ASME B&PV Code for In-Service Inspection of Nuclear Containment Buildings

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ASME BPV Code for In-Service Inspection of
Nuclear Containment Buildings

• Steven G. Brown, PE

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Introduction

• Why is this of interest outside the nuclear
  industry?
• Professional Development Hour
• More than that sharing information across
  various industries for improvement of the
  profession
• Acknowledgements
• K. R. Rao Campion Guide to ASME Boiler and
  Pressure Vessel Code
• Working Group Containment
• Entergy
• Disclaimer The views presented are my own
• If its right, its because my mentors got it
  right,
• If its messed up, its probably my original
  idea.

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Terminal Objective

• At the conclusion of the class the engineer will
  have a basic understanding of the current rules
  requiring inservice inspection of nuclear
  containment vessels.

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Enabling Objectives

• State the purpose of containment vessel as used
  at commercial nuclear power plants in the US
• Describe the general types of containment vessels
  currently used in the US commercial nuclear power
  industry.
• State the difference between Class MC and Class
  CC components.
• State the regulations requiring inservice
  inspection of nuclear containment buildings.

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Enabling Objectives (cont)

• Be able to state the section of ASME Code
  providing requirements for inservice inspection
  of Class CC components of nuclear containment
  vessels.
• Discuss the type and frequency of inservice
  examinations for nuclear power plant containment
  vessels.

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Purpose of Containment

• 10 CFR 50 - GDC 16 Containment Designs - Key
  design requirement for all U.S. commercial
  nuclear plants.
• Establish an essentially leak tight barrier
  against the uncontrolled release of radioactivity
  into the environment
• Ensure that the containment design conditions
  important to safety are cont exceeded for as long
  as required for post-accident conditions.

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Typical Steel Containment Vessels

• Steel Pressure Vessel Class MC
• Typically Carbon Steel
• Approx. 40 to 60 psi
• gt 100 Feet Diameter
• gt 200 Feet Tall
• Shell thickness 1.5 or more
• Concrete Shield Building

Containment Design Diagrams on this and
subsequent slides are from EPRI TM-102C
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Typical Steel Containment Vessels

• BWR Mark I Class MC (typical)
• Nominal 62 psi
• Removable Head
• Torus suppression pool

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Typical Steel Containment Vessels

• BWR Mark II (Shown) Clas MC Typical
• Nominal 45 psi
• Removable Head
• Suppression pool below
• BWR Mark III (Not Shown) May be MC or CC
• Large vessel with internal drywell
• Suppression pool internal around drywell

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Typical Concrete Containment

• Concrete Structure with steel liner
• Concrete provides structural element Class CC
• Steel liner provides leak tightness Class MC

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Typical Concrete Containment

• Post-Tensioned Concrete Containment
• Concrete is kept under compression by a system of
  steel tendons
• Tendon system and rebar are Class CC.

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Provisions for Containment Inspections and Testing

• 10 CFR 50 - GDC 53 Containments shall be
  designed to permit
• Appropriate periodic inspection of all important
  areas, such as penetrations
• An appropriate surveillance program
• Periodic testing at containment design pressure
  of the leak tightness of penetrations

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Philosophy of Containment Examination

• ASME IWE and IWL define requirements for
  containment examination
• Preservice
• Inservice
• Requirements based on Industry Experience and
  Environmental Conditions
• Visual Examination of Containment
• Testing for Tendons
• Pressure / Leakage Testing per 10 CFR App J

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History of Code Requirements

• IWE 1st published 1981 (Class MC Components)
• Weld Based Examinations
• Very similar to rules for Class 1 and 2 nuclear
  components.
• Subsequently addressed general degradation of
  surface areas
• Incorporated by rulemaking (10 CFR 50.55a) in
  1996
• Required all containments to be treated as MC or
  CC
• Included conditions for use

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History of Code Requirements

