ML13309A161

Provides Results of Evaluation of Use of Checmate Code During 1991 Unit 2 Refueling Outage to Assess Erosion/ Corrosion of Piping Sys

ML13309A161
Person / Time
Site:	San Onofre
Issue date:	12/20/1991
From:	Ray H Southern California Edison Co
To:	Martin J NRC/IE, NRC/RGN-V
References
NUDOCS 9201070315
Download: ML13309A161 (5)

Text

ACCELERATEDI DI RIBUTION DEMONST TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9201070315 DOC.DATE: 91/12/20 NOTARIZED: NO DOCKET #

FACIL:50-206 San Onofre Nuclear Station, Unit 1, Southern Californ 05000206 50-361 San Onofre Nuclear Station, Unit 2, Southern Californ 05000361 50-362 San Onofre Nuclear Station, Unit 3, Southern Californ 05000362 AUTH.NAME AUTHOR AFFILIATION RAY,H.B.

Southern California Edison Co.

R RECIP.NAME RECIPIENT AFFILIATION MARTIN,J.B.

Region 5 (Post 820201)

SUBJECT:

Provides results of evaluation of use of CHECMATE Code during 1991 Unit 2 refueling outage to assess erosion/

D corrosion of piping sys.

S DISTRIBUTION CODE: IE01D COPIES RECEIVED:LTR / ENCL SIZE:

TITLE: General (50,Dkt)-Insp Rept/Notice of Violation Response

/

NOTES:License Exp date in accordance with 10CFR2,2.109.

05000206 A RECIPIENT COPIES RECIPIENT COPIES D

ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D

PD5 PD 1

KALMAN,G 1

KOKAJKO,L.

1 S

INTERNAL: ACRS 2

AEOD 1

AEOD/DEIIB 1

AEOD/DSP/TPAB 1

DEDRO 1

NRR HARBUCK,C.

1 NRR MORISSEAU,D 1

NRR/DLPQ/LHFBPT 1

NRR/DLPQ/LPEB10 1

NRR/DOEA/OEAB 1

NRR/DREP/PEPB9H 1

NRR/DST/DIR 8E2 1

NRR/PMAS/ILRB12 1

NUDOCS-ABSTRACT 1

1 OGC/HDS3 1

FILE 02 1

RGN5 FILE 01 1

EXTERNAL: EG&G/BRYCE,J.H.

1 NRC PDR 1

NSIC 1

R I

D S

A D

D NOTE TO ALL "RIDS" RECIPIENTS:

S PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM P1-37 (EXT. 20079) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 2---

Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 HAROLD B. RAY TELEPHONE SENIOR VICE PRESIDENT 714-458*4400 December 20, 1991 Mr. John B. Martin, Administrator U. S. Nuclear Regulatory Commission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368

Subject:

Docket Nos. '50-206, 50-361 and 50-362 Erosion/Corrosion of Piping Systems San Onofre Nuclear Generating Station My letter to you dated September 24, 1991, indicated that we were usingthe CHECMATE Code during the 1991 Unit 2 refueling outage and would complete an evaluation of CHECMATE based on this use by the end of 1991.

This letter provides the results of our evaluation.

BACKGROUND My September 24 letter provided the results of our assessment of whether the use of the EPRI Chexal-Horowitz-Erosion-Corrosion (CHEC) code would have resulted in detection of the associated wall thinning and avoidance of the resulting leaks in the San Onofre Units 2 and 3 feedwater bypass lines. The conclusion of our assessment was that minimal application of the CHEC Code, with the then-existing guidance, would not have resulted in timely detection of excessive erosion/corrosion (E/C) in these lines. Our assessment also noted that a broader application of the results of the CHEC code (i.e., expansion of the inspection scope substantially beyond the minimum 15 points indicated by CHEC) could have resulted in detection of excessive E/C before the leaks developed.

Two points from our previous assessment which I included in my September 24 letter were:

o Experience and engineering judgement continue to play key roles in the design of.an E/C monitoring program. The codes available for use are helpful tools, but they are not sufficient by themselves.

-~2Q:1c~

3 0

Mr. John December 20, 1991 o

The CHEC/CHECMATE Users Group (CHUG) is an important forum

-for the sharing of experience. Industry success in preventing excessive wall thinning should show steady improvement as a result of this forum.

DISCUSSION In preparation for the recently completed Unit 2 refueling outage more than 3,000 components in the condensate, feedwater and steam systems were ranked using the CHECMATE Code, an improved version of the CHEC Code. In addition to using the results of this ranking to identify the components for our inspection, we made extensive use of recent experience at San Onofre and other plants, and engineering judgement to identify other components which we believed were more susceptible to E/C. Based on this evaluation, 378 components were initially selected for inspection; far more than the 15 components associated with a minimal application of the CHECMATE Code. Subsequently, 108 additional components, for a total of 486, were added to the inspection scope based on E/C indications identified during the initial 378 component inspections.

Although evaluation of the results of the San Onofre Unit 2 E/C inspection continues, we believe that this inspection was very successful, and supports our previous conclusions that the codes must be aggressively and broadly applied and that extensive use must be made of experience and engineering judgement.

The CHECMATE Code has a provision to use the results 'of previous inspections to adjust its predictions for future inspections. We believe that use of this provision will improve the ability of future inspections at San Onofre to detect excessive E/C before leaks develop. In addition, the results of our experience from the San Onofre Unit 2 inspection were presented to the CHUG on December 6, 1991, and EPRI has agreed to review the inspection data and to revise the code, or guidance for its use, if appropriate.

SUMMARY

In summary, aggressive and broad application of the CHECMATE Code in combination with extensive use of experience and engineering judgement provides an adequate basis for an E/C inspection program. Our expectation is that, as we gain more experience, the code and our confidence in detecting excessive E/C before leaks develop will further improve.

Mr. John December 20, 1991 If you have any questions, or if you would like additional information concerning the above, please let me know.

Sincerely, cc:

G. Kalman, Senior Project Manager, SONGS 1, 2, and 3 D. F. Kirsch, Chief Reactor Safety Branch, Region V C. W. Caldwell, NRC Senior Resident Inspector, SONGS John J. Taylor, Vice President Nuclear Power Division, EPRI

Mr. John December20, 1991 bcc: Gary D. Cotton (SDG&E)

R. G. Lacy (SDG&E)

A. R. Watts (Rourke & Woodruff)

E. K. Aghjayan (City of Anaheim)

B. D. Carnahan (City of Riverside)

Harold B. Ray H. E. Morgan R. M. Rosenblum H. W. Newton R. D. Plappert