Page 207 - Dynamics and Control of Nuclear Reactors

15.3 Desk-top simulators 205

15.3.1.2 Using an IAEA simulator
Figs. 15.1 and 15.2 show typical screen displays for an IAEA PWR simulator and a
BWR simulator. These PC-based simulators were developed by Micro-Simulation
Technology [9].
The schematics display important plant parameters during a transient. Both
numerical values and plots of selected process variables and reactor power may
be displayed as needed and the information may be stored in data files. Both normal
operation and accident scenarios can be simulated. The simulation platform,
PCTRAN, was developed by Micro-Simulation Technology [15, 16] and is available
from IAEA for member nations.

15.3.2 Simulation of PWR and BWR plant transients

15.3.2.1 PWR simulation
The computer platform used by the IAEA for training purposes has the ability to sim-
ulate various dynamic features of a PWR. The variables that can be changed fall
under the following categories: basic, thermal, and rad (radiation) data. These vari-
ables affect the initial conditions and are monitored using the transient plots during
the run. The plots are displayed in real time, showing different variables as the sim-
ulation proceeds. The graphing options include axes scaling, labeling, selection of
variables, and saving the choices.
An example of load reduction transient in a typical PWR is shown in Fig. 15.3.
The simulation shows that reactor power follows the turbine demand. The effect
of temperature feedback is seen in the transient when the demand power changes.
Various accident scenarios can be simulated with this PC-based software. The
effect of the selected malfunction can be displayed using process variables that
are relevant to the selected scenario. While the malfunction is in place, new graphics
will appear to show the conditions of process variables. It is possible to take actions
to prevent the continuation of the malfunction, and thus avoid a severe accident
condition.
The simulation may be performed either in the manual or automatic mode by
selecting appropriate action buttons. It is necessary provide necessary information
to the program if run in the manual mode. It is possible to revert to automatic mode
at any time during the transient. The plant schematic visual aid displays variations in
certain parameters, such as water levels, valve actuation, control rod motion, etc.,
during plant transient.
All the graphical plots and raw data can be saved for future use.

15.3.2.2 BWR simulation
BWR simulation is more involved than the PWR simulation. One of the key param-
eters is the initial reactor power level, since this value determines the approach for
further power changes, either an increase or a decrease.
The “Power/Flow Map & Controls” option contains a graph that displays recir-
culation flow rate (%) versus reactor power (%). The program allows the choice of