Environmental Engineering Reference
In-Depth Information
sequence number does not exist).If all groups are
in LLS position a group with a sequence number
1 is selected as the main group.
In other cases, the main group is previously
defined CR group (while upwards movement) or
a group with the closest lower sequence number
(while downwards movement).
The condition for simultaneous movement
of the main and auxiliary groups is a location of
the main group near upper or lower performance
range limit in the positions, which are figuratively
called upper intermediate switch (UIS) and lower
intermediate switch (LIS) position. The same as
for limit switches, the used names mean not the
physical elements, but CR positions, for, which the
performance of the functions below is provided. It
is considered that the group reached a set position
after this position was reached by any four (while
upwards movement) or three (while downwards
movement) CR, which are in the group of six
control rods (groups 1-4, 7-10 in Figure 1), or by
any CR in a group, which consists of nine control
rods (group 6 in Figure 1).
After the group, which moves upwards reached
UIS position, the closest auxiliary CR group with
higher sequence number starts moving with it.
In case of stop of the main group after it reached
ULS position, or after the auxiliary group reached
LIS position, the main group sequence number
automatically increases by one (auxiliary group
becomes main group). For example, lift of groups
from the position when all they are in lower limit
switch is performed in the following design order:
• Upon reaching of upper limit switch by
four of main group CR (or upon reaching
of lower intermediate switch position by
four auxiliary groups CR) the main group
becomes group 2. Following the lift of new
main group the other CR of group 1 reach
upper limit switch position according to
the set algorithms.
The mentioned actions repeat for all groups
(except the fifth one not included into the design
order) successively in increasing order of indices
until four CR of group 10 reach the position shown
in Figure 1, or until exit this mode by operator's
initiative.
During power operation group with a sequence
number 10 is in the operative position, and the
rest groups - in ULS position. If power decrease
required, CR lowering is performed in the follow-
ing design order:
• A group with a sequence number 10, which
starts moving downwards is selected as the
main;
• Upon reaching of lower intermediate switch
position by, at least, three any main group
CR, the auxiliary group with a sequence
number 9 starts moving downwards;
• Each CR of the main group, which reached
lower limit switch position stops by the
signal of its sensor of control rod position
and stays in this position;
• Upon reaching of lower limit switch posi-
tion by three of main group CR (or upon
reaching of upper intermediate switch
position by three auxiliary group CR) the
main group becomes group with number
9. Following the lowering of new main
group, the delayed group 10 CR reach low-
er limit switch position according to the set
algorithm.
• The main group with a sequence number 1
starts moving upwards;
• Upon reaching of upper intermediate
switch position by, at least, four any CR of
the main group, the auxiliary group with a
sequence number 2 starts moving upwards;
•
Each CR of the main group, which reached
upper limit switch position, spots by the
signal from its sensor of control rod posi-
tion and stays in this position;
The mentioned actions continue for all groups
included into the design order consequently in the
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