ML20210P392
| ML20210P392 | |
| Person / Time | |
|---|---|
| Issue date: | 08/06/1999 |
| From: | Charemagne Grimes NRC (Affiliation Not Assigned) |
| To: | Walters D NUCLEAR ENERGY INSTITUTE (FORMERLY NUCLEAR MGMT & |
| References | |
| PROJECT-690, REF-GTECI-***, REF-GTECI-NI, TASK-***, TASK-OR NUDOCS 9908120169 | |
| Download: ML20210P392 (9) | |
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NUCLEAR REGULATORY COMMISSION
'2 WASHINGTON, D.C. 20555 4001 49......
August 6,1999 Mr. Douglas J. Walters Nuc!aar Energy Institute 1776 i Street, NW, Suite 400 Washington, DC 20006-3708
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON THE INDUSTRY'S EVALUATION OF FATIGUE EFFECTS FOR LICENSE RENEWAL
Dear Mr. Walters:
This letter provides the staff response to your letters of April 8 and April 20,1999. Your April 8 letter addresses the November 2,1998, staff request for additionalinformation (RAI) concerning two industry reports developed to address the issue of environmental effects on fatigue life of metal components for the license renewal term. The issue of environmental effects on fatigue life for license renewal is addressed by NRC Generic Safety issue (GSI) 190,
" Fatigue Evaluation of Metal Components for 60-year Plant Life." Your Apr'I 20 letter provided a copy of a paper referenced in your first letter plus supplemental information regarding the
- weighted-average" approach used to calculate the environmental factor discussed in the industry reports. The industry reports, submitted by the Electric Power Research Institute (EPRI), were EPRI Report TR-107515, " Evaluation of Thermal Fatigue Effects on Systems Requiring Aging Management Review for License Renewal for the Calvert Cliffs Nuclear Power Plant," and EPRI Report TR-105759, "An Environmental Factor Approach to Account for Reactor 'Nater Effects in Light Water Reactor Pressure Vessel and Piping Fatigue Evaluations."
These reports are referenced in the Baltimore Gas and Electric Company (BGE) license renewal application for the Calvert Cliffs Nuclear Power Plant. The staff RAI was discussed in an April 27,1999, meeting with NEl. The staff assessment of the NEl response to the staff questions is contained in the enclosure to this letter.
You expressed three industry concems in your April 8,1999, letter. Your first concem involved the validity of the new Argonne National Laboratory (ANL) environmental data. You recommended that NRC formally publish the data for public review. This data has been presented by ANL at technical conferences and published in PVP conference proceedings and NRC NUREG reports. The data correlations and reference publications were provided in our RAl. Subsequent to the RAI, the new ANL stainless steel data was also published in NUREG/CR-5704.
Your second concem is the treatment of fatigue as GSI-190, " Fatigue Evaluation of Metal
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Components for 60-Year Plant Life." The staff discussed GSI-190 at the April 27 meeting. The primary effo af GSI-190 is to provide a risk study that is applicable to a 60-year period of g
operation. Tne results of the risk study will be used by the staff in formulating its position
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regarding the consideration of environmental fatigue effects for license renewal.
Your third concem is in linking the Generic Safety Issue to the decision on license renewal. The concem involves the staff position in the Calvert Cliffs safety evaluation report which states that if GSI-190 is not resolved prior to the period of extended operation, the applicant must adequately resolve environmental effects on high-usage factors with bounding analyses or a
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r adeq ately resolve environmental effects on high usage factors with bounding analyses or a monito 'ng program on a plant specific basis. The staff considers its position consistent with the license r ewal rule as discussed in the statement of considerations (SOC) (60 FR 22484, May 8,19
). The staff understands that BGE intends to submit a plant specific resolution to address the aff poskion.
