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NEI Slides - Risk Insights for Aging Management Presentation June 2, 2022
	ML22152A094
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Issue date:	06/02/2022
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	Johnson M, 301-415-5861
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Background and Overview Selective Leaching Inaccessible Non-EQ Cables Next Steps Jolynn Oquist Barry Thurston Fernando Ferrante Dylan Cimock Xcel Energy Constellation Energy EPRI*

EPRI Andrew Burgess Drew Mantey Jessica Bock Ameren Missouri EPRI EPRI Brett Titus NEI Agenda

EPRI - Electric Power Research Institute

Background and Overview

Maintenance Rule Risk-informed Oversight Risk-Informed Plant Licensing Basis Changes Risk-Informed In-Service Inspection Risk-Informed Categorization of SSCs (§50.69)

Risk-Informed Technical Specifications Risk-Informed Fire Protection All operating reactors have invested heavily on site-specific PRA models that added significant quality and level of detail since the 1990s While the focus of each risk-informed application may be different, there are insights that can be leveraged to inform aging management effects Risk Insights for Aging Management

©2022 Nuclear Energy Institute 5 CY22 - Development of NEI Technical Report on Risk Insights for Aging Management May 2, 2022 - Publication of EPRI Report, Leveraging Risk Insights for Aging Management Program Implementation: 2022 March 10, 2022 - Regulatory Information Conference Technical Session (https://ric.nrc.gov/docs/abstracts/sessionabstract-33.html)

January 12, 2022 - Submitted Selective Leaching and Inaccessible Cable AMP mark-ups for incorporation into GALL-SLR and GALL Risk Insights for Aging Management

Selective Leaching

Utility implementation of the Selective Leaching (SL) Aging Management Program (AMP) has identified areas for improvement

Selective Leaching industry operating experience provides new information that can be used in revising the Selective Leaching AMP

Ongoing research by the industry and EPRI has identified opportunities to improve the effectiveness and efficiency of the Selective Leaching AMP

Background

Objective 1: improve clarity of element 4 by re-structuring from long paragraphs to bullets and tables, using XI.M41 as a model.

Objective 2: introduce the allowance for new NDE techniques, based on recent advancements and demonstrations of NDE technology

Objective 3: introduce use of risk-insights into sample methodologies

Objective 4: streamline the required corrective actions to credit utilities well-established Corrective Action Program to determine appropriate extent of condition and extent of cause commensurate with safety significance

The extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR guidance) was reduced when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance) based on six deterministic factors outlined in NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192.

The NEI document proposes a further reduction down to 2-3 components per population. Please provide the technical basis for this reduction.

Response Summary

NEI proposal provides the option to use existing GALL-SLR sampling requirements or a risk-informed sampling methodology.

Proposed revisions to Element 4 restructured existing sampling requirements into a tabular format - but did not change sampling quantities.

Risk-informed sampling methodology may not reduce the number of components inspected.

Risk-informed sampling methodology will drive smarter sampling than existing guidance.

The risk insights framework was developed very similarly to other previously NRC-approved risk-informed categorization methodologies.

SL - Staff Question #1

The extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR guidance) was reduced when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance) based on six deterministic factors outlined in NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192.

The NEI document proposes a further reduction down to 2-3 components per population. Please provide the technical basis for this reduction.

Detailed Response

Large revisions to Element 4 were largely focused on recommending a re-structuring of the existing content to improve the readability and flow of the AMP. Changes included taking large paragraphs and converting into a table format with footnotes and bullet points, similar to how XI.M41 is structured.

New proposed Table XI.M33-1 addresses inspections on a per unit basis, including for all populations 3%, maximum of 10 components - consistent with GALL-SLR.

Risk-informed sampling methodology results in the same number or more inspections for sample populations up to 116.

At the pilot plant in the EPRI study, proposed risk-informed sampling methodology would result in more inspections than required by current GALL-SLR requirements.

