ML23079A263

General Visual Examination of Containment Surfaces Covered by Insulation - 3/23/23 Public Meeting Slides from NRC

ML23079A263
Person / Time
Issue date:	03/23/2023
From:	Siva Lingam Licensing Processes Branch
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Download: ML23079A263 (1)

Text

Visual Examination of Containment Surfaces Covered by Insulation March 23, 2023 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission

Meeting Agenda

• Introduction / Opening Remarks NRC / NEI

• NRC Presentation NRC

• NEI / Industry Presentation NEI / Industry

• Brainstorming / General Discussion / Questions All

• Closing NRC March 23, 2023 2

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Background===

• Previous Public Meeting (1/19/23; ML23024A262)

• Alignment not reached on interpretation of existing code requirements

• Significant discussion about permanent vs removable

• General agreement that current wording could be clarified

• Actions:

• NEI agreed to provide examples of inaccessible evaluations

• NRC agreed to schedule a followup meeting

• Topic also discussed during ASME Containment working group meeting, ASMENRC management call, PWROG Executive Management Meeting, and NEINRC management meetings March 23, 2023 3

Staff Actions Since Previous Meeting

• Reviewed examples provided by NEI:

• Examples of two licensees properly expanding the scope to inaccessible areas when degradation is identified in accessible areas

• Staff concerned this requirement may not address the areas currently being discussed

• If the penetrations in question are classified as inaccessible under the inspection plan, ISI inspectors will not inspect the penetration

• Needs to be a requirement to inspect the general area around the penetration March 23, 2023 4

Staff Actions Since Previous Meeting

• Review of past relief requests and generic communications

• Additional discussions with inspectors and licensees:

• Some licensees planning to remove insulation from readily accessible penetrations during upcoming outages

• Some licensees have and are removing this insulation to conduct the IWE general visual exams, or have sought relief for not removing the insulation

• Current Staff Position: These areas need to be inspected on some frequency during the life of the plant March 23, 2023 5

Staff Actions Since Previous Meeting

• Staff acknowledges NRC position needs additional review

• NRR issued memo to regions on March 10, 2023, providing guidance on any identified issues during ongoing generic evaluation of issue (ML23046A398):

• Use VLSSIR if low safety significance and plantspecific licensing basis not clear

• Coordinate with NRR for other situations

• Focus today should be on discussing what level of inspection is necessary for safety:

• The staff does not believe these areas should never be inspected; and inspection every period is likely unnecessary for safety March 23, 2023 6

Path Forward: Safety Focused Solution Engage stakeholders during the 50.55a rulemaking process and in ASME Code engagement to develop a solution that balances safety and risk

• Where do we need to inspect?

• Focused on likelihood of degradation or ease of access?

• Sampling basis or 100% over an given timeframe?

• Define what is considered readily accessible?

• If penetrations are identified as inaccessible how do inspectors know to inspect the surrounding areas?

• How often do we need to inspect?

• Once an interval?

• Can we inform the interval based on corrosion rates?

March 23, 2023 7

Operating Experience

• Staff reviewed past containment liner degradation.

• Operating Experience indicates that degradation can initiate on the inner or outer surfaces of the containment liner.

• Almost all degradation examples were discovered due to routine IWE General Visual Examination.

• Outside surface degradation is typically not discovered until perforation of the liner.

• Inside surface degradation has ranged from surface corrosion to about 50% throughwall when first identified.

March 23, 2023 8

Operating Experience

• Outer surface degradation is typically caused by unexpected foreign objects embedded in the concrete (wood, gloves, tools, etc).

• For Inner surface degradation, Information Notice 1997010 specifically identifies five areas of increased likelihood for liner plate corrosion:

1. Junction of containment cylinder and intermediate floors or basemat concrete.

2. Junction of drywell and the base or intermediate concrete floors.

3. Adjacent to crane girder rails and supports attached to the liner plate.

4. Watersoaked areas where carbon steel liner plate is used.

5. Behind insulation and ice condenser baskets due to likelihood for moisture to condense.

March 23, 2023 9

Path Forward: Safety Focused Solution Brainstorming Session after NEI / Industry presentation

• Where to inspect?

• When to inspect?

• General Discussion / Questions March 23, 2023 10

Brainstorm: Where to inspect?

March 23, 2023 11

Brainstorm: When to inspect?

March 23, 2023 12

General Discussion / Questions March 23, 2023 13

Backup Slides March 23, 2023 14

IWE Wording

• IWE1232(c): Surface areas of Class MC containment vessels, parts and appurtenances, and surface areas of Class CC metallic shell and penetration liners are considered inaccessible if visual access by line of sight from permanent vantage points is obstructed by permanent plant structures, equipment, or components, provided these surface areas do not require examination in accordance with the inspection plan or IWE1240.

• IWE2310(d): (d) Visual examinations shall be performed, either directly or remotely, by line of sight from floors, platforms, walkways, ladders, or other permanent vantage points, unless temporary access is required by the inspection plan.

March 23, 2023 15

Interpretation XI11325

• Q1: Is it a requirement of IWE1230 that containment surface covered by thermal insulation be considered accessible for general visual examination in accordance with Table IWE25001, Examination Category EA?

• Reply(1): No.

• Q2: Is it a requirement of IWE1230 that containment surface covered by thermal insulation be considered accessible for augmented examination in accordance with Table IWE25001, Examination Category EC, if these surfaces are subject to accelerated degradation and aging?

• Reply(2): Yes.

• ASME Record Number: 132137; Issued 3/7/2014

• The original interpretation question noted that in many cases, [the]

insulation material is not intended to be removed and is physically attached to the containment surface.

March 23, 2023 16

Approved Code Change March 23, 2023 17

NRC Comment

• During the initial discussion of this item, proposed (d) included wording that required an evaluation of inaccessible areas to demonstrate they are not experiencing accelerated degradation or exposed to conditions described in IWE-1240. Ultimately, the working group determined this wording was unnecessary for this action and focused the proposed changes on incorporating the existing ASME position on the accessibility of surfaces covered by insulation, as captured in Interpretation XI-1-13-25. The NRC believes the proposed edits capture the ASME position on accessible surfaces as documented in Interpretation XI-1 25, which is why the staff is voting yes. However, the staff believes the code is unclear how IWE-1241 is implemented to identify surfaces requiring augmented examination in accordance with Table IWE-2500-1. Therefore, the staff may consider a future condition related to inaccessible surfaces and paragraphs IWE-1232 or IWE-1240.

March 23, 2023 18