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Official Exhibit - NYS000489-00-BD01 - Slides, EPRI, Industry-NRC Meeting, CASS Screening Criteria for Thermal and Irradiation Embrittlement for BWR and PWR Internals (July 15, 2014) (ML14211A661)
	ML15331A170
Person / Time
Site:	Indian Point
Issue date:	07/15/2014
From:	; State of NY, Office of the Attorney General
To:	; Atomic Safety and Licensing Board Panel
	SECY RAS
References
	RAS 27898, ASLBP 07-858-03-LR-BD01, 50-247-LR, 50-286-LR
	Download: ML15331A170 (52)
	v • d • e

United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of: Entergy Nuclear Operations, Inc.

(Indian Point Nuclear Generating Units 2 and 3)

ASLBP #: 07-858-03-LR-BD01 Docket #: 05000247 l 05000286 Exhibit #: NYS000489-00-BD01 Identified: 11/5/2015 Admitted: 11/5/2015 Withdrawn: NYS000489 Rejected: Stricken:

Other: Submitted: June 9, 2015 Industry-NRC Meeting CASS Screening Criteria for Thermal and Irradiation Embrittlement for BWR and PWR Internals July 15, 2014 NRC Offices Washington, DC

Agenda 8:00 Introductions NRC 8:15 Meeting Objectives NRC, Industry 8:30 Industry Position on Thermal and Irradiation Industry Embrittlement Screening Criteria 9:45 Break 10:00 Industry Position on Thermal and Irradiation Industry Embrittlement Screening Criteria (contd) 10:30 NRC Position on Thermal and Irradiation NRC Embrittlement Screening Criteria 11:15 Discussion of Industry Comments on NRC Position NRC 12:00 P.M. Lunch 1:00 Discussion of Industry Comments on NRC Position NRC (Cont) 2:00 Steps to Move Forward and Obtain SE? on Industry All Position on Generic Screening Criteria for PWRs and BWRs Utility Required Actions to Meet Staff Guidance 2:45 Break 3:00 Closure and action item review 3:30 Adjourn

Meeting Objectives

Review proposed industry and NRC positions regarding thermal and irradiation embrittlement criteria

Establish a full understanding of each position

- Discuss responses to industry comments on NRC position

Discuss issues associated with industry burden to comply with current NRC position

Identify actions required to obtain a Safety Evaluation and/or final NRC position

Discuss options and potential actions going forward

Outline of Presentation

Background

Formation of Working Group

Interactions with NRC

Thermal Embrittlement Criteria

Irradiation Embrittlement Criteria

Synergy Effects

Industry Burden Based on Current NRC Position

Comments on NRC Screening Position

Review of Industry Comments

Summary

Background

During 2013, NRC issued RAIs on MRP-227-A to several PWR utilities regarding evaluation of CASS components

In May 2013, NRC issued a 2nd set of RAIs on BWRVIP-234

The industry determined that some RAIs were common to BWRs and PWRs

Industry/NRC meeting held in Washington, DC on May 21, 2013 to review issues related to evaluation of CASS

- Follow-up meetings with NRC in August 2013, November 2013 and December 2013

- NRC requested a common BWRVIP/MRP screening approach for Thermal Embrittlement (TE) and Irradiation Embrittlement (IE)

PWR/BWR Industry Working Group formed in June 2013 to address CASS issues

- Significant work conducted to date to address BWRVIP and MRP issues

MRP/BWRVIP Working Group Approach

Develop responses to BWRVIP-234 RAIs

Develop PWR/BWR screening criteria for TE and IE

- Review the technical bases of the Grimes letter, along with other approaches for evaluating metallurgical effects of thermal aging and irradiation embrittlement of CASS

- Provides a basis for response to MRP-227-A LAI No. 7

2014 Interactions

February 3 telecon with NRC

- Presented updated PWR/BWR CASS screening criteria

Late February - industry submitted additional information on Synergy Effects of TE & IE in CASS

- Follow up discussion between industry and staff on March 12, 2014

Staff subsequently forwarded their initial position paper regarding TE and IE on March 13, 2014

Industry submitted response to BWRVIP-234 RAI which included industrys proposed generic TE and IE screening criteria to NRC on May 23, 2014 (ML14174A841)

NRC Position on Aging Management of CASS Reactor Vessel Internal Component, provided to industry on June 20, 2014 (ML14174A719)

Industry TE Screening Criteria

Industry proposal is to screen for TE based on delta ferrite prior to screening for IE - use ferrite limits from current pressure boundary practice (i.e., Grimes Letter)

- TE relevant for internals when delta ferrite > 20% and, in some cases, delta ferrite >14%

Thin-section CASS structural internals intentionally have lower delta ferrite than primary pressure boundary components

- Chemical composition of CASS internals is distinctly different from that of CASS piping, i.e., typical internals have delta ferrite < 20%

CASS internals are not as susceptible as thick-section castings (e.g., piping, pump casings, valve bodies) to solidification cracking during cooling

High ferrite is not needed in small casting to improve casting process yield

- Supporting evidence documented in BWRVIP-234

TE Screening Criteria

Grimes letter susceptibility based on ferrite content

- TE relevant for internals when delta ferrite > 20%

(in some cases when delta ferrite > 14%)

