The safety of high-level radioactive waste (HLW) disposal is one
of the essential assurances needed to realize the nuclear fuel
cycle. High-level radioactive waste will be disposed of into a
deep, stable rock mass at a depth of several hundred meters. The
disposal system consists of a series of engineered and natural
barriers (multibarrier system) that will isolate radionuclides
effectively and retard radionuclide migrations to the environment.
JAERI has developed an integrated computer code system, GSRW,
that evaluates the dissolution of radionuclides from a vitrified
HLW, radionuclide migrations through engineered and natural barriers
by groundwater flow, transport in the biosphere, and the resulting
radiological consequence to the public. Safety analyses were performed
on the reference disposal system that involves HLW corresponding
to 16,000 MTU of spent fuels. The individual dose due to the exposure
pathway of ingesting drinking water was calculated using conservative
values of geochemical parameters. This is shown in Fig. 4-12.
The committed dose equivalent calculated here is on the order
of 0.1micro-Sv. This will be a smaller value in a realistic situation
because radionuclides will be fixed on minerals in the geologic
media. Thus, the geologic disposal of HLW may be feasible if the
disposal conditions assumed here remain unchanged throughout the
periods assessed here. |