- 15.1 -

The Service Evaluation and Measures for

Long Time Operation of Piping Systems

L. Junek Institute of Applied Mechanics, Brno, CZ

J. Hahn CEZ Temelin, CZ

J. Bartonicek JBC Consulting, Neckarwestheim

35th MPA-Seminar

“Materials and Component Behaviour in Energy & Plant Technology ”

October 9, 2009, Stuttgart

- 15.2 -

ABSTRACT

There are piping systems in industrial equipment and nuclear power plants that are important

regarding safety and economical operation. The required quality of these piping systems has

to be safeguarded during operation. The integrity concept is applied in these cases. Technical

basics are:

required quality approved after design, manufacturing and assembly,

safeguard of quality in operation,

regular re-assessment of quality in operation.

Design should include all degradation mechanisms but some of them cannot be controlled

by analysis. They have to be excluded using appropriate measures. In most of the cases, these

damage mechanisms are a result of local effects (like loads, medium, material characteristics)

that cannot be determined exactly in advance. Examples for piping systems are fatigue caused

by vibration or dynamics loads and material corrosion phenomena. For cases like these and

given medium, suitable materials have to be chosen in combination with appropriate

manufacturing procedures (incl. welding), optimized constructions and operation. The loads

and the water chemistry in operation have to be monitored and the efficiency of the measures

has to be verified, regularly, taking into account the actual state of knowledge.

Design specification can determine global temperature, pressure, sustained loads and time

history loadings during normal, abnormal and emergency operation only. Goal of design

analysis (stress, fatigue) is to demonstrate, that the results are within given limits. It is

obvious that this formal procedure does not provide conclusion regarding the state of

components quality after a given period of operation.

The manufacturing process is important for the quality status too. The demanded quality can

only be achieved if there is a through control of material composition and behaviour, of

constructive details and of the desired fault-free state.

Control of reasons for specified and unspecified degradation during operation is the first

redundant provision to insure appropriate level of piping quality in operation. Timely

- 15.3 -

assessment of results controls and prediction operation influence on piping quality must be

done. Appropriate measures are necessary to provided for minimisation of negative service

influence at the time. Control of degradation consequences is second redundant provision.

Relevant consequences have to ensure at the time before piping failure. Provisions are

necessary periodically updated about actual status knowledge. Assessment convertibility of

the new knowledge is needful done too. Measures have to be determined immediately in the

case of detection of relevant effects for preclusion of these effects during next operation.

The required quality has to be proven before the integrity concept is applied to a piping

system including to the approach or after long term operation in the rank of the approach.

Basics of the assessment are actual design, real geometry, performed attachments, piping

supports and relevant operation loadings including status media and specified postulated

rapture on the knowledge base. Potential degradation mechanisms in operation have to be

eliminated or at least minimized on the basis of monitoring.

Three levels are assigned in the concept regarding piping quality in future operation:

quality has to be guaranteed (integrity concept - prevent break – proactive approach)

by monitoring of causes for damage

quality has to be maintained (preventative maintenance - reactive approach) by

monitoring of results of damage

no specific demands on quality (maintenance triggered by damage - reactive approach)

statistical approach for damage

The paper deals about theoretical background of the integrity concept and example of

practical application are presented on Czech NPPs.

1. INTRODUCTION

The operating licence of nuclear power plants is limited to the expected operation period in

many countries except Germany. For the piping systems stress and fatigue analysis and

proves have to be performed during design for enveloping global loads specified for this time.

Choosing suitable procedure and calculations methods included in codes and rules permitted

values (stress, usage factor) has to be kept. In order to this performance and to dependence of

material degradation on operation loads real quality status for mechanical components in

- 15.4 -

operation or after expected operation time cannot be dedicated in this case. This missing

knowledge was the reason to extended evaluation for understanding possible aging

mechanisms and determination of boundary conditions for life time extension starting about

1985 in USA (Nuclear Power Plant Ageing Research Program – NPAR Program) and Japan

(Programs to Plant Life Management – PLIM and Plant Life Extension – PLEX), /1/ to /9/.

The results of this evaluations allowed life time extension older nuclear power plants. The

long term operation is discussed recently, /10/ and /11/. The life time of components can be

safeguarded by means of measures allowed control of damage mechanisms during operation.

