Civil Engineering Reference
In-Depth Information
- Flooding protection of diesel generators and direct current batteries is essential.
Independent direct current connection should be provided for critical instrumen-
tation, critical valve operation and control functions
- Ensure adequate dike heights against flooding of the emergency diesel genera-
tors and the direct current batteries. Provide diversity for both alternate and
direct emergency power supply
- Provide robustness of the reactor core isolation cooling system (steam driven
pumps and generators) in Boiling Water Reactors
- Improve the reliability to depressurize the reactor pressure vessel and maintain it
depressurized during station black out (loss of all electrical power)
- Improve the reliability to vent
the primary containment
in Boiling Water
Reactors
- Improve the instrumentation in the reactor pressure vessel to provide the oper-
ator with more knowledge about the course of a core accident.
- Provide the inner containment of Boiling Water Reactors with hydrogen
recombiners
- The possibility of an earthquake damaging the wall of the liner of the spent fuel
pool causing cooling water to be lost should be considered. A hardened strong
pipe—as already realized in US reactor plants—should be installed which
allows water to be fed to the spent fuel pool from the outside.
9.3.6.2 Additional Recommendations Drawn from the Fukushima
Accident
The emergency power supplies (diesel generators, gas turbines, fuel cells direct
current batteries) should be arranged in a building protected against tsunamis,
flooding, earthquakes, hurricanes etc. An emergency operation room with the
essential instrumentation power supply and the ability to operate the plant in case
it cannot be operated from the main operator room should be available.
9.4 Comparison of Severe Reactor Accident
on the International Nuclear Event Scale
The International Atomic Energy Agency (IAEA) introduced in 1990 the Interna-
tional Nuclear and Radiological Event Scale (INES) as a measure to compare
severe nuclear accidents and their radiological impact on international scale. It
represents seven increasing levels. Each level about a factor more severe than the
previous level [
22
]. Figure
9.13
shows the INES scale in form of a pyramid.
