parts fabricated of incorrect material had been installed in the

strainers.  Three potential conditions could have existed.



     1.   The threads in the SA-240 Type 304 nut plates would have been

          subjected to shear forces that exceed the ASME code allowable

          values.  The threads may have sheared during the installation

          torquing process, in which case the material discrepancy would

          have been discovered prior to plant operation.



     2.   The threads in the SA-240 Type 304 nut plates would have

          locally yielded and strain hardened, but would have held the

          applied torque and resulting bolt preload.  The preload was

          specified at a level that exceeds specified operational

          loadings up to and including Level D loadings.  Since the

          temperature at operation is well below the threshold for creep

          relaxation, the bolt preload would remain as intended during

          use.  Shop testing by US Tool and Die Company indicates that

          this is the most likely result.



     3.   During installation at high torque values, some SA-240, Type

          304 threads may have yielded and galled.  Galling of the

          threads during installation could result in a failure to

          achieve the design bolt preload, even though the proper torque

          is applied.  The propensity for galling of these incorrect

          materials is about the same as for the specified materials for

          lower torque values.  It is the greater potential for local

          yielding at high torque values that increases the risk of

          galling of the incorrect materials in this application.

          Failure to achieve the proper bolt preload could result in the

          strainer modules separating by more than the design limit of

          1/8 inch during some loading cases.  It should be noted that

          shop torque testing at US Tool and Die Company of nut and

          washer plates fabricated from the incorrect materials did not

          result in galling at torque values equal to or higher than that

          prescribed.



The Attachment contains information specifically required by 10 CFR 21.



                                        Very truly yours,

                                        COMBUSTION ENGINEERING, Inc.



                                        Ian C. Rickard, Director

                                        Operations Licensing



cc:  M.  F.  Barnoski (ABB-CE)



Attachment to

LD-97-031

                                    1



              ABB Combustion Engineering Nuclear Operations

            10 CFR 21 Report of a Defect or Failure to Comply



The following information is provided pursuant to 10 CFR 21.21 (c)(4):



(i)       Name and address of the individual informing the Commission:



               Ian C.  Rickard, Director

               Operations Licensing

               Combustion Engineering

               2000 Day Hill Road

               Windsor, CT 06095-0500



(ii)      Identification of the facility, the activity, or the basic

          component supplied for such facility or such activity within

          the United States which fails to comply or contains a defect:



          The basic components are nut plates and washer plates for ECCS

          suction strainer bolted connections.



(iii)     Identification of the firm constructing the facility or

          supplying the basic component which fails to comply or contains

          a defect:



          The nut plates and washer plates were supplied to ABB-CE by US

          Tool and Die Company, and were subsequently provided to the

          nuclear plant identified in item (vi) below by:



               Combustion Engineering, Inc.

               2000 Day Hill Road

               Windsor, CT 06095-0500



(iv)      Nature of defect or failure to comply and the safety hazard

          which is created or could be created by such defect or failure

          to comply:



          The defect is the use of incorrect material in the fabrication

          of nut plates and washer plates used in ECCS suction strainer

          bolted connections.  The incorrect material could result in

          failure to achieve proper bolt preload, potentially resulting

          in strainer modules separating by more than the design limit of

          1/8 inch during some loading cases.



                                    2                       Attachment to

                                                                LD-97-031



(v)       The date on which the information of such defect or failure to

          comply was obtained:



          ABB-CE received information regarding incorrect nut plate and

          washer plate material on September 18, 1997.



(vi)      In the case of a basic component which contains a defect or

          fails to comply, the number and location of all such components

          in use at, supplied for, or being supplied for one or more

          facilities or activities subject to the regulations of this

          part:



          ABB-CE supplied 208 nut plates and 208 washer plates to PECO

          for use at Peach Bottom Unit 3.  The incorrect material was

          discovered during receipt inspection by PECO, and the affected

          nut plates and washer plates were not installed.



(vii)     The corrective action which has been, is being, or will be

          taken; the name of the individual responsible for the action;

          and the length of time that has been or will be taken to

          complete the action:



          ABB-CE is preparing training classes to strengthen its own

          internal review processes to prevent a recurrence of this

          error.  These training classes will be held by the end of

          December, 1997.  US Tool and Die Company is currently revising

          its internal procedures to prevent a recurrence of this error.

          US Tool and Die Company has initiated a requirement that all

          contract material be receipt inspected in accordance with

          approved customer documents.



(viii)    Any advice related to the defect or failure to comply about the

          facility, activity, or basic component that has been, is being,

          or will be given to purchasers or licensees:



          ABB-CE intends to provide an information copy of this 10 CFR 21

          report to PECO Energy, Stone and Webster Engineering

          Corporation, and utilities owning an ABB-CE designed NSSS.

          Within the scope of ABB CE's activities, this issue applies

          only to PECO Energy's Peach Bottom Unit 3.



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