Molybdenum (wt. %) Casting Method Susceptibility Delta ferrite %

TE > 14%

static No 14%

High 2.0-3.0%

(CF-8M)

TE > 20%

centrifugal No 20%

TE > 20%

static Low 0.5% max No 20%

(CF-3 and CF-8) centrifugal No All

Thermal Embrittlement (TE) of CASS

TE of CASS occurs when aging of ferrite phase results in transition to cleavage fracture

CASS material is susceptible to TE when ferrite volume fraction and distribution are sufficient to support a cleavage failure path

- Determination of volume ferrite fraction is inexact

Spatial variations within casting

Multiple measurement techniques

NUREG/CR-4513, Rev. 1 provides basis for estimating lower bound fracture toughness

- Correlations based on composition

- Utilizes Hulls equivalent factors and material composition

Resolution of NUREG/CR-4513, Rev. 1 and EPRI TR-106092 provided the basis for the criteria in the Grimes letter

Industry Proposal for TE Screening Criteria

Retain Grimes letter criteria to determine TE susceptibility

- Chemical composition, casting method and delta ferrite

- Screening levels based on prediction of delta ferrite using Hulls equivalent factors

Consistent with current practice for pressure boundary components

Industry IE Screening Criteria

When necessary screen for IE using fluence of 1 dpa

- Industry efforts to date show that IE accelerates but does not enhance embrittlement process, especially for CASS materials with moderate delta ferrite content

Industry data support the premise that 20% delta ferrite CASS embrittlement is controlled by the behavior of the austenite phase

The effect of irradiation on austenite phase is well understood

- Data show onset of embrittlement occurs at 3-5 dpa

- Screening criteria are conservatively established at 1 dpa

- Current data are inconclusive with respect to IE and TE for high

(> 20%) delta ferrite CASS materials

- Accelerates but does not enhance premise provides the basis for TE screening followed by IE screening

1 dpa = 6.7 x 1020 n/cm2 (E >1MeV)

Consideration of Synergistic Effects

Grimes letter states:

- For RVI components fabricated from CASS and hence subject to thermal embrittlement, concurrent exposure can result in a synergistic effect wherein the service degraded fracture toughness (that) is reduced from the levels predicted independently for either of the mechanisms.

Synergistic effects

- Accelerate the embrittlement?

Temperature effects shown to accelerate the rates of attaining the same saturation values of embrittlement

- Exacerbate the embrittlement?

Database is sparse (nonexistent!) to support exacerbation

Mechanistic considerations suggest separable effects

- Mechanistic approach requires that there is no (significant) exacerbation effect in IE

Industry Data Supporting Accelerating-Only Effect of Synergy

NUREG-4513, Rev. 1 demonstrated that fully embrittled ferrite <20%

does not significantly embrittle the bulk CASS material

Full Thermal Aging heat treatment was ineffective in embrittling the low ferrite content CF8 high Jq and very high J2.5mm

Full Thermal Aging plus 0.08 dpa irradiation was ineffective in the embrittlement of low ferrite content CF3 fuel nozzle very high Jq and J2.5mm

Effect of irradiation becomes significant in the range of 6-10 dpa but for these materials does not appear to saturate until ~12 dpa

Thermal aging prior to irradiation has no significant effect on post irradiation toughness - full thermal age + irradiation actually exhibited greater remaining toughness than partial thermal age + similar irradiations (6.3 to 12 dpa)

Industry data support the premise that low ferrite content ( 20%) CASS embrittlement is controlled by the behavior of the austenite phase

Mechanistic View of Embrittlement of CASS

Embrittlement of duplex CASS structure depends on controlling phase:

- If delta ferrite phase is of sufficient volume fraction and distributed to provide a continuous path for brittle fracture, then delta ferrite fraction will be controlling

- If delta ferrite phase is less than of a sufficient volume fraction or is distributed in an isolating dispersion, then austenite properties will be controlling Controlling Thermal Embrittlement Irradiation Embrittlement Phase Susceptibility Susceptibility Ferrite Potentially Susceptible to Potentially Susceptible to IE if Thermal Embrittlement Fluence > crit Austenite Not Susceptible to Thermal Potentially Susceptible to IE if Embrittlement Fluence > crit

- Susceptibility to TE can be assessed using Grimes Letter Table 2 criteria (Mo content, casting method, delta ferrite)

- Delta ferrite is calculated using Hulls equivalent factors consistent with the NUREG/CR-4513 correlations of loss of toughness (Cvsat, J-R) vs. delta ferrite surrogate In all cases the ANL predictions of J-R curves were accurate or conservative compared to the measured values

Methodology for Revised Screening Approach TE and IE Hierarchy and IE Criterion Molybdenum Casting Delta-Ferrite Susceptibility (Wt%) Method % Determination

> 14% Potentially Susceptible to TE Static 14% Not Susceptible to TE Thermal High 2.0-3.0 > 20% Potentially Susceptible to TE Screening Centrifugal 20% Not Susceptible to TE Criteria Low > 20% Potentially Susceptible to TE 0.5 max Static 20% Not Susceptible to TE Centrifugal All Not Susceptible to TE Controlling Thermal Embrittlement Irradiation Embrittlement Phase Susceptibility Susceptibility Ferrite Potentially Susceptible Potentially Susceptible to IE if Mechanistic to TE Fluence > crit approach Austenite Not Susceptible to Potentially Susceptible to IE if Thermal Embrittlement Fluence > crit

