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Reporting on I&C Status and Recommendations to IAEANEK - Nuclear Power Plant Krško

Slovenia

Damir MandićNuclear Power Plant Krško – NEK

Slovenia

Meeting Of the IAEA Technical Working Group on Nuclear Power Plant Instrumentation and Control (TWG – NPPIC)

Vienna, 24-26 May, 2011

IAEAInternational Atomic Energy Agency

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NEK nuclear power plant is located in Slovenia, on the river Savain the neighborhood of Krško town. It was constructed and it isowned by two power utilities of Slovenia and Croatia.

Owner…………………….. GEN Energija (Slovenia) - 50%HEP (Croatia) - 50%

Operator ………………… Nuklearna elektrarna Krško NSSS supplier…………... Westinghouse Reactor type……………. PWR Construction permit…… 1975 Commercial operation… 1983 Operating license………. 40 years Number of employees…. ~600

Gross plant output………. 727 MW

More information is available at NEK web site:http://www.nek.si/en/about_nuclear_technology/technical_data/

FACTS ABOUT NPP KRŠKO - NEK

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SIMPLIFIED SCHEMATIC NPP KRŠKO - NEK

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NPP NEK - ELECTRICITY PRODUCTIONNet Electric Energy Production Since Start of

Commercial Operation of Krško NPP

[Year]

[TWh]

Cumulative : 133,22 TWh

Goal NEK for 2011:>5,9 TWh

3-year average: 5,6 TWh

Improving Production Trend in NPP Krško

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NUCLEAR POWER PLANT KRŠKO – NEKPerformance Indicators

Unplanned Capability Loss Factor

NPP Krško goal: ≤ 1%

Unit Capability Factor

NPP Krško goal: ≥ 98%

88,4591,75 91,35 91,15

98,55

89,59 90,75

98,59

90,49 89,19

25

50

75

100

PER

CE

NT

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010YEAR

0,00

0,83 0,83 0,90

1,451,29

0,01

1,41

0,76

1,52

0

1

2

3

4

5

6

PER

CE

NT

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

YEAR

High Records of Production Efficiency

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Automatic Scrams per 7000 Hours Critical

NPP Krško goal: ≤ 1%

Forced Loss Rate

NPP Krško goal: ≤ 1%

0,00

0,83 0,83 0,90

1,451,29

0,01

1,41

0,76

1,52

0

1

2

3

4

5

6

PER

CE

NT

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

YEAR

High Records of Safety Performance

NUCLEAR POWER PLANT KRŠKO – NEKAchieving Nuclear Safety

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Since the year 1983, the large number of plant design changes(>850) have been implemented and are currently being preparedfor implementation. Most of them, even if not declared as pure I&Cmodifications, have some I&C changes or additions in their scope.

CONTINUOUS NPP NEK MODERNIZATION

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Power (MW)Design1983

SGRuprate 2000

New LP TU 2006

Reactor Thermal Power 1876 1994 1994

NSSS Thermal Power 1882 2000 2000

Gross Plant Electrical Output 664 707 727

Net Electrical Output 632 676 696

CONTINUOUS NPP NEK MODERNIZATIONPower Evolution

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Continuous NPP NEK ModernizationMajor Investment Projects

Already implemented since year 2000:– Steam generator replacement– KFSS: Krško Full Scope Simulator– Low Pressure Turbine replacement – Main transformer replacement (1 of 2 replaced) – Spent Fuel Pit Re-racking – Process Computer Information System– RCP motor replacement– MSR and FW&CY heaters replacement– Cooling Towers extension– Replacement of Chillers (CGD of digital I&C)– MCR annunciators system replacement– Replacement of HD system I&C (new digital I&C) – 110kV field relocation– Digital Electro Hydraulic Turbine control

system replacement– Replacementt of the main electric generator stator

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Continuous NPP NEK ModernizationMajor Investment Projects

Ongoing and planned projects:– Main electric generator rotor replacement– Reactor Vessel Head Replacement– Emergency AC power system enhancement,

installation of the 3rd Diesel Generator– Electrical and I&C equipment replacement based

on EQ program analysis– RCS temperature measurement optimization,

RTD bypass removal– 400 kV switchyard reconstruction– The second main transformer replacement

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NEK working group – project team has been founded and started to work.

