jansi guidelines for inspection and evaluation of … laser clad welding for preventive mmaintenance...

JANSI Guidelines for Inspection and Evaluation of

Reactor Vessel Internals

H.Seki (JANSI), H.Kobayashi (JAPCO)

M.Nakano (KEPCO), A.Taniguchi(TEPCO)

Fourth International Conference on

Nuclear Power Plant Life ManagementLyon,France

24 October 2017

1

Outline

1. Background

2. Overview of JANSI Guidelines for Reactor Internals

3. Example of Inspection/Evaluation and Repair method

4. Present Works and Future Item

5. Conclusions

2

1. Background

Background of establishing the committee

• SCC(Stress Corrosion Cracking) found in the Shroud Supports of the Tsuruga

NPP, questions raised about the inspection method of internals in 1999.

• TENPES(Thermal and Nuclear Power Engineering Society in Japan) organized

review committee to clarify important facts, evaluate aging portions, prepared

guidelines for inspection and evaluation.

• The Review Committee was transferred to the JANTI(Japan Nuclear Technology

Institute) in 2007, and then to the JANSI(Japan Nuclear Safety Institute) which

was founded in the reorganization of JANTI in 2012, the activities of the

Committee are being continued

Member Composition of the committee(since 2017FY)

• Chair of the Committee; Dr. Mochizuki, Prof.of Osaka Univ.,

• Member; 7 from Academy and 20 from Industry(Utility, Vendor, Third Party),

NRA(Nuclear Regulation Authority) joined as an observer.

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4

Example of ＢＷＲ internals

炉心支持金物

Hold down spring

Thermal shield

照射試験片ホルダ案内管

Clevis Insert

（RPV）

（Fuel）

Control rod guide tube

Upper support plate

Core barrel

Upper core plate

Lower core plate

Lower support column

Former plate

Baffle plate

Upper support column

Lower support column

Radial support key

Example of PWR Internals

Baffle former bolt

Barrel former bolt

Bottom mounted instrumentation column

Radial support key

Secondary core support column

Irradiation Specimen Guide

5

Outline

1. Background




5. Conclusions

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2.1 Basic Principle of the Guideline

• The guidelines serve maintenance activities for core internals by providing

fundamental items and detailed methods for autonomous and continuous

securing of safety.

• Inspection defined in the guidelines is divided into “Individual Inspection“

which is performed for ageing degradation of safety related internals and

“General Inspection“ which means baseline inspection by time-based VT-3.

• Application of repair and preventive maintenance methods for reactor

internals, and application process are covered.

• The guidelines are implemented in accordance with the Japan Electric Association’s

“Management Rules for Nuclear Safety (JEAC 4111), and “Maintenance Management

Rules for Nuclear Power Stations (JEAC 4209).

• “Rules on Fitness–for–Service for NPP (JSME S NA1 etc.)” are also referred.

・ US EPRI-VIP and IAEA document, as below are closely followed.

TECDOC-1471(Ageing of BWR internals),-1557 (Ageing of PWR internals),

No. NS-G-2.12. (Ageing Management), SRNo.82 I-GALL, etc.

AMP109 BWR Vessel Internals referred JANSI Guidelines, as specific guide.

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2.1.1 Layer Structure of the Guideline

The inspection and evaluation guidelines consist of “Structure evaluation guide”, “Inspection guide”, “Repair guide”, and “Preventive maintenance guide” for each internals.

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2.1.2 Conservative Assumption on Structural Strength Evaluation

initiation

9

2.1.3 Determination of Individual Inspection Time

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( ex. BWR Shroud Support)

2.1.3 Determination of Individual Inspection Time(Cont.)

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( ex. PWR Baffle Former Bolt)

Steam DryerSeparatorFeed Water SpargerGuide RodHead Spray Nozzle

Core ShroudShroud SupportTop GuideCore PlateJet PumpCS Piping and SpargerICM HousingCRD HousingSLC Injection Piping

LPCI CouplingFuel SupportCR Guide TubeHPCS Piping and Sparger

2.2 Internals Classification

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2.2 Internals Classification (Cont.)