Approach for Implementation of Revised Hierarchy Screening Molybdenum Casting Method Delta- Thermal Embrittlement Irradiation Embrittlement (Wt%) Ferrite % Susceptibility Susceptibility

>14% Potentially Susceptible to TE No need for IE screening Static 14% Not Susceptible to TE Screen for susceptibility to IE if Fluence > crit High 2.0-3.0

>20% Potentially Susceptible to TE No need for IE screening Centrifugal 20% Not Susceptible to TE Screen for susceptibility to IE if Fluence > crit

>20% Potentially Susceptible to TE No need for IE screening Static 20% Not Susceptible to TE Screen for susceptibility to IE if Low 0.5 max Fluence > crit All Not Susceptible to TE Screen for susceptibility to IE if Centrifugal Fluence > crit

Initial screening on TE Susceptibility criteria also screens for components/material compositions that will manifest IE at lower irradiation fluences

Subsequent IE screening can be performed addressing components/material compositions that will manifest IE due to embrittlement of the austenite

The appropriate IE screening criterion is crit = 1 dpa

Summary of Revised Screening Process and Criteria

Screen for TE first

- No need to further screen for IE when materials already determined to be susceptible to TE

Screen for IE based on threshold fluence of 1 dpa for embrittlement of austenitic phase Industry operating experience over 30-40 years supports this approach Comparison of NRC and industry positions on next slide

TE Screening IE Screening Molybdenum Casting Susceptibility

% Ferrite Position Susceptibility Result (wt. %) Method Result Yes or No Yes or No NRC No Yes, > 1.5 dpa 0-10 Industry No Yes, > 1 dpa NRC No Yes, > 0.45 dpa static 11-14 Industry No Yes, > 1 dpa High 2.0- NRC Yes N/A 15 3.0% Industry Yes N/A (CF-3M &

CF-8M) NRC No Yes, > 1.5 dpa 0-15 Industry No Yes, > 1 dpa NRC No Yes, > 0.45 dpa centrifugal 16-20 Industry No Yes, > 1 dpa NRC Yes N/A 21 Industry Yes N/A NRC No Yes, > 1.5 dpa 0-15 Industry No Yes, > 1 dpa NRC No Yes, > 0.45 dpa Low 0.5% static 16-20 Industry No Yes, > 1 dpa max (CF-3 & CF-NRC Yes N/A

8) 21 Industry Yes N/A NRC No Yes, > 1.5 dpa centrifugal All Industry No Yes, > 1 dpa

Example: Embrittlement in Lower Core Support Columns Industry Proposal NRC Proposal 68/68 Columns 62/68 Columns

Ferrite <20%

Ferrite <15%

IE Above Dashed Line

IE in Red

No Embrittlement - Below

No Embrittlement - Green, Dashed Line Blue & Below 6/68 Columns

15%< Ferrite <20%

IE + TE in Red & Green All Columns

No Embrittlement - Blue &

Below

Impact of NRC Proposed Guidance on Thermal and Irradiation Embrittlement of Cast Austenitic Stainless Steel on Lower Support Column Evaluations

Practical Implications of NRC Guidance

Consider impact of NRC guidance on full range of potential plant-specific Lower Support Column (LSC) evaluations.

- Six Potential Cases

Cases are not intended to represent any existing plant conditions.

In all cases the LSC CASS materials are low Mo, statically cast.

Lower Support Column Case #1: Thermal Embrittlement

Hulls Ferrite Evaluation: average content calculated for all support columns >20%

- Material susceptible to thermal embrittlement

- Top few inches susceptible to irradiation embrittlement

(>1.5 dpa)

- No known examples of this case

A/LAI 7 Response: Require either

- Functionality Analysis

- Flaw Tolerance Analysis No impact of NRC proposed screening guidance

Lower Support Column Case #2: Partial Thermal Embrittlement

Hulls Ferrite Evaluation: Content calculated for 10% (e.g. 6/60) of support columns >20%

- Limited number of columns subject to thermal embrittlement

- Top few inches susceptible to irradiation embrittlement (>1.5 dpa)

- No known examples of this case

A/LAI 7 Response: Require either

- Functionality Analysis

Demonstrate ability to lose 10% of LSCs?

- Flaw Tolerance Analysis No impact of NRC proposed screening guidance

Lower Support Column Case #3: No Thermal Embrittlement

Hulls Ferrite Evaluation: Content calculated for all support columns <15%, or support columns not CASS

- No columns subject to thermal embrittlement

- Large fraction of known cases

A/LAI 7 Response

- Not susceptible to thermal embrittlement (or synergistic effect)

- Top few inches susceptible to irradiation embrittlement (>1.5 dpa)

- Are Functionality or Flaw Tolerance Assessments required?

Remaining Issues

- Include in Functionality Analysis?

IASCC unlikely due to higher stress and dose threshold

- CRGT flange weld fluence lower not appropriate primary link (below IE threshold)

No impact of NRC proposed screening guidance

Lower Support Column Case #4: Incomplete Data

Hulls Ferrite Evaluation: Content calculated ferrite content for 85% of support columns <15%, remaining columns undocumented

- Limited number of columns might be subject to thermal embrittlement

- Several known cases

A/LAI 7 Response

- 85% of columns not susceptible to thermal embrittlement (or synergistic effect)

- 15% of columns might be subject to thermal and/or irradiation embrittlement

Statistical analysis suggests high probability that ferrite < 15%

- Top few inches of all columns susceptible to irradiation embrittlement (>1.5 dpa)

Remaining Issues

- Are Functionality or Flaw Tolerance Assessments required?

