Analysis of Worldwide Events Related to The Construction ... ConE… · CNRA International Workshop...

CNRA International Workshop on New Reactor Siting, Licensing and Construction Experience, 15-17/09/2010, Prague 1

Analysis of Worldwide Events Related to The Construction

and Commissioning of Nuclear Power Plants:

Lessons Learned and Recommendations

Marc Noël

EC-DG Joint Research Center

[email protected]

http://clearinghouse-oef.jrc.ec.europa.eu/


• Background

• Methodology

• Trends • Trends

• Lessons learned

• Recommendations


European Clearinghouse - NPP OEF

OEF Clearinghouse

Centralized Office (JRC)

Coordination and Communication

Review of draft IRS reports

Event Data management

Dissemination and Training

Services at request

EU Safety Authorities

International

Community

IAEA

OECD-NEA

MembersFinland Hungary Lithuania

The Netherlands Romania Slovenia

Switzerland

Observers Services at request

EU Technical

Support Organizations

OECD-NEA

Others (bilateral)

ObserversCzech Republic

FranceGermany

Spain

Main deliverables

for EU Safety Authorities:

- Improved draft IRS

- Topical reports


On-going programme of Topical Studies

Topic

Reactivity management - 1999 Shika NPP criticaliy event

2006 Forsmark NPP event

Maintenance events

Fuel damaging events

Construction & commissioning events

External events (natural and man-induced origin)

2009

2010

2008

Event related to supply of NPP components

Events related to plant modifications

Events related to ageing of NPPs

Loss of safety-classified electrical equipment due to generator

high voltage peak

Events related to decommissioning of NPPs


Background

The challenge:

• Roughly more than 50 NPP construction projects are currently launched or under consideration worldwide.

• Much of the earlier experience and resources have progressively been lost from the nuclear industry.

• No recent comprehensive study published yet on lessons learned from events related to pre-operational phases.

• No dedicated repository of worldwide construction experience yet.

⇒ EU Clearinghouse members launched an up-to-date in-depth analysis of both past and current construction experience


Methodology

• 3 main sources of information:– IRS database– US NRC Licensee Event Reports (LERs)– WGRNR Inspection findings

• Selection criterion:– All events initiated during NPP pre-operational stages (construction,

US

LERWGRNR

IRSDB

Data sources

US

LERWGRNR

IRSDB

Data sources

– All events initiated during NPP pre-operational stages (construction, commissioning and component supply).

– Events occurring both before start of commercial operation or long after.

• Screening from the beginning of these DB until end 2009 : 1090 IRS reports, 857 LERs and 100 WGRNR findings have been screened.

⇒ After final screening, total of 582 events applicable


Methodology

• Distribution of events in categories (construction, manufacturing, commissioning)

and sub-categories (civil works, electrical components, welding, valves…)

• Final aim = to raise concrete lessons learnt and recommendations

Construction Manufacturing

Commissioning

Cab

les

Break

ers

Electrical Civil Works ….

….

….

….

….

….

….

….

Lesson

s learnt

Lesso

ns learn

t

Lesson

s learnt

…

Lesso

ns le

arnt

Lesso

ns learn

t

….

Electrical Civil Works Electrical Civil Works ….


Trends

• I&C, electrical components, and welds are the items leading to the highest number of reported events

Civil Work

8%

Diesel

5%Other

2%

Weld

14% commissioning

13%

Electrical

19%

Fire protection

5%

I&C

17%Ventilation

1%

Pipes

9%

Pumps

5%

Valves

10%

2%

SG

5%

construction

48%

manufacturing

39%


Trends

• Average detection time of the issues is ~8 years after the start of commercial operation.

– Up to 40 years for some events!

– Shorter detection for active components - diesels (2.6 y), pumps (4.5 y)

– Longer detection time for passive components - civil structures (8.9 years), pipes (11.7 y) or welds (12.7 y).

50

60

40

50

• High average rate of Common Cause Failures (CCF): 34%. More than 50% for civil work and fire protection, 45% for electrical components.

0

10

20

30

40

Civil Work Diesel Electrical Fire

protection

I&C Pipes Pumps SG Valves Weld

% o

f C

CF

-10

0

10

20

30

Op

era

tio

n Y

ears

% of CCF AVERAGE DETECTION TIME Maximum detection time Minimum detection time


Trends

• More than 75% of the events are found out fortuitously (following failure, spurious actuation, fire, flooding or “by chance” through unrelated tests or inspections)

70

80

90

100

0

10

20

30

40

50

60

70

Civ

il W

ork

Die

sel

Ele

ctric

alFire

pro

tect

ion

I&C

Pip

es

Pum

ps SG

Val

ves

Ven

tilat

ion

Weld

s

% of fortuitous detection Average


Trends

• Some families accumulates a long detection time, a high rate

of common cause failure and a high rate of fortuitous

detection, mainly:

– Building structures

– Anchors & supports

– Electrical components

⇒⇒⇒⇒ Potential latent failures

• High rate of I&C issues in commissioning events

Diesel

9%

Electrical

12%

Fire protection

12%

I&C

43%

Pipes

6%

Pumps

9%

Valves

9%


Lessons learned

• Approx. 60 concrete lessons learned identified for 21 separate sub-families

• Among lessons learned:

Welds .Welds .