Your April 8,19, letter, concludes that the industry position has not changed as a result of the analyses summa ed in the enclosure. In addition, you state that information in the letter is sufficient to close 1190, even in the absence of a completed risk assessment. As indicated
- 1 in the enclosed staff ssessment, the additional information provided in your letters has not resolved all the techni,lissues identified in the staff RAI and, consequently, the staff does not find that the industry t ical reports provide a sufficient basis to resolve GSI-190. The most significant issue that rem s unresolved involves the calculation of an environmental adjustment
. factor based on the ANL s istical correlations. The staff does not agree with the industry calculation of the environmegal adjustment factor, At the April 27 meeting, the industry agreed to consider the staff comments, N
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Sincerely,
\\ Christopher I, Grimes, Chief kicense Renewal and Standardization Branch D(vision of Regulatory improvement Programs Office of Nuclear Reactor Regulation l
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monitoring program on a plant specific basis. The staff considers its position consistent with the license renewal rule as discussed in the statement of considerations (SOC) (60 FR 22484, May 8,1995). The staff understands that BGE intends to submit a plant specific resolution to address the staff position.
Your April 8,1999, letter, concludes that the industry position has not changed as a result of the analyses summarized in the enclosure. In addition, you state that information in the letter is sufficient to close GSI-190, even in the absence of a completed risk assessment. As indicated in the enclosed staff assessment, the additionalinformation provided in your letters has not resolved all the technical issues identified in the staff RAI and, consequently, the staff does not find that the industry technical reports provide a sufficient basis to resolve GSI-190. The most significant issue that remains unresolved involves the calculation of an environmental adjustment factor based on the ANL statistical correlations. The staff does not agree with the industry calculation of the environmental adjustment factor. At the April 27 meeting, the industry agreed to consider the staff comments. For our planning purposes, we request that you provide a schedule for considering the staff comments within 30 days following receipt of this letter.
Sincerely, WWW Christopher I. Grimes, Chief License Renewal and Standardization Branch Division of Regulatory Improvement Programs Office of Nuclear Reactor Regulation Project No. 690
Enclosure:
As stated cc: See next page
- See previous concurrence DOCUMENT NAME: G:\\EMEB\\ FAIR \\GSl190.NEl IN06CATE IN BOX: "C"eCOPY W/O ATTACHMENT / ENCLOSURE, *E"mCOPY WIATT/ ENCL, "N"mNO COPY OmCE EMEB DE E
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DATE 7/20/99 7/20/99 7/20/99 7/20/99 7/20/99 OFFICIAL RECORD COPY
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Distribution:
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-Central Filei RLSB RF License Renewal Steering Committee N. Dud;ey, ACRS - T2E26 i
E-mail:
D. Matthews i
S. Newberry i
C. Grimes -
t C. Carpenter.
B. Zaleman J. Strosnider R. Wessman E. Imbro W. Bateman J. Calvo T. Hiltz B.Boger G. Holahan T. Collins
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C. Gratton R. Correia R. Latta J. Moore J. Rutberg R. Weisman M. Mayfield i
J. Vora S. Bahadur A. Murphy W. McDowell S. Droggitis F. Cherny -
S. Shaukat K. Manoly K. Wichman J. Fair RLSB Staff G. Tracy A. Thadani D. Chamberlain L. Chandler M. Federline J. Craig C. Julian W. Lanning R. Gardner D.Chyu
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1 NUCLEAR ENERGY INSTITUTE (License Renewal Steering Committee) l l
Project No. 690 cc:
Mr. Dennis Harrison Mr. Robert Gill l
U.S. Department of Energy Duke Energy Corporation NE-42 Mail Stop EC-12R Washington, D.C. 20585 P.O. Box 1006 Charlotte, NC 28201-1006 l
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Mr. Ricard P. Sedano, Commissioner Mr. Charles R. Pierce State Liaison Officer Southem Nuclear Operating Co.
Department of Public Service 40 invemess Center Parkway 112 State Street BIN B064 Drawer 20 Birmingham, AL 35242 Montipelier, Vermont 05620-2601 Mr. Douglas J.. Walters Mr Barth Doroshuk
. Nuclear Energy Institute Baltimore Gas & Electric Company
.1776 l Street, N.W.
1650 Calvert Cliffs Parkway Washington, DC 20006 Lusby, Maryland 20657-47027 DJW@NEl.ORG National Whistleblower Center Chattooga River Watershed Coalition 3233 P Street, N.W.