Between Case 2 (Partial TE) and Case 3 (No TE)

Lower Support Column Case #4: Incomplete Data (Continued)

Hulls Ferrite Evaluation: Content calculated ferrite content for 85% of support columns <15%, remaining columns undocumented

- Limited number of columns might be subject to thermal embrittlement

- Several known cases

Remaining Issues

- How many observations are required from Westinghouse/CE fleet to demonstrate following:

Reasonable assurance that all lower support columns <20% ferrite

Basis for assuming that limited fraction of undocumented columns are between 15% and 20% ferrite.

Statistical analysis suggests that a small number of undocumented columns may have ferrite content between 15% and 20% and would be impacted by NRC guidance. However worst case assumptions on CASS composition predict ferrite content >20%.

Lower Support Column Case #5: Synergistic Embrittlement

Hulls Ferrite Evaluation: Content calculated ferrite content for all support columns >15%, but <20%

- Fluence threshold for irradiation/thermal embrittlement lowered to 0.45 dpa

- No known cases

A/LAI 7 Response:

- 100% of columns not susceptible to thermal embrittlement

- Top few inches of all columns susceptible to synergistic irradiation/thermal embrittlement (>0.45 dpa)

- Are Functionality or Flaw Tolerance Assessments required?

Same as Case 3 (No TE), except volume of LSC over threshold fluence slightly expanded

Remaining Issues

- Include in Functionality Analysis?

IASCC unlikely due to higher stress and dose threshold

- CRGT flange weld fluence lower not appropriate primary link (below IE threshold)

NRC proposed screening guidance would increase volume of lower support column material considered to be susceptible to irradiation embrittlement.

Lower Support Column Case #6: Partial Synergistic Embrittlement

Hulls Ferrite Evaluation: Content calculated ferrite content for 80% support columns <15%, remaining 20% are between 15 and 20% ferrite

- Fluence threshold:

80% @ 1.5 dpa (irradiation embrittlement)

20% @ 0.45 dpa (synergistic effect)

- Realistic situation

A/LAI 7 Response:

- 80% of columns not susceptible to thermal embrittlement

- Top few inches of all columns susceptible to irradiation embrittlement (>1.5 dpa)

- 20% of columns with embrittlement range extended 0.45 dpa

- Are Functionality or Flaw Tolerance Assessments required?

Same as Case 3 (No TE) except 20% of columns with volume of LSC over threshold fluence slightly expanded

Remaining Issues

- Include in Functionality Analysis?

IASCC unlikely due to higher stress and dose threshold

- CRGT flange weld fluence lower not appropriate primary link (below IE threshold)

NRC proposed screening guidance would increase volume of lower support column material considered to be susceptible to irradiation embrittlement.

Impact of NRC CASS Screening Proposal Lower Support Columns Lower Support Columns

- Impact of Synergistic embrittlement range between 15% and 20% Ferrite (Case 5 and Case 6)

A/LAI 7 Response (Modified Case 3):

- Not susceptible to thermal embrittlement

- Top few inches susceptible to irradiation embrittlement (>1.5 dpa or >0.45 dpa)

- Remaining Questions:

- If Cases 3, 5 and 6 are not susceptible to thermal embrittlement, is functionality or flaw assessment required?*

- Include in functionality analysis?

IASCC unlikely due to higher stress and dose threshold

- CRGT flange weld fluence lower not appropriate Primary link (Below IE threshold)

If Case 3 does not require functionality/flaw assessment and Cases 5 & 6 do, then the plants with ferrite contents between 15% and 20% carry an extra burden. It is not clear that there are any clear safety benefits to be gained from this additional effort.

Impact of NRC CASS Screening Proposal

Other Reactor Internals Components

- Top surface of upper core plate near 1 dpa

Decreasing Fluence threshold to 0.45 dpa may increase volume of CASS material subject to irradiation embrittlement in upper internals.

- A/LAI 7: The requirement may not apply to components that were previously evaluated as not requiring aging management during development of MRP-227.

NRC Position on TE and IE

Comments on NRC Proposed CASS Screening Criteria for Thermal and Irradiation Embrittlement

Industry Comment #1 Components with Adequate Toughness are Screened-in by NRC Position The screening differences between the NRC revised position and the industry position (BWRVIP Letter 2014-086, ML14174A841) may seem to be small from a technical perspective. However, the two positions are very different when implementation and demonstration required by licensees is taken into consideration because of component locations screened in (current NRC position) versus those same locations screened out (industry position). For a CASS component internals location with delta ferrite content of 16% and neutron exposure of 0.5 dpa, the NRC revised position seems to recognize that existing data implies that the fracture toughness remains adequate to maintain component functionality. However, where the industry position relied on these existing data to screen out this particular component location, the NRC revised position will require demonstration of that adequacy, with all of the attendant difficulties for each licensee to provide actual -

as opposed to implied - data to support the demonstration. It seems likely that a fairly significant number of component locations will involve delta ferrite content between 16 and 20%, with neutron exposures in the 0.2 dpa to 0.75 dpa range, which will eventually lead to extensive functionality demonstration costs, and where the NRC revised position appears to recognize that - while the fracture toughness has been reduced considerably - the component functionality is not threatened.