� Events related to welds show the very high importance of appropriate weld QA, QC & inspection programme.

� All welds should be inspectable during the construction stage.

� The welding environment (on construction site) should allows the compliance with the construction code.

� The original welding documents and inspection results should be carefully kept as they are needed for the further in service inspection.


Lessons learned - examples

• Electrical cables .

� A comprehensive cable condition monitoring programme should be implemented already at the construction stage. Cable sheathing of the safety-significant systems should be checked where it is accessible, in particular at the bends and at the electrical connection. During the construction, inspection should be performed in the cable trays before there are closed.there are closed.

� For installation of multiples cables in a single penetration, a specific procedure should be written in order to avoid damage during installation. Installation of designed separations in the penetrations should be checked.

� During cable manufacturing, special attention should be paid to:

• In PVC sheathing, homogenous blending of additives

• the eccentric arrangement of the conductor towards the protective sheath



• Penetrations and building seals .

� To ensure adequate follow-up during further plant operation, every single penetration and building seal should be properly documented (location, role, characteristics, design bases, etc).

� The initial design of inter-building seals should take into consideration the need to be able to conduct checks on the quality of installation at the construction stage and subsequently. To do so, the seals should be construction stage and subsequently. To do so, the seals should be accessible over their entire length.

� When a penetration seal functions as both fire and flood barrier, it is important to consider both functions in the design, installation, inspection, and maintenance. This includes accounting for static head pressure to ensure watertight seals do not dislodge.



• Building structures .

� The minimum thickness of lubricant on the external wire layers following manufacture of containment pre-stressing system cables should be precisely specified.

� The humidity and the lubrication inside the channelling device of the pre-stressing cables should be monitored during construction.

� The concrete pouring should be validated by mock-up for locations where the access for concrete consolidation may be difficult (high density of steel reinforcement, etc)

(see also transversal recommendations – QC, SC, …)



• Pipes .

� A rigorous management of temporary devices should be implemented to avoid remaining temporary blind flanges, orifices, etc. inside the pipes after commissioning of the plant.

� Pipe clogging: measure will be taken to avoid pipe clogging by construction debris and other foreign materials. A FME + cleanliness / housekeeping policy will be implemented from the very beginning of the housekeeping policy will be implemented from the very beginning of the project.

� The pipes should be exhaustively inspected during construction.

� Special attention should be paid to proper installation of pipe support and restraints intended to mitigate consequences of earthquakes and HELB.

� The installed pipes insulation weight should be verified to comply with the seismic qualification of pipes supports.



• I&C .

� The probes installation should be closely monitored during construction and appropriate commissioning tests should be made up and carried out in order to detect a defect of each single component of a measuring channel (including namely impulse lines).

� The minimal distance allowing functional redundancy should be ensured between redundant impulse lines.between redundant impulse lines.

• Others .

� Cranes should be included in the commissioning programme and test should be performed before 1st load lifting.

+ ~40 other lessons learned identified


Transversal recommendations

• Based on the analysis of each individual event, more than 30 concrete transversal recommendations have been identified.

• A lot of them are at the level of the management of the construction project and at QM level.

• Among them:

Communication .

� Special attention should be paid to the communication between the different companies and/or entities involved in a plant construction. This communication should be done through pre-defined and documented procedures, and submitted to a Quality Control Programme. Moreover, this communication should enable the information transfer about the safety significance of components or equipment from the design stage until the contractor and its sub-contractors in charge of the installation of the components or equipment


Recommendations - examples

• Management of non-conformances .

� The requirements for handling the non-conformances should be clearly identified. These requirements should specify the definition of the non-conformances, the roles and responsibilities of the licensee, the vendor and the subcontractor for reporting and correcting the non-conformances, as well as the regulatory approval process. The compliance with those requirements should be checked by the licensee and the regulatorrequirements should be checked by the licensee and the regulator

• Tasks interfaces .

� The interfaces between different tasks should be clearly identified and managed in such a way that the departments or companies in charge of these tasks are aware of the precise scope of their work, and that interface works are not omitted.



• Change management .

� Any changes from the design, the installation or the manufacturer procedures should be properly documented and assessed.

• Quality assurance and quality control scope .

� Handling, packaging, transportation and storage conditions of safety significant components should be covered by and monitored through a

� Handling, packaging, transportation and storage conditions of safety significant components should be covered by and monitored through a Quality Assurance Programme.

