Regional Basic Professional Training Course in Korea

For disposal of LILW from NPPs, the two main concepts are:
❙ 1037 ❙
20. Waste Management
Disposal into concrete vaults at shallow depth (shallow ground disposal); and
Disposal into rock caverns at intermediate depth (a few tens – one hundred meters).
The basic difference between these concepts is that the former requires active institutional
control, such as environmental and hydrological monitoring and strict land use controls,
for several tens – a few hundreds of years after the closure of the facility. Disposal of
LILW in rock caverns is generally planned so that long‐term safety is not dependent on
active institutional control; only passive controls are needed to prevent intrusive actions,
such as drilling, at the disposal site.
Shallow ground disposal normally aims at isolating waste packages from groundwater,
either by placing them above the groundwater table or by means of a special drainage
system. Infiltration of rainwater into the closed vaults is prevented by means of overlying
protective layers. In order to maintain the isolation, maintenance during the institutional
control period may be needed.
Shallow ground disposal without effective engineered barriers is nowadays allowed only
for LLW. A modern shallow ground disposal facility consists of monolithic vaults made
of reinforced concrete; the vaults are isolated from the geological medium by means of a
clay layer or similar. The waste packages are transferred into the vaults with a crane and
the spaces between packages are back filled with cement grout. Finally, the top cover of
concrete and other protective layers above the vault are made.
Disposal into rock caverns may occur in a host formation, which is entirely dry, such as
salt formation. If this is not the case, safety is based on the idea that waste packages may
get into contact with groundwater soon after the closure of the repository, but the
groundwater flow rate inside the repository is very low due to the impermeable host rock