ML20059H941

Informs That Calibration Blocks Used in Inservice Insp Were within +/-25 Range therefore,re-examinations Not Performed

ML20059H941
Person / Time
Site:	Prairie Island
Issue date:	01/14/1994
From:	Richard Anderson NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9401310246
Download: ML20059H941 (2)

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Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401 1927 Telephone (612) 330 5500 January 14, 1994 10 CFR Part 50 Section 50.73 i

I U S Nuclear Regulatory Commission Attn Document Control Desk Washington, DC '20555 i

PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 ASME Section XI ISI Examinations Performed with Incorrect Calibration Blocks 1

We submitted a Licensee Event Report (Unit 1 LER sequential number 93-04) with f

the above title in March 1993. We had reported that during the Fall 1992 Prairie Island Dual Unit Outage, we had used ultrasonic calibration blocks of the wrong thicknesses in performing ASME Section XI inservice inspections. We reported that we would evaluate the examinations for unacceptable sensitivity or with less than required coverage and would repeat those examinations.

This letter is intended to inform you that further review of the requirements revealed that the calibration blocks which we had used actually were within the 125% range which is allowed by Code case N-461.

We therefore did not.

perform any re-examinations.

We also reported the use of a calibration block made of the wrong material f r the examination of the pressurizer spray nozzle inner radius on both units.

This was discussed in the Licensee Event Report although it would'not have been reportable by itself since there was still allowable time to perform re-examinations and we are proceeding to do so.

We made the following NRC commitments in that Report [in brackets are the disposition of those commitments):

, (1) The examinations associated with incorrect calibration blocks will be evaluated and, if the evaluation demonstrates that the sensitivity'is off by more than -2dB (Section V recalibration tolerance), the examinations will be. repeated at the next refueling outage."

[Since the calibration blocks were found to be within the allowable 125%

thickness range, we have not and do'not intend to repeat these examinations.)

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January 14, 1994

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i (2) ISI NDE procedures, plans and administrative procedures will be

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revised to require verification of use of correct calibration blocks and to improve records maintenance.

i (We have changed our method of developing ISI plans, so that we now verify that we have correct calibration standards prior to the outage.)

i (3) Actual material used for the pressurizer spray nozzle is being determined.

Based on the results of that determination, the resultant examination sensitivity will be determined.

If the sensitivity is off by more than -2dB (Section V recalibration tolerance), the examination will be repeated at the next refueling outage.

Drawing corrections will be made based on the result of i

this evaluation.

1 (The actual spray nozzle material has been determined and the examination will j

be re-done for Unit 1 in the Spring 1994 outage and Spring 1995 outage for Unit 2.

The drawing corrections have been made.]

(4) Corrective measures have been. initiated to improve the maintenance I

and retrievability of the ISI Program records.

[This commitment has been completed by compiling exam results in books, arranged in a manner for easy retrievability.)

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(5) ISI personnel are continuing to review the ISI plan for any other deficiencies, k

(The review for deficiencies has been dono concurrently with the development i

of the new 3rd 10-Year Interval Inservice Inspection Program which has just-l been completed for Unit 1 and will be completed for Unit 2 this summer.)

j (6) An independent audit of the ISI Program is planned for late 1993 to determine the effectiveness of the corrective actions taken.

l (This audit has been completed and results were acceptable.]

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o Northem States Power Company January 14, 1994 Page 3 Please contact Jack Leveille (612-388-1121, Ext. 4662) if you require additional-information related to this event.

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Ro er O Anderson Director l

Licensing and Management Issues i

c: Regional Administrator - Region III, NRC NRR Project Manager, NRC Senior Resident Inspector, NRC Kris Sanda, State of Minnesota i

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