・Upper support plate

・Upper support column

・Upper core plate

・Core barrel

・Lower core plate, etc.

・Baffle former bolt

・Control rod guide tube

・Bottom mounted instrumentation column

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System safety ofnuclear power plants

Reactor internals Safety functions Related components / parts

①Core Support and MaintainCooling Geometry

②Control Rod Insertion

③Reactivity Control

④Direct and Contain Emergency Cooling Flows

⑤Core Instrumentation

⑥Maintain long term Core Coolable Geometry

⑦Assure Pressure Boundary

Shroud Support, Core Shroud, Top Guide, Core Plate, CRD Housing ,CR Guide Tube, Fuel Support

Shroud Support, Core Shroud, Top Guide, Core Plate, CRD Housing, CR Guide Tube, Fuel Support

SLC Injection Piping

ICM Housing

Shroud Support, Core Shroud, Jet Pump,Access Hole Cover

Shroud Support, ICM Housing,CRD Housing, CR Guide Tube, SLC Injection Piping

Core Shroud, CS Piping and Sparger, Jet Pump, LPCI Coupling, HPCS Piping and Sparger

2.3 Safety functions of BWR internals and components/parts

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BWR Components / parts related to the function

Core Plate

Code Shroud

Top Guide

CRD Housing

Fuel Support

CR Guide Tube

Core

（Fuel）

：Water Flow

(Vertical Load) (Horizontal Load)

Fuel Fuel

Fuel Support

CR Guide Tube

CRD Housing

RPV

Top Guide

Core Plate

Core Shroud

Shroud

Support

RPV

Core Plate Plug

CR Guide Tube

Ex.1. Core Support and Maintain Cooling Geometry

Shroud Support

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System safety ofnuclear power plants

Reactor internals Safety functions Related components / parts

1. Supporting and positioning the core

Upper support plate.Upper support columnUpper core plateCore barrelLower core plateLower support columnLower support plate

Control rod guide tubeUpper support plate*2Upper support column*2Upper core plate*2Fuel alignment pin*2Guide tube support pin*2

Control rod guide tubeUpper support plateUpper core plateCore barrelLower core plateLower support plate

Upper support columnLower support columnSecondary core support columnBottom mounted instrumentation columnThermocouple conduitWater level gauge

2.4 Safety functions of PWR internals and components/parts

Hold down spring

Secondary core support column

Radial support key

Clevis insert

Fuel alignment pin

RV alignment pin Upper core plate alignment pin

2. Inserting and guiding control rods

3. Maintaining core cooling geometry

4. Guiding core instrumentations

Baffle plate

Former plate

Spray nozzle

Baffle former bolt*2

Barrel former bolt*2

*1: The function “Shielding neutrons” is not the safety functions but listed for reference*2: Indirectly related to the functions 16

PWR Components / parts related to the functionEx.3. Maintaining core cooling geometry

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2.5 Overall composition of the Guidelines as of Oct.2017

