A reactivity hold-down strategy for soluble boron free operation by introducing Pu-238 added fuel

A new concept of Pu-238 added fuel is introduced to control the reactivity and power distribu- tion in soluble boron free (SBF) pressurized water reactor (PWR) core. Though extensive use of burnable poison and control rods is inevitable for reactivity suppression in SBF core, it causes the core power distribution control to be so dicult that a practical SBF operation is far distant. In thiswork, it is con®rmed that the excess reactivity can be greatly suppressed by introducing the Pu- 238 added fuel. As a result of the conceptual core design of the 600MWe SBF PWR using Pu-238 added fuel, the core reactivity is well controlled in comparison with the results obtained from the earlier 600MWe SBF core design works. Especially, the axial power shape control is performed successfully with the aid of simple axial zoning scheme, developed in this study, by using Pu-238 enrichment zoning. The Pu-238 added fuel is also tested for 1300MWe SBF PWR core design, in which the power distribution control can be more dicult than that of smaller plants if soluble boron control is not available. The results show that the core excess reactivity and the power dis- tribution can be well controlled without using soluble boron even in a large-sized PWR. Hence, one of the dicult control problems arising in SBF core design can be greatly mitigated by intro- ducing the new fuel concept. It is further expected that the Pu-238 added fuel, the simple axial zoning scheme, and the control bank operation strategy introduced in this study are directly applicable to practical SBF core design.