25 years of Experience in the Use of Self-developed PC ... · PDF fileSelf-developed PC Based Basic Principle Simulators ... • nuclear power plant training centers for NPP ... •

25 years of Experience in the Use of

Self-developed PC Based Basic

Principle Simulators

Szabolcs Czifrus and Sándor Fehér

Budapest University of Technology and Economics (BME)

Institute of Nuclear Techniques (NTI)

Technical Meeting on Developing a Systematic Education and Training

Approach Using Personal Computer Based Simulators for Nuclear Power

Programmes

15-19 May 217, IAEA, Vienna

Budapest University of Technology

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IntroductionIndustrial background

• 4 VVER-440 type units (4x500 MWe) in operation since 1982 - 1987

• 46% share in the domestic electric energy production

• Continuous upgrading of safety and production performance through innovative development

• Excellent availability and safety indicators

• Extended service time (30 → 50 years)

• Strong scientific-educational system and associated infrastructure

• Maintenance Training Centre with full size reactorcomponents

• Extensive knowledge and experiences accumulated from more than 100 reactor-years of operation

• Two new VVER-1200 units are planned

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IntroductionTraining background

• The Institute of Nuclear Techniques (NTI) of the Budapest University of Technology and Economics (BME) is the leading organization in nuclear training in Hungary since the 1970s

• The Institute operates a small reactor facility, which is equipped with various laboratories

• The Training Reactor (100 kW) started operation in 1971, provides place for reactor and radiation related exercises for undergraduate and graduate students

• NTI is also involved in research in fields as Monte Carlo calculations, thermal-hydraulics/CFD analysis, radiochemistry, Gen IV reactor research and development, fusion research and medical physics.

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Introduction and historyBasic principle simulators at NTI

PC-based basic principle simulators have been developed for over 25 years at the Institute of Nuclear Techniques (NTI BME) with two main goals:

• provide the nuclear engineering education with tools capable to illustrate the fundamental physical processes of an NPP

• serve the regular basic training/retraining of the technical personnel of NPP Paks

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Introduction and history

Simulators

In the last three decades, five different simulators have been developed at NTI:

• PC2 – primary circuit basic principle simulator (DOS, 1987-88);• demonstration of the dynamic processes of the primary circuit

• STEGENA – steam generator analyzer (’part task simulator’) (DOS, 1991-93);• detailed studies on the thermodynamic and thermal-hydraulic processes of the steam

generator

• SSIM – secondary circuit basic principle simulator (MS Windows, 1993-95);• dynamic processes of the secondary circuit in fine detail

• PC2 for Windows – primary circuit basic principle simulator with a more complexmodel (MS Windows, 1997-99);

• REMEG – reactor trip analyzer (DOS, 1989-96).

All of above (except REMEG) are related to VVER-440

The fundamental processes, construction and control principles of a PWR with the aid of a VVER-440 as example can be studied.

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Integration of the simulators into education

• Elaborate educational concepts and student exercises belong to all four simulators

• The simulators and educational aids have proven to be useful and effective in nuclear engineering education at BME and for retraining at Paks NPP

• Systematic approach in training: students study reactor physics, measuringmethods, thermal hydraulics etc.

• The simulators have been integrated into the training courses (both in Hungarian and in English) of our Institute for over 25 years

• Most of the BME engineering/physics students study with the simulators a fewtimes during their studies, each occasion being approximately four hours long.

• The simulators are also used in• Post-graduate courses• Continuing education for engineers• International courses• Demonstrations, exibitions, „shows”

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PC2 – primary circuit basic principle simulator for NPP

fundamentals training

• PC2 is an educational tool designed for use in

• nuclear engineering higher education and

• nuclear power plant training centers for NPP fundamentals training

• The PC2 package consists of a software (executable under DOS or in DOSBoxunder MS Windows) and educational exercises. The PC2 program runs as an interactive and real-time simulator capable to illustrate the fundamental physical processes going on in the primary circuit of a PWR nuclear power plant.

