United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9706250258


Omaha Public Power District

444 South 16th Street Mall

Omaha NE 68102-2247

June 17, 1997


U. S. Nuclear Regulatory Commission

Attn: Document Control Desk

Mail Station P1-137

Washington, DC 20555

Reference:     Docket No. 50-285

SUBJECT:       10 CFR 21 Report on Nonconforming Raw Water Pump Impellers

Pursuant to 10 CFR 21 (d)(3)(ii), Omaha Public Power District (OPPD)

provides the attached written notification of a defect in a basic

component (Raw Water pump impellers) at Fort Calhoun Station Unit No. 1.

Initial notification of this condition was made to the OPPD responsible

corporate officer and to the NRC Operations Center on May 23, 1997.

Please contact me if you have any questions.


S. K. Gambhir

Division Manager

Engineering & Operations Support



c:   Winston & Strawn

     E. W. Merschoff, NRC Regional Administrator, Region IV

     L. R. Wharton, NRC Project Manager

     W. C. Walker, NRC Senior Resident Inspector

45.5124             Employment with Equal Opportunity

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                   Omaha Public Power District (OPPD)

            Report on Nonconforming Raw Water Pump Impellers

This report is submitted pursuant to 10 CFR 21.21(d)(3)(ii).  The items

below address the specific information required by 10 CFR 21.21.(d)(4).

(i)       Identification of individual providing this notification:

          S. K. Gambhir

          Division Manager - Engineering & Operations Support

          Omaha Public Power District

          Fort Calhoun Station

          P. O. Box 399

          Fort Calhoun, NE 68023-0399

(ii)      Basic components containing defect:

          Replacement impellers for Byron Jackson Raw Water pumps had

          blade dimensions out of tolerance.  Pumps are Model 28RXL 2-

          stage VCT.

(iii)     Identification of supplier:

          BW/IP International, Inc.

(iv)      Nature of Defect:

          Raw Water pump assembly AC-10D was replaced due to normal wear

          On the pump internals, namely the pump impellers and impeller

          liners.  The replacement assembly had been rebuilt with new

          internal components.  After installation, post maintenance and

          operability testing was performed using a station procedure.

          The pump did not satisfy the acceptance criteria contained in

          the test; therefore, the pump remained inoperable.  The fact

          that the pump did not pass the test was very unusual especially

          considering the pump was completely rebuilt with all new

          internal subcomponents.  The impeller lift setting was

          reverified and then the post maintenance/ operability test was

          again performed.  Again the pump did not pass the test, so the

          pump assembly was removed and replaced with a another spare

          pump assembly.

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          The "defective" pump assembly was then disassembled for

          inspection to determine the cause of the extremely poor

          performance.  Upon inspection of the first stage pump impeller,

          it was noticed that the blade profile was significantly

          different when compared to the second stage impeller.  At least

          two of the four blades on the first stage impeller appeared to

          have a "droop" causing the opening or suction eye between the

          blades to decrease.  The size of the suction eye for these

          particular type of pumps has a large influence on the amount of

          discharge flow the pump is able to produce.  This is because

          the decreased suction eye size causes the impeller to become

          extremely inefficient.  With the defective impeller installed

          in the first stage of the pump, discharge flow was drastically


          One other replacement impeller in the warehouse was determined

          to have similar deficiencies.

          Potential Safety Significance

          The subject impellers contained dimensional inaccuracies which

          prevented pump discharge flows from satisfying the acceptance

          criteria.  The estimated reduction of design flow was 20%.  The

          Plant Review Committee conservatively determined that operation

          of a Raw Water pump AC-10D at the maximum allowable river

          temperature (90 degrees F) with the defective impeller

          installed could have created a substantial safety hazard by

          exceeding a safety limit or causing a major degradation of

          essential safety-related equipment, considering a single

          failure in addition to the degraded performance of AC-10D.  The

          river water temperature at the time of discovery was 36 degrees


(v)       Date information of defect was obtained:

          The installation of the replacement pump assembly with the

          defective impeller and unsuccessful testing was initially

          identified on April 8, 1997.  Based on review of an engineering

          evaluation of this condition, OPPD management on May 22, 1997

          conservatively determined that a defect existed.  The OPPD Vice

          President with executive authority over Part 21 issues was

          informed on May 23, 1997.

(vi)      Number and Location of components containing defect:

          Two defective impellers passed the OPPD receipt inspection and

          were stocked in the warehouse.  Because dimensional information

          is considered proprietary by BW/IP International, the receipt

          inspection relied on verification of the part number and the

          fact that BW/IP International is an Appendix B supplier.  One

          of these impellers was used to rebuild a spare pump assembly

          which was

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          installed as Raw Water pump AC-10D.  The supplier has not

          reported these impeller defects.  The existence of other

          similarly defective impellers from this supplier is unknown to


(vii)     Corrective action which has, or is being taken:

          The defective impellers are being returned to the supplier.

          Raw Water pump AC-10D was replaced with a rebuilt pump assembly

          which passed all post-maintenance Surveillance test

          requirements.  The supplier has been notified about this


(viii)    Advice related to defect to be given to licensees:



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