ML18095A241

Submits Special Rept 90-4 Addressing Steam Generator Tube Plugged During Fifth Refueling Outage.Plugging Completed on 900516.Cause of Tube Degradation Attributed to Normal Wear Due to Erosion/Corrosion Factors

ML18095A241
Person / Time
Site:	Salem
Issue date:	05/30/1990
From:	Miller L Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9006050288
Download: ML18095A241 (4)

Text

PS~G *

• Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station May 30, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 SPECIAL REPORT 90-4 This Special Report addresses the Steam Generator tubes plugged during the current fifth refueling outage. This report is submitted pursuant to the requirements of Technical Specification Surveillance 4.4.6.5.a. This report is required within fifteen (15) days of completion of tube plugging.

Sincerely yours,

1. ~

L. K. Miller General Manager -

Salem Operations MJP:pc Distribution 9006050288 900530

~DR ADOCK 05000277

,.- F'DC The Energy People 95-2189 (10M) 12-89

SPECI~L REPORT NUMBER ~4 P~ANT IDENTIFICATION:

Salem Generating Station - Unit 2

• Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

Steam Generator Tubes Plugged During the Fifth Refueling Outage Event Date: 5116190 Report Date: 5130190 This report was initiated by Incident Report Nos.90-277 and 90-331.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 6 - Refueling Outage DESCRIPTION OF OCCURRENCE:

On May 16, 1990, Steam Generator (SIG) tube plugging was completed.

Tubes were plugged either due to exceeding the percent degradation of

~ 40% (as per Technical Specification 4.4.6.4.6) or were between 30%

and 40% as a conservative measure (as determined by ISI). The following are the tubes plugged:

No. 21 SIG No. 22 SIG Row Column  % Degradation Row Column  % Degradation 32 61 53 31 78 37 32 63 41 34 59 42 32 65 41 34 63 48 33 45 44 39 44 45 33 48 38 34 59 46 39 43 55 40 56 36 No. 24 SIG No. 23 SIG Row Column  % Degradation Row Column  % Degradation 33 38 45 4 38 56 33 56 42 14 62 47 34 79 39 25 10 46 35 77 40 32 34 37 42 44 73 34 49 45 42 45 62 38 43 48 42 63 32 40 40 61 43 32 33 40 47 59 43 36 DRI* 40 49 44 43 45 39 40 52 52

43. 61 49 40 57 35 41 32 37 43 64 84

• - Distorted Roll Transition 43 62 84 Indication 45 36 37

t?NIT ,~ SPECIAL REPORT * - 4

• During the eddy current inspection of No. 23 S/G, the inspectors discovered that a tube thought to be plugged was not. As indicated in the above list the No. 23 SIG tube associated with Row 25 Column 10 was plugged this outage. However, during the second refueling outage, this same tube was identified as being plugged.

APPARENT CAUSE OF OCCURRENCE:

The root cause of the tube degradation has been attributed to normal wear caused by erosion/corrosion factors.

The root cause of the wrong tube being plugged, in No. 23 S/G, has been attributed to personnel error associated with procedural noncompliance.

Investigation revealed that the No. 23 SIG tube associated with Row 10 Column 25 was in fact plugged during the second refueling outage and not the one associated with Row 25 Column 10. Apparently, the robotics operator reversed the Row and Column for this one tube, thereby marking the wrong tube to be plugged. The S/G tube plugging procedure requires a Quality Assurance inspection to verify that the correct tube is marked prior to plugging. This was not completed for this tube. On December 6, 1984, a QA inspection was performed for tubes which were to be plugged due to tube wear caused by vibration of the tube lane blocking device. On December 12, 1984, another tube was identified to be plugged as determined from eddy current inspections. This tube is the one for Row 25 Column 10 in No. 23 S/G. This tube was never verified by QA as being correctly marked, subsequently, the wrong tube was marked and eventually plugged. A second tube marking and plugging procedure had not been initiated; the original procedure {with its signoffs} was used for plugging the December 12, 1984 tube.

The procedure for identifying those S/G tubes required to be plugged during the second refueling outage involved the use of remotely controlled robotics equipped with TV cameras. Tubes to be plugged are marked with a zyglo penetrant mixed with a Nissan marker. A Quality Assurance signoff is performed verifying that the correct S/G tube had been marked. Additionally, both Inservice Inspection Services {ISI) and Quality Assurance personnel viewed a live remote showing of the tube{s) plugged after which they sign the procedure certifying that the tube marked has been appropriately plugged. This second inspection {performed by QA and ISI inspectors) is not a verification that the correct tube has been plugged, only that the tube marked has been plugged.

A possible contributor to the plugging of the wrong tube is that the SIG Tube Map does not indicate which axis represents rows and which represents columns. This should be self evident though since there are more than twice the number of columns than rows {i.e., 94 columns and 46 rows).

ANALYSIS OF OCCURRENCE:

The tube which should have been plugged during the second refueling outage had a percent degradation of 38% when inspected in December 1984. During the recent inspection, its percent degradation

?NI:._.2 SPECIAL REPORT * - 4 AMALYSIS OF OCCURRENCE: (cont'd)

• increased to 46%. Since the Technical Specifications for the maximum allowable percent degradation were not violated, as per the December 1984 inspection, this event is not reportable as per NUREG 1022, "Licensee Event Report System".

In summary of the entire fifth refueling inspection, the tubes found with ~ 40% degradation is considered normal. Also, primary to secondary leakage was not observed during the Unit 2 operating period between the fourth (4th) outage and this outage. Therefore, the events identified by this report did not affect the health or safety of the public.

This report satisfies Technical Specification Surveillance 4.4.6.5.a which states:

"Following each inservice inspection of steam generator tubes, the number of tubes plugged in each steam generator shall be reported to the Commission within 15*days."

CORRECTIVE ACTION:

Modifications to the independent review process were implemented prior to completion of tube plugging this outage. The process now requires SQA to prepare a separate map of the tubes to be plugged and to then independently verify that the correct tubes have been marked.

The plugging of the incorrect tube in No. 23 SIG was an isolated occurrence. All tubes previously plugged have been verified as being correctly plugged.

The S/G Tube Maps will be revised to label the axis.

This event has been reviewed by Station Quality Assurance (SQA) management. The circumstances surrounding the incorrect tube plugging event will be reviewed with appropriate !SI and Quality Assurance personnel. The accident analysis, associated with S/G tube rupture, will be reviewed in respect to the significance of not plugging the correct tube.

A summary of the incorrect tube plugging event will be sent over the INPO Nuclear NETWORK as information for all other utilities.

/t(Mµ General Manager -

Salem Operations MJP:pc SORC Mtg.90-061