NRC Staff Response:

No comment provided.

Industry Comment #2 Lower Screening Criteria Not Required for Conservative Fracture Analysis of Assumptions Applied to Reactor Internals.

The current NRC position observes correctly that the 255 kJ/m2 J value at 2.5 mm of crack extension was based on elastic-plastic fracture toughness assessment of simplified CASS piping components. This is likely overly conservative for RVI CASS components that are largely subjected to compressive stresses, which may be configured within a redundant structural system, and whose functionality does not include pressure boundary functions.

From this observation, one might have expected a slightly less conservative set of screening criteria, more along the lines of the industry position. That is not the case. The level of required technical demonstration for CASS RVI component locations will be substantial.

NRC Staff Response Staff and industry agree in principle that 255 kJ/m2 is probably too conservative, but this needs to be demonstrated via generic flaw tolerance evaluations of RVI components justifying a lower toughness to be used as a basis for the revised screening levels.

Industry needs to perform this work not NRC instead of asking NRC to rely on engineering judgment with regard to an appropriate toughness level. (EPRI TR-112718 appears to show that this type of work has already been done for certain cases.)

Industry Comment #3 J value at 2.5 mm (for 20% or lower ferrite) is >255 kJ/m 2 For the BWRs, the critical concern is to maintain the 20% ferrite level with the preferred position being 1 dpa as the screening criteria. There must be agreement that the J value at 2.5 mm (for 20% or lower ferrite) is >255 kJ/m2 as supported by the BWRVIP response to the RAI-9a. This is consistent with BWRVIP-234 Table 6-1 which built a series logic for the acceptability of the CASS components.

NRC Staff Response:

No comment provided.

Industry Comment #4 BWR components listed in Table 6-1 of BWRVIP-234 do not require any augmented inspections.

Given the original arguments put forth supporting the 255 kJ/m2 toughness arguments presented in BWRVIP-234 and supported in detail by the latest RAI-9a response, it is important to affirm that the BWR components listed in Table 6-1 of BWRVIP-234 do not require any augmented inspections. We believe that these data provide sufficient technical bases to allow the NRC to accept this position. The discussion that the toughness requirement is very likely conservative and was generated for piping further supports this position. If the NRC position is that inspections are required with the current data, it would be beneficial to understand the safety benefit of inspections when the expected variation in toughness is small. Further, it will be necessary to understand whether and what type of generic calculations can be used to justify a lower required value of J that will still demonstrate adequate fracture toughness for a component.

NRC Staff Response:

See staff response to Comment 2. Also, the staff observes there are only a couple of components in BWRVIP-234 Table 6-1 that would exceed 0.45 dpa. A component-specific fracture toughness basis could be developed for these components (fleet generic flaw tolerance evaluation for specific components).

Industry Comment #5 Request NRC Comment on Austenite vs. Ferrite Control The TE section of the current NRC position notes that NUREG/CR-4513, Rev. 1 provides lower-bound fracture toughness J-R curves for aged CASS materials in three categories

(<10%, 10-15%, and >15% delta ferrite contents) and that it also correlates with molybdenum contents and casting method (centrifugal vs. static). It also notes that the Grimes letter provides screening criteria correlated with J-R curves exhibiting a minimum J value at 2.5 mm crack extension of 255 kJ/m2. However, it does not provide any discussion of the industrys approach for addressing TE relative to austenite control versus ferrite control.

NRC Staff Response:

Addressing TE via austenite control requires acceptance of the mechanistic theory that if the ferrite volume fraction is 20% or less, the toughness of the ferrite phase does not affect the bulk toughness. The NRC staff does not believe there is no effect on bulk toughness no matter how brittle the ferrite becomes, and is not aware of data that support the industrys position.

Industry Comment #6 Request NRC Comments on MRP-175 and MRP-276 The IE section of the current NRC position notes that fracture toughness for CASS materials decreased due to neutron irradiation above about 0.3 dpa, and considers this level as a threshold for changes in the measured fracture toughness. But, NRC notes also that embrittlement becomes significant at slightly higher fluence levels, 0.5-2 dpa, depending on the material. However, there is no discussion of the industrys evaluation of data that was reported in MRP-276 or the screening criterion and its basis developed in MRP-175.

NRC Staff Response:

Dated evaluated in MRP-276 was the Kim et. al data. The staff feels this data is of limited value because it was tested at room temperature, used small specimens, and lacks data in the transition fluence range of 0.5-2 dpa.

Industry Comment #7 Fluence Range for Fracture Toughness Curve in NUREG/CR-7207 The NRC staffs position section notes that the 0.45 dpa fluence selection correlates to a fracture toughness of 255 kJ/m2 when toughness is predicted with Equation 25 from NUREG/CR-7027. It is not clear how 0.45 dpa is chosen since, as is stated in NUREG/CR-7027 (page 78, paragraph below Figure 64), the lower bound curve indicates that for cast SSs and welds irradiated up to 1.0 dpa, the predicted J at 2.5 mm is above the screening value of 255 kJ/m2 (1456 in.-lb/in.2). (Note: bolded text and underline added for emphasis)

NRC Staff Response:

The statement in the NUREG text is not accurate. When J@2.5 is calculated using 1 dpa in equation 25, the actual value is 208 kJ/m2.