SL - Staff Question #1

The extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR guidance) was reduced when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance) based on six deterministic factors outlined in NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192.

The NEI document proposes a further reduction down to 2-3 components per population. Please provide the technical basis for this reduction.

Detailed Response (cont.)

Lesser inspection quantities are justified considering:

Current guidance is susceptibility/probability biased.

Component consequence of failure is not considered.

Risk-informed sampling methodology considers both susceptibility/probability and consequence of failure.

Risk-informed sampling is based on a systematic, structured process that identifies the highest risk components in a given population and selects inspection samples based on assessing the structural integrity of those highest risk components.

Guidance on inspection sample selection does not need to drive inspections of components whose failure is within currently acceptable bounds of incremental plant safety risk as determined through PRA.

Populations are overly inflated if lower risk components are included; however, they should be (and are) considered for inspection as surrogates.

Proposed guidance is intended to set the minimum required inspections given that populations will vary significantly.

SL - Staff Question #1

The extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR guidance) was reduced when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance) based on six deterministic factors outlined in NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192.

The NEI document proposes a further reduction down to 2-3 components per population. Please provide the technical basis for this reduction.

Detailed Response (cont.)

Similar RI-categorization and sampling methodologies have been applied to pressure boundary components and approved by the NRC:

Foundational methodology is in NRC-approved topical report TR-112657, REV B-A.

A key component of this methodology is the EPRI RI-ISI Risk Matrix, in which pressure boundary components are assigned to one of seven risk categories based upon the results of separate and independent evaluations (i.e.

consequence of failure set to 1.0, failure potential evaluation is conducted even if the consequence of failure is low).

Significant industry experience with applying RI-ISI to safety related and non-safety related systems has shown portions of the pressure boundary receiving increased inspections (e.g. those with higher failure potential and consequence). Other portions of the pressure boundary may see a reduction in inspections.

SL - Staff Question #1

The extent of inspections for selective leaching during the subsequent period of extended operation (i.e., 3 percent with a maximum of 10 components per GALL-SLR guidance) was reduced when compared to the extent of inspections for selective leaching during the initial period of extended operation (i.e., 20 percent with a maximum of 25 components per GALL Report, Revision 2 guidance) based on six deterministic factors outlined in NUREG-2222, Disposition of Public Comments on the Draft Subsequent License Renewal Guidance Documents NUREG-2191 and NUREG-2192.

The NEI document proposes a further reduction down to 2-3 components per population. Please provide the technical basis for this reduction.

Detailed Response (cont.)

Similar RI-categorization and sampling methodologies have been applied to pressure boundary components and approved by the NRC:

Per TR-112657, REV B-A, eliminating a large population of piping inspections in safety related systems in lowest risk locations will have a negligible on plant risk, to the point that a quantitative change in risk assessment is not required when eliminating these inspections.

Industry experience with RI-ISI has shown that when there is a reduction in the inspection population for other risk categories, the NRC approved change in risk acceptance criteria is always met. Further demonstrating the robustness of the evaluation processes (e.g.

consequence of failure, failure potential), criteria (e.g.

CCDP/CLERP ranges) and inspection populations.

SL - Staff Question #1

Stations that have applied the industry-accepted risk framework (EPRI TU 3002020623 Leveraging Risk Insights for Aging Management Program Implementation Update) to the AMP have the option of using risk-informed inspection sample selection or the 3% of population/10 components inspection sampling methodology.

Risk-informed sampling methodology:

Any SSCs that could not be fully evaluated for the likelihood and/or consequence risk factor using the risk framework must be placed in the high category for the applicable risk factor(s).

A minimum of 2 SSCs classified as high consequence, regardless of likelihood, in each applicable population must be included in the inspection sample.

This minimum number of high consequence SSCs to be inspected may be reduced to 1 if 2 or more surrogates are inspected. A surrogate is defined as an SSC within the same population with the same or higher likelihood of failure, but with a lower consequence of failure.