The long term operation is possible, if requested quality is created during design and

manufacturing (new component) or quantified proofed after given operation time and

safeguarded by means of suitable measures during operation. In Germany such procedure was

developed from “Basic Safety Concept” (principle of break exclusion) and it is called since

mid. nineties as “integrity concept”, /12/ to/17/. This procedure for creating the required

quality in design and manufacturing for components without findings is sufficiently defined

in German safety standard KTA 3201.1 to 3201.3, safeguarding of the quality in operation in

3201.4, /18/.

Main goal of the design analysis is to safeguarded every possible damage mechanisms of the

future operation. Damage mechanisms that cannot be safeguarded by specifications and

analysis have to be excluded by design, water chemistry and operation mode. The

effectiveness of these measures must be proven during initial startup and operation. Examples

for such damage mechanisms are:

Fatigue caused by vibrations and short-time dynamic loads like cavitational hammer,

water hammer or shock pressure.

Relevant corrosive damage mechanisms like stress corrosion cracking (SCC) for

austenitic or strain induced corrosion cracking (SICC) and pitting for ferrites that cover

the influence of environment.

The effectiveness of the safeguard depends on the knowledge in the design state and has to be

validated during operation.

To safeguard the damage mechanisms in design the relevant global loads and environments

are specified based on the intended operation modes assuming correct operation of the

relevant components (no internal leakages of valves, proper function of supports) for the

- 15.5 -

certificates required. Local loads and environments are not taken into account at first because

only specified loads are expected to occur. Taking into account the complexity of the systems

and the long term operation loads caused by leaking valves, unintentional switching or

unintended operation modes can not be specified in a reasonable way.

The manufacturing process is important for the quality status too. The demanded quality can

only be achieved if there is a through control of material composition and behaviour, of

constructive details and of the desired fault-free state. After design and monitoring real (as

built) construction is known, fig. 1.

During operation as built quality of piping systems can be affected generally by ageing

phenomena, fig 2:

Ageing of basic safety concept,

Ageing of technology,

Ageing of materials.

The ageing of basic safety concept (conceptual aging) includes the demands on system or

components and changes in the overall safety philosophy, which results from experience or

safety analysis. The existing status of systems and components has to be analysed

periodically. If they are deficits, component must be optimized or replaced or even new

systems have to be built in.

The technology ageing is caused by changes of knowledge, e.g. regarding possible damage

mechanisms, material or components characteristics, test and calculation procedures. These

changes result from research or product development projects or from analysis of operation

experience. These knowledge are necessary to quantify the influence of existing causes of

damage mechanisms on as built construction.

Ageing of materials is a result of existing causes in operation (physical aging). Generally,

changes of material characteristics, existing loads and medium can cause material damage

like fatigue, corrosion, wear and combination. For systems and components where damage

mechanisms have to be under control, monitoring of causes is the most appropriate measure.

- 15.6 -

If ageing phenomena are not control sufficiently relevant results of damage mechanisms or

failure are possible. Depending on the quality requirements, three groups have been defined to

classify the scale of measure applied:

group 1: integrity concept (guarantee of quality or integrity – control ageing

phenomena)

group 2: preventive maintenance (maintain quality level – prevent systematic failure),

group 3: failure oriented maintenance (re-establish initial quality).

The procedure in group 1 is sufficient for long term operation. This one in group 2 can be

used, if possible failures have not relevant influence on safety and efficiency of nuclear power

plant.

In this paper technical basis for long term operation will be defined and their use for piping

systems described.

2. TECHNICAL BASIS FOR LONG TERM OPERATION

In the integrity concept for piping systems (and vessels likewise)

quality after design and manufacturing

safeguard quality during operation

proof of existent quality for further operation

has to be handled according to the requirements of the corresponding integrity classification,

fig. 3.

To safeguard the quality during operation redundant measures are necessary which are:

Monitoring of causes for possible damage mechanisms (loads, water chemistry).

Evaluation of results and establishing of suitable measures to control and minimize

corresponding consequences.

Monitoring of consequences (NDT, integral visual inspection).

Pursuing of knowledge (applicability).

It is important to assess whether the existent procedure is sufficient or not and to define

additional measures to master causes and consequences if necessary.

- 15.7 -

Results of monitoring and evaluation have to be reported annual (to supervisory authority and

experts). In consequence of this procedure the monitoring of consequences must not detect

effective operational damage mechanisms (otherwise the procedure was not sufficient). The

requirements are defined in the German KTA 3201.4 (edition 06/99), fig. 4.

