4,3 Nuclear Systems
4.3.5 Analysis of Results
The main findings of the analysis are discussed in this section considering the full energy chain. Results obtained in the earlier LCA study on present systems are used for comparison. In particular, total requirements and emissions calculated for the chains associated with the Swiss and the UCPTE nuclear mixes are considered here. For the
future, the European nuclear mix assumed for the decade 2020-2030 and the two analysed types of LWRs are considered. The results were normalised by the unit of electricity.
The calculated consumption of uranium per unit of electricity generated decreases by approximately 8% to 26 kg/GWh because of the assumption of higher average burn-up.
Figures 4.3.2 and 4.3.3 show the steel and concrete calculated for the chain and compared to the use in the power plant. The total steel normalised by the unit of electricity is predicted to reduce by nearly 50%, mostly because of the reduced masses and the longer lifetime of the power plants. About the same reduction is calculated for the total requirements of concrete, with the plants expected to have the strongest decrease. The lower material consumption that can be observed in the rest of the chain are mostly due to reductions in the transport needs. The differences that can be noticed between the Swiss and the European chains for the present conditions depend on the different average load factors (almost 85% for Swiss NPPs vs. 70% for UCPTE), and consequently the total energy generated during the lifetime.
50Ch
• For Full Chain excl. Power Plant B Direct for
Power Plant
UCPTE CH UCPTE AP600 ABWR 1990 1990 2025
Figure 4.3.2 Steel requirements for present and future nuclear full energy chains.
4000-
3000-/GWh
O)
100
0--n
—Era—BS8—1 1
• u • UTJlL
SB
• For Full Chain excl. Power Plant B Direct for
Power Plant
UCPTE CH UCPTE AP600 ABWR 1990 1990 2025
Figure 4.3.3 Concrete requirements for present and future nuclear full energy chains.
Figure 4.3.4 shows the results for the total electricity needs. The requirements for the enrichment of uranium by gaseous diffusion are currently about 80% of the total consumption of electricity. The total electricity needs should decrease from approximately 4% for the current conditions to less than 0.5% for the entire chain, mainly because of the predicted change in the processes used for enrichment.
• From Grids B Direct from PWR
for Enrichment via Diffusion
UCPTE CH UCPTE AP600 ABWR 1990 1990 2025
Figure 4.3.4 Electricity input requirements as a fraction of the total generated by present and future nuclear full chains.
Greenhouse gas (GHG) emissions are shown in Figure 4.3.5 in terms of CO2-equivalent calculated with the GWP100 from (IPCC, 1994) considering only direct effects of halocarbons (see footnote 1 in Section 5.2). CFCs leakages at diffusion enrichment plants may at present contribute roughly 25% to the total GHG emission calculated for the nuclear chain. This contribution will nevertheless reduce during the next decade due to substitution of coolant gases, to reach negligible values for future conditions.
• CFCs B Other GHGs
UCPTE CH UCPTE AP600 ABWR 1990 1990 2025
Figure 4.3.5 Greenhouse Gases (GHG) emissions to air from present and future nuclear full energy chains.
The calculated total greenhouse gases, which in the future will depend almost exclusively on the indirect contributions through the energy needs, in particular from the electricity mixes, should decrease by approximately 50% to about 6 t(CO2-equiv.)/GWh. Other emissions to air which are typical products of combustion processes are more appropriately commented in Chapter 5 where the various energy systems are compared.
The total radioactive emissions to air and water from the entire chain are shown in Figures 4.3.6 through 4.3.9. Eight classes are considered for simplicity; the releases are again normalised by the unit of electricity. The reduction predicted for radon to air is a direct effect of the assumed restoration of the mill tailings.
• UCPTE 1990
• CH1990 H UCPTE 2025 H AP600 H ABWR
Radon Other gases
Figure 4.3.6 Radon and other radioactive gases emissions to air from present and future nuclear full energy chains.
x : CD
COcr
J
1000-
750-
500-
250-
n-1
raj W8H&M&.
III
UCPTE 1990 CH1990 UCPTE 2025 I AP600
ABWR
Actinides Aerosols
Figure 4.3.7 Radioactive aerosols and actinides emissions to air from present and future nuclear full energy chains.
By far the highest contribution to "Other gases" (Figure 4.3.6) is Kr-85 from reprocessing, which decreases because of the assumed higher burnup (i.e., less spent fuel per unit of energy generated); nevertheless, the value shown has to be taken with care, because it is based on reprocessed fuel with lower burnup (in the end, it may be expected that the total remains as high as at present). The substantial reduction in the releases of aerosols to air occurs in the reprocessing step; this also applies to the actinides (Figure 4.3.7).
The normalised value for emissions of tritium to water, mostly from reprocessing, slightly changes with the increasing burnup (Figure 4.3.8). The actinides released to water substantially decrease in the milling and reprocessing steps (Figure 4.3.9). The strong reduction in the release of mixed nuclides is a direct effect of the new input for the reprocessing step (Figure 4.3.9).
100-f
• UCPTE 1990
• CH1990 H UCPTE 2025 M AP600 H ABWR
Radium Tritium
Figure 4.3.8 Radium and Tritium releases to water from present and future nuclear full energy chains.
100-ti
I
u
CO
75- B UCPTE 1990
• CH1990 H UCPTE 2025 H AP600 H ABWR
Actinides Mixed nuclides
Figure 4.3.9 Radioactive actinides and mixed nuclides releases to water from present and future nuclear full energy chains.
As shown in Figure 4.3.10, which summarises the considered eight radioactive emissions classes (the four on the left-hand side: to air; the four on the right-hand side: to water), according to the estimations the future nuclear power plants (50% AP600, 50% ABWR) give negligible direct contributions to the total emissions of gases and aerosols to air as well as tritium and mixed nuclides to water, whereas there are no direct releases of isotopes of the other classes (see Table 4.3.IX).
l.E+09- l.E+08- l.E+07- 1.E+O6-
l.E+04-S
l.E+021 .E+0l.E+021 - 1.E+00-l.E-01From Chain Direct from Power Plants
o des
c
Acti sols
o
Aei lum
o c:
ium des
c
ActI ucl.
X)c
S
Figure 4.3.10 Radioactive releases to air and water from future nuclear full energy chains.
Figure 4.3.11 shows the conditioned solid radioactive wastes from the reprocessing of spent fuel which should be disposed of in Switzerland in the two planned final repositories for intermediate level and high level. The calculated reductions in the volumes normalised by the unit of electricity depend both on the smaller values which are expected to be attained by the operators of reprocessing plants, and the assumed higher average burnup of the fuel.
0.11
0
CO
0.01-0.001J
• UCPTE 1990
• CH1990 UCPTE 2025 AP600 ABWR
Medium active High active
Figure 4.3.11 Conditioned radioactive solid wastes for present and future nuclear full energy chains.