For populations with no high consequence SSCs, a minimum of 2 SSCs should be inspected, with a focus on assessing the structural integrity of the higher consequence SSCs in the population. The SSCs to be inspected can be selected from either the highest consequence group or surrogates.

Stations must retain auditable records of the risk framework results and update these results as new information becomes available that may change the initial results.

Hardness testing was replaced with mechanical examination techniques and destructive examinations with the issuance of GALL-SLR.

Hardness testing can theoretically identify the presence of selective leaching but is unable to characterize the extent of selective leaching.

Please provide the technical basis for re-introducing hardness testing.

Response Summary

Hardness testing was proposed to be re-introduced as it can be an effective means to support detection of selective leaching.

The intent of re-introducing hardness testing was to maximize the number of available inspection techniques utilities are able to leverage in order to detect the presence of the selective leaching in components.

SL - Staff Question #2

Hardness testing can theoretically identify the presence of selective leaching but is unable to characterize the extent of selective leaching.

Please provide the technical basis for re-introducing hardness testing.

Detailed Response

Hardness testing is a point measurement and does not reveal information about the condition of a component in other areas away from where the test was done.

However, hardness testing is proven to identify whether selective leaching has occurred where the test has been done.

The proposed wording of XI.M33 acknowledges that it is not effective at characterizing the extent or depth of selective leaching.

Industry operating experience has found successful use of hardness testing in conjunction with visual exams.

As such, it can be a useful tool to confirm selective leaching in suspected areas found through visual inspection. In this context, hardness testing can improve the objectivity of visual inspection and should not be discarded.

SL - Staff Question #2

Hardness testing can theoretically identify the presence of selective leaching but is unable to characterize the extent of selective leaching.

Please provide the technical basis for re-introducing hardness testing.

Detailed Response

Proposed changes to Element 4 also state, If a given inspection method yields inconclusive or potentially unsatisfactory results, a more capable method may be chosen for follow-up inspection and disposition of results.

The proposed changes are structured such that if acceptance criteria were not satisfied, the inspection would either need to be considered unsatisfactory, or the extent of selective leaching would need to be further investigated using more capable techniques.

Use of hardness testing is analogous to a screening approach for selective leaching.

SL - Staff Question #2

The NEI document introduces [n]ondestructive examination techniques demonstrated to be capable of detecting the presence and/or extent of selective leaching on the component as an inspection method.

The AMP should identify specific NDE techniques which are capable of detecting selective leaching in cast irons and copper alloys. (See reference below which notes that NDE for selective leaching has not achieved widespread acceptance.)

Uhligs Corrosion Handbook, 3rd Edition, page 148, "Several researchers have reported on attempts to develop method of in situ nondestructive inspection for dealloying, but they have not achieved widespread acceptance."

Response Summary

Selective leaching is an inherently difficult aging mechanism to detect. The proposed revisions to XI.M33 include recommendations to permit the use of nondestructive examination techniques in order to maximize the available methods that utilities can leverage in order to detect selective leaching.

Recommendations to permit NDE techniques are based largely on EPRI research (see next page), including 2 recently published reports in 2021.

3002020830, Ultrasonic NDE Techniques for Detection of Selective Leaching in Complex Shaped Gray Cast Iron Components 3002020832, Electromagnetic NDE Techniques for Detection of Selective Leaching in Gray Cast Iron Piping SL - Staff Question #3

©2022 Nuclear Energy Institute 23 SL - Staff Question #3 EPRI Selective Leaching NDE Research Title Product ID Year Selective Leaching NDE Technical Basis Document - 2022 Research Update TBD 2022 Ultrasonic NDE Techniques for Detection of Selective Leaching in Complex Shaped Gray Cast Iron Components 3002020830 2021 Electromagnetic NDE Techniques for Detection of Selective Leaching in Gray Cast Iron Piping 3002020832 2021 Selective Leaching: State-of-the-Art Technical Update 3002016057 2019 Guidance for Conducting Ultrasonic Examinations for the Detection of Selective Leaching 3002013168 2018 Assessment of Available Nondestructive Evaluation Techniques for Selective Leaching: Technology Review 3002008013 2016 Correlation of Selectively Leaching Thickness to Hardness for Gray Cast Iron and Brass 1025218 2012 Update to NDE for Selective Leaching of Gray Cast Iron Components 1019111 2009 NDE for Selective Leaching of Gray Cast Iron Components 1018939 2009

The NEI document introduces [n]ondestructive examination techniques demonstrated to be capable of detecting the presence and/or extent of selective leaching on the component as an inspection method.

