ML12333A227

RAI for the Review of the STP, Units 1 and 2, LRA - Set 26

ML12333A227
Person / Time
Site:	South Texas
Issue date:	12/18/2012
From:	Daily J License Renewal Projects Branch 1
To:	Rencurrel D South Texas
Daily J, 415-3873
References
TAC ME4936, TAC ME4937
Download: ML12333A227 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 18, 2012 Mr. D. W. Rencurrel Chief Nuclear O'fficer STP Nuclear O'perating Company P.O'. Box 289 Wadsworth, TX 77483

SUBJECT:

REQUESTS FO'R ADDITIO'NAL INFO'RMATIO'N FO'R THE REVIEW O'F THE SO'UTH TEXAS PRO'JECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATIO'N - SET 26 (TAC NO'S. ME4936 AND ME4937)

Dear Mr. Rencurrel:

By letter dated O'ctober 25, 2010, STP Nuclear O'perating Company (STPNO'C or the applicant) submitted an application pursuant to Title 10 of the Code of Federal Regulations Part 54, to renew operating licenses NPF-76 and NPF-80 for South Texas Project, Units 1 and 2, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained'in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review.

These requests for additional information have been presented to your staff, and we request that, since it may take longer 30 days to prepare your response, you indicate to the staff your anticipated time frame for responding. If you have any questions, please contact me by telephone at 301-415-3873 or bye-mail at john.daily@nrc.gov.

Sincerely,

~:w:~r:Sager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos.50-49E and 50-499

Enclosure:

As stated cc w/encl: Listsell

SOUTH TEXAS PROJECT, UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION, SET 26 (TAC NOS, ME4936 AND ME4937)

RAI B2.1.37-5

Background

The staff has completed its evaluation of the response to request for additional information (RAI)

B2.1.37 -4 related to the Selective Leaching of Aluminum Bronze plant-specific aging management program (AMP). As a result of this review, there are several open questions.

Issue a) The wording of the commitments (Le., 39, 44, and 45), the updated final safety analysis report (UFSAR) Supplement, and the aging management program (AMP) is not clear in relation to testing and inspection of removed components (e.g., Commitment No. 45, states that fracture toughness testing will be conducted but it does not discuss pressure and bend testing; Commitment Nos. 39 and 45, overlap in their descriptions of examinations). The staff believes that the intent of the proposed testing and inspections is as follows:

Profile Exam (PE) - removed leaking components will be tested/inspected for chemical composition (including aluminum content), mechanical properties, microstructure, degree of dealloying and cracking in order to establish the progression of dealloying, its impact on structural integrity, and to confirm the acceptability of using the existing correlation of observed outside diameter (00) crack angle to project internal degradation.

• Analysis Confirmatory Test (ACT) - removed leaking components will be pressure tested and bend tested to confirm the results of the analytical methodology used to demonstrate structural integrity. In addition, samples will be tested/inspected for chemical composition (including aluminum content), mechanical properties, microstructure, degree of dealloying, and cracking.

The staff recognizes that different terminology might be established for the above tests and inspections in order to best communicate the program requirements. However, given the currently proposed language in the AMP, UFSAR Supplement, and Commitments, the staff does not believe that testing and inspection requirements will be correctly interpreted in the future.

b) Subsequent to the public meeting conducted on August 27,2012, the staff determined that an additional 14 PEs and 8 ACTs would be required to establish a reasonable basis that a susceptible component would be able to perform its intended function throughout the period of extended operation (PEO). The additional 14 PEs will result in a total of 22 PEs being conducted, including those conducted in 1994 (reference AES-C-1964-5, "Evaluation of the Significance of Oealloying and Subsurface Cracks on Flaw Evaluation Method"). The staffs position is that the ACTs should include a sufficiently wide range of component sizes and internal crack angles to validate the analytical methodology.

Specifically, a minimum of 3 component sizes, with 3 tests in each size, is recommended. The staff recognizes that a six-inch fitting was subjected to an ACT in 1994.

ENCLOSURE

- 2 The number of tests described above is based on the test outcomes supporting current design documents, such as calculation output curves that provide the critical bending stress versus crack angle and the correlation of OD crack angle to internal degradation.

If any of these tests do not support the pertinent design output documents, further testing will be required. This testing to establish reasonable assurance will have to be completed and submitted to the staff prior to issuance of the final SER.