• IWL 1st published 1988 (Class CC Components)
• Provided rules for examination of concrete
  surfaces
• Similar to regulatory requirements already in
  Regulatory Guides 1.35 and 1.35.1
• Regulatory Guides only required for post
  tensioned containments
• Incorporated by rulemaking (10 CFR 50.55a) in
  1996
• IWL replaced use of the Regulatory Guides
• Transition period was allowed for plants using
  regulatory guides
• Applicable to ALL concrete containments

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Current Regulatory Requirements

• 10 CFR 50.55a
• Incorporates ASME BPV Code Section XI by
  reference with conditions
• References ASME Section XI Sub-Section IWE for
  Class MC containments and Liners of Class CC
  containments
• References ASME Section XI Sub-Section IWL for
  Class CC containments

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Containment Leak Testing

• 10 CFR 50 Appendix J
• Periodic testing of containment vessel and
  penetrations
• Type A tests Integrated Leak Rate Test
• Type B and C tests Local Leak Rate Tests

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IWE Examinations

• IWE-1100 SCOPE
• This Subsection provides requirements for
  inservice inspection of Class MC pressure
  retaining components and their integral
  attachments, and of metallic shell and
  penetration liners of Class CC pressure retaining
  components and their integral attachments in
  light-water cooled plants.

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IWE Examinations

• Exempted Components
• Components outside the boundaries of the
  containment system
• Embedded or inaccessible portions of containment
  (with limitations on what modifications to plant
  can embed)
• Piping, pumps, and valves (examined per either
  IWB or IWC)

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IWE Examinations

• General Schedule for Inservice
• 10 year inspection interval
• Divided into 3 inspection periods (3 or 4 years)
• Provisions for shifting interval (and one of the
  periods) by one year
• Preservice (in general)
• Exam conducted prior to placing component
  inservice
• Includes repair or replacement
• Same exam as required for periodic inservice exam

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IWE Examination Tables
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IWE Examination Tables
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IWE Details

• Category E-A Containment Surfaces
• E1.11 Accessible Surfaces
• General Visual Each Period.
• Includes Bolted Connections VT-3 per 10 CFR
  50.55a
• E1.12 Wetted Surfaces of Submerged Areas
• General Visual Each Interval
• VT-3 per 10 CFR 50.55a
• E1.20 BWR Vent System (Mark I)
• General Visual Each Interval
• VT-3 per 10 CFR 50.55a
• E1.30 Moisture Barriers
• General Visual Each Period

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IWE Details Moisture Barriers
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IWE Details

• Category E-C Augmented Examination
• Applicable to areas subject to accelerated
  degradation or with previously noted degradation
• E4.11 Visible Surfaces
• Detailed Visual Each Period.
• VT-1 per 10 CFR 50.55a
• E4.12 Surface Area Grid
• Ultrasonic Thickness Measurement (UT) Each Period

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IWL Examinations

• IWL-1100 SCOPE
• This Subsection provides requirements for
  preservice examination, inservice inspection, and
  repair/replacement activities of reinforced
  concrete and the post-tensioning systems of Class
  CC components, herein referred to as concrete
  containments as defined in CC-1000 Section III
  Design Code.

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IWL Examinations

• Exempted Components
• Steel portions not backed by concrete
• Shell metallic liners
• Penetration liners
• Inaccessible tendon end anchorages (with
  limitations)
• Concrete surfaces covered by the liner,
  foundation material, or backfill or otherwise
  obstructed. (Aging concerns for buried concrete
  addressed in later editions of code.)