The AMP should identify specific NDE techniques which are capable of detecting selective leaching in cast irons and copper alloys. (See reference below which notes that NDE for selective leaching has not achieved widespread acceptance.)

Uhligs Corrosion Handbook, 3rd Edition, page 148, "Several researchers have reported on attempts to develop method of in situ nondestructive inspection for dealloying, but they have not achieved widespread acceptance."

Detailed Response

Proposed wording to address NDE techniques in XI.M33 specified that the techniques shall be volumetric in nature.

More specific forms of NDE were not listed for the following reasons:

Use of the term volumetric was intended to capture both ultrasonic and electromagnetic techniques recently demonstrated in EPRI research.

Many electromagnetic NDE techniques go by vendor-specific names.

Use of the generic term volumetric aligns with similar wording found in other AMPs (e.g., XI.M30, XI.M38, XI.M41) and was intended to convey that the methods would be capable of detecting wall loss (vs. surface techniques).

Desire for flexibility in AMP implementation to allow use of technology as it continues to evolve and advance beyond todays state-of-the-art. A statement included that the NDE methods must be demonstrated to be able to detect selective leaching. Similar concepts can be found in XI.M41 Element 4.

SL - Staff Question #3

The NEI document introduces [n]ondestructive examination techniques demonstrated to be capable of detecting the presence and/or extent of selective leaching on the component as an inspection method.

The AMP should identify specific NDE techniques which are capable of detecting selective leaching in cast irons and copper alloys. (See reference below which notes that NDE for selective leaching has not achieved widespread acceptance.)

Uhligs Corrosion Handbook, 3rd Edition, page 148, "Several researchers have reported on attempts to develop method of in situ nondestructive inspection for dealloying, but they have not achieved widespread acceptance."

Detailed Response

Each inspection technique referenced for SL (visual, mechanical, hardness) will have their own specific set of capabilities and limitations. Allowance for relatively new, or future, NDE techniques is intended to permit utilities to better leverage new technology to more effectively and efficiently implement this aging management program.

SL - Staff Question #3

GALL-SLR Report AMP XI.M33 recommends visual/mechanical and destructive examinations for each population.

The NEI proposal states [i]nspections and examinations may consist of any [of] the following methods (referring to either visual/mechanical, hardness, nondestructive, or destructive examinations).

Please provide the basis for going from two inspections techniques in our current guidance down to one inspection technique.

Response Summary

The referenced wording in Question #4, cited from the proposed NEI revisions, was not intended to address the quantity of inspection techniques that are to be performed.

Rather - the cited paragraph was intended to simply introduce the types of inspections that are acceptable in a more structured manner:

By material type

In successive order of increasing complexity (to deploy) and capability of detection SL - Staff Question #4

GALL-SLR Report AMP XI.M33 recommends visual/mechanical and destructive examinations for each population.

The NEI proposal states [i]nspections and examinations may consist of any [of] the following methods (referring to either visual/mechanical, hardness, nondestructive, or destructive examinations).

Please provide the basis for going from two inspections techniques in our current guidance down to one inspection technique.

Detailed Response

Inspection quantities listed in proposed Table XI.M33-1 reference footnote 3. Footnote 3 similarly states that for the inspections to be performed for a given population, some quantity shall be of a nondestructive or destructive variety.

This is similar to the existing guidance in GALL-SLR.

The only intended difference is that (demonstrated) volumetric NDE techniques could be deployed in lieu of the destructive testing as an option.