The staff also believes that continuing confirmation testing will need to be conducted through the end of the PEO in order to either (a) demonstrate that the nature (e.g.,

plug-like versus layer-like) and rate of degradation continue as they have in the past and therefore can be managed by the program, or (b) demonstrate, through trending, the need to replace the susceptible components prior to signs of external leakage. In its consideration of this continuing testing, the staff noted the long period of time before the renewed license will expire, the importance of the essential cooling water system, and the fact that further degradation will continue to occur. The staff's position is that, for PEs, 100% of leaking components should be tested/inspected until the end of PEO. In regard to ACTs and following completion of the above-mentioned 9 ACTs, 20% of future leaking components should be tested until the end of PEO.

c) The RAI response did not address the minimum level of degradation (e.g., degree of dealloying) that a component must exhibit in order to be used as an ACT specimen. The degree of dealloying in a tested component must be sufficient so that its material properties (e.g., fracture toughness, yield strength) are representative of an advanced degree of dealloying. Therefore, some removed leaking components may not be acceptable specimens for validating the analytical methodology. An example would be a specimen that has a very narrow angle of through-wall dealloying and minimal layer-type dealloying around the circumference.

d) The response to RAI B2.1.37-4, Issue 3, U[d]escribe how the percentage of dealloying is identified when testing specimens," does not account for areas where dealloying has penetrated through-wall, but not progressed to completion (i.e., significant depletion of aluminum). While the AMP, UFSAR Supplement, and Commitments state that samples will be tested for chemical composition including aluminum, it is not clear how this data will be used in conjunction with determining the degree of dealloying.

There are many references to 1 DO-percent dealloyed tensile properties throughout the analyses credited by the program. It is not clear to the staff that the tensile properties were obtained from specimens that were 1 ~O-percent dealloyed from both a dimensional (Le., percent through-wall) and chemical composition basis (Le., aluminum depletion).

Table 2.5, "Tensile Test results on Dealloyed Samples of CA-954 Material from Fittings,"

of ST-HL-AE-2748, "Failure Analysis and Structural Integrity of Leaking Small Bore Aluminum Bronze Cast Valve Bodies and Fittings in the ECW System," provides a compilation of test sample tensile values and the percent dealloyed. A footnote to the percent dealloyed column of this chart states, "[b1ased on SCM of tensile fracture surface." The staff does not know what "SCM" stands for, and no other criterion for the percent dealloyed values is stated in the document.

The staff believes that if the degraded components that are tested are not 100-percent dealloyed from both a dimensional and chemical composition basis, the material properties obtained from those tests may not represent the lowest possible values.

- 3 Therefore, the program needs to state how partially dealloyed material property results will be integrated into trending data.

e) While the revised AMP, Enhancements, UFSAR Supplement, and Commitments describe acceptance criteria for tensile, yield and fracture toughness properties, the RAI response does not describe specific follow-on actions that would be taken when abnormal test or inspection results are obtained, beyond stating that results would be trended, an engineering evaluation would be performed, or that the condition will be documented in the corrective action program. The acceptability of the Selective Leaching of Aluminum Bronze plant-specific AMP will be based upon (a) either empirical testing results or attainment of dealloyed material properties to be used in revised structural integrity analyses, and (b) the continuing demonstration of the ability to detect aging using external visual inspections prior to the degradation adversely impacting the ability of a susceptible component to perform its intended function. The staff notes the possibility that results of the tests and inspections could invalidate the analytical assumptions to such an extent that structural integrity could not be reasonably expected to be demonstrated for leaking components, or that an in-situ leaking fitting could be found that cannot be shown to meet structural integrity requirements. In the latter case, given that there are approximately 300 other susceptible components, it would be unreasonable to assume that only this component was not capable of meeting its intended function, and therefore the basis of the program (i.e., using external visual inspections to detect degradation prior to adversely impacting the ability of a susceptible component to perform its intended function) would be invalidated. The staff requires further details to understand what speCific actions will be taken for the following outcomes:

During a PE or ACT, a crack or degree of dealloying is discovered outside of the current correlation as shown on page 12 of AES-C-1964-5. It is unclear to the staff whether a new correlation curve will be developed and whether existing leaking components will be reanalyzed with the new correlation. It is the staff's position that, given that the correlation of 00 crack angle to projected internal degradation will have been demonstrated to be nonconservative, some additional fittings will need to be immediately examined, even though not leaking, to determine whether this was a one-off data point or whether there are many more susceptible fittings which have larger internal cracking or dealloying than would be projected from observing the through-wall indications on the 00.

