AECM-83-0481, Responds to 830727 Request for Info Re Intergranular Stress Corrosion Cracking.Rev 1 to Rept, Effects of Intergranular Stress Corrosion Cracking on Operation of Grand Gulf Nuclear Station,Unit 1, Encl

Responds to 830727 Request for Info Re Intergranular Stress Corrosion Cracking.Rev 1 to Rept, Effects of Intergranular Stress Corrosion Cracking on Operation of Grand Gulf Nuclear Station,Unit 1, Encl

ML20080C092
Person / Time
Site:	Grand Gulf
Issue date:	08/17/1983
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20080C095	List: AECM-83-0481, Responds to 830727 Request for Info Re Intergranular Stress Corrosion Cracking.Rev 1 to Rept, Effects of Intergranular Stress Corrosion Cracking on Operation of Grand Gulf Nuclear Station,Unit 1, Encl ML20080C098
References
AECM-83-0481, AECM-83-481, TAC-56304, NUDOCS 8308190070
Download: ML20080C092 (5)

Text

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.e MISSISSIPPI PO\NER & LIGHT COMPANY

]

P. O, Helping Build Mississippi B O X 16 4 0, J A C K S O N, MISSISSIPPI 39205 NuctsAn nocucTON DEPARTMENT U. S. Nuclear Regulatory Commission Office of Nuc1 car Reactor Regulation Washington, D. C. 20555 Attention: Mr. Harold R. Denton, Director

SUBJECT:

Grand Gulf Nuc1 car Station Unit 1 .

Docket No. 50-416 License No. NPF-13 File: 0260/L-860.0 Intergranular Stress Corrosion Cracking AECM-83/0481 Your letter to Mississippi Power & Light (MP&L), dated July 27, 1983, requested certain information pertaining to intergranular stress corrosion cracking (IGSCC) for Grand Gulf Nuclear Station (GGNS). This information was requested an a result of inspections at other boiling water reactor plants which have identified extensive IGSCC in certain large-diameter piping. The information provided below along with the enclosed report is submitted in response to your request, referenced above.

QUESTION 1: Identify the materials used and special fabrication methods employed (br's in the shop and in the field) to minimize or mitigate ICSCC in piping systems which form the reactor coolant pressure boundary. For non-conforming materials describe, by piping systems, the actions taken or eetnods utilized (e.g.,

solution annealing, induction heat stress improvement program, etc.) to mitigate potential IGSCC in the reactor coolant pressure boundary. If measures are planned to be responsive to this concern, provide a detailed schedule for the completion of these actions.

RESPONSE: The materials used in the GGNS reactor coolant pressure boundary (RCPB) are listed in Section 2 of the attached report.

.For non-conforming materials, the fabrication methods employed both in the shop and in the field by GGNS to minimize or mitigate ICSCC are described in Section 3 of the attached report.

Mitigation techniques were not implemented on certain welds in somelargediameterpipingsectionsintherecirculationsystem.f The affected piping sections are discussed in FSAR section 5.2.3.5 and in Table 5.2-12. There are a total of twenty-two (22) non-mitigated welds in this category, all in recirculation 8308190070 830917 PDR ADOCK 05000416 P PDR Member Middle South Utilities System l

AECH-83/0481 1 Ml;212OIPPI POWER Q LIGHT COMPANY Page 2 l l

1 I

system piping. The subject piping had been installed by the time that industry experience indicated even large diameter piping was susceptible to ICSCC.

For those welds in RCPB piping not yet mitigated, plans are being established that will implement mitigation techniques prior to startup following our first refueling outage. Techniques under consideration are induction heat stress improvement and last pass heat sink welding.

4 QUESTION 2: Provide a justification for operation with non-conforming materials in the reactor coolant pressure boundary.

RESPONSE: Justification for the operation of Grand Gulf prior to the first refueling outage, when tha remaining susceptibic welds will be mitigated, is based on the following information:

1. Crack Growth Rate Evaluation: This study was performed to determine if an undetected, pre-existing crack could grow to a critical flaw size in the time period between plant startup and the first refueling outage. The evaluation considered expected' operating time and conditions, a circumferential crack geometry, a 5% initial flaw depth, and the worst-case stress and material information pertaining to the i non-mitigated welds. The calculated flaw size after 22 months of operation was well below the ASME Section X1 code allowabic for wall thickness. The results of this conservative evaluation indicate crack growth Icading to either leaks or pipe break is not expected prior to the first outage. (See Section 8 of the attached report.)