The proof of existent quality is another important redundant measure in the integrity

concept. Fundamentals for the evaluation of the existent quality are:

As-built construction

Actual media

Relevant loads

Changes in knowledge and verification procedures

For the integration of a component into the integrity concept based on the technical

fundamentals the premises to comply with and to document are:

Prevention from unacceptable vibrations and short-time dynamic loads like cavitational

hammer, water hammer or shock pressure by determination of design an operation mode.

Prevention from relevant corrosive damage mechanisms (SCC, SICC, erosion-corrosion,

pitting) by suitable water chemistry, material selection, design and construction and

monitoring during operation combined with pursuing of knowledge.

Approved quality (Basissicherheit KTA 3201.1-3. or Quasi-Baisissicherheit including

specification of required additional measures and validations for Quasi-Basissicherheit).

Safeguard of postulated consequences of possible operational damage mechanisms

(minimum detectable failure size combined with fracture mechanics analysis, reaction

force from postulated leak opening combined with stress validation) in the design phase.

Specification of measures and verifications for the registration and control of possible

operational damage mechanisms.

Pursuing of knowledge including aging phenomena and evaluation of the applicability the

plant.

Proof of a consistent concept with graduated redundancies.

- 15.8 -

3. CZECH LAWS, RULES AND STANDARDS

Used safety philosophy concludes all requirements with Czech, national standards and

international requirements:

Requirements on design safety analysis of all operation conditions as normal, abnormal

and emergency, which are specified by design, /19/,

Requirements on technical procedures and measures for managing of all design assumed

emergency situation,

Requirements on system quality of piping systems during design, construction assembly

and commissioning, /20/,

Requirements on system quality of piping systems during all period of planned operation

till to their decommission, /20/,

Requirements on of actual Czech and International lows, regulations and standards, /19,

20,21,22/,

Requirements on following of actual experiences of nuclear power plant of the same type,

Requirements on applying of actual science knowledge.

4. PRACTICAL CONCEPT APPLICATION

Practical integrity concept application on dissimilar welds is presented. Important piping

systems for safety were manufactured from low alloy carbon steel with anticorrosion cladding

inside on NPP WWER 1000MW. It is restricted to perform welding without preheating on

this kind of steel. It is a reason why an assembly welds on this systems are dissimilar metal

welds made with buttering and austenitic filler material. Integrity concept requires appropriate

data (complex data collection) which are retained for the life of the plant. These data also

provide the basis for a plant life management program and will aid in justifying continued

operation of the plant to the regulatory authority. Implementation of results will identify data

collection and record keeping requirements to support ageing management evaluations.

Extent of data collection was separated in three parts:

Important design information

Information from operation including commission period

Information from in-service inspections and maintenance

- 15.9 -

4.1. DESIGN DATA COLLECTION

Research of dissimilar welds was in progress more than 15 years at the producers before

components manufacturing. Results were presented in the research publications and material

studies. More than 55 research reports were issued during this works. Attention was

concentrated on material property of dissimilar welds which can be used in the future during

operation.

Results of design reports of systems and components are very important. Results indicate

regions with maximum stressors due to design normal and abnormal operation condition.

Fatigue assessment results (damage factor) and assessment results of other potential

degradation mechanisms were collected for all selected piping systems too.

Plant Design Management System (PDMS) computer system was used for determination

actual geometry, performed attachments, piping hanging etc. We received actual trajectories

of selected piping systems with all system components as fast action valves, safety valves,

check valves and other components. Fourteen piping with all system components for

assessment were selected – fig.5, example of surge line system in PDMS. Assembly

procedures of dissimilar welds for all systems were collected too. Extent and number of pre-

service inspections during erection was evaluated. Attention was concentrated on weld root

control because weld damage usually starts from this region. The following criteria were

applied for decision about importance from design point of view at the end of the first part of

analysis:

Safety Class (SC). First and the most important criterion. For pressure-retaining

components gives a 3-level classification associated with the role of the component or

system in the installation. SC classification was done in accordance with Czech

regulations [20]. Criteria SC 1, 2 or 3.

Results from design analysis reports. Second criterion is aimed on dissimilar weld

design analysis models and their assessment. Attention was paid whether dissimilar

welds were evaluated individually or together with piping systems. Dissimilar welds

were usually evaluated with component nozzles only. Piping systems models did not

separate individual welds. Criterion Yes/No.