CODE/ID

Core Spray Piping and Sparger JANTI-VIP-15 2012

Jet Pump JANTI-VIP-14 2012

SLC Injection Piping JANSI-VIP-13 2015

CRD Housing JANSI-VIP-07 2014

ICM Housing JANSI-VIP-08 2014

Core Shroud JANSI-VIP-06 2015

Shuroud Support JANSI-VIP-17 2015

Top Guide JANSI-VIP-11 2015

Core Plate JANSI-VIP-12 2015

General Inspection JANSI-VIP-20 2017

Core Barrel JANSI-VIP-10 2015

Baffle Former Bolt JANSI-VIP-05 2015

Barrel Former Bolt JANSI-VIP-09 2015

Control Rod Cluster Guide Tube JANSI-VIP-02 2013

In-core Instrumentation Tube JANSI-VIP-01 2013

Reactor Vessel Nozzle Welds JANTI-VIP-08 2009


Weld Overlay Repair（BWR) JANSI-VIP-14 2015

RV Nozzle Spool-Piece replasement（PWR) JANSI-VIP-04 2013

Inlay Welding Repair JANTI-VIP-01 2008

Induction Heating Stress Improvement for Piping Repair JANTI-VIP-12 2012

Underwater Laser Beam Repair Welding JANTI-VIP-16 2012

Heating Stress Improvement for Preventive Mmaintenance JANTI-VIP-02 2008

Peening for Preventive Mmaintenance JANTI-VIP-03 2008

Underwater Laser Clad Welding for Preventive Mmaintenance JANTI-VIP-07 2009

Polishing for Surface Stress Improvement JANTI-VIP-10 2009

Application Process of Maintenance Technologies JANTI-VIP-11 2010

Evaluation of Environmental effects by Hydrogen Water Chemistry

(BWR)JANSI-VIP-18 2017

Repair Method

and Preventive

Mmaintenance

BWR Inspection

and Evaruation

PWR Inspection

and Evaruation

Guideline

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Outline

1. Background




5. Conclusions

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Composition of Guidelines for Inspection and Evaluation

Guideline CODE/ID

BWR Inspection and

Evaluation

Core Spray Piping and Sparger JANTI-VIP-15 2012

Jet Pump JANTI-VIP-14 2012

SLC Injection Piping JANSI-VIP-13 2015

CRD Housing JANSI-VIP-07 2014

ICM Housing JANSI-VIP-08 2014

Core Shroud JANSI-VIP-06 2015

Shroud Support JANSI-VIP-17 2015

Top Guide JANSI-VIP-11 2015

Core Plate JANSI-VIP-12 2015


PWR Inspection and

Evaluation

Core Barrel JANSI-VIP-10 2015

Baffle Former Bolt JANSI-VIP-05 2015

Barrel Former Bolt JANSI-VIP-09 2015

Control Rod Cluster Guide Tube JANSI-VIP-02 2013

In-core Instrumentation Tube JANSI-VIP-01 2013

Reactor Vessel Nozzle Welds JANTI-VIP-08 2009


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3.1 Example of Inspection and Evaluation

BWR Individual Inspection（Core Shroud, Shroud Support）

� Significant Degradation Mode

・Stress Corrosion Cracking

� Inspection Scope

・Possible inspection zone of the circumferential

weld lines (H1～H7)

� Inspection Period(in case of H7 with ring)

・Initial Inspection：11 years operational pｅｒｉｏｄ

・Re-inspection：7years operational period

� Inspection Method：VT and/or UT,ET

Core Shroud

Shroud Support

Visual inspection on 1 mil (0.025mm) width wire identified.

Evaluation Applied on Onagawa NPP, Kashiwazaki Kariwa NPP，Hamaoka NPP，Shimane NPP, Tokai-daini NPP）,etc.

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PWR Individual Inspection（Baffle Former Bolt）

○ Significant Degradation Mode

・IASCC(Irradiation Assisted Stress Corrosion Cracking)

○ Focused Subject

・Number of Damaged Bolts

○Inspection Period

・Initial Inspection Time

Assumed Damaged Bolts ≈ 20% of Total Bolts

・Re-Inspection Time

Determined by Initial

Inspection Result

○Inspection Method

・UT (Ultrasonic Test)

Estimate of

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PWR Individual Inspection (CR Cluster Guide Tube）

○ Significant Degradation Mode

・Wearing

○ Focused Subject

・ Wear Length of CR Cluster

Guide Plate

○Inspection Period

・ Initial Inspection Time

Half of the period to reach allowable

maximum wear

・ Re-inspection Time

Evaluate First Inspection Result

○Inspection Method

・ Measurement of the wear length

Evaluation Applied on Tomari NPP, Mihama NPP，etc.