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The simulation model was designed to demonstrate a wide range of primary circuit operations, control of the plant and response of the system to malfunctions. Capabilities include reactor start-up, power range operations and study of xenon-poisoning in accelerated mode. The most important simulated systems and components:

• Reactor core and fuel

• Control rods

• Pressurizer, including cold water injectors and electric heaters

• Steam generators

• Boron control system

• Main circulating pumps

• Primary circuit piping

• Instrumentation, control and safety system

• Turbine main regulating valve

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In order to improve effectiveness of training, PC2 was furnished with the following important features:

• Modification of program constants (eg. Doppler),

• Freeze/continue the simulation,

• Save simulation history in file,

• Playback previously saved exercise,

• Restart simulation under the same conditions,

• Real-time, fast time, slow-time,

• Snapshot and backtrack.

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Based on experiences accumulated in basic principle training and gained during the first courses, a training program consisting of 10 exercises were developed:

1) Introductory exercise (a survey, how to use, extent of the model)

2) The effect of reactor physical parameters (delayed neutron fraction, neutron generation time, etc.) on the operational characteristics of the primary circuit

3) The effect of reactivity coefficients (Doppler, moderator temperature) on the operational characteristics of the primary circuit

4) Study of self-control capability and power control system

5) Study of Xe-poisoning from reactor physics aspect

6) The effect of Xe-poisoning on the operation

7) Critical experiment and reactivity measurements

8) Investigation of different operational situations

9) Study of main circulating pumps breakdown transients

10) Study of emergency shutdown, turbine breakdown, etc.

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STEGENA - part task simulator/analyzer for the

steam generator of a VVER-440 type NPP

• Can be considered as a simulator/analyzer program (’part task simulator’),

• Detailed studies on the thermodynamic and thermal-hydraulic processes going on in the steam generator of a VVER-440 nuclear power plant.

• The simulation model has been designed to demonstrate a wide range of steam generator operation:

• heat transfer from the primary to secondary circuit,

• steam generation on the secondary side,

• feed-water input,

• steam extraction,

• measuring and control of the secondary water level

are all comprehensively modelled.

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Main graphic screen of the STEGENA simulation program displaying the scheme and the most important parameters of the steam generator.

The auxiliary diagram in the lower right quarter shows the temperature difference between the primary and secondary coolants along the coolant tubes.


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• Heat transfer from the primary to the secondary side: heat transfer equations are solved in one-dimension (along the primary coolant tubes), thus the program illustrates not only the time dependence but partly the spatial dependence of the processes, too. This feature is of special importance in making the model more realistic.

• The simulation program allows the user to set the values of some construction parameters of the steam generator, e.g. the inner and outer diameter, the heat transfer coefficient and the number of the primary coolant tubes are all changeable.

• Fouling, leakage from primary to secondary side and leakage originated radioactivity in the secondary circuit can be taken into account.

• In order to use the STEGENA simulator more efficiently a training program consisting of six student exercises has been developed.

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Auxiliary diagrams/tables available in the STEGENA:

a) Temperature difference between the primary and secondary coolants along the coolant tubes,

b) Temperature of the primary and secondary coolants as a function of thermal power,

c) Heat transfer through the pipe wall,

d) Table of most important parameters.


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SSIM – basic principle simulator for the secondary circuit

of a VVER-440 type NPP

• SSIM illustrates non-stationary thermodynamic and thermal-hydraulic processes of the secondary circuit of a VVER-440 nuclear power plant

• SSIM models only one of the two (independent, saturated steam) turbines with the corresponding feed-water system and three steam generators in order to save computing power

• The SSIM was run under 32-bit MS Windows and made efficient use of the graphic capabilities of these operating systems:

• 17 different schemes showing main components of the secondary circuit, and

• 29 auxiliary diagrams related to these components

can be displayed.

• Using these schemes and additional time-diagrams provided by the program more than 300 different parameters can be followed and analyzed as a function of time.

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Main scheme window of the SSIM simulator showing the main components and their connections:

a) 3 steam generators

b) All HP and LP turbine stages

c) Moisture separator and reheater

d) Turbine and generator axle,

e) Condenser

f) 8 feed-water pre-heaters

g) Feed-water tank with degasser


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Typical screen of the SSIM simulator with the scheme of HP turbine and its important process parameters.

Auxiliary diagrams show turbine stage power, moisture content of the steam in the turbine stages, steam pressure in the turbine stages, and some process parameters as functions of time.


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• Stationary and non-stationary processes can be studied.

