Civil Engineering Reference
In-Depth Information
Fig. 3.21
Shutdown systems of BWR-1,300 and SWR-1,000 (KERENA) [
14
-
16
]
3.3.2 Boiling Water Reactor Safety Systems
If there are perturbations in the criticality or effective multiplication factor, k
eff
,or
losses of coolant flow, the reactor is shut down in a short time by rapid insertion of
the absorber plates. As a backup shutdown system, the coolant (moderator) can be
poisoned by a neutron absorbing boric acid solution and, in this way, also quench
the nuclear reaction and shut down the reactor (Fig.
3.21
).
Ruptures in any pipe in the primary cooling system (e.g., the recirculation
system) cause the main steam pipes and the feed water pipes to be blocked by
two series-connected isolation valves and by two series-connected non-return
valves, respectively. This action isolates the reactor pressure vessel within the
containment from the outer turbine and condenser cycles. When these isolation
valves are closed, or if there is overpressure in the reactor pressure vessel, BWR
safety/relief valves are automatically actuated, allowing a path for steam to be
discharged from the reactor vessel. In this case, the steam is discharged into a large
water pool inside the pressure suppression containment.
In case of the BWR-1,300 of Kraftwerk Union steam is discharged into a large
pressure suppression pool (Fig.
3.22
). In case of SWR-1,000 (KERENA) of
AREVA more passive safety systems are installed as compared to BWR-1,300
and the steam is discharged into four core flooding pools. In the following part both
designs are described separately.