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Composition of Guidelines for Repair Method and Preventive Maintenance

CODE/ID

Weld Overlay Repair（BWR) JANSI-VIP-14 2015

RV Nozzle Spool-Piece replasement（PWR) JANSI-VIP-04 2013

Inlay Welding Repair JANTI-VIP-01 2008

Induction Heating Stress Improvement for Piping Repair JANTI-VIP-12 2012

Underwater Laser Beam Repair Welding JANTI-VIP-16 2012

Heating Stress Improvement for Preventive Mmaintenance JANTI-VIP-02 2008

Peening for Preventive Mmaintenance JANTI-VIP-03 2008

Underwater Laser Clad Welding for Preventive Mmaintenance JANTI-VIP-07 2009

Polishing for Surface Stress Improvement JANTI-VIP-10 2009

Application Process of Maintenance Technologies JANTI-VIP-11 2010

Evaluation of Environmental effects by Hydrogen Water Chemistry

(BWR)JANSI-VIP-18 2017

Repair Method

and Preventive

Mmaintenance

Guideline

24

3.2 Example of Repair Method and Preventive Maintenance

Repair Method (Countermeasure – IHSI:

Induction Heating Stress Improvement )

IHSI countermeasure is a repair method with the addition of application conditions to IHSI for preventive maintenance, in order to deter the growth of a SCC defect that was generated on the inner surface of a pipe at a weld joint of equipment (vessel, pipe, pump, valve).

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Peening

・ In the process of peening, impact pressure occurs on the surface. This pressure

plastically deforms the surface. The formation of the compressive residual stress

have the effect for SCC.

26

Evaluation of Environmental Effect by

HWC（Hydrogen Water Chemistry)

・HWC in BWR as a countermeasure for improvement of corrosive environments of core internals. The Guidelines for inspection & evaluation of each component enable the setting of an inspection period for the effect of environmental Effect by hydrogen injection, and also provide a SCC crack growth rates diagram under the HWC.

・The environmental Effect is defined by ECP (electro-chemical potential).

27

Application process from Technical Development to NPP Field

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This Guideline specifies items to achieve the target performances, items for clarifying the methods, and items for verifying technical development from the viewpoint of structural integrity.


• In 2017,the Committee is updating Guidelines for PWR Baffle Former Bolt,

BWR Jet Pump , Core Spray/Sparger, with initiation of risk informed

approach.

• Guideline for General Inspection for ABWR internals and Guideline for

“Application Process of Maintenance Technologies” are under discussion.

• These Guidelines will be revised and issued hopefully in 2018.

• As future item, respond to change of nuclear community in Japan,

improvement points for more active use of guidelines are,

- Make sure to the risk informed performance based approach.

- Fitting to International safety-focused and proactive activity.

- Feed back from communication with NPP staffs.

・ It is critical to develop continuous activity with learning, responding,

monitoring and anticipating.

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5. Conclusions

• “JANSI guideline committee for the inspection and evaluation of reactor vessel

internals” developed and maintained 30 guidelines. Background and overview

of the guidelines are introduced.

• The guidelines cover inspection program of internals to define the basic concepts

about how to determine the scope of inspection or inspection period and the

technical basis for those concepts. Also the guidelines cover repair methods for

internals. The guidelines are shown in the JANSI Japanese website.

http://www.genanshin.jp/archive/coreinternals/

• In order to maintain the safety functions, such as core supporting, evaluation of

the ageing degradation and structural integrity of the internals are important.

・ The committee continues to discuss for further improvement of the guidelines,

risk informed and performance based approach , learning from operating

experience and international excellence.

• The guidelines are expected to construct a mechanism to conduct autonomous

activities for improving safety within the PDCA cycle.

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Thank you for your attention

Nuclear community all in one boat

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