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

Steven G. Brown, PE

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 it’s right, it’s because my mentors got it right, If it’s messed up, it’s probably my original idea.

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.

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.

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.

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.

Typical Steel Containment Vessels

       Steel Pressure Vessel – Class MC Typically Carbon Steel Approx. 40 to 60 psi > 100 Feet Diameter > 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

Typical Steel Containment Vessels

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

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

Typical Concrete Containment

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

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.

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

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

History of Code Requirements

 IWE 1 st 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

History of Code Requirements

  IWL 1 st    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

Current Regulatory Requirements

 10 CFR 50.55a

 Incorporates ASME B&PV 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

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

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.

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)

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

IWE Examination Tables

IWE Examination Tables

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

IWE Details – Moisture Barriers

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

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}.

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.)

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

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

IWL Examination Tables

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

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

Overview of Post-Tension Containment

Parts of a Tendon Anchorage

Exposed Tendon Anchorage

Uninstalled Tendon

Parts of a Tendon Anchorage

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

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

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.

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.

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

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

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.

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.

References

 10 CFR 50.55a

 ASME B&PV Code Section XI, Subsections IWE and IWL, 2004 Edition  Rao, K. R. (editor), Companion Guide to the ASME Boiler and Pressure Vessel Code, 3 rd Edition  EPRI TM-102C

Questions ?