Industry Comment #8 Request Technical Basis for Lower Ferrite Screening Levels in Proposed NRC Guidance The NRC staffs position section also notes that the staff applies criteria to two different ferrite screening levels depending on neutron exposure. The staff suggests changing the ferrite screening to the levels described in NUREG/CR-4513, Rev. 1 (10% and 15% ferrite) from the current ferrite screening levels (14% and 20%) accepted both by the staff and industry for license renewal (e.g., the Grimes letter, MRP-175, and MRP-227-A) without a described technical basis. The basis data for the 14% and 20% screening levels of ferrite are established in industry documentation that clearly states the conservatism used in determining these values and thus it is not clear why additional conservatism (i.e.,

decreasing the ferrite screening levels to 10% and 15%) is required.

See following slide for NRC Staff response

Industry Comment #8 Request Technical Basis for Lower Ferrite Screening Levels in Proposed NRC Guidance NRC Staff Response:

Basis for Reduced Ferrite Screening Levels at > 0.45 dpa

- NRC reduced ferrite content

Accounts for uncertainty of end state toughness due to IE+TE

NUREG/CR-4513 J-R curves for TE alone show significant margin above 255 kJ/m2 at 2.5 mm crack extension at:

15% ferrite for low-moly

- <10% ferrite for high-moly

- This provides margin for uncertainty wrt additional embrittlement due to fluence See Figure 1 below for an illustration of the principle. The figure shows there is considerable margin for the lower bound curves for CF-3 and CF-8 above the 255 kJ/m2 toughness level at 2.5 mm crack extension. However, for the CF-8M with the same ferrite range, the toughness is right around 255 kJ/m2. Therefore, for the CF-8M there is no additional margin for reductions in toughness due to irradiation effects. Figure 2 shows a similar plot for <10 ferrite, which shows even CF-8M has some margin of toughness above 255 kJ/m2 at 2.5 mm crack extension.

Industry Comment #8 Request Technical Basis for Lower Ferrite Screening Levels in Proposed NRC Guidance Figure 1 - NUREG/CR-4513 Lower Bound J-R Curves for 10-15% Ferrite Showing Margin Above 255 kJ/m2 at 2.5 mm for CF-3 and CF-8 Figure 2 - NUREG/CR-4513 Lower Bound J-R Curves for <10-Ferrite Showing Margin Above 255 kJ/m2 at 2.5 mm for CF-8M

Industry Comment #9 Proposed NRC Position Appears to Imply that IE and TE effects re additive The NRC staffs position section of the position also notes in item 3 of its numerical summary that components may also be susceptible to TE. It is not clear as to why this statement is necessary. The first sentence (Above 1.5 dpa, all stainless steel and CASS) states it clearly that at high fluence levels loss of fracture toughness requires aging management. The second sentence appears to suggest that embrittlement is additive, which it is not; once the material is embrittled, it is embrittled.

NRC Staff Response:

The staff agrees IE and TE may not simply be additive but the potential for a lower end of life toughness should be considered in any evaluation using estimated fracture toughness properties.

Industry Comment #10 Lower Screening Criteria Not Required for Conservative Fracture Analysis of Assumptions Applied to Reactor Internals.

Table D has a column listed as FN. This is incorrect; the column should correctly be listed as Delta Ferrite %.

NRC Staff Response:

Noted - the staff made this change.

Industry Comment #11 Additional Sources of Conservatism in Analysis Under the NRC Staffs Position, it states that the 255 kJ/m2 may be over-conservative considering non-pressure boundary applications and redundancy of function. It then discounts those conservatisms without providing any discussion as to what the magnitude of the conservatisms might be. The additional information to address the conservatisms is partly available empirically or from structural fundamentals; for example:

- The lack of a credible mechanism that would cause multiple initiations in the PWR environment in a narrow time frame.

- The low probability of any undetected pre-service flaws, and the likely random spatial distribution of their occurrence in an assembly.

- The lack of observed failures or confirmed cracking in any CASS components after many years of operating experience in PWRs and BWRs.

- Consideration that much of the operational stress loading is secondary; i.e.,

displacement controlled self-relieving stresses, mostly thermal, and that the sizing of the structural members is conservative for safety function primary loads.

See following slide for NRC Staff response

Industry Comment #11 Additional Sources of Conservatism in Analysis NRC Staff Response:

The bullets above are describing elements of what the staff would consider a functionality analysis. This would typically be done for components that did not pass the screening criteria, such as for an MRP-227-A Action Item 7 evaluation. Such elements could be considered in a generic industry evaluation justifying a lower fracture toughness value as the basis for the screening criteria. Quantitative demonstrations are typically more compelling.

Industry Comment #12 Impact of NRC Proposed Screening Criteria As requested, industry will provide comments on Table D of the current NRC position at the July 15, 2014 meeting.

NRC Staff Response:

No staff response necessary.

NRC Summary - General Comments

There is very little data for CASS subject to both thermal aging and irradiation representative of reactor vessel internals operating conditions.

There is almost no IE+TE fracture toughness data for CASS in the 0.5 dpa-2 dpa transition range of interest.

NRC screening criteria are similar, but a little more conservative than industrys.