P. O. Box 2006 Washington, DC 20007 Clayton, GA 30525 Mr. William H. Mackay Entergy Operations, Inc.
Arkansas Nuclear One 1448 SR 333 GSB-2E Russellville, Arkansas 72802 r
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I Assessment of NEl April 8 and 20,1999, Letters Responding to the NRC Staff Request for AdditionalInformation Regarding Industry Evaluation of Environmental Fatigue for License Renewal l
RAI 1 EPRI Report TR 107515, " Evaluation of Thermal Fatigue Effects on Systems Requiring Aging Management Review for License Renewal for the Calvert Cliffs Plant," contains an i
evaluation of environmental effects on the chemical and volume control system (CVCS) charging inlet nozz'e using methodology developed in EPRI Report TR-105759, "An I
EnvironmenMI Factor Approach to Account for Reactor Water Effects in Light Water I
Reactor Pressure Vesse! and Piping Fatigue Evaluations." The staff provided an assessment of the methodology discussed in EPRI Report TR-105759 as an attachment to its RAl. Based on this assessment, the staff requested that NEl provide the following information:
(a)
The staff requested that NEl discuss the impact of the current Argonne National l
Laboratory (ANL) statistical correlations of environmental test data on the Calvert Cliffs fatigue evaluation. The current ANL statistical correlations were provided in the attachment to the request for additional information (RAI).
The NEl response states that an industry evaluation of the ANL data concluded that the findings from the previous Calvert Cliffs calculations remain the same.
The industry evaluation of the current ANL data is contained in Appendix A to. The evaluation involves the calculation of an environmental factor (Fen) using the current ANL statistical correlation (Fen is the ratio of the fatigue life in air to the fatigue life in the reactor water environment). This environmental factor is then divided by a factor (4 for carbon steel and 2 for stainless steel) to obtain an effective environmental factor (Fen,eff). This effective environmental f actor is then compared to the environmental factor used in the Calvert Cliffs study.
The staff does not agree with the method used to calculate Fen from the ANL statistical correlation. ANL provided statistical correlations to determine the fatigue life of carbon, low alloy and stainless steel components in both air and reactor water environments. In these correlations, the fatigue life is a function of temperature. Fen is calculated from the ANL correlations by taking the ratio of fatigue life in air to the fatigue life in reactor water at the same temperature. The staff believes that Fen should be calculated by taking the fatigue life in air at room temperature to the fatigue life in the reactor water environment at operating temperature. The product of temperature times strain rate has a significant l
impact on the fatigue life using the ANL air statistical correlation for stainless steels. Equation 8 in Appendix A contains the equation used to obtain Fen for stainless steel. The staff believes that Fen should be calculated by setting T(=0.
I The industry argument for using the ANL air statistical correlation at the component operating temperature is that the ASME stainless steel fatigue curve was developed considering test data at higher temperatures. The staff agrees that some of the data used to develop the ASME fatigue curve was obtained from air tests at higher temperatures. However, Equation 8 contains a factor which multiplies the strain rate factor times the temperature. On the basis of ANL's Enclosure i
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4 assessment of the stainless steel air test data, the effect of strain rate on fatigue life at higher temperatures is significant. Therefore, the appropriate strain rate for the T,* term should be based on the strain rate used in the air test at the corresponding component operating temperature. The strain rates for the high temperature tests used to establish the ASME Code fatigue curves are not i
published, but are probably relatively high strain rates. In the ANL stainless steel statistical correlation for air, shown in Equation 6 of Appendix A, the strain rate factor equals zero at high strain rates. This is the equivalent of letting T,*=0 in Equation 8. The calculation Fen,eff is discussed below.
- (b)
The staff requested that NEl provide the technical basis for the industry assertion that the ASME Code stainless steel fatigue curve contains sufficient conservatism to account for moderate environmental effects. The staff requested that the response include a discussion of the factor required to adjust the laboratory test data for size and surface finish effects and the margin necessary to account for scatter of test data. The staff also requested the response include a discussion of the effect on margin due to potentialinconsistencies between the ASME mean curve and the ANL air environment data.
The NEl response refers to work pedormed by the Pressure Vessel Research Council (PVRC) and published in 1995," Status of PVRC Evaluation of LWR Coolant Environmental Effects on the S-N Fatigue Properties of Pressure Boundary Materials," by W. A. Van Der Sluys and S. Yukawa, PVP Volume 306, 1995. The response also refers to PVRC work published in 1998, "S-N Fatigue Properties of Pressure Boundary Materials in LWR Coolant Environments," by W.
A. Van Der Sluys and S. Yukawa, PVP Volume 374,1998. These papers form the basis for the factors used to establish the Fen,eff discussed above.