2. Leak Detection: The leak-before-break concept is also supported by the above evaluation as well as by historical evidence. Whfic, no leakage due to ICSCC is expected to l

occur, Grand Gulf presently employs several methods of Icak detection and monitoring in the drywell including parameters such as gaseous and particulate radioactivity, floor sump level, drywell ambient temperature and pressure, drywell air cooler performance, etc. Drywell Icakage in excess of Technical Specification limits requires controlled shutdown i

and identification of the source of leakage. By virtue of the diversity of leakage detection systems and strict centrols enforced by the Technical Specifications, there is j adequate assurance that RCPB Icakage will be detected and timely corrective action executed, i.e., controlled reactor i

shutdown to identify exact leakage source. (See Section 7 of I

the attached report.)

3. Summary: The diverse leakage detecticn capability and the conservative crack growth evaluation provide adequate justification for interim operation until the first refueling outage when proper mitigating techniques can be implemented on the subject welds.

QUESTION 3: Describe what preservice inspections have been accomplished which would serve as the baseline for further identification of IGSCC.

AECM-S3/0481

1. E' MISSISSIPPI POWER O LIGHT COMPANY

! RESPONSE: The baseline data for CCNS consist of Ultrasonic Examinations (UT) using procedures meeting the requirements of ASME Section XI. In addition to the UT, the ASME Section III radiographs for

{

both fic1d welds and shop welds are available for baseline data.

l Also, certain area,s of weld inspection programs, as described in l

Section 4 of the attached report, will be enhanced and/or

developed by MP&L at the first regularly scheduled refueling  ;

outage.

! QUESTION 4: Describe what programs are to be implemented in water chemistry

! control to minimize or mitigate IGSCC.

I RESPONSE: The most important primary system contaminants for IGSCC are oxygen and chlorides. The GGNS water chemistry program, established to monitor these contaminants in the primary system on periodic intervals are described in Section 6 of the attached report. The chloride concentration limits are set by GGNS Technical Specification 3.4.4. The oxygen concentration limits are established as procedural operational requ"yM.ents. These

limits are specified to prevent stress corrosion cracking in stainless steel. On-going research will determine if future enhancements (e.g., hydrogen injection) to the water chemistry [

program are required, j CONCLUSION:

For all the systems that make up the RCPB, only the recirculating water system contains materials which do not meet the selection requirements of NUREG 0313 Rev. 1. The only areas within the recirculating system susceptible to IGSCC are the heat affccted zones of the non-mitigated welds. Based on the

information provided herein and in the attached report, interim operation is

' considered justified to the first refueling outage, at which time mitigation i techniques will be implemented. Also at that time, the inservice inspection i program will include improved UT procedures and the augmented inspection i program to address 1GSCC will be developed and implemented.

The information contained in this submittal is in response to your letter dated July 27, 1983, and provides supplemental information and clarification of information presented in Chapter 5 of the GGNS FSAR. Appropriate portions of Chapter 5 will be revised to reflect the information presented in the attached report and will be included in the FSAR update in accordance with 10CFR50.71(c) .

If you have any further questions regarding this matter, please call.

Yours truly, k _=

T ort-.

L. . Dale Manager of Nuclear Services JilS/JGC:rg Attachment ec: See next page

AECM-83/0481 E#

MCClZCIPPI POWER Q LIGHT COMPANY cc: Mr. J. B. Richard (w/a)

Mr. R. B. McCchee (w/o)

Mr. T. B. Conner (w/o)

Mr. C. B. Taylor (w/o)

Mr. Richard C. DeYoung, Director (w/a) ,

Office of Inspection & Enforcement I U. S. Nucicar Regulatory Commission Washington, D. C. 20555 Mr. J. P. O'Reilly, Regional Administrator (w/a)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region 11 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30303 l

BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION LICENSE NO. NPF-13 DOCKET NO. 50-416 IN THE MATTER OF MISSISSIPPI POWER & LIGHT COMPANY and MIDDLE SOUTH ENERGY, INC.

and SOUTH MISSISSIPPI ELECTRIC POWER ASSOCIATION AFFIRMATION I, J. P. McGaughy, Jr., being duly sworn, stated that I am Vice President

- Nuclear of Misaissippi Power & Light Company; that on behalf of Mississippi Power & Light Company, Middle South Energy, Inc., and South Mississippi Electric Power Association 1 am authorized by Mississippi Power & Light Corcpany to sign and file with the Nuclear Regulatory Commission, this submittal in response to your request for information dated July 27, 1983; that I signed this application as Vice President - Nuclear of Mississippi Power & Light Company; and that the statements inade and the matters set forth therein are true and correct to the best of my knowledge, information and belief.

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w)0 = la<w

.P.McGanghy,fJp/.p STATE OF HISSISSIPPI-COUNTY OF llINDS SUBSCRIBED AND SWORN TO before me, a Not. y Public, in and for the County and State above named, this / 1 day of m (L.g/ .i983.

(SEAL)

-j. l hd-QAug '

Notary Public My commission expires:

Jw4 D,/917 F12sp

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