Pre-service inspections. Criterion shows if the individual dissimilar weld was inspected

by NDT volume inspection during construction or erection. Criterion Yes/No.

- 15.10 -

Weld performance. Criterion if dissimilar weld joint was done during erection or during

manufacturing in the shop. Criterion yes was applied if the weld was done during

erection.

Material property. Last criterion in design section. Criterion documents sufficient

quality of used materials of classified equipments. Known material behavior can predict

material sensitivity on any degradation mechanisms in the future. Criterion Yes,

known/No, unknown.

4.2. OPERATION DATA COLLECTION

It is important from operation point of view to define potential degradation mechanisms

which can occur during operation and to define their detection - information from operation.

We can use for separated components of piping systems with dissimilar welds:

information of diagnostic and I&C systems form commissioning operation till up analysis

time,

information from in-service inspections,

information from walk round,

information from maintenance.

Attention was paid to degradation mechanisms (DM) which were not evaluated in design

analysis reports. Six ageing mechanisms are usually determined during operation that tends to

reduce the life of system important to safety: thermal fatigue of pipes and nozzles with

dissimilar welds, fatigue due to vibration, thermal ageing, primary water stress corrosion

cracking, boric acid corrosion and atmospheric corrosion. Following screening criteria were

applied:

Thermal mixture. First DM on thermal fatigue base. Criterion yes was applied if exists

the information from diagnostic systems or we can suppose this DM due to function of

the system (branch connection on systems). Otherwise criterion no was applied.

Criterion Yes/No. – fig.5.

Thermal shock. Criterion yes was applied on the base the same analysis as in the first

case. Thermal shock is very important degradation mechanism and it can occur during

operation (periodic blow down, could water in non flow pipes - passive emergency

system etc.).

- 15.11 -

Thermal stratification. This mechanism mainly regards horizontal piping systems or

pipes with very low slope. Criterion yes was applied on the base diagnostic detection or

presumptions (passive emergency system, surge line etc.).

Two-phase medium. Similar DM as thermal stratification. Two-phase (steam/water)

medium can occur during operation inside piping systems. Criterion yes was applied if

exists the information from diagnostic systems or we can suppose this DM due to

function of system (mainly on spray line).

Failure influence. Criterion yes was applied if exists substantial reasons (due to

component function and component disposition on system) that component failure can

damage other important component (SG, RPV, RCS) in the system (armature leakage,

functionality damage etc.). The analysis was done by using PDMS drawings.

Operation information. Sufficiency of operation information was analyzed and

evaluated in this criterion. Criterion yes was applied if the measurement can confirm

thermal fatigue mechanism (mixing, thermal shock, stratification, steam/water medium)

in individual region of the piping system. It means thermocouples measurement is

implemented in area of assessment. Criterion no was applied if the information was not

sufficient. Additional recommendation was done on diagnostic measurement extension in

the case of necessity.

Thermal aging (change of material property). Criterion was used in case of the cast

steel only and austenitic weld joints.

Criteria for other degradation mechanisms:

Erosion. Turbulent flow or high velocity of dump steam can evoke erosion mechanism.

Criterion yes was applied if substantial reasons were located on piping systems area.

Vibration. It is high cycles fatigue degradation mechanism. Criterion yes was applied if

information from the walk round or from controllers were obtained.

Corrosion. The criterion covers all types of corrosions including stress corrosion

cracking. Criterion yes was used if exist information from operation (from other NPP

too).

Operation information. Sufficiency of operation information was analyzed and

evaluated in this criterion. Criterion yes was applied if the control mechanism can

confirm erosion, corrosion or vibration in individual region of the analyzed piping

system. Criterion no was applied if the information was not sufficient. Additional

recommendations on in-service inspection (ISI) extension were done.

- 15.12 -

4.3. ISI AND MAINTENANCE DATA COLLECTION

Effective ageing management requires timely detection and characterization of any significant

ageing degradation of the piping. In-service inspection plays an important role in detecting a

crack early enough so that appropriate mitigation/repair steps can be taken before it grows

beyond allowable size. Monitoring of stressors causing ageing degradation, especially fatigue

damage (fig.6) aids in more accurate assessment of the damage and in identification of the

most damaging pressure and temperature transients. Following criteria were used:

Scheduled ISI. Criterion yes was applied if the piping area with dissimilar welds is

periodically controlled during regular ISI program.

Control period. The control period was extracted from ISI program if controls are

provided.