• The user can interact with the simulated processes, changing the values of various parameters (e.g. reactor thermal power, turbine load, temperature and flow rate of condenser feedwater, etc.)

• Failure of different componentsmay be initiated

• Detailed schemes illustrate the structure and important process parameters.

• Diagrams show the thermodynamic characteristics of main components :

• Moisture content, turbine stage power, steam flow rate, steam temperature and pressure in HP and LP turbines,

• Surface area - temperature and thermal power - temperature diagrams for the heat exchangers.

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• The model is extended to simulate the following control systems:

• control of the water level in the

• condenser sump,

• feed-water tank and

• steam generators,

• and control of the turbine for-pressure.

These control systems can be switched off or their parameters can be modified by the user.

• SSIM package includes a detailed model description and a training program consisting of 10 different student exercises.

• This offers more than 40 hours exercises applicable in nuclear engineering education and nuclear power plant personnel retraining.

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PC2 for Windows – primary circuit basic principle

simulator with a more complex model

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Typical screen of the ’PC2 for Windows’ simulator with the ’graphs window’, scheme of primary circuit, reactor, pressurizer and the diagram of temperature distribution in a fuel pin, its cladding and coolant around it.

The six primary loops are modelled separately (accounting for the interactions),

with the main circulating pumps and steam generators

More realistic modelling

of the main circulating

pumps


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Reactor window of the ’PC2 for Windows’ simulator with the diagram of vertical distribution of the fuel and coolant average temperature.

Thermal-hydraulics modelling of the primary coolant and of the steam-generators

can account for the reverse flow in case of pump failure – in case of drop of all

pumps, natural circulation is

modelled correctly


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Pressurizer window of the ’PC2 for Windows’ simulator with the related important parameters (water level, heater power, pressure, and diverse mass flow rates).

The loops are modelled by

dividing the primary circuit to 84

control volumes; the pressurizer

phenomena are modelled using

non-equillibrium thermal-hydraulics

The simulator software is

executable under 32-bit MS

Windows.


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Scheme of the primary circuit loops in the’PC2 for Windows’ simulator with the most important thermal-hydraulics operating parameters of

a) steam generators (fresh steam production rate, fresh steam pressure, power transmitted through the generator, primary coolant inlet and outlet temperature);

b) main circulating pumps (speed of the pump (revolution per minute), coolant mass flow rate and pressure rise); and

c) the reactor (thermal power, coolant inlet and outlet temperature, coolant mass flow rate and pressure drop in the reactor vessel.


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Diagrams of vertical temperature profiles of the fuel pins and the coolant for different subchannels in the reactor.


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REMEG – reactor trip analyzer

• The program solves the coupled system of point kinetic equation with 6 delayed neutron groups and the equations of heat transfer from the fuel pin to coolant through the cladding for a reactor trip caused by a reactivity insertion.

• The time dependence of the reactivity insertion can be given as input.

• The user can modify the default values of nuclear, reactor physics and thermal-hydraulics parameters:

• Effective delayed neutron fraction

• Moderator and fuel temperature coefficients and their temperaturedependence

• Heat transfer coeffcients between fuel-clad and clad-coolant

• Specific heat of materials and their temperature dependence

• The simulator software is executable under DOS or in DOSBox under MS Windows.

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REMEG – reactor trip analyzer

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Reactor power changes duringthree different trips

Reactor power and fuel temperature changes during four different trips


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Some pictures from the 25 year history

of the PC2 simulator

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Classroom training using the PC2 simulator in the Institute of Nuclear Techniques


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Some pictures from the 25 year history

of the PC2 simulator

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Students from Vietnam during and after a classroom training using the PC2 simulator in the Institute of Nuclear Techniques


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Experience accumulated

• A large amount of experience on both the development and application of simulators have accumulated at NTI in the last two decades.

• Interesting fact: even today the most often and most widespread used simulator is the one developed first, ie. the PC2 primary circuit simulator.

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Experience accumulatedWhy is PC2 a „popular” simulator?