The staff feels that erring on the conservative side is appropriate, particularly when there is a lack of data to support either position.

Industry should develop analyses supporting a lower fracture toughness basis for the screening criteria, such as generic flaw tolerance analyses.

NRC staff is not convinced that industrys mechanistic argument regarding austenite controlled or ferrite controlled CASS toughness is valid. I.e., staff does not believe ferrite toughness has no effect on bulk toughness just because ferrite is below 20%.

Some data does show toughness can be lower for CASS with IE+TE, than that caused by IE or TE alone.

Lower fluence screening criteria and adjustments to ferrite screening criteria above this fluence are intended to make address uncertainties in behavior of CASS under IE+TE.

See Figure A-2 of 2014-086 (Fig. 60 of NUREG/CR-7027, for Heat 75 - J @ 2.5 for fully aged + irradiated ~ 125 kJ/M2 vs. same heat, fully aged and unirradiated, from Table 7 of the Supplemental Information in 2014-086, J@ 2.5 is 418 kJ/m2.

NRC Staff Interpretation of Industry Position

Toughness drops due to ferrite embrittlement and austenite embrittlement - Staff agrees.

Screen on thermal, everything with high ferrite is in - Staff agrees.

For high dpa, everything screens in - Staff agrees.

For those things not already in, screen for IE - Staff agrees

Set IE screening level so that (effectively) most things screen out

Recognize that chosen level is beyond where embrittlement starts, i.e., chosen level is where degradation in toughness is significant - Staff agrees

For those things that are embrittled by IE, but not fully embrittled, screen them out because they have adequate toughness because not much toughness is needed. Even the NRC admits that the 255 kJ/m2 J value at 2.5 mm is conservative, but NRC has not quantified what the conservatism means, so NRC should just let us screen everything out because these components really dont need to be tough.

Industry doesnt like the NRC screening because some things might screen in, and then the industry would need to perform analyses to show how much toughness is required, and that is hard and expensive.

If there is less than 20 volume percent of a microstructural component, changes in material properties of that component has zero effect on the bulk properties.

Summary

Common (PWR and BWR) approach for screening of TE and IE developed

- TE before IE

Once screened in for TE, no additional screening required for IE

If not screened in for TE, then screen for IE

- IE screening at 1 dpa

More conservative in several locations compared to staff

Where less conservative, no meaningful impact on safety with less effort/burden in the screening process

TogetherShaping the Future of Electricity United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of: Entergy Nuclear Operations, Inc.

(Indian Point Nuclear Generating Units 2 and 3)

ASLBP #: 07-858-03-LR-BD01 Docket #: 05000247 l 05000286 Exhibit #: NYS000489-00-BD01 Identified: 11/5/2015 Admitted: 11/5/2015 Withdrawn: NYS000489 Rejected: Stricken:

Other: Submitted: June 9, 2015 Industry-NRC Meeting CASS Screening Criteria for Thermal and Irradiation Embrittlement for BWR and PWR Internals July 15, 2014 NRC Offices Washington, DC

Agenda 8:00 Introductions NRC 8:15 Meeting Objectives NRC, Industry 8:30 Industry Position on Thermal and Irradiation Industry Embrittlement Screening Criteria 9:45 Break 10:00 Industry Position on Thermal and Irradiation Industry Embrittlement Screening Criteria (contd) 10:30 NRC Position on Thermal and Irradiation NRC Embrittlement Screening Criteria 11:15 Discussion of Industry Comments on NRC Position NRC 12:00 P.M. Lunch 1:00 Discussion of Industry Comments on NRC Position NRC (Cont) 2:00 Steps to Move Forward and Obtain SE? on Industry All Position on Generic Screening Criteria for PWRs and BWRs Utility Required Actions to Meet Staff Guidance 2:45 Break 3:00 Closure and action item review 3:30 Adjourn

Meeting Objectives

Review proposed industry and NRC positions regarding thermal and irradiation embrittlement criteria

Establish a full understanding of each position

- Discuss responses to industry comments on NRC position

Discuss issues associated with industry burden to comply with current NRC position

Identify actions required to obtain a Safety Evaluation and/or final NRC position

Discuss options and potential actions going forward

Outline of Presentation

Background

Formation of Working Group

Interactions with NRC

Thermal Embrittlement Criteria

Irradiation Embrittlement Criteria

Synergy Effects

Industry Burden Based on Current NRC Position

Comments on NRC Screening Position

Review of Industry Comments

Summary

Background

During 2013, NRC issued RAIs on MRP-227-A to several PWR utilities regarding evaluation of CASS components

In May 2013, NRC issued a 2nd set of RAIs on BWRVIP-234

The industry determined that some RAIs were common to BWRs and PWRs

Industry/NRC meeting held in Washington, DC on May 21, 2013 to review issues related to evaluation of CASS

- Follow-up meetings with NRC in August 2013, November 2013 and December 2013

- NRC requested a common BWRVIP/MRP screening approach for Thermal Embrittlement (TE) and Irradiation Embrittlement (IE)

PWR/BWR Industry Working Group formed in June 2013 to address CASS issues

- Significant work conducted to date to address BWRVIP and MRP issues

MRP/BWRVIP Working Group Approach

Develop responses to BWRVIP-234 RAIs

Develop PWR/BWR screening criteria for TE and IE

- Review the technical bases of the Grimes letter, along with other approaches for evaluating metallurgical effects of thermal aging and irradiation embrittlement of CASS

