Emergency and Preventive Reactor Protection Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 300

• The reception of technological process

control parameters and equipment condi-
tion data from sensors and/or adjacent in-
strumentation and control systems;

of all control rods into the core, causing a reac-
tor subcritical state and power unit shutdown. It
defines an essential role of the emergency reactor
protection in NPP safety assurance as the last way
to avoid the accident.
On the other hand, the cost of “false” power unit
shutdowns (unnecessary) due to false operation
of the emergency reactor protection, which can
be the result of failure or SHC E&PRP malfunc-
tion, is obvious.
It would lead to the necessity to regulate the
technical specification in such a way to provide
quality of the development, production, testing
and operation of SHC E&PRP, which correspond
to its role in safety assurance, and to make certain
that such correspondence is actually achieved.
Thus, one of the fundamental safety principles was
considered, according to which I&C systems and
its equipment should be designed, produced and
maintained in such a way, that their specification,
verification and validation, quality assurance,
quality control and reliability met their safety
classification.

• The forming and output from ERP or PRP

commands to adjacent I&C systems in case
of any conditions regimented in the appro-
priate algorithms of emergency or preven-
tive reactor protection;

• The archiving, display and data registration

on the technological process controlled
parameters, equipment condition, reactor
protections actuations, and the reasons of
such actuations;

• The continuous monitoring (diagnostics)

of its technical state, fault detection and
identiication, archiving, display and regis-
tration of diagnostics results;

• The data output into unit computer infor-

mation system (CIS) and personnel warn-
ing facilities in the main control room.

The preventive reactor protection is the func-
tion of normal operation (category B), aimed to
prevent the possibility of emergency in case of
the deviation of technological process parameters
beyond the admissible operational limits and/or
in case of normal operation conditions violation
set by the project. It is achieved by forced power
reduction and / or blocking of any commands,
which could initiate power increase.
The emergency reactor protection belongs to
the safety functions (category А) and activates in
the case of the violation of the provided design
limits or conditions, which cannot be eliminated
with the help of a relevant systems of normal opera-
tion (e.g., due to its failure), or in the case of the
events, which could lead to technical parameters
variation, being too fast for adequate response
of the systems of normal operation, and also in
case of violation of unit design conditions safety
operation. In such cases, ERP command should
be output, which initiates simultaneous insertion

BACKGROUND

Chapter 9 provides a short description of the
devices and systems performance, which fulfill
emergency and preventive reactor protection
functions, being a part of the reactor control and
protection system at the Ukrainian NPPs. This
chapter provides more detailed information about
the purpose, performed functions, technical speci-
fications, composition and structure of E&PRP
systems, as well as functional safety assurance on
the system life cycle stages.
The requirements to E&PRP systems and
SHC E&PRP are determined by common prop-
erties of safety important I&C systems and their
components, outlined in Chapter 3, and consider
the purpose, categories of performed functions
and safety class.