Based on the preliminary analysis results obtained up to now the following actions will be needed:• NEK will have to improve scope of available mobile equipment that can be used

for mitigation of emergency events that exceed the plant design basis:o Mobile DG units in order to improve availability of the 400V and 6,3kV

power sources.o Mobile pumps that could be used for water supply to the SG - Steam

Generators and to the containment building.o Mobile air compressors.o Additional protection, communication & measurement equipment for the

plant crew.• Implement plant modifications that will enable fast and effective usage of the

new mobile equipment (DGs, pumps and air compressors).• Revisions and amendments to the EOP and SAMG procedures.• Revision of the RERP (Radiological Emergency Response Plan)

Preparation of the additional PSR (Plant Safety Report) and its submission to the Slovenian nuclear regulatory body.

NUCLEAR POWER PLANT KRŠKO – NEKPost Fukushima Accident NEK Action Plan

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• Improved performance: availability 93%, automatic scrams 0, forced loss rate ≤1%, Outage duration 25days/18month,collective radiation exposure <0.5 man Sv/year.

• Investment of € 300-400 million in the next 10 years to increase nuclear safety, improve material condition, reduce environmental impact.

• Periodic safety review each 10 years, implementation of recommendations.

• Plant life extension to 40+10+10 years, manage change of generation. NEK application for the first ten years of life extension (from 2023 to 2033) was submitted to Slovenian nuclear regulatory body and NEK is waiting on response (expected in 2012).

• Effective on site waste management solutions for LILW and spent fuel.

NUCLEAR POWER PLANT KRŠKO – NEKMain objectives for the future

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This presentation will contribute to the TWG NPPIC meeting bycommenting three (see items 1, 3 and 5 below) out of the five topicsproposed by IAEA:

(1) I&C modernization projects in operating NPPs;

(2) I&C systems being installed in NPPs under construction;

(3) Country‘s plan to build new NPPs;

(4) I&C research and development projects; new I&C technologies;

(5) Recommendation to the IAEA regarding the content andformat of future I&C activities;

Introduction to TWG NPPIC MEETING TOPICS

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The current focus of all operating NPPs is:

SAFE OPERATION & ECONOMIC SURVIVAL.While producing electricity in a productive and efficient manner, operatingNPPs strictly follow safety and reliability requirements.The existing NPP‘s life is being extended from 40 to 50 and/or 60 years.In order to continue meeting safety and reliability requirements and at thesame time to optimize nuclear power plant operating costs, NPP licenseesmust be able to replace and upgrade equipment in a cost effective mannerusing approaches that reduce licensing and technology risks.Regardless the safety classification of the particular plant modernizationproject (SR or Non SR), the in-depth planning of upgrades or plantmodifications and their careful preparation and implementation withaugmented or SR quality manners that is supported by design changecontrol, plant configuration control from the design point of view anddocument control must be always applied, because when speaking aboutmodernization projects, such approach is the main contributor forsuccessful continuation of safe and reliable operation & economic survival.

TWG NPPIC MEETING TOPIC No. 1:I&C Modernization projects in operating NPPs

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Continuous NPP NEK plant modernizationMajor projects that contain significant I&C scope

Implemented since 2009, ongoing & planned:– Replacement of HD system I&C (new digital I&C) – SR Chillers replacement with CGD digital I&C– TCS (Turbine Control System) replacement – Replacement of TU supervisory instrumentation– Main electric generator monitoring and GN auxiliaries

control (expansion of digital TCS)– Expansion and upgrade of the fire detection system– I&C equipment replacement based on EQ program analysis– RTD bypass removal

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RECENTLY IMPLEMENTED PDEH(Programmable Digital Electro Hydraulic)

TCS (Turbine Control System)REPLACEMENT PROJECT

NEK Modification Number 500-TU-L

PDEH TCS was installed in outage 2009.NEK & WEC still work on resolution of some deficiencies

detected during the PDEH TCS on-line usage.It is expected that the last set of software corrections and

some minor hardware upgrades will be implemented in the outage 2012 (April).

*** Short project description follows ***

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SCOPE OF THE PROJECT 500-TU-L

The scope of project 500 TU-L can be enveloped with the basic DEH turbine control system (TCS) replacement and additional five functional items as listed below all amended with significant functional, reliability & HMI improvements: Replacement of the old DEH (Digital Electro Hydraulic) Mod II Turbine Control

System with the new PDEH (Programmable Digital Electro Hydraulic) system built by Westinghouse Electric Corporation on Emerson Ovation DCS platform.

