PROSPECTS FOR POISONING REACTOR CORES OF THE FUTURE

In this article, the most interesting rare earth nuclides for neutroni cs (gadolinium, samarium, erbium, europium and dysprosium) are studied and compared from the point of view of their possibilities for the co ntrol of potential core reactivity in PWRs to increase the cycle lengt h. By modifying the absorption of the fuel network, burnable absorbers , modify the spectrum to a lesser or greater degree. The study present ed shows that only gadolinium and erbium will be considered to control the reactivity of the PWRs. For these two burnable poisons, we furthe r present a better way to use both these burnable absorber. Some explo ratory variations of the poisoning solutions that are usually implemen ted, like comilling gadolinium and fuel are presented. Erbium, by mean s of a very homogeneous poisoning mode, has proved to lead to signific ant variations in the behaviour of the moderator temperature coefficie nt with both uranium and plutonium fuels. (C) 1997 Elsevier Science S. A.