• An ACT test result yields a data point below the size-appropriate acceptance curve (e.g., Figure 4-2, "Evaluation of Flange Bend Test Results," in AES-C-1964-5). It is unclear to the staff whether the analytical methodology will be revised to reflect the lower data point. For example, if it is suspected that the lower data point occurred because an appropriately low fracture toughness value was not used, it is unclear whether the fracture toughness value in the calculation would be decreased until the curve is sufficiently shifted. Also, it is unclear whether existing leaking components will be reanalyzed with the revised methodology. It is the staff's position that any existing leaking component should be considered not capable of performing its intended function until the cause of the discrepancy is understood, a new analysis curve is developed, and any existing degraded components are evaluated against the new analysis curve.

-4

• The in-situ evaluation of a newly-discovered leaking fitting (Le., the fitting has not yet been removed from service) results in a determination that the degraded component is not operable. It is the staff's position that such a result invalidates the effectiveness of the program, since the program is based on the capability of external visual examinations to manage aging prior to loss of intended function.

Consequently, the staff believes that all susceptible fittings should be considered not capable of performing their intended functions until a revised technical basis is established or the components are repaired or replaced.

PE or ACT results demonstrate a trend where, due to continuing dealloying, tensile strength, yield strength, or fracture toughness properties are projected to be below the acceptance criteria prior to the end of the PEO. It is the staffs position that the initial testing used to establish reasonable assurance and the continuing confirmatory testing can provide a timely projection of degraded mechanical properties, and all susceptible components should be repaired or replaced prior to the as-found properties or the as-trended properties fall below the acceptance criteria.

PE or ACT results demonstrate that layer-type dealloying is becoming predominant over plug-type, such that it is no longer possible to project internal degradation based on external observations. The staff recognizes that there is some level of layer dealloying occurring in most fittings, as illustrated in Figure 3-1, "Typical Oealloying/Cracking Cross Sections," of AES-C-1964-5. However, the through-wall dealloying of the samples inspected in 1994 demonstrated a plug-like nature and a correlation of 00 crack angle to internal degradation was able to be reasonably established. It is the staffs position that continued use of the correlation requires that a maximum percent of cross-sectional layer-type dealloying be established and justified as an acceptance criterion.

PE or ACT results demonstrate that cracking has extended into the un-dealloyed region. AES-C-1964-5 sections 3.0, "Method of Approach," and 5.0, "Significance of Part-Through Cracks," assume that cracking does not extend into the un-dealloyed portion of a component. Although under this scenario the specific component that had cracking extending into the un-dealloyed portion would have already been replaced, anyone or more of the hundreds of susceptible fittings could potentially have cracking of this nature. It is the staff's position that all susceptible components should be considered not capable of performing their intended functions until the cause of the extended cracking is understood, a new analysis curve is developed, and the existing degraded components are evaluated against the new analysis curve.

t) The staff has questions regarding how field observations of leaking degraded components are used in conjunction with the analytical output of AES-C-1964-1, "Calculation of Critical Bending Stress for Oealloyed Aluminum-Bronze Castings in the ECW System," and the existing pipe stress analyses in order to analyze for structural integrity as it relates to the component performing its intended function. In particular, the staff has concerns related to:

In the correlation in AES-C-1964-5, the observed 00 crack angle is used to derive an average through-wall dealloying angle. However, the critical bending

- 5 stress curves in AES-C-1964-1 use a crack angle, not an average through-wall dealloying angle. The staff lacks sufficient information to be able to understand the link between the correlation and its use in the critical bending stress curves.

Note that the response to RAI B2.1.37 -4, Enclosure 1, page 3 of 9, incorrectly characterizes the correlation, "[t]he examination results were used to establish a correlation between length of a flaw on the outer diameter and the size of any internal crack and the extent of the dealloyed region of the component."

Also, it is not clear to the staff why an average angle would be used when Figures C-2200-1, "Flaw Characterization-Circumferential Flaws," and C-431 0-1, "Circumferential Flaw Geometry," of ASME Code Section XI, and Figure 5-1, "Circumferential Flaw Geometry - Net Section Collapse Model," of AES-C-1964-1 use the inside dimensions of the flaw.

The staff plotted the 00 and inside diameter (ID) crack and dealloying angle data from Section 4.1, "Metallurgical Data," of AES-C-1964-5 (i.e., dealloyed 00 vs.

dealloyed 10 and crack 00 vs. crack ID). Two crack data points and three dealloying data points fell outside (nonconservative) of the correlation. If it is not appropriate to use an average through-wall dealloying angle, a new correlation using inside dimensions will need to be developed. The staff lacks sufficient information to understand whether such a new correlation could affect the structural integrity determination of recently degraded components, and by extension, degraded components discovered during the PEO.

• The wording of the response to part (e) of RAI B2.1.37-3 is not clear on what minimum structural factor will be used for the normal/upset conditions and emergency and faulted conditions.

It is not clear to the staff how external dimensions of the indication are sized. For example, when an indication consists of a crack within a larger dea"oyed region, it is not clear which feature is measured. Also, it is not clear how a singular rounded (surface) indication, or multiple in-line rounded (surface) indications, are characterized.

It would appear that, based on the external dimensions of the flaw, an average flaw angle is developed based on the AES-C-1964-5 correlation and used as input into the critical bending stress analyses in AES-C-1964-1, regardless of whether the through-wall degradation is dealloying with no crack, a part-through crack with dealloying, or through-wall crack with dealloying. However, the staff seeks confirmation that this is correct. The responses to the scenario-based questions in the request should resolve this issue.

• Given the ambiguities between the calculations, it is not clear to the staff that the steps in a structural integrity determination of a degraded susceptible aluminum bronze component in the essential service water system can be consistently performed without a procedure. In addition to the ambiguities, based on plant-specific OE, consistent performance is also challenged since these evaluations are conducted infrequently.

g) The staff also seeks the following information to complete its evaluation of the proposed AMP:

- 6

• A list of the number of remaining susceptible components, broken down by size

• A copy of AES-C-1964-4, "Evaluation of6-lnch Flange Test," submitted on the docket

• An update on leaking components that have occurred since July 28, 2011, the last entry in Table 1, "ECW De-Alloying Data," of the response to RAI B2.1.37-1.

• The results of the leak rate analysis stated in Commitment No. 46, in response to RAI B2.1.37-4Issue 5.

• The "scope of program" and "parameters monitored or inspected" program elements of the Selective Leaching of Aluminum Bronze program state,

"[c]omponents greater than one inch will be replaced by the end of the subsequent refueling outage." The staff noted that UFSAR Section 9A, "Assessment of the Potential Effects of Through-Wall Cracks in ECWS Piping,"

states, in part, that relief requests are submitted when leaks are identified except for, uleaks in lines 1 inch or under which are exempt from ASME Code Section XI replacement rules." The staff cannot find a basis for allowing one inch and under lines to have repair or replacement times extend beyond the subsequent refueling outage.

Request:

a) Revise the AMP, UFSAR Supplement, and Commitments to clearly state the intent of each test and the parameters that will be inspected or tested.

b) Amend the AMP, UFSAR Supplement, and Commitments to reflect the recommended number of continuing confirmation tests discussed above, or provide a statistical or engineering judgment basis for using an alternative number of tests.

c) State and justify the minimum level of degradation that a component must exhibit in order to be used as an appropriate test specimen for ACTs.

d) State or provide the following:

• a description of "SCM testing," as referenced in Table 2.5 of ST-HL-AE-2748, and what criteria were used to establish the percent dealloyed from this testing

• a copy of any other testing results that correlate tensile properties to percent dealloying based on both a dimensional (Le., percent through-wall) and chemical composition (i.e., aluminum depletion) basis, if available how the percentage of dealloying will be determined, from a dimensional and chemical composition basis, for testing that will be conducted in the future how partially dealloyed material properties will be integrated into trending data e) For the following test or inspection result outcome examples, state what specific actions would be taken and the basis for those actions. Amend the AMP, UFSAR Supplement, and Commitments to state the specific actions for these examples:

During a PE or ACT. a crack or degree of dealloying is discovered outside of the current correlation as shown on page 12 of AES-C-1964-5, "Evaluation of the Significance of Dealloying and Subsurface Cracks on Flaw Evaluation Method,"

In responding to this scenario, include a statement of how many additional fittings

- 7 will be immediately examined, even though not leaking, to determine whether this is a one-off data point or whether there are many more susceptible fittings which have larger internal cracking or dealloying than would be projected from observing the through-wall indications on the 00. If no additional fittings will be immediately examined, state the basis for not conducting this expansion of inspection scope.

• An ACT test result yields a data point below the size-appropriate acceptance curve (e.g., Figure 4-2, "Evaluation of Flange Bend Test Results," in AES-C-1964-5).

• The evaluation of a newly-discovered leaking fitting results in a determination that the degraded component would not have been operable (i.e., the local critical bending stress is too high as compared to the observed external crack or dealloying angle).

PE or ACT results demonstrate a trend where, due to continuing dealloying, tensile strength, yield strength, or fracture toughness properties are projected to be below the acceptance criteria prior to the end of the PEO.

