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or by operator error, often during testing of the ECCS.
The safety aspects of the event are as follows:
❙ 495 ❙
8-A. Deterministic Accident Analysis (Non‐LOCA)
(a) RCS pressurization due to an increase of the coolant inventory.
(b) Emergency injection of cold coolant, leading to non‐symmetric reduction of the
coolant temperature at the RV inlet, potentially affecting vessel integrity.
(c) Pressurizer overfilling that could lead to the pressurizer safety valve becoming
stuck in the open position.
(d) Containment pressurization in the case of loss of integrity of the pressurizer relief
tank.
CVCS malfunction may be initiated by a failure in the CVCS control system, which leads
to an increase of the RCS coolant inventory. Safety aspects are the same as for the ECCS
startup. Moreover, there is a potential for injecting non‐borated water, which would cause
an RIA. Figure 8‐6 shows one example of predicted RCS and SG Pressures trends versus
time for a CVCS Malfunction.
PRESSURI ZER PRESSURE, psi a
2 6 0 0
2 5 0 0
2 4 0 0
2 3 0 0
2 2 0 0
2 1 0 0
2 0 0 0
1 9 0 0
1 8 0 0
1 2 7
0 3 0 0 6 0 0 9 0 0 1 2 0 0 1 5 0 0 1 8 0 0
TI ME, S E C O N DS
1 8 3
1 7 6
1 6 9
1 6 2
1 5 5
1 4 8
1 4 1
1 3 4
PRESSURI ZER PRESSURE, kg/c m 2 A
STEAM GENERATOR PRESSURE, psi a
1 4 0 0
1 3 0 0
1 2 0 0
1 1 0 0
1 0 0 0
9 0 0
8 0 0
5 6
0 3 0 0 6 0 0 9 0 0 1 2 0 0 1 5 0 0 1 8 0 0
TI ME, S E C O N DS
(a) RCS Pressure (b) SG Pressure
Fig. 8‐6 Changes in RCS and SG Pressures for a CVCS Malfunction
9 8
9 1
8 4
7 7
7 0
6 3
STEAM GENERATOR PRESSURE, kg/c m 2 A