Not many cost estimates of hybrid reactors are available. It is, however, interesting to check whether the adjunction of a high-intensity accelerator to a reactor would not lead to an unacceptable cost increase. In this respect, although there are obviously large uncertainties, the CERN group cost estimate of its proposed Energy Amplifier [162] is interesting. The IEPE of Grenoble [53] has evaluated the estimate of the CERN group and has examined several cost scenarios differing by the intercalary costs, the standardization effects, the size and prototype cost incidence, as well as the fuel cycle reprocessing cost. Before giving the global results of these cost calculations[58] we review some of the elements given by the CERN

group, especially those corresponding to non-classical parts of the Energy Amplifier:

• The accelerator system involves four cyclotrons:

1. Two injector cyclotrons yielding 6 mA of 10 MeV protons with a cost of 4Mc each, and a total of 8Mc.

2. One intermediate energy separated sector cyclotron yielding 120 MeV protons for a total cost of 32 Mc.

3. The main separated sector cyclotron yielding 1 GeV proton for a cost of 80 Mc.

The total cost of the accelerator system, including the beam handling, power supplies and biological shieldings, amounts to 160 Mc.

• The cost of the subcritical system is evaluated at 50 Mc including:

1. 6Mc for the 10000 tons of lead.

2. 12 Mc for the main vessel with a total weight of 400 tons.

Table 12.1 is taken from the work of the IEPE. It compares the invest­ment costs given by the CERN group with those revised by the IEPE and with those of a PWR (with French conditions).

The investment costs would be of the same order for the PWR and the Energy Amplifier. Note that the cost of the non-classical part amounts only to a relatively small fraction of the total cost, so that the rather large uncertainties on this part have a limited influence on the total cost.

Table 12.2 compares the kWh production cost according to the CERN estimate and to the three scenarios considered by the IEPE to that of the PWR.

One sees that the cost of the energy produced by the Energy Amplifier would be, at worst, comparable to that of present PWRs. It is hoped that

the additional cost of the accelerator complex would be balanced by the simplifications on the reactor, due to its inherent subcriticality. Reductions on the fuel cost stem from the suppression of the uranium enrichment step and from the fewer reprocessings (larger burn-up). Note that an uncertainty exists concerning the best reprocessing technology (Thorex or pyro-electrolysis). Furthermore, the costs presented above also have large uncertainties and should be considered as preliminary approaches. Indeed, an alternative approach was made by Bacher [172] based on the experience of sodium cooled fast breeders. This analysis found a kWh cost twice as expensive as that obtained with PWRs.

The price comparison of electricity produced by different techniques and in different countries is instructive and is given in table 12.3, taken from the IEPE study. The table[59] shows that the conditions under which nuclear plants are built have a very large influence on their cost.