PE or ACT results demonstrate that layer-type dealloying predominates over plug-type, such that it is no longer possible to project internal degradation based on external observations. In addition:

i. State the step-by-step process an examiner will use, when conducting profile exams to determine the transition point between layer-type and plug-type dealloying and thereby derives the internal dealloying angle.

ii. State the acceptance criterion for the maximum percent of cross-sectional layer-type dealloying that will be allowed to occur within the use of the current methodology for determining the acceptability of a degraded component.

PE or ACT results demonstrate that cracking has extended into the un-dealloyed region.

f) State:

• Why an average through-wall dealloying angle is the output of the correlation in AES-C-1964-5 rather than the inside wall dimension.

How the correlation from AES-C-1964-5 will be modified if use of the average dealloying angle is not appropriate. Additionally, reconsider the structural integrity evaluation for any degraded components discovered since 2011 and state whether the components would still be considered to meet structural integrity criteria (using this modified correlation) and therefore would still be capable of performing their intended function with the new correlation.

• Whether the structural factor for the normal/upset conditions will always be at least 2.77, and for emergency and faulted conditions at least 1.39. If not, state what the minimum structural factors would be and the basis for the values being less than those stated in ASME Code Section XI.

• For the four scenarios of 00 observed degradation below:

- 8

i. Four small rounded indications of through-wall dealloying located in a circumferential axis at 10:00, 11 :00, 1 :00, and 2:00 on a 1 O-inch flange.

ii. One indication at 10:00, one-half inch long, with what appears to be rounded ends and no measurable width on a 4-inch flange.

iii. One "greenish" stain approximately 1/8 inch diameter at the 10:00 position on a 6-inch flange.

iv. One crack-like indication, one-half inch long, within a larger greenish stain with a circumferential length of one inch.

State:

• the size of the 00 flaw

• the corresponding size of the internal flaw that would be used in the structural integrity determination

• which figure would be used from AES-C-1964-1

• the stress component input values that would be utilized from the highest stress location in the essential service water system with susceptible components for that size as obtained by the stress analyses on record and how they would be combined in the structural integrity determination

• what structural factor will be used

• the critical bending stress as derived from the figures in AES-C-1964-1

• whether the component would be considered to be capable of meeting its intended function

• What site procedure prqvides step-by-step instructions for determining the structural integrity of a degraded susceptible aluminum bronze component in the essential service water system? If no such procedure is currently used, state the basis for why it is acceptable to have the staff completing the evaluation steps in the absence of written instructions.

g) Provide the following:

• A list of the number of remaining susceptible components broken down by size.

This list is required for the staff to conduct an independent review of the analytical output information in relation to flaw size tolerance.

• A copy of AES-C-1964-4, "Evaluation of 6-lnch Flange Test." This calculation will be used by the staff as input to determine the acceptability of the proposed aging management program and, therefore, should be on the docket.

• An update to Table 1 of the response to RAI B2.1.37-1 to reflect leaking components that have occurred since July 28, 2011.

• The basis for why 1-inch and under lines are not replaced by the end of the subsequent outage. Also, state the basis for why 1-inch and under lines can be demonstrated to meet their intended function prior to replacement.

December 18, 2012 Mr. D. W. Rencurrel Chief Nuclear Officer STP Nuclear Operating Company P.O. Box 289 Wadsworth, TX 77483

SUBJECT:

REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION - SET 26 (TAC NOS. ME4936 AND ME4937)

Dear Mr. Rencurrel:

By letter dated October 25, 2010, STP Nuclear Operating Company submitted an application pursuant to Title 10 of the Code of Federal Regulations Part 54, to renew operating licenses NPF-76 and NPF-80 for South Texas Project, Units 1 and 2, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review.

These requests for additional information have been presented to your staff, and we request that, since it may take longer than 30 days to prepare your response, you indicate to the staff your anticipated time frame for responding. If you have any questions, please contact me by telephone at 301-415-3873 or bye-mail at john.daily@nrc.gov.

Sincerely, IRA!

John W. Daily, Sr. Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/encl: Listserv DISTRIBUTION:

See next page ADAMS Accession No. ML12333A227

• concurrence via email PM: DLR/RPB1 OFFICE PM:

LA: DLRI RPB1 JDaily DMorey NAME JDaily IKing 12/18/12 12/18/12 12/12/12 DATE 12/13/12 OFFICIAL RECORD COpy

Letter to D. W. Rencurrel from John W. Daily dated December 18, 2012

SUBJECT:

REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SOUTH TEXAS PROJECT, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION - SET 26 (TAC NOS. ME4936 AND ME4937)

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