The only time a single inspection technique would apply to a population would be if 100% of the population were to be inspected by volumetric NDE or destructive examination.

SL - Staff Question #4

GALL-SLR Report AMP XI.M33 recommends visual/mechanical and destructive examinations for each population.

The NEI proposal states [i]nspections and examinations may consist of any [of] the following methods (referring to either visual/mechanical, hardness, nondestructive, or destructive examinations).

Please provide the basis for going from two inspections techniques in our current guidance down to one inspection technique.

Detailed Response

NUREG-2221 characterizes destructive exams as providing quantitative assessments of SL, while the other techniques (visual/mechanical) are referred to as providing qualitative assessments.

Given this characterization, it is proposed that volumetric NDE techniques can be viewed in a similar perspective as that of destructive exams as they can provide a measurable or quantifiable extent of wall loss.

Refer to previously cited EPRI Reports on NDE.

SL - Staff Question #4

Susceptibility to selective leaching is considered in a qualitative manner to provide input into the process along with consequence information.

This is included to provide better insight into high/low consequence impacts and to avoid overly conservative assessment of the SSC population.

The consequence information is still available, such that the susceptibility is not unduly driving decisions on inspection focus.

Based on engineering and research insights, considering susceptibility and loss of intended function for the SSC would provide a more complete picture of the inspection focus (along with consequence).

SL - Staff Question #5 When using the risk-informed sampling methodology, inspections focus on consequence not risk (i.e.,

the product of susceptibility and consequence).

Is susceptibility to selective leaching considered while using this methodology?

Current aging management guidance from the GALL-SLR takes into consideration only likelihood of / susceptibility to selective leaching for in-scope SSCs when determining sample selection.

For selective leaching there has been a limited understanding of material and environmental susceptibility factors that lead to the inception and/or progression of selective leaching hence, the likelihood of occurrence.

The pilots and research performed indicate an approach that leverages risk insights to sample selection can be implemented that includes consideration of both likelihood and/or consequence of failures.

The approach allows for conservative decisions to be made that do not over-rely on risk results (risk-based) nor give undue credit to qualitative susceptibility attributes.

The framework does not discount consequence-based information, which are included in the framework, with a rationale for the appropriateness/basis of its inclusion.

SL - Staff Question #5 When using the risk-informed sampling methodology, inspections focus on consequence not risk (i.e.,

the product of susceptibility and consequence).

Is susceptibility to selective leaching considered while using this methodology?

The attributes used to consider susceptibility to selective leaching, the scoring used, and the criteria for high/medium/low likelihood results are provided in the EPRI document.

Susceptibility to selective leaching is used to place all SSCs on the risk matrix-which is the key output of the risk insights framework

The placement of SSCs on the risk matrix is then used directly to determine not only sampling for inspections, but most importantly, to determine the ideal aging management strategies for in-scope SSCs.

Susceptibility to selective leaching is specifically referenced in the definition of a surrogate component, which can be inspected in lieu of higher consequence components.

SL - Staff Question #5 When using the risk-informed sampling methodology, inspections focus on consequence not risk (i.e.,

the product of susceptibility and consequence).

Is susceptibility to selective leaching considered while using this methodology?

Additional precedent from NRC-approved RI-categorization methodologies.

For RI-repair / replacement (RI-RRA) and 10CFR50.69 purposes, plants are using essentially the consequence portion of the RI-ISI methodology contained in TR-112657, REV B-A.

As such, this is a consequence-based approach to pressure boundary categorization rather than a pure risk approach.

The rationale behind this change in approach was that RI-RRA and 10CFR50.69 can be applied to many different pressure boundary component types and possibly subjected to a wide spectrum of degradation mechanisms,.

This conservative approach to component categorization (i.e. failure probability of 1.0) also provided a more streamlined (i.e. less costly) categorization process.

In contrast, this change is focused solely on the selective leaching mechanism.

