CONTROL ROD CUSPING EFFECT IN THE RFSP CODE

Abstract

The rod cusping effect is a known artificial phenomenon arises when the presence of partially inserted control rod in a relatively large spatial mesh node is represented by homogenous cross sections whose magnitude are proportional to the volume of the control rod present. The utilization of the volume- weighted cross sections artificially adds worth to any reactivity control device partially inserted between two mesh lines in the model. The current version of the Reactor Fueling Simulation Program (RFSP) code, which is used to perform full-core calculations for CANada Deuterium Uranium (CANDU) reactors, also inherits this effect. The objective of this paper is to demonstrate the rod cusping effect in observed when determining the worth of reactivity control devices in a typical CANDU reactor, to provide some discussions on how to manage the rod cusping effect in the current analyses, and to discuss available methodologies that could be implemented to correct this effect.