Replacement of the old Turbine ETS (Emergency Trip System). Replacement of the old MSR (Moisture Separator Reheater) Control System. Integration of controls and indications that are used for remote control and testing

of 12 EX (Extraction Steam) valves within the new PDEH. Remote control and monitoring of the main electric generator hydrogen purge

system for which the new PDEH system provides HMI platform and programmable digital platform on which HMI and control algorithms will be implemented.

Implementation of the new PDEH system on background and foreground KFSS(Krško Full Scope Simulator).

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GOALS OF THE PROJECT IMPLEMENTATION

Redundant design of the PDEH TCS built with industry proven hardware and software components shall ensure immunity to single hardware failure and based on that the reliability and availability of the turbine control and turbine emergency trip systems will be improved.

Improved PDEH system reliability and availability shall significantly decrease probability of the occurrence of events with the following consequences:

– Disturbances in operator capabilities to control or monitor TG set.– Fault activations caused by failures in turbine control or protection systems.– Omission of control or protective action caused by failures in turbine control

or protection systems.– Plant power transient.– Plant trip (RX trip) as consequence of an unwanted turbine or generator trip.

PDEH shall ensure implementation and operability of large number of significantfunctional improvements and additions compared to the existing DEH, turbine ETS and MSR control.

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PDEH system shall decrease number and frequency of needed maintenanceactivities, thus making whole maintenance easier and cost effective.

PDEH system shall provide improved computerized HMI platform that presents state of the art for the NPP MCR applications. Enhanced PDEH HMI features shall reduce operator burden and provide additional functionalities. PDEH system shall ensure system scalability, upgradeability and expandability on all platform levels when and if needed in development of future digital I&C plant modifications.

PDEH system shall ensure flexible programmable digital platform with all needed hardware and software tools for design, development and process computer configuration control in compliance with NEK programs, that shall enable trained NEK personnel to develop, test and implement software changes and software expansions with new application software modules when and if needed.

Project 500-TU-L will be the pilot project for similar digital I&C upgrades that will definitely follow in NEK. This project will be used to exercise full scope of AQ PDS requirements and processes as they will be required in particular application, and then to use experience feedback from this project to improve and tune NEK programs and implementing procedures.

GOALS OF THE PROJECT IMPLEMENTATION(Continuation)

20Figure 1: PDEH System Architecture Layout

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PDEH SYSTEM SPECIFICS & IMPROVEMENTS AGAINST THE OLD DEH

PDEH TCS platform was built on Ovation® DCS platform, based on three redundant Ovation OCR400 controllers and rack-mount DELL Poweredge III 2950 servers used both for servers and OWS, and the most outstanding PDEH specifics and improvements are: Immunity to single hardware failure. Redundancy with diversification for the most important PDEH features Triple redundancy for all measurements that are included in turbine

protection scheme and in turbine control scheme, with sophisticated programmable median select logic and system response in the case of (multiple) signal failures that is defined based on results of FMEA (Failure Mode Effects Analysis) and FTA (Fault Tree Analysis).

Redundancy (two inputs) for all signals related to auxiliary controls and monitoring.

Significant improvement of the PDEH MCB & MCR HMI Continuous on-line equipment testing and troubleshooting with status/error

reporting. All equipment supplied from two uninterruptible power supply sources. PDEH TCS is expandable for future needs regarding addition of new I/O

signals and/or new pairs of Ovation® controllers (new DCS subsystems) as well as addition of new control and/or monitoring applications and HMI graphics for MCR monitors. New modification that was implemented in outage 2010 (October) and that was related to the main electric generator monitoring and generator auxiliaries control, has already added one more RIO (Remote I/O) cabinet and about 120 new I/O signals.

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Removal of mechanical turbine overspeed protection & interface diaphragm valve Installation of additional – second (diversified: different manufacturer and design)

turbine trip hydraulic manifold with four AST (Auto Stop Trip) solenoids. Former ETS turbine protection that was mostly based (except for turbine speed

and TG set axial rotor position) on pressure monitoring with pressure switches was replaced with pressure monitoring by triple redundant pressure transmitters.

Four governor valves were equipped with the redundant set of two LVDT (Linear Variable Differential Transformers) as position sensing devices.

Turbine latch sequence was modified and improved. Turbine protection on high acceleration has been introduced in order to anticipate

and prevent possible turbine overspeed and turbine trip on 110% of rated speed as consequence of the LDA event (Load Drop Anticipator - total or partial loss of load).

Two different scenarios related to the LDA have been recognized: opening of the switchyard breaker and or opening of the generator breaker and total loss of load.

Improved frequency control response (better sensitivity) or improved capabilities for PDEH TCS and NEK to participate in the electric grid primary frequency control according to the power utility requirements.

THE MOST IMPORTANT PDEH SYSTEM IMPROVEMENTS AGAINST THE OLD DEH

(Continuation #1)

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Initiated by operator, but after that automatic computer controlled execution of the whole sequence of STOP valves testing (and associated governor) on higher loads (up to 97%) than with the old DEH Mod II TCS (up to 92%).

Faster and smoother (regarding possible oscillations in HP turbine impulse pressure and reactor power) transfer from SINGLE to SEQUETIAL and vice versa transfer of governor valve positioning/control.

Monitoring, control and testing of twelve EX valves was removed from manual control panel behind MCB section A to the PDEH HMI platform (soft controls).

MSR control related to the controlled opening of four valves that are installed on the fresh steam MSR heating lines for two MSRs was improved.

H2 Purge Control was added as new functionality related to the remote operation of four solenoid valves and two CO2 heaters that are included in sequence and line-up related to the hydrogen purge out of the main electric generator.

Zero turbine speed detection and turning gear engagement. Reliability of HP turbine moisture detection and opening of HP turbine drain

valves was enhanced based on redundant temperature inputs. Monitoring, signalization and alarming related to the Auto Synchronization

sequence was improved. Supervision of the main electric generator and alarming based on calculated

generator capability curve was improved.

THE MOST IMPORTANT PDEH SYSTEM IMPROVEMENTS AGAINST THE OLD DEH

(Continuation #2)

24Figure 2: Old DEH & ETS (the last cabinet in row) Electronic I&C Cabinets

25Figure 3: Old DEH Cabinets Removed & Preparations for Installation of New PDEH Cabinets

26Figure 4: New PDEH Ovation Cabinets

27Figure 5: Front side of the PDEH Ovation cabinet with two redundant Ovation OCR400 controllers and I/O modules

28Figure 6: Rear side of the PDEH Ovation cabinet with

two redundant Power Supplies and I/O modules

29Figure 7: PDEH field cabling termination cabinet

30Figure 8: Old MCB Section A Layout with DEH HMI – before PDEH installation

31Figure 9: New MCB Section A Layout with the new PDEH HMI

32Figure 10: Detail of Old Turbine Control & Monitoring HMI Part of MCB Section A

33Figure 11: Old Turbine Control and Monitoring Devices That Were Removed

34Figure 12: Removal of Old DEH Turbine Control HMI and Other Monitoring Devices

35Figure 13: Detail of New Turbine Control & Monitoring PDEH HMI Part of MCB Section A

36Figure 14: Impacts of the PDEH Installation to the MCR – Main Control Room

37Figure 15: PDEH MCR Cabinets With Rack-Mount Servers and OWS CPUs

38Figure 16: HP Turbine Governor Pedestal With ETS XMTRs & AST blocks

39Figure 17: The second (newly installed) Emergency Trip Control block – AST2

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Figure 18: Triple redundant transmitters for turbine protection

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Figure 19: Redundant (double) LVDTs for Governor Valve position indication

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SOME PROJECT RELATED FIGURESSome characteristic project figures and statistics are listed below that can give better impression about the project scope and associated mostly installation efforts on all three PDEH platforms (BG KFSS, FG KFSS, plant PDEH): 900 meters of new metal tube type electric conduits with supports and hangers. 130 meters of new cable trays with their supports and hangers . 15.000 m of new multi-wire cables were installed and terminated. 45 old cables were rerouted. 106 old cables were re-terminated. 104 old cables were voided and pulled out of the existing routing. Approximately 5000 electrical terminations were made. Major Equipment installed and tested on all three platforms:

11 new cabinets with computers and I&C equipment. 3 redundant PLC (Ovation OCR400 Controller configurations). 25 rack mount Dell Poweredge 2950 servers. 3 rack mount Kontron terminals 11 computer network switches 1 desktop PC EWS (Engineering & Development Workstation). 8 MCB monitors (4 MCB + 4 MCB KFSS) and 2 hardwired functional keyboards 4 MCB desktop monitors (2 MCB + 2 MCB KFSS) AST turbine trip hydraulic manifold 24 new pressure transmitters, 1 new MW transducer, 6 new speed pick-ups

12 days from the very first day of old DEH TCS decommissioning until the first power-upof the new PDEH equipment, 18 days up to the start of SAT (Site Acceptance Testing).