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IWL Examinations

• General Schedule for Inservice Examination
• 1, 3, and 5 years following Structural Integrity
  Test (SIT)
• Within 6 months on either side of anniversary
• Total inspection window of 1 year
• 10 years after SIT and every 5 years thereafter
• Within 1 year on either side of anniversary
• Total inspection window of 2 years
• 1 year plus or minus 3 months for concrete
  repairs
• Preservice
• Similar to IWE
• Unique role of RPE

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IWL Examinations

• Two Major Divisions
• Category L-A Concrete Surfaces
• All concrete containments
• Category L-B Unbonded Post-Tensioning System
• Post tension design only
• Tendons divided by type
• Separate population for tendons impacted by
  repairs
• Provisions for sites with multiple plants / units

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IWL Examination Tables
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IWL Details

• Category L-A Concrete Surfaces
• L1.11 All Accessible Areas
• General Visual Each Inspection to identify
  suspect areas
• Resolution per RPE
• L1.12 Suspect Areas
• Detailed Visual
• Up close exam to determine if the area is a
  problem
• Performed by or under the direction of a
  Registered Professional Engineer

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IWL Details

• Category L-B Unbonded Post-Tensioning Systems
• Sample Size
• Sample of Tendons
• 4 of Each Type
• Minimum of 4 and Maximum of 10
• Reduced sample for good inspection history
• 2 of Each Type
• Minimum of 3 and Maximum of 5
• Separate population with reduced sample size for
  tendons affected by repair

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Overview of Post-Tension Containment
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Parts of a Tendon Anchorage
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Exposed Tendon Anchorage
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Uninstalled Tendon
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Parts of a Tendon Anchorage
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IWL Details

• L2.10 Tendon
• Tendon Force / Elongation Test
• Hydraulic Ram connected to end of tendon
• Load cell measures force needed to lift tendon
  off of the shims
• Common Tendon
• One tendon is measured in each inspection
• Results trended to ensure tendon stress remains
  above the minimum needed by design for life of
  the plant

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IWL Details

• L2.20 Wire or Strand
• Destructive sample of one wire (typical tendon up
  to 186 wires) from one tendon of each type NOT
  the common tendon
• Visual exam for entire length
• Sample from each end, the middle and area of most
  severe degradation tested for
• Yield Strength,
• Ultimate Strength, and
• Elongation

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IWL Details

• L2.30 Anchorage Hardware and Surrounding
  Concrete
• Detailed Visual Entire Sample Population
• Includes
• bearing plates,
• anchor heads,
• wedges,
• buttonheads,
• shims, and
• concrete extending 2 feet from edge of the
  bearing plate.

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IWL Details

• L2.40 Corrosion Protection Medium
• Sample from each end of each examined tendon
• Chemical analysis for
• Water content,
• Water soluble chlorides, nitrates, and sulfides
• Reserve Alkalinity (expressed as milligrams of
  Potassium Hydroxide)
• L2.50 Free Water
• The amount of any free water (if any) contained
  in the tendon cap is documented and analyzed to
  determine pH.

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IWL Examinations

• Additional 10 CFR 50.55a exam
• Grease caps that are accessible must be visually
  examined to detect grease leakage or grease cap
  deformations.
• Grease caps must be removed for this examination
  when there is evidence of grease cap deformation
  that indicates deterioration of anchorage
  hardware

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Additional 10 CFR 50.55a Requirements

• The licensee shall evaluate the acceptability of
  inaccessible areas when conditions exist in
  accessible areas that could indicate the presence
  of or result in degradation to such inaccessible
  areas.
• Reporting Requirements
• Other provisions

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Objectives

• State the purpose of containment vessel as used
  at commercial nuclear power plants in the US
• Describe the general types of containment vessels
  currently used in the US commercial nuclear power
  industry.
• State the difference between Class MC and Class
  CC components.
• State the regulations requiring inservice
  inspection of nuclear containment buildings.

45
Enabling Objectives (cont)

• Be able to state the section of ASME Code
  providing requirements for inservice inspection
  of Class CC components of nuclear containment
  vessels.
• Discuss the type and frequency of inservice
  examinations for nuclear power plant containment
  vessels.

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References

• 10 CFR 50.55a
• ASME BPV Code Section XI, Subsections IWE and
  IWL, 2004 Edition
• Rao, K. R. (editor), Companion Guide to the ASME
  Boiler and Pressure Vessel Code, 3rd Edition
• EPRI TM-102C

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Questions ?