Comparison between the perturbed flux of the ILL nuclear reactor and the perturbed flux of a spallation source

In this paper we compare the neutron flux of the Institute Laue Langevin (ILL) reactor with that of a spallation source. The basic question is, how much beam power a spallation source will need in order to produce the same flux as the ILL reactor [H. Conrad, J. Neutron Res. 6 (1997) 3; Commisariat a lʹEnergie Atomique, Bull. Inf. Sci. Tech. 165 (1971) and 166 (1972)]. The results show that the beam power, which is needed to get the same perturbed flux as ILL, is somewhere between 5 and 20 MW, depending on the geometry of the spallation source. Secondly, we discuss the possibility of a mercury target and compare our results with that of the report on the European Spallation Source [The European Spallation Source Study, Vol III, The Technical Study, Report ESS-96-53-M, November 1996]. This comparison shows that our results contradict the ESS statement that for an infinite reflector, Pb performs as good as Be.