Areva EPR

Limitation functions and protection
of the reactor (level 1)
Four-channel limitation functions are implemented to rule out
impermissible operational conditions that would otherwise cause
reactor trip actions to be initiated. They also ensure that process
variables are kept within the range on which the safety analysis is
based, and they initiate actions to counteract disturbances that are
not so serious as to require the protection system to trip the reactor.
The protection system counteracts accident conditions, first by
tripping the reactor, then by initiating event-specific measures. As
far as reasonably possible, two diverse initiation criteria are available
for every postulated accident condition.
Reactor trip is actuated by cutting off the power to the electromagnetic
gripping coils of the control rod drive mechanisms. All the
control assemblies drop into the core under their own weight and
instantaneously stop the chain reaction.
† An enhanced and optimized degree
of automated plant control, associated
to an advanced Man-Machine interface
for operator information and action.
Man-Machine interface (level 2)
At the design stage of the EPR, due consideration has been given
to the human factor for enhancing the reliability of operators’ actions,
during operation, testing and maintenance phases. This is achieved
by applying appropriate ergonomic design principles and providing
sufficiently long periods of time for the operators’ response to
encountered situations or events.
Sufficient and appropriate information is made available to the
operators for their clear understanding of the actual plant status,
including in the case of a severe accident, and for a relevant
assessment of the effects of their actions.
The plant process is supervised and controlled from the Main Control
Room which is equipped, regarding information and control, with:
• two screen-based workstations for the operators,
•a plant overview panel which gives information on the status and
main parameters of the plant,
•a screen-based workstation for presenting information to the shift
supervisor and the safety engineer,
• an additional workstation for a third operator to monitor auxiliary
systems.
The Remote Shutdown Station is provided with the same information
and data on the process as the Main Control Room.
The plant also comprises a Technical Support Centre. It is a room
with access to all the data concerning the process and its control,
to be used, in case of accident, by the technical team in charge of
analysing the plant conditions and supporting the post accident
management.
A computerized screen-based control room designed to maximize operator efficiency. Chooz B1, France (N4, 1,500 MWe).
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