ML021400333
| ML021400333 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 05/20/2002 |
| From: | Cotton K NRC/NRR/DLPM/LPD2 |
| To: | Byrne S South Carolina Electric & Gas Co |
| Cotton K, NRR/DLPM, 301-415-1438 | |
| References | |
| TAC MB4870 | |
| Download: ML021400333 (6) | |
Text
May 20, 2002 Mr. Stephen A. Byrne Senior Vice President, Nuclear Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station Post Office Box 88 Jenkinsville, South Carolina 29065
SUBJECT:
VIRGIL C. SUMMER NUCLEAR STATION - REQUEST FOR ADDITIONAL INFORMATION REGARDING MECHANICAL STRESS IMPROVEMENT PROCESS (MSIP) ANALYSIS AND VERBAL APPROVAL OF THE MSIP ANALYSIS RESULTS (TAC NO. MB4870)
In our Safety Evaluation dated February 20, 2001, the U.S. Nuclear Regulatory Commission (NRC) stated that the V. C. Summer Nuclear Station could operate for one fuel cycle with eddy current indications in the B and C reactor coolant hot leg nozzle welds. In a letter dated January 9, 2001, South Carolina Electric & Gas Company (SCE&G) committed to perform the best and most meaningful nondestructive examination inspection available to ensure the integrity of the B and C reactor coolant hot leg nozzles at the completion of one cycle, which is Refueling Outage 13. At the end of Refueling cycle 13, by letter dated May 4, 2002, SCE&G transmitted the results of the nondestructive examination (NDE) performed on the B and C reactor coolant hot leg nozzles conducted prior to the MSIP application. By letter dated May 13, 2002, SCE&G transmitted the results of the examination conducted following the MSIP application. The post MSIP NDE was performed using the same techniques as described in the May 4, 2002, letter. The results showed no new indications and the amplitudes and lengths of the eddy current detection were consistent with the pre-MSIP values. The eddy current examination also confirmed that there was no growth in crack length.
S. Byrne The NRC staff has found the results of the analysis acceptable. Based on our findings, we verbally informed you during our May 16, 2002, teleconference that operation of the Summer Nuclear Station was acceptable for an additional cycle. However, in order to complete the Safety Evaluation and grant final approval of the analysis results, the staff is requesting that you provide the information requested in the enclosed list of questions.
Sincerely,
/RA/
Karen R. Cotton, Project Manager, Section 1 Project Directorate ll Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-395
Enclosure:
Request for Additional Information on V.C. Summers MSIP Analysis cc w/encl: See next page
S. Byrne The NRC staff has found the results of the analysis acceptable. Based on our findings, we verbally informed you during our May 16, 2002, teleconference that operation of the Summer Nuclear Station was acceptable for an additional cycle. However, in order to complete the Safety Evaluation and grant final approval of the analysis results, the staff is requesting that you provide the information requested in the enclosed list of questions.
Sincerely,
/RA/
Karen R. Cotton, Project Manager, Section 1 Project Directorate ll Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-395
Enclosure:
Request for Additional Information on V.C. Summers MSIP Analysis cc w/encl: See next page DISTRIBUTION:
PUBLIC PDII-1 R/F J. Nakoski K. Cotton E. Dunnington OGC ACRS K. Landis, RII Accession Number: ML021400333 OFC PDII-1/PM PDII-1/LA PDII-1/SC NAME KCotton EDunnington JNakoski DATE 05/20/02 05/20/02 05/20/02 OFFICIAL RECORD COPY
Enclosure REQUEST FOR ADDITIONAL INFORMATION ON V.C. SUMMERS MSIP ANALYSIS V.C. Summer Report 3768-4-001-00 1.
On page 8 of 36, it states, Also, the nodes at the free end of the pipe are coupled in the axial direction. This ensures that these nodes all move in the axial direction at the same amount. Provide justification for this assumption considering piping supports specific to your plant. Is this consistent with the finite element modeling mentioned in Chapter 6 of the Electric Power Research Institute (EPRI) report that was provided to us earlier?
2.
On page 11 of 36, it states, The elastic and inelastic properties used in the finite element analysis are provided in the table below.... What is the stress-strain curve after yielding? Is this consistent with the finite element modeling mentioned in Chapter 6 of the EPRI report that was provided to us earlier?
3.
Your finite element analysis does not consider the effect of existing weld repairs on the pre-mechanical stress improvement processing (MSIP) and post-MSIP piping weld stresses. Provide an assessment of this effect.
EPRI Report Dated September 27, 1993 4.
Chapter 6 reports the simulated and measured residual stresses at the inside-diameter (ID) and outside-diameter (OD) of the piping and weld after receiving MSIP. To assess the effectiveness of MSIP, we need corresponding information on the pre-MSIP residual stresses. Measured ID residual stresses shown in Tables 6-1 and 6-2 do not seem to relate to the finite element method (FEM) model. Provide the FEM and measured residual stresses at the ID and OD of the piping and weld before receiving the MSIP.
5.
The wall thickness for the EPRI boiling-water reactor nozzle to safe-end is 1.2 inches, and the wall thickness for the Summer pipe is 2.42 inches. We do not think (r/t) ratio, which is used to determine the applicability of thin-shell theory, is the right parameter for determining the appropriateness of the pre-MSIP residual stresses.
Provide justification for using the MSIP experience documented in the EPRI report for a thin-wall pipe to the current case for a thick-wall pipe. Provide information on the MSIP application to pipes of similar thicknesses by other plants.
Mr. Stephen A. Byrne VIRGIL C. SUMMER NUCLEAR STATION South Carolina Electric & Gas Company cc:
Mr. R. J. White Ms. Kathryn M. Sutton, Esquire Nuclear Coordinator Winston & Strawn Law Firm S.C. Public Service Authority 1400 L Street, NW c/o Virgil C. Summer Nuclear Station Washington, DC 20005-3502 Post Office Box 88, Mail Code 802 Jenkinsville, South Carolina 29065 Mr. Stephen A. Byrne Vice President, Nuclear Operations Resident Inspector/Summer NPS South Carolina Electric & Gas Company c/o U.S. Nuclear Regulatory Commission Virgil C. Summer Nuclear Station 576 Stairway Road Post Office Box 88 Jenkinsville, South Carolina 29065 Jenkinsville, SC 29065 Chairman, Fairfield County Council Drawer 60 Winnsboro, South Carolina 29180 Mr. Henry Porter, Assistant Director Division of Waste Management Bureau of Land & Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, South Carolina 29201 Mr. Gregory H. Halnon, General Manager Nuclear Plant Operations South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station, Mail Code 303 Post Office Box 88 Jenkinsville, South Carolina 29065 Mr. Melvin N. Browne, Manager Nuclear Licensing & Operating Experience South Carolina Electric & Gas Company Virgil C. Summer Nuclear Station, Mail Code 830 Post Office Box 88 Jenkinsville, South Carolina 29065