OECD Nuclear Energy Agency (NEA), Gesellschaft
für Anlagen und Reaktorsicherheit(GRS) mbH,
Penn State University (PSU)
KALININ-3 Coolant Transient Benchmark – Switching-off of One
of the Four Operating Main Circulation
Nominal Reactor Power
During the last several years a considerable effort was devoted and
progress has been made in various countries and organizations in
incorporating full three-dimensional (3D) reactor core models into
system transient codes. The coupled thermal-hydraulic (TH) and neutron
kinetics (NK) code systems allow performing of a "best-estimate"
calculation of interactions between the core behaviour and plant
dynamics. Several benchmarks have been developed to verify and validate
the capability of the coupled codes in order to analyze complex
transients with coupled core-plant interactions for different types of
The Nuclear Energy Agency (NEA) of the Organization for Economic
Cooperation and Development (OECD) has recently completed the VVER-1000
Coolant transient benchmark (V1000CT-1) and (V1000CT-2) for evaluating
coupled TH system NK codes by simulating transients at the Bulgarian
NPP Kozloduy Unit #6. The available real plant experimental data made
these benchmark problems very valuable.
This benchmark is a continuation of the above activities and it defines
a coupled code problem for further validation of thermal-hydraulics
system codes for application to Russian-designed VVER-1000 reactors
based on actual plant data from the Russian NPP Kalinin Unit #3
(Kalinin-3). The selected transient 'Switching-off of one Main
Circulation Pump (MCP)' is performed at a nominal power and leads to
asymmetric core conditions with broad ranges of the parameter changes.
The experimental data is very well documented. Measurements were
carried out with a quite high frequency and their uncertainties are
known for almost all measured parameters. This fact allows applying the
studied transient not only for validation purposes but also for
uncertainty analysis as a part of the NEA/OECD LWR Uncertainty Analysis
in Modelling (UAM) Benchmark.
This report provides the specifications for the international, coupled
VVER-1000 Coolant Transient (KALININ-3) benchmark problem. The
specification report has been prepared jointly by leading specialists
of the All-Russian Research Institute Nuclear Power Plant Operation
(VNIIAES), the Russian Research Centre "Kurchatov Institute"(KIAE), the
Gesellschaft für Anlagen und Reaktorsicherheit mbH (GRS) and the
Pennsylvania State University (PSU).
The specification covers the four exercises: point kinetics model
inputs, transient core calculations, transient coupled calculations,
and uncertainty analysis In addition, a CD-ROM is also made available
with the detailed data for the transient boundary conditions, decay
heat values as a function of time, and cross-section libraries.
In December 2008 the NEA Nuclear Science Committee (NSC) Bureau has
expressed support for the coupled Kalinin-3 benchmark problem in
general to become an international standard problem for validation of
the best-estimate safety codes. The Working Party on Scientific Issues
of Reactor Systems (WPRS) discussed in its February 2009 meeting the
proposal and endorsed it as it is of particular importance for the last
phase of the Uncertainty Analysis in Modelling (UAM) activities.
Background and Purpose of the Benchmark
Under the guidance of the NEA/OECD many benchmarks have been performed
concerning the application of coupled 3D TH/NK codes. Some of them have
utilized code-to-code comparisons, others have compared code
predictions with real measured data.
Most transients in a VVER reactor can be properly analyzed with a
system thermal-hydraulics code, with simplified neutron kinetics models
(point kinetics). A few specific transients require more advanced
modeling for neutron kinetics for a proper description. A coupled
thermal-hydraulics 3D neutron kinetics code would be the right tool for
The proposed benchmark problem has already been analyzed by the coupled
system code ATHLET-BIPR-VVER. This allowed a better fixing of the
Benchmark Specifications. However, within the present context the
results of participants will be compared against the measurements.
Interesting additional problems have to be solved in order to perform
correctly the comparisons. This experience is incorporated in the text
of the specification.
The reference problem chosen for simulation is the MCP #1 switching off
at nominal power when the other three main coolant pumps are in
operation, which is a real transient of an operating VVER-1000 power
plant. This event is characterized by rapid rearrangement of the
coolant flow through the reactor pressure vessel resulting in a coolant
temperature change, which is spatially dependent. This leads to
insertion of spatially distributed positive reactivity due to the
modeled feedback mechanisms and a non-symmetric power distribution.
Simulation of the transient requires evaluation of core response from a
multi-dimensional perspective (coupled 3D neutronics/core
thermal-hydraulics) supplemented by a one-dimensional (1D) simulation
of the remainder of the reactor coolant system. The purpose of this
benchmark is four-fold:
To verify the capability of system codes to analyze
complex transients with coupled core-plant interactions and complicated
fluid mixing phenomena.
To fully test the 3D neutronics/thermal-hydraulic
To evaluate discrepancies between predictions of
the coupled codes in best-estimate transient simulations with measured
To perform uncertainty analysis having at disposal
not only the measured values but also their accuracy
The benchmark includes a set of input data for the NPP Kalinin-3 and
consists of four exercises
1 - Point kinetics plant simulation
The purpose of this exercise
is to test the primary and secondary system model responses. Provided
are compatible point kinetics model inputs, which preserve the axial,
and radial power distribution, and CR #10 and #9 reactivity obtained
using a 3D code neutronics model and a complete system description.
The purpose of this exercise
is to model the core and the vessel only. Inlet and outlet core
transient boundary conditions are provided by the benchmark team on the
basis of calculations performed with the ATHLET-BIPR-VVER coupled code
system: alternatively the participants can apply the measured data. HFP
state (Exercise #2a) of the core is required for comparison.
This exercise combines
elements of the first two exercises of this benchmark and represents an
analysis of the transient in its entirety. For participants that have
already taken part in the Kozloduy-6 NEA/OECD Benchmark , it is
suggested to start directly with this exercise. As a preliminary step
for these latter participants it is recommended to perform steady state
core calculations at HZP state (Exercise #3a), HFP (Exercise #3b) and
deliver the results for comparisons. Exercise #3a and Exercise #3b will
ensure and check out the correct application of the cross section
libraries, the core loading and the core design geometry.
Exercise 4 - Performing
of uncertainty analysis for the purpose of Phase-III
Phase) of the OECD Benchmark for Uncertainty Analysis in Best -Estimate
Modelling (UAM) for Design, Operation
and Safety Analysis of LWRs.
The aim and the specification
of this exercise will be described in a separate volume, which will
depict the state of the art of the results and requirements identified
after performing the UAM Phases I and II.
The specification document
(Edition 1) that covers Exercises 1-3 of the OECD Kalinin-3 VVER-1000
Coupled Code Benchmark and the corresponding experimental database and
report will be available to participants