Rod Group and Individual Control System - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 325

decreasing order of indices until 3 CR of group 1
reach lower limit switch position or until they exit
this mode by the operator's initiative. CR group,
which are already in lower limit switch position,
for example, dropped earlier by the command of
accelerated preventive protection, is excluded from
the design order. If such drop takes place during
downwards movement of the groups, the main
group stays the previously selected CR group; if
the group, which was the main at the moment was
dropped, a new main group becomes a group with
the closest lower sequence number.
Control commands to control rod drives
are formed in rod group and individual control
(RG&IC) system. Automatic control by the com-
mand PRP1 from the adjacent E&PRP system
or by the command of RPwU from the adjacent
RPwCUL&APP system provides moving of the
groups downwards in the design order starting
from the group, which has the highest sequence
number and is not in lower limit switch position.
During the action of PRP1 and RPwU the
commands of automatic control B↑ and D↓ are
blocked from RPwCUL&APP system and from
group control key. Blocking of automatic control
commands can also be performed by the opera-
tor with the help of the key on remote control in
the main control room (MCR) premises. In case
of absence of PRP1 and RPwU commands and
unlocked commands of automatic control, the
latter initiate (by command B↑) or lowering (by
command D↓) influence to main and auxiliary
groups, as well as the group, which provide CR
“dragging” (if required).
CR group manual control mode provides group
control of the position of any CR group selected
by the operator or individual control of the posi-
tion of any selected CR.
Selection of CR group is performed by set-
ting up the switcher on remote control in one of
the positions (from 1 to 10), which corresponds
to the group number control over, which will be
performed via group control key, for example, can
be selected a group dropped by the signal from

accelerated preventive protection for its lift to the
design level. While working in the automatic mode
for manual control can be selected a group, which
is auxiliary (or a group, in which CR “dragging” is
provided). For example, if some CR delayed from
the positions of other CR of the group, operator
chooses this group and drags such CR to ULS
(or LLS) positions holding the group control key
in B↑ (or D↓ accordingly) direction. Commands
from the group control key influence only the
selected CR group. Selection of the group for
manual control does not influence the conditions
and sequence of group movement by the automatic
control commands PRP1, RPwU, B↑ or D↓. In
case of simultaneous commands entry the higher
priority have PRP1, RPwU and D↓ commands in
comparison with B↑.
Selection of CR for individual control is per-
formed on remote control located in MCR, for
example, by input of this CR coordinates (see
Figure 1) or by pushing the respective button on
a core map, which shows the location of all CR.
Movement direction (lift or dropping) is set by
“Boost” (B↑) and “Decrease” (D↓) commands
from individual control key in the MCR. Move-
ment of the selected CR does not influence the
position of other control rods and does not depend
on their movement in the group the selected CR to.
Individual control mode has the following
features:

• The selected control rod retains the abil-

ity to move along with the other CR of the
respective group in group control mode
(retaining the above mentioned priorities
concerning movement directing);

• If the selected CR to the main or auxiliary

group, which is at the moment moving by
the automatic control command B↑ or D↓,
individual control of this CR is possible
only after the automatic control commands
blocking;

• In case of simultaneous inluence on CR

of the commands initiated by individual