Date of the last control. It is needed information at the time of analysis. Information

indicates time of the next period ISI control.

Type of ISI. The non-destructive inspection (NDT) methods are broadly classified as

either volumetric or surface inspection methods. Sufficiency of NDT methods was

evaluated (visual, penetration, UT, X-ray, magnetic, functionality test, etc.)

Aging management. Last criterion shows whether evaluated area with dissimilar weld

was included in aging management process before analysis. Criterion Yes/No.

The results of analysis were documented and in the table presented. Analyzed welds of

systems could be separated on the groups on the presented results base. We received complex

list of all piping system components for the integrity concept. The effectiveness of aging

management should be periodically evaluated and updated in the light of current knowledge

and adjusted, as appropriate. Current relevant knowledge consists of information on systems

operation, surveillance and maintenance histories, and information from the results of

research and development, and generic operating experience.

- 15.13 -

5. CONCLUSION

The ultimate success or failure of the aging management depends upon the degree of

understanding, acceptance and support of the staff of the nuclear power plant. A

multidisciplinary approach to ageing management requires the frequent use of working parties

and teams. Training in team skills (e.g. problem solving) and selecting capable team

facilitators will help ensure that the teams are effective.

The human aspects of ageing management can best be addressed by making the relevant

nuclear power plant organizations key members of ageing management teams.

The implementation of a systematic ageing management process requires an organization that

builds on and systematically co-ordinates all relevant existing plant and external programmes

and activities.

Reviews, inspections and assessments required by regulations should be carried out to

determine the effectiveness of ageing management programmes. Both the ageing management

policy of the licensee and aging management should be assessed and improved by the

licensee. The result of the reviews, inspection and assessment and improvement should be

submitted to the regulatory body.

Consideration should be given to arranging for peer reviews of aging management to obtain

an independent assessment to establish whether the aging management is consistent with

generally accepted practices and to identify areas for improvement.

There should be adequately funded research and development programmes to respond to any

new ageing issues and provide for continuous improvement of the understanding and

predictability of ageing mechanisms and their kinetics, and associated monitoring and

mitigation methods/practices.

- 15.14 -

REFERENCES

/1/ NUREG-1144, J.P. Vora : Nuclear Plant Aging Research (NPAR) Program, Rev. 1

/2/ IAEA-293/33, G.A.Arlotto, J.E.Richardson: NRC-Program to Understand Aging and Manage its Effects in Nuclear Power Plants

/3/ IAEA-295/27, D.R. Hosteller, G.Neils, Utility Life Extension Initiatives in the USA

/4/ Nureg-1377, N.N.Koudic, NRC Research Program on Plant Aging Listing and Abstracts of Reports Issued Through February 1, 1989

/5/ IAEA, Technical Reports Series No. 338, 1992: Methodology for The Management of Aging of Nuclear Power Plant Important to Safety

/6/ IAEA, Safety Report Series No. 15, 1999 Implementation and Review of Nuclear Power Plant Ageing Management Programs

/7/ US NRC, Nureg-1801, Vol. 1 and 2, 2001, Generic Aging Lessons Learned (GALL) Report

/8/ NEA, NEA/SEN/NDC(2000)6, Status Report on Nuclear Power Plant Life Management

/9/ NEA:NEA/CNRA/R(2001) 1 and 2, Regulatory Aspects of Life Extension und Upgrading of NPPs

/10/ IAEA/NSNI, Working Material, 2001, Good Practices for Minimizing Premature Ageing

/11/ IAEA-EBP-Salto, 2007, Final Report of the Programme on Safety Aspects of Long Term Operation of Water Moderated Reactors

/12/ Kußmaul,K., D. Blind : Basis safety – a challenge to reactor technology. Trends in Reactor Pressure Vessel and Circuit Development. Proc., IAEA Specialists Meeting, Madrid 1979, Londen: Applied Science Publishers 1980, pp1/13

/13/ Kußmaul, K.: German basis safety concept rules and possibility of catastrophic failure

Nuc. Eng. Int. 12 (1984), pp 41/46

/14/ Jonas, Bartonicek, Schoeckle : Piping Integrity Monitoring System for GKN PWRS

ASME PVP Conference, Honolulu, Hawaii, 1995

/15/ Bartonicek, Metzner, Schoeckle : Life Time Management – a practical Approach of nuclear power plants ASME PVP Conference, Vancouver, 2002