We believe that this fact is caused by two circumstances:

• The calculation model of this simulator is practically analog to the volume of knowledge presented during our lectures on Reactor physics (theory) and Thermal-hydraulics

• The user interface is simple enough so that student can learn it very quickly and thus they may gain interesting simulation experience and new knowledge even during a single 4-hour-long exercise

• With more complex tools, such as the simulator ’PC2 for Windows’, getting to know the controls may take several hours; such tools are only suitable for longer courses (which span several occasions)

• Another intelligent trait of this simulator is that the graphics screen representing the time behavior of physics quantities is very easy to understand due to the well thought-out ergonomic design

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Experience accumulated

The 25 year experience „purified” the range of originally developed 10 exercises.

The exercises, which conform mostly to the theoretical and laboratory courses, and which are most often used in the education are the following:

• Study of the effect of reactivity feedback on the operational parameters of the primary circuit,

• Analysis of the self-regulating ability of the reactor and the power control system,

• Study of the phenomenon of xenon poisoning in reactor physics and operational aspects.

These exercises have become fundamental elements in the Hungarian and English courses on nuclear energy at our Institute.

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Renewal of the basic principle simulator PC2

Need for renewal

• The basic principle simulator PC2, which is used most often at our Institute, was developed in DOS operating environment and in Fortran source code in the second half of 1980s.

• The renewal was absolutely necessary since today it is practically impossible to run such programs on modern, mostly 64-bit architectures without functional errors.

• A plan for the renewal was developed about a decade ago. Actual work only started at the end of 2015 in frame of the National Nuclear Research Programme

• The renewal is practically equivalent to fully replanning and recoding the program.

• If the financial resources allow, we will renew the secondary circuit simulator SSIM, as well.

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Development principles

Based on our earlier software development experience, the most important planning and development principles during the renewal were the following:

• modularity,

• standardization and

• portability (platform-independence).

According to our intention, these principles help to develop a simulator program package, which is stable, maintainable for a long time and which can be developed further.

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Development principles

Modularity means

• the option to use various programming languages (mainly C/C++ and Fortran);

• handling of the functionally separable part as separate units; and

• modular handling of the units of the simulation model in order that simpler or more complex simulations may be possible to run on the same software, according to the requirements of the application.

Standardization is mainly used for the programming languages. When writing the C++ sources, we used the 2011 C++ standard, while for Fortran, the Fortran95 standards and related recommendations were applied.

Due to portability requirements we used only types of software which are equally available for operating systems MS Windows, Linux and OSX.

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Software development tools

According to the above specified principles and aspects the following software development tools were chosen and used:

• C++ and Fortran compilers (GCC/Gfortran) of the GNU Operating System [GNU16];

• Code::Blocks – a free, open source, cross platform integrated development environment (IDE) [CdB16] – for the maintenance of source codes;

• FLTK (Fast Light Toolkit) – a cross-platform widget (graphical control element) library (GUI) [FLT16] – for the creation of user interface of the simulator (which serves for, among others, setting of simulation parameters and initial values of some simulated variables);

• Cairo(Graphics) – an open source, vector graphics-based, device independent, 2D graphics programing library (API) [Cai16] – for the visualization and animation of graphical schemes and plotting;

• ZeroMQ – a high-performance asynchronous messaging library [ZMQ16] – for the communication between the simulation model computing and user interface (visualization/interaction) program modules.

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Due to the development principles and applied software tools, the new simulator version (named provisionally PC2+) has the following characteristics:

• Platform-independent (momentarily tested on Windows and Linux systems);

• 32-bit and 64-bit versions equally available;

• There is fast, message-based communication between the user interface (screen) program unit and the simulation model computing program block;

• The user screen and the model are two separate programs (executable codes), which may run on a single or on two different computers as well (in the latter case, TCP/IP network connection must exist between the computers);

• Edge smoothed vector graphics representation, prepared to appear on HIGH DPI monitors.

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Essential characteristics and features of the renewed PC2+ simulator


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Redesign and restructuring of the simulator program

• The original PC2 was born as a result of organic development – the computationalmodel, design and structure of the program was formed during the developmentand application

• Some functions were not structured in the best way

• It was necessary to do a full recoding

• The program structure could be carefully designed in a most up-to-date manner

• Using modern software technology

• The computational model, user interaction, ergonomy of graphical screenswere reconsidered with a systematic aproach

• More than 25 years of experience accumulated with PC2 in training/educationplayed a very important role in this process

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The beta-version of the new simulator is ready

It has two main structural components:

• A program doing the model computations, written in Fortran95

• The graphical user interface (GUI), written in C++

The two components are controlled by a C++ program

The user interface and the model are two separate programs (executable codes), which may run on a single or on two different computers as well (in the latter case, TCP/IP network connection must exist between the computers).