Substantial work was undertaken to understand this mechanism and the attributes necessary for this mechanism to be operative in pressure boundary components that are within the scope of LR/SLR AMP programs.

As such, coupling of these two separate and independent evaluations (i.e.

consequence of failure equal to 1.0, failure potential due selective leakage) is consistent with previously NRC RI-applications and provides a more informed approach to AMP for the selective leaching mechanism SL - Staff Question #5 When using the risk-informed sampling methodology, inspections focus on consequence not risk (i.e.,

the product of susceptibility and consequence).

Is susceptibility to selective leaching considered while using this methodology?

Response

The Corrective Action Program is a well-established and regulated program at the utilities.

The proposed change credits the Corrective Action Program to determine the appropriate causal analysis, extent of condition, extent of cause, etc., commensurate with safety significance of the identified issue.

This proposed change cross-cuts several AMPs.

SL - Staff Question #6

The corrective actions program element of AMP XI.M33 (with the issuance of GALL-SLR) was revised to include specific recommendations for conducting extent of condition examinations when acceptance criteria are not met.

This is consistent with several other GALL-SLR Report AMPs.

The NEI document proposes deleting this language, please provide a technical basis for this change.

Inaccessible Power Cables Not Subject to 10 CFR 50.49 Environmental Qualification Requirements

©2022 Nuclear Energy Institute 37 Duration between testing Please specify a duration between testing for the provision have been tested at least twice in the good range (is this once -6 years prior to entering the period of extended operation and once more when entering the period of extended operation?).

Do the test results need to be tested in the good range twice consecutively?

Response

Cables should be tested on a 6-year frequency and two consecutive good test are required to extend to a 10-year frequency.

The two consecutive tests can occur anytime prior to or during the PEO.

Cables - Staff Question #1

Response

Certain cable types have more operating experience of cable failures (e.g., XLPE, a compact EPR design, and black EPRs). However, since the industry adoption of the VLF tan delta test method there have been no known industry OE for any cable type that suggests failures soon after a good tan delta test as a common occurrence.

Cable insulations that have a higher number of failure OEs was considered in the XI.E3 RIAM pilot. Each insulation type has different characteristics when exposed to water or other adverse environments. This was accounted for in development of the likelihood table. For instance, XLPE, butyl rubber, and compact insulation were weighted higher because they are more susceptible to long-term, water-related degradation mechanisms compared to pink/brown EPR or tree-resistance XLPE.

Cables - Staff Question #2

Explain how using only two data points can establish a meaningful trend to inform changes to testing frequency.

Response

EPRI PMBD vulnerability study indicates no increased failure rate for cables unless the test frequency is > a 10-year test period.

EPRI review of industry test data since 2009 had no instances of long-term wetted cables failing when tested on a 6-year frequency, and very cables that tested good did not test less than good on subsequent tests.

The test data points are very well defined by three different acceptance criteria (3002000557) each time the cable is tested. The acceptance criteria is based on an expert solicitation (1021070) and validated by EPRI review of industry test data between 2009-2015 (3002005321, 1025262).

It is not just two data points that establish the trend, but every tests of a particular cable insulation type at each plant that uses that insulation are used to establish the health of a particular insulation type. When combined with industry OE shared via the EPRI Cable User Group provided input into the weighting factors in the Cable Pilot study.

Using two consecutive tests helps to ensure the cable remains in good condition over a longer period. This helps to better understand the cable characteristics and responses in the installed environment prior to considering extending the monitoring frequency.

If the test frequency is extended to a 10 years, if any subsequent test results suggests additional degradation is occurring, then accelerated test frequency or corrective action should be pursued accordingly based on the severity of the results.

Cables - Staff Question #3

©2022 Nuclear Energy Institute 40 Electrical Slides Back-up Information EPRI Preventive Maintenance Basis Database Vulnerability Result EPRI Report 3002005321 breakdown of cable issues for cables evaluated between 2009-2015 EPRI Report 3002000557 VLF Tan Delta Acceptance Criteria for Various Insulation types

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