Study of molybdenum-99 production in IEA-R1m reactor using a beryllium irradiator

The IEA-R1 reactor has undergone a modernization to increase its operating power to 5 MW, in order to allow a more efficient production of the 99 Mo radioisotope. An irradiation element made of Be was acquired for the reactor and studies were initiated for determining its performance when compared to other irradiators available in the reactor, the water and graphite types. The results obtained showed some advantages of the Be irradiation element for producing 99 Mo: the epithermal neutron flux in the irradiation element is approximately 15% greater than in the water and in the graphite irradiation elements; the negative reactivity introduced in the reactor by the Be irradiation element is substantially smaller than the those introduced by the other elements: - 1636 pcm for the Be irradiator, -2568 for the graphite irradiator and -2977 pcm for the water irradiator. It is concluded that the production of the 99Mo radioisotope with the Be irradiation element can be increased by 15% in the IEA-R1m reactor. It also requires less fuel for the reactor operation due to the smaller negative reactivity introduced in the reactor core. (author)