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Logical structure of the renewed PC2+ simulator program


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User interface of the new PC2+ simulator

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Primary circuit scheme in the renewed PC2+ simulator


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Reactor scheme in the renewed PC2+ simulator


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Plot screen in the renewed PC2+ simulator


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Educational aspects and considerations

• In some cases parts or functions of a simulator may be too difficult to understand for students at lower levels of education.

• For such cases we consider it very important that certain functions of the simulator can be turned on or off, depending on the level of education.

• In this way, the instructor can adjust the amount of information to convey during the training session to the course participants.

• As an example we may mention the temperature dependence of reactivity coefficients. In courses/training sessions short of time, constant coefficients (in lieu of the temperature dependent ones) may be used, depending on the consideration of the instructor.

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The scope of simulation of new PC2+ simulator is practically the same as that of PC2 . At the same time, the new simulator has various minor model extensions and new features compared to the old program, most of which are of didactical importance:

• Now the simulation can take into account the dependence of vertical power profile on the burnup

• The neutron flux depression effect of the control and safety rods is modelled

• The remanent heat power is now modelled with a more accurate scheme

• For modelling reactivity feedbacks and boron worth, two and three (more and more complex) levels can be selected, depending on the level of knowledge ofstudents and training goal

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Model extensions and new didactical features of

the renewed PC2+ simulator


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Modelling the dependence of vertical power profile on the burnup

The undistorted vertical power profilecan be distorted by the user with a simple model according to theburnup level


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Modelling neutron flux depression effect of the control and safety

rods in the PC2+ simulator

Change of vertical profile of fuel temperature after a SCRAM(test results of the reactor kinetic and thermal-hydraulic computing modul of the PC2+ program).

The time evolution of the profilewell visualizes the effect of theinserted control rods on the neutron flux / power profile / fueltemperature


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Remanent heat power modelling in the new PC2+ simulator

Now the decay heat power is modelled with a significantly better formula foundin NUREG/CR-6999, US NRC Regulatory Guide 3.54 [NRC10]

The contribution of fission products to the decay heat power, uncorrected for neutron capture, is calculated from the individual contributions from fission of the four major fissionable isotopes in low-enriched uranium fuel: 235U, 239Pu, 238U, and 241Pu. These four actinides account for more than 99% of the fissions in typical LWR fuel

The percentage of the above isotopes in the computational model is set toaverage burnup level (20 MWday/kg(HM) )


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Conclusions

• Five simulators were developed at BME NTI

• Along with the programs, training materials / exercises were also worked out

• More than a thousand students have been trained

• They have been applied for short courses, BSc/MSc education, fundamentalstraining, at exibitions

• Very good experience

• Based on the experience, the first simulator is being renewed

• According to the replanning and recoding, the quality of simulator and details of the documentation have increased considerably

• Eight manuals will be developed for exercises with the new simulator

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References

[Cai16] Cairo - A 2D graphics library with support for multiple output devices; http://cairographics.org/

[CdB16] Code::Blocks - The open source, cross platform, free C, C++ and Fortran IDE; http://www.codeblocks.org/

[FLT16] Fast Light Toolkit - A cross-platform C++ GUI toolkit for UNIX®/Linux®

(X11), Microsoft® Windows®, and MacOS® X; http://www.fltk.org/,

[GNU16] GNU Operating System; http://www.gnu.org

[NRC10] I.C. Gauld, B.D. Murphy (U.S.NRC): Technical Basis for a Proposed Expansion of Regulatory Guide 3.54 – Decay Heat Generation in an Independent Spent Fuel Storage Installation; NUREG/CR-6999, ORNL/TM-2007/231, Oak Ridge National Laboratory (February 2010)

[ZMQ16] ØMQ - Distributed Messaging; http://zeromq.org/

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Documents

25 years of Experience in the Use of Self-developed PC ... · PDF fileSelf-developed PC Based Basic Principle Simulators ... • nuclear power plant training centers for NPP ... •