Environmental Engineering Reference
In-Depth Information
Application of FL-BBN Method for
NPP Reactor Safety Assessment
states of important RCIC components. Among
critical parameters that evaluate pump stare are
feed (F), pressure (P), rate of revolution (RR),
water reserve in the condenser (C), etc. Increase
(decrease) in these parameters with respect to
certain values may be an indication of malfunc-
tions or failures resulting in RCIC safety function
degradation.
In this way, in order to assess RCIC safety it
is necessary:
FLI block application.
NPP reactor safe condition
is a function of a number of systems. Let us focus
on the Reactor Core Isolation Cooling (RCIC)
System and the Emergency Gas Removal System
(EGRS) as an illustrative example. Importance
of these systems for safe reactor condition was
clearly demonstrated by NPP accidents. Their
condition and reliable operation are critical for
reactor safety.
RCIC is the first parent system for the reactor
in terms of BBN (child system). It is designed
for core emergency cooling. It is comprised of
three interrelated systems: primary, back-up and
continued cooldown subsystems.
EGRS is the second parent system, which
performs the function of noncondensable gases
removal from the first circuit, protects fuel ele-
ments, prevents natural circulation failure in the
first circuit.
Consider the use of the FLI block to assess the
criticality state of the RCIC.
The RCIC safety assessment task is repre-
sented as the task to find a representation in the
following form:
•
to determine values of parameters describ-
ing RCIC components functioning
*
*
*
*
*
X
=
(
x x x
,
,
, ...,
x
n
)
; (18)
1
2
3
•
to plot diagrams of RCIC safety linguistic
terms membership function
µ
a
jp
(
*
)
;
i
i
•
to determine values of the membership
function
µ
a
jp
*
at ixed values of param-
(
i
i
*
*
*
*
*
eters
X
=
(
x x x
,
,
, ...,
x
n
)
;
1
2
3
•
using logic equations in the following
form:
m
1
m
1
m
1
m
2
d
a
a
a
a
µ
(
x x
,
, ...,
x
)
=
µ
(
x
)
∧
µ
(
x
)
∧
....
µ
(
x
)
∨
µ
(
x
)
∧
...
m
1
2
n
1
1
2
n
1
2
n
1
m
2
m
2
mk
m
mk
m
mk
m
a
a
a
a
µ
a
∧
µ
(
x
)
∧
µ
(
x
)
∨ ∨
...
µ
(
x
)
∧
µ
(
x
)
∧
...
∧
(
x
),
2
n
1
2
n
2
n
1
2
n
X
*
=
(
x x x
*
,
*
,
*
, ...,
x
*
)
→ ∈ =
d
D
( ,
d d d
,
, ...,
d
),
∨−
log
ical OR
,
∧−
log
ical AND
,
1
2
3
n
j
1
2
3
m
(19)
to determine values of membership functions for
all possible RCIC safety values.
A knowledge base used to derive logic equa-
tions for RCIC is presented in Table 10.
Within the scope of the example, the logic
equations are of the form:
where
X
*
- a set of parameters describing the
state of RCIC components; D - a set of probable
d j
=
1
RCIC safety values.
The first subtask of the block is to choose
the set of components that are most important
in terms of RCIC core cooling performance. For
example, pumps, the condenser can be treated as
such components. Reliable operation of any of the
pumps is the critical aspect from the viewpoint of
RCIC safety functions.
The second subtask of the block is to select
functional parameters
x
j
,
,
m
,
(
= =
[0.12
∧
0.55
∧
0.7
∧
0.66]
∨
[0.12
∧
1.0
∧
0.7
∧
0.66]
∨
[0.12
∧
1,0
∧
0.87
∧
0.66]=0.12;
µ
Y
Crt High
1
1
÷
x
n
that evaluate the
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