Civil Engineering Reference
In-Depth Information
Fig. 10.18
Potential
committed effective doses
for different filter systems in
case of radioactivity release
through exventing filters
[
85
]
A pure aerosol filter causes only relatively small dose reductions. Therefore the
combination of aerosol filters with elemental and organic iodine filters (both with
99 % filter efficiency) is much more efficient.
A much higher quality of the containment function against radioactivity release
after a severe core melt accident can be achieved if a double containment with an
inner steel containment or inner concrete containment with steel liner is designed. If
the inner containment has a leak rate of 0.3-1 % during or after the severe core melt
accident, then the leak rate from the inner containment into the annulus between
inner containment and outer concrete containment can be only 0.3-1 % of the
radioactivity released in the annulus, i.e. 0.3-1 % of the noble gases and 0.3-1 % of
the radioactive aerosols (iodine, cesium, strontium etc.). This leaking radioactivity
is collected in the annulus and can be released only through the exventing filters and
filters for elemental and organic iodine into a stack and from there into the
environment. This is shown in Fig.
10.19
by the double containment of the EPR.
In this case the effective radioactive doses in the environment around the plant are
decreased by at least a factor of 100 compared to the case described above
(exventing filters for presently operating plants (Figs.
10.17
and
10.18
)[
85
]. Such
a double containment fulfills the requirement of KHE safety concept. No evacua-
tion is necessary outside the reactor plant.
In this way the objective of the KHE safety concept defined in Sect.
10.2
is
achieved.
spray water from the dome of the containment and condense vapor in the contain-
ment. In this way a decrease of the containment pressure is possible from 0.65 MPa
to about 0.2 MPa within 1 day. The water for the spray system is taken from the
