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4.4 Risk and hazard assessment over time
While the radiotoxic inventory is a physical-biological concept intrinsically based on the laws
of radioactive decay and the radiological damage due to a quantity of radioactivity incorporated in the
human body, the risk and hazard concepts on the contrary rely on the extent of conditioning and
packaging of waste streams, on the long-term behaviour of waste packages in geological media and on
the routes which could be followed by radioactive releases on their return to the biosphere and to
mankind.
• In a first phase one has to assess the direct radiological impact of additional fuel cycle
operations.
• The second step is the radiological assessment of the waste types created by the AFC
operations.
• Finally the hazard assessment over time is closely related to the repository design and
location.
4.4.1 Pre-disposal waste management of RFC operations
The first positive impact is the expected decrease in uranium mining requirements. It may be
estimated that recycling Pu in LWR-MOX reduces the uranium needs by 20%. If the MAs were also
recycled a maximum benefit of 25% could be expected.
The present world-wide uranium requirements [172] are about 63 700 t natural uranium per
year (in 1997) and this quantity might increase to values ranging between 62 500 and 82 800 t in 2015.
The collective dose taken by about 250 000 workers world-wide is 1 300±300 man-Sv. The hypothetical
reduction of uranium needs throughout the world by universal Pu recycling would decrease the mining
requirements by 11 000 to 13 000 t based on the present needs, and 13 000 to 16 000 t based on future
extrapolated needs. According to UNSCEAR data [173,174] the average effective dose for underground
workers is 5 to 10 mSv/year depending on the type of mining a) .
The uranium requirements can also be expressed in t/GWe-year (load factor = 0.8). In the
present conditions this corresponds to 183 t/GWe-year or 26 t/TWhe. The average dose to workers
expressed in amount of uranium extracted is 23 ± 3 man-mSv/t natural uranium. World-wide recycling
of Pu as LWR-MOX would consequently reduce the collective dose by 20 to 25% or 260~375 man-Sv
to about 1 000 man-Sv. But this is a hypothesis which cannot be taken for granted since it would imply
a drastic change in the national fuel cycle and reprocessing policies of some major countries.
However, we may deduce the specific dose rate saving per GWe-year or TWhe in order to
compare these “savings” with the other contributions in the fuel cycle. The uranium requirements can be
reduced from 183 tHM to 138-146 t/GWe-year or 20.8-19.5 t/TWh in case of Pu and actinide recycling
in LWRs.
a) A recent report indicated overestimation of the dose from U-mining activities by a factor of 200-400,
see Long-Term Population Dose Due to Radon (Rn-222) Released From Uranium Mill Tailings,
SENES Consultants Limited, Canada, April (1998)
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