1.7 Cybersecurity of Power Facilities: Past, Present, and Future
81
Defense-in-depth concept provides limits within the frameworks of each level
(echelon) of consequences of potential failures of hardware and human errors and
guarantees that single time hardware failure or human error shall not cause hazardous
consequences. In case of numerous human errors and\or hardware failures applying of
this principle reduces the probability of adverse impact at the stuff, local community,
and environment.
Defense-—in-depth concept applies not only at the hardware and systems influencing the safety of nuclear power plants, but also at human activities (like organization of operation, administration monitoring, training and qualification of the
stuff).
Cause analysis of large-scale accidents demonstrated that their course and consequences happened to be in direct dependence upon how correctly the activities as
stipulated by defense-in-depth concept were applied.
The first level of nuclear power plant protection involves as follows:
(a) Perfectly prepared nuclear power plant design project where all design solutions
are well grounded and seem to be a way conventional and traditional in terms
of safety;
(b) Level of training and qualification of the stuff.
In the cause of the technological process, the first level of protection of the physical
processes is assured due to holding the performances of the nuclear power plant within
the specified rated design limits, when no threat of damaging the barriers exists. The
efficiency of the first level of protection is significantly influenced by the advancement
of internal self-protectiveness properties of reactor unit, i.e., properties defining the
stability against dangerous deviations of the parameters of the technological process
and ability to parameters restoration within the tolerable values within the admissible
limits.
The second level of protection is assuring availability of the hardware and systems
essential for plant safety through troubleshooting. At this level, it is important to
control properly power plant when deviations from the conditions of normal routine
operation occur, and the employees took the measures for their elimination in good
time manner. Technically the second level is ensured by booking the hardware and
systems and availability of diagnostics systems to check the status of elements and
hardware.
The third level of nuclear power plant protection is safeguarded by safety systems
envisaged by the plant project. Its target is to prevent escalating of deviations from
conditions of routine operation into Design Basis Accidents and Design Basis Accidents into Beyond Design Basis Accidents. At this level, the main goals are emergency shutdown of reactor, heat dissipation from the reactor by means of special
systems, accumulation of radioactive substances inside the premises of facilities of
the nuclear power plant as the plant project specified them.
The fourth level of Defence-in-Depth protection of the nuclear power plant is
the so-called accidents management. This level of plant protection is safeguarded
by scheduled and tried and true activities to control the development of beyond
design basis accidents. These activities imply maintaining the serviceable state of
81
Defense-in-depth concept provides limits within the frameworks of each level
(echelon) of consequences of potential failures of hardware and human errors and
guarantees that single time hardware failure or human error shall not cause hazardous
consequences. In case of numerous human errors and\or hardware failures applying of
this principle reduces the probability of adverse impact at the stuff, local community,
and environment.
Defense-—in-depth concept applies not only at the hardware and systems influencing the safety of nuclear power plants, but also at human activities (like organization of operation, administration monitoring, training and qualification of the
stuff).
Cause analysis of large-scale accidents demonstrated that their course and consequences happened to be in direct dependence upon how correctly the activities as
stipulated by defense-in-depth concept were applied.
The first level of nuclear power plant protection involves as follows:
(a) Perfectly prepared nuclear power plant design project where all design solutions
are well grounded and seem to be a way conventional and traditional in terms
of safety;
(b) Level of training and qualification of the stuff.
In the cause of the technological process, the first level of protection of the physical
processes is assured due to holding the performances of the nuclear power plant within
the specified rated design limits, when no threat of damaging the barriers exists. The
efficiency of the first level of protection is significantly influenced by the advancement
of internal self-protectiveness properties of reactor unit, i.e., properties defining the
stability against dangerous deviations of the parameters of the technological process
and ability to parameters restoration within the tolerable values within the admissible
limits.
The second level of protection is assuring availability of the hardware and systems
essential for plant safety through troubleshooting. At this level, it is important to
control properly power plant when deviations from the conditions of normal routine
operation occur, and the employees took the measures for their elimination in good
time manner. Technically the second level is ensured by booking the hardware and
systems and availability of diagnostics systems to check the status of elements and
hardware.
The third level of nuclear power plant protection is safeguarded by safety systems
envisaged by the plant project. Its target is to prevent escalating of deviations from
conditions of routine operation into Design Basis Accidents and Design Basis Accidents into Beyond Design Basis Accidents. At this level, the main goals are emergency shutdown of reactor, heat dissipation from the reactor by means of special
systems, accumulation of radioactive substances inside the premises of facilities of
the nuclear power plant as the plant project specified them.
The fourth level of Defence-in-Depth protection of the nuclear power plant is
the so-called accidents management. This level of plant protection is safeguarded
by scheduled and tried and true activities to control the development of beyond
design basis accidents. These activities imply maintaining the serviceable state of