NUREG/CR-6583," Effects of LWR Coolant Environments on Fatigue Design Curves of Carbon and Low Alloy Steels," and NUREG/CR-5704," Effects of LWR Coolant Environments on Fatigue Design Curves of Austenitic Stainless Steels,"'
contain a discussion by ANL of the adjustment factors needed to account for the effect of various parameters on the fatigue life when using laboratory data to obtain the design fatigue curves. The staff does not believe the factors of 4 for carbon steel and 2 for stainless steel presented in the NEl response are sufficient to cover these concerns. On the basis of ANL assessments, the staff believes that the maximum factors that can be attributed to moderate environments in the ASME fatigue curves are 3 for carbon and 1.5 for stainless steels.
(c)
The staff requested that NEl provide the technical basis for the strain threshold values.
The NEl response refers to the same PVP papers discussed in sub item (b) above.- The discussion in Appendix A to Enclosure 1 asserts that the ANL proposed threshold value is overly conservative because it recommends a factor of safety of 2 on the lower bound of the test data. This assertion is not correct since ANL applied its factor of safety to the mean of the test data consistent with the ASME procedure used to establish the design fatigue curves. The staff 2
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l considers the strain threshold values recommended by ANL appropriate for assessing environmental fatigue effects.
RAI 2 In its license renewal application, BGE asserted that environmental effects do not apply j
to RCS components because of low oxygen concentrations and because the RCS carbon steel surfaces are clad with stainless steel. The staff requested that NEl discuss the applicability and impact of the latest stainless steel fatigue correlation from ANL on this conclusion.
The NEl response indicates that none of the component locations evaluated in EPRI l
Report TR-107515 involved carbon steel clad with austenitic stainless steel. In addition, NEl indicated that the construction code did not require evaluation of the stainless steel cladding. The staff agrees with the statement that the construction code does not require an evaluation of the cladding. However,if the licensee wants to credit the cladding for protecting the base material from the environmental effects on fatigue life, then the licensee should assure the cladding integrity. Otherwise, the licensee should evaluate the base material considering the environmental effects.
l RAI 3 The staff requested that NEl discuss the app!icability and impact of the latest stainless steel correlation from ANL on the surge line evaluation contained in EPRI Report TR-105759. The industry assessment is discussed in RAI 1(a).
l RAI 4 The staff requested that NEl indicate whether the " weighted average" approach was used to obtain the environmental factor calculated in EPRI Report TR-107515. The staff also requested that NEl provide the data used to develop the approach including a statistical assessment of the data scatter. The staff further requested that NEl compare the results of the statistical assessment with the ANL assessment contained in l
NUREG/CR 6335," Fatigue Strain-Life Behavior of Carbon and Low Alloy Ferritic Steels, Austenitic Stainless Steels, and Alloy 600 in LWR Environments," and indicate whether the " weighted average" approach will provide an adequate margin to account for test data scatter.
The NEl response indicates that all of the environmental factors calculated in EPRI Report TR-107515 were based on the " weighted average" approach. NEl presented the results of a study of three locations on the Calvert Cliffs pressurizer surge line. The results of the study indicated that the standard approach resulted in environmental factors that were approximately 20% greater than the " weighted average" approach. In addition, NEl discussed the results of an assessment of three idealized transients. The staff was concerned that these idealized assessments only looked at the strain variation whereas the EPRI procedure also considered the temperature variation in the calculation.
The basis for the staff concern is that there are insufficient test data to verify the procedure. During the April 27,1999, meeting, the industry representatives indicated I
that tb " weighted average" approach was only applied to the strain transient and that the maximam temperature during the transient was considered in the evaluation of the environmental factor. On the basis of that clarification, the staff considers the " weighted average " approach adequate.
RAI 5 The staff requested that NEl discuss the applicability and impact of the latest ANL stainless steel data correlation on the BGE conclusion that environmental effects do not 3
apply to the safety injection components because of the low oxygen concentrations and stainless steel materials used in the construction of the components.
The NEl response indicated that the Industry evaluation did not cover the safety injection system components. However, NEl also indicated that the discussion in response to RAls 1(a) and 3 would apply to safety injection components fabricated from austenitic stainless steel. The staff comments regarding these RAls are also applicable.
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