- Provides a basis for response to MRP-227-A LAI No. 7

2014 Interactions

February 3 telecon with NRC

- Presented updated PWR/BWR CASS screening criteria

Late February - industry submitted additional information on Synergy Effects of TE & IE in CASS

- Follow up discussion between industry and staff on March 12, 2014

Staff subsequently forwarded their initial position paper regarding TE and IE on March 13, 2014

Industry submitted response to BWRVIP-234 RAI which included industrys proposed generic TE and IE screening criteria to NRC on May 23, 2014 (ML14174A841)

NRC Position on Aging Management of CASS Reactor Vessel Internal Component, provided to industry on June 20, 2014 (ML14174A719)

Industry TE Screening Criteria

Industry proposal is to screen for TE based on delta ferrite prior to screening for IE - use ferrite limits from current pressure boundary practice (i.e., Grimes Letter)

- TE relevant for internals when delta ferrite > 20% and, in some cases, delta ferrite >14%

Thin-section CASS structural internals intentionally have lower delta ferrite than primary pressure boundary components

- Chemical composition of CASS internals is distinctly different from that of CASS piping, i.e., typical internals have delta ferrite < 20%

CASS internals are not as susceptible as thick-section castings (e.g., piping, pump casings, valve bodies) to solidification cracking during cooling

High ferrite is not needed in small casting to improve casting process yield

- Supporting evidence documented in BWRVIP-234

TE Screening Criteria

Grimes letter susceptibility based on ferrite content

- TE relevant for internals when delta ferrite > 20%

(in some cases when delta ferrite > 14%)

Molybdenum (wt. %) Casting Method Susceptibility Delta ferrite %

TE > 14%

static No 14%

High 2.0-3.0%

(CF-8M)

TE > 20%

centrifugal No 20%

TE > 20%

static Low 0.5% max No 20%

(CF-3 and CF-8) centrifugal No All

Thermal Embrittlement (TE) of CASS

TE of CASS occurs when aging of ferrite phase results in transition to cleavage fracture

CASS material is susceptible to TE when ferrite volume fraction and distribution are sufficient to support a cleavage failure path

- Determination of volume ferrite fraction is inexact

Spatial variations within casting

Multiple measurement techniques

NUREG/CR-4513, Rev. 1 provides basis for estimating lower bound fracture toughness

- Correlations based on composition

- Utilizes Hulls equivalent factors and material composition

Resolution of NUREG/CR-4513, Rev. 1 and EPRI TR-106092 provided the basis for the criteria in the Grimes letter

Industry Proposal for TE Screening Criteria

Retain Grimes letter criteria to determine TE susceptibility

- Chemical composition, casting method and delta ferrite

- Screening levels based on prediction of delta ferrite using Hulls equivalent factors

Consistent with current practice for pressure boundary components

Industry IE Screening Criteria

When necessary screen for IE using fluence of 1 dpa

- Industry efforts to date show that IE accelerates but does not enhance embrittlement process, especially for CASS materials with moderate delta ferrite content

Industry data support the premise that 20% delta ferrite CASS embrittlement is controlled by the behavior of the austenite phase

The effect of irradiation on austenite phase is well understood

- Data show onset of embrittlement occurs at 3-5 dpa

- Screening criteria are conservatively established at 1 dpa

- Current data are inconclusive with respect to IE and TE for high

(> 20%) delta ferrite CASS materials

- Accelerates but does not enhance premise provides the basis for TE screening followed by IE screening

1 dpa = 6.7 x 1020 n/cm2 (E >1MeV)

Consideration of Synergistic Effects

Grimes letter states:

- For RVI components fabricated from CASS and hence subject to thermal embrittlement, concurrent exposure can result in a synergistic effect wherein the service degraded fracture toughness (that) is reduced from the levels predicted independently for either of the mechanisms.

Synergistic effects

- Accelerate the embrittlement?

Temperature effects shown to accelerate the rates of attaining the same saturation values of embrittlement

- Exacerbate the embrittlement?

Database is sparse (nonexistent!) to support exacerbation

Mechanistic considerations suggest separable effects

- Mechanistic approach requires that there is no (significant) exacerbation effect in IE

Industry Data Supporting Accelerating-Only Effect of Synergy

NUREG-4513, Rev. 1 demonstrated that fully embrittled ferrite <20%

does not significantly embrittle the bulk CASS material

Full Thermal Aging heat treatment was ineffective in embrittling the low ferrite content CF8 high Jq and very high J2.5mm

Full Thermal Aging plus 0.08 dpa irradiation was ineffective in the embrittlement of low ferrite content CF3 fuel nozzle very high Jq and J2.5mm

Effect of irradiation becomes significant in the range of 6-10 dpa but for these materials does not appear to saturate until ~12 dpa

Thermal aging prior to irradiation has no significant effect on post irradiation toughness - full thermal age + irradiation actually exhibited greater remaining toughness than partial thermal age + similar irradiations (6.3 to 12 dpa)

Industry data support the premise that low ferrite content ( 20%) CASS embrittlement is controlled by the behavior of the austenite phase

Mechanistic View of Embrittlement of CASS

Embrittlement of duplex CASS structure depends on controlling phase: