Environmental Engineering Reference
In-Depth Information
• in the AS 3 ET LLOCA PO/HL (leak from the hot loop, reactor at
power)
- common cause failure of emergency make-up pumps (5% of the total
risk);
- failure of the control system for automatic switching to recirculation
through the sump due to human error when configuring four relays (3% of
the total risk of CDF);
• in the AS 2 ET LLOCA PO/GL (leak from the cold loop, reactor
under power) ;
- common cause failures of RWST level sensors (8% of the total risk);
- common cause failures of spray pumps function and the failure to open
motor-driven valves V13 and V14 contribute less than 3% to the total CDF.
It should be noted that the common cause failures of the RWST level
sensors and control system failure in the automatic switching to recirculation
through the sump due to human error when configuring the four relays, have
already been observed when analyzing the reliability of spray systems in
various studies as major contributors to the unavailability of the system.
In this case, in the framework of analysis at the level of event trees, these
minimal cross sections (MC) correspond to accident sequences associated
Table 6.2
Distribution of risk in relation to the location of the leak and the
state of the reactor
Contribu-
tion to total
risk of CDF
IE fre-
quency
Contribution to
ET, %
IE code
AS number
CDF
LLOCA PO/HL
1.61 ·10
-5
2
6.22·10
-9
30
3
1.42 ·10
-8
69
20%
4
4.78 ·10
-11
0
Total ET
2.05 ·10
-8
LLOCA PO / CL
2.41 ·10
-5
2
9.32 ·10
-9
19
13
3
3.97 ·10
-8
79
55
4
1.27·10
-9
3
Total ET
5.03 ·10
-8
LLOCA HS / HL
1.79 ·10
-7
2
6.89 ·10
-11
21
3
2.65 ·10
-10
79
4
5.33 ·10
-13
0
Total ET
3.34 ·10
-10
LLOCA HS / CL
2.68 ·10
-7
2
1.03·10
-10
14
3
6.04 ·10
-10
84
4
1.42 ·10
-11
F2
Total EW
7.21·10
-10
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