Prospects for poisoning reactor cores of the future

In this article, the most interesting rare earth nuclides for neutronics (gadolinium, samarium, erbium, europium and dysprosium) are studied and compared from the point of view of their possibilities for the control of potential core reactivity in PWRs to increase the cycle length. By modifying the absorption of the fuel network, burnable absorbers, modify the spectrum to a lesser or greater degree. The study presented shows that only gadolinium and erbium will be considered to control the reactivity of the PWRs. For these two burnable poisons, we further present a better way to use both these burnable absorber. Some exploratory variations of the poisoning solutions that are usually implemented, like comilling gadolinium and fuel are presented. Erbium, by means of a very homogeneous poisoning mode, has proved to lead to significant variations in the behaviour of the moderator temperature coefficient with both uranium and plutonium fuels. (C) 1997 Elsevier Science S.A.