Documentation: More than 1300 drawings, 59 manuals, TOP in 62 document binders

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LESSONS LEARNED REGARDING 500-TU-LNEK has recognized the following lessons learned: Current NEK organization is made to support activities associated with plant

operation and maintenance and it is not optimized to be able to efficiently support large development type plant design change projects. For such large development projects that have to be implemented in a limited time specific and project dedicated human resources should be assured that are in current NEK organization hardly available.

Although we used the most contemporary means of communications (E-mails, phone conferences, phone calls) for the project communication, NEK concluded that the best and the most efficient way for communication during the project development is joined work and discussion at the same table. NEK considers that there should be more of such joined working meetings of NEK and WEC experts.

Unavailability of some Ovation specific technical information that Emerson declares as proprietary and unavailable to the end user customers is not appropriate for the nuclear customers. Unlikely for non nuclear industry and even for some NPP that do not aim towards the excellence, whenever unwanted operational event or some failure occurs, NEK is extremely mobilized in order to obtain full understanding of the event or failure scenario, root cause answers and consequences. In order to continuously improve reliability and safety of NEK operation each unwanted operational event or equipment failure must result with corrective actions & lessons learned. Without availability of the full scope of currently missing Ovation related technical information that could be the problem for NEK.

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CONCLUSSIONS BASED ON 500-TU-LSolution for the augmented quality programmable digital systems is in full implementation of the regulatory related requirements and plant quality programs and implementing procedures, consistent implementation and documentation through the all life cycle processes, consistent configuration control, design change control and effective project planning and scheduling.There are no two identical NPP digital I&C upgrade projects and associated software solutions on two different plants that were implemented in different timeframe and that are 100% same. We can not just copy digital I&C upgrade solution from one plant to another plant without seriously reconsidering applicability of each and every functional topics and readjusting them when and if needed.Testing and V&V is very important, but quality of the software can not be achieved solely by the post development and post-installation testing.Regarding safe and reliable operation during the NPPs life that is being extended up to 60 years, all plant licensees have established very demanding quality requirements and expectations that are usually not common for conventional power plants and all NPPs aim towards excellence in all areas of plant life cycle. Regarding the I&C upgrades and modernizations, the following possibilities for significant improvement still exist: project management processes (contracting: reach up-front scope understanding, planning and scheduling, overall AE system design, software configuration control, document control, V&V,…), and production of good quality project customized technical documentation.

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The current status regarding plans for construction of new NPPs inRepublic of Slovenia is the following:

The idea about construction of second Krško NPP unit exists. The national - Slovenian long term program for energy supply is

under development. Looking from political aspects it is hard to believe that the

construction of second Krško NPP unit will become part ofnational program for long term energy supply withoutconfirming that idea with public consensus obtained on thenational referendum.

The Fukushima accident has definitely delayed any decisions inRepublic of Slovenia regarding the construction of new NPPsand at the current moment it is hard to say for how long.

TWG NPPIC MEETING TOPIC No. 3:Country‘s plan to build new NPPs

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Speaking about all operating NPPs that are in process or that already performed I&Cand HSI digitalization upgrades, there is a discrepancy between very positive potentialthat digital I&C and digital HSI could bring to the operating NPPs and feedback that weobtained after the NPP I&C modernization and exchange of operating experience withupgraded I&C. There are many benefits and successes obtained, but we are notsufficiently listening to the early warnings based on events that already happened.Obviously it is not enough that recommendations, guidelines, standards and reports inthat area exist, NPPs must be aware of them and they have to be implemented.IAEA and TWG participants should do their best in order to raise awareness aboutspecific aspects and questions of digital I&C modernization among which I would like torecommend and emphasize mostly the same as two years ago (TWG NPPIC 2009):

Augmented Quality up-front QA planning of all digital I&C and HSI upgradelife cycle phases (no matter if NSR or SR) should be strictly enforced.

Configuration Control of Programmable Digital Systems should be developedand implemented as part of overall Plant Configuration Control.

The NPP digital upgrades experience, NPPs operational feedback experienceand I&C experts knowledge exchange should be exchanged more openly.

TWG NPPIC MEETING TOPIC No. 5:RECOMMENDATIONS TO THE IAEA REGARDING THE CONTENT

AND FORMAT OF FUTURE I&C ACTIVITIES

IAEA TWG NPPIC should discuss and pass recommendations regarding thefrequently applied vendor‘s practices that the simple I&C technicaldocumentation is nowadays becoming not available for customers, becauseit is being declared by vendors as proprietary.

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END SLIDE

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