/16/ Roos, Herter, Schuler, Bartonicek, Schoekle : Integrity concept for Piping Systems, 32. MPA Seminar, Stuttgart 2006

/17/ Junek, Bartonicek, Vrana : Degradation Mechanisms Control of Mechanical Components During Operation ASME PVP Conference, Prague, 2009

/18/ KTA Standard 3201.1 to 3201.4, Components of the Reactor Coolant Pressure Boundary of Light Water Reactors

.1 Materials and Product Form, 1998

.2 Design and Analysis, 1996

.3 Manufacture, 2007

.4 In-service Inspections and Operational Monitoring

- 15.15 -

/19/ Czech Law No. 18/1997 Sb., Peace exploitation of nuclear energy and ionising radiation, from date January 24, 1997 (in Czech)

/20/ Regulation No.132/2008 Sb. from April 4, 2008 about Quality Assurance during Implementation and Operation Provision Contextual with Nuclear Energy Utilization and Radiation Activities and about Quality Assurance Classified Equipments in accord with their Safety Class Range (in Czech)

/21/ Standard Technical Documentation of the A.M.E. 2007, Strength Assessment of Equipment and Piping of WWER type Nuclear Power Plants, Section III, Issued in Prague and Brno May 2007, Identification No. NTD ASI-II-Z-5/07

/22/ Standard Technical Documentation of the A.M.E. 2007, Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs, Section IV, Identification No. NTD ASI-IV-Z-5/04

- 15.16 -

Figure 1: Change of quality and requirements on quality in operation

- 15.17 -

conceptual ageing physical ageing

changes in demands damage mechanisms in operation like:

changes in safety philosophy material embrittlement material fatigue

technological ageing corrosion

new knowledge about: wear

possible damage mechanisms combination of above mechanisms

materials and design characteristics causes are in general:

test procedures material (degradation)

procedures for analysis load history

calculation procedures medium / environment history

Figure 2: Ageing phenomena

- 15.18 -

Figure 3: Technical basis of integrity concept

proof of quality

quality afterdesign and manufacturing

design approval / as-built design

spec

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safeguarding quality in operation

real causes /control of causes /

no active damage mechanisms

re-assessment of quality in operation

safety margin as requiredsafety margin as required

- 15.19 -

Figure 4: Safeguarding of quality in operation, KTA 3201.4, 06/1999

Monitoring of the consequences of operational damage mechanisms to be assumed

(e.g. non destructive testing, monitoring of loos parts, destructive testing)

Assessment of the present

design

Determination of the relevant

loading conditions

Redundant measures(e.g. detailled analyses,additional monitoring)

Requirementsof the „Basis Safety“

are fullfilled ?

Specifiedloads are

kept ?

Evaluation of the actual state of quality

Identification and monitoring of the causes possible operational damage mechanisms

mechanical and thermal water chemistryloads

Evaluation of the loads and strengthe.g. stress analysis, fatigue analysis,

fracture mechanics analyssis

Determination of measures to monitor the consequences of operational damage mechanisms

areas of test testrelevance method interval

Evaluation of thegeneral concept

Closed concept

Additional measures

no

yes

Ch

ang

eso

fth

e st

ate

of

the

art

Determination ofoperational damage

mechanisms

no

yes

positiv

Monitoring of the consequences of operational damage mechanisms to be assumed

(e.g. non destructive testing, monitoring of loos parts, destructive testing)

Assessment of the present

design

Determination of the relevant

loading conditions

Redundant measures(e.g. detailled analyses,additional monitoring)

Requirementsof the „Basis Safety“

are fullfilled ?

Specifiedloads are

kept ?

Evaluation of the actual state of quality

Identification and monitoring of the causes possible operational damage mechanisms

mechanical and thermal water chemistryloads

Evaluation of the loads and strengthe.g. stress analysis, fatigue analysis,

fracture mechanics analyssis

Determination of measures to monitor the consequences of operational damage mechanisms

areas of test testrelevance method interval

Evaluation of thegeneral concept

Closed concept

Additional measures

no

yes

Ch

ang

eso

fth

e st

ate

of

the

art

Determination ofoperational damage

mechanisms

no

yes

positiv

- 15.20 -

Measurement points

Figure 5: Surge line system with measurement points in PDMS computer system

- 15.21 -

Figure 6: Fatigue usage factor prediction in [%] per years (till 2041)

Surge line FEM model with 3D weld joints