Neutron Multiplication Studies in Beryllium for Fusion Reactor Blankets

Beryllium is used as an efficient neutron multiplier in several fusion reactor blanket designs. In the framework of the experimental research program on the neutronics of fusion reactor blanket designs established at the Institut für Reaktorentwicklung der Kernforschungsanlage Jülich GmbH, measurements of the neutron multiplication in beryllium produced by 14-MeV neutrons were carried out to check basic nuclear data. The measurements were made in rectangular geometry as a function of beryllium thicknesses of up to 20 cm. The experimental values of the neutron multiplication were found to be 25% lower than the calculated values for all thicknesses. The low value of the multiplication casts doubts as to the suitability of beryllium as a neutron multiplier in fusion reactor blankets to yield useful tritium breeding ratios.