• Specific nuclear requirements .

� Each call for tender about safety-related components should include and emphasize the specific nuclear requirements and local nuclear regulations concerning namely quality management and safety culture. The compliance with those requirements should be properly checked at the stage of contracts awarding and until the work is fully implemented.



• Third party quality control .

� The oversight and the quality control of on-going works should be performed by an organization which is competent and experienced in the works, clearly identified as responsible of the quality control, and independent from the organization in charge of the works.

• Temporary devices .• Temporary devices .

� Temporary devices used at manufacturing, construction and commissioning stages should be properly documented so that to allow removing all the temporary devices after their use, in order to ensure that the remaining devices are not temporary devices and to track a potential constraint that the temporary devices may have caused on the component.



• Safety culture .

� The adherence to nuclear safety principles should be the top priority already during construction and manufacturing.

� The safety culture and safety awareness of the personnel involved in the pre-operational stages should be ensured through an adequate training, highlighting the role and the safety significance of the components concerned. Each person attending the project needs to understand the safety significance of his / her work, to promote personal responsibility. safety significance of his / her work, to promote personal responsibility.

� This is necessary for all the staff involved in the process, including the manufacturer’s staff, the vendor’s staff, contractors and sub-contractors, the staff in charge of the surveillance of the activities, and the staff in charge of the acceptance of the components.

� This safety awareness should be ensured not only for “complicated” works like welding but even for “more simple” tasks like anchoring, especially since some sub-contractors may not have any experience of working for the nuclear industry.



• Construction .

� Impact on nearby NPP units in operation: The potential consequences of construction works on the safety of operating units should be assessed (Risk Analysis). In particular, the consequences of the potential pollution from a construction site on the operating units should be assessed and if needed, the pollution should be monitored. All other potential risks should be assessed (digging, excavation, spurious fall of cranes, use of explosives, etc.).

� Labelling - The labelling of the components should be in place as soon as the components are installed.

� Torque - The applied torque should be submitted to independent verification during the related sequence of assembly operations.

� Welding - Special attention should be paid to the Quality control of the welding and the control sampling rate should be adapted to the safety-significance of the welds and to the welding technique. Moreover, the welding should be carried out by appropriate trained and experienced welders.

� Wiring - Wiring checks should follow any cabling installations – it should be a part of the installation procedure or program and should be verified by the regulator.



• Component manufacturing .

� Special attention should be paid to the purchasing of commercial grade components for safety-related equipment by the equipment manufacturer, which should be properly documented.

� The mastership of technologies should be proven and � The mastership of technologies should be proven and verified by the licensee, not only through final acceptance tests but also by checking that proven state-of-the-art technology is used. Augmented regulatory approach and inspections should verify that new manufacturing techniques and new type of equipment meet the specifications set by the designer.



• Commissioning .

� Time of tests performance - In case of a standby component, which is normally not in operation, its functionality must be regularly tested, as a long period of inactivity and the construction of other equipment during this period could question the test results.

� Scope of the tests:

• Tests conditions - The safety systems should be tested in conditions simulating the real accidental conditions and if not possible, provisions should be taken for the concerned systems in terms of acceptance tests, QA, etc.

• Tests comprehensiveness - The scope of the tests should include all the components and devices that are used during normal operation or under accidental conditions, including the passive components like pipes, as they may be during normal operation or under accidental conditions, including the passive components like pipes, as they may be clogged, and including the manufactured components, as the QC at the manufacturing plant may be deficient.

• Fragmented tests - Safety systems should be submitted to overall functional tests as far as possible to ensure not only the performance of each single component but the performance of the whole system, including the interactions between different components.

• Non-actuation tests - The tests should allow to detect an unexpected (spurious) actuation of a safety system.

• Simultaneous tests - The commissioning tests should be made up considering the fact that simultaneous tests may have an influence on each other’s results.

� The test acceptance criteria should allow verifying not only the functionality of a system or component but as well its level of performance.

� The proper reconfiguration of the systems after the commissioning tests should be checked.


Conclusions

• 582 events reports from various sources were analyzed.

• Lessons learnt and recommendations about pre-operational stages can be raised from operational experience

• OE shows that anomalies during pre-operational stages can lead to serious breaches of nuclear safety during the operation of the plant.

• More than 50 concrete lessons learned for individual components or activities have been raised.

•• More than 30 transversal generic recommendation have been raised (→management of the construction project and QM!)

• The IRS database is not specific to the construction experience:

⇒ Non-conformances corrected before operation are generally not included

because no consequences on safety

⇒ The reports focus more on corrective actions for the operating plants and the

lessons learnt for other construction projects are often not fully considered.

⇒ Need for improvement of experience capture from anomalies related to preoperational stages, at international level.


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