A Theory and Model of Molten Salt Reactor Xenon Behavior After the Solubility Limit

Due to the circulating nature of the fuel, there is a qualitative difference between xenon behavior in a molten salt reactor (MSR) compared to a solid fuel reactor. Therefore, the equations that describe 135Xe behavior in a molten salt reactor must be formulated differently. Prior molten salt reactor xenon models have focused on behavior below a solubility limit in which the 135Xe is partially dissolved in the fuel salt. It is foreseeable that a molten salt reactor may operate with a concentration of gas dissolved in the salt sufficiently high such that no further gas may dissolve in the fuel salt. This paper introduces a theory of molten salt reactor xenon behavior for a reactor operating above the solubility limit. A model was developed based on this theory and analyses performed are discussed. Results indicate: (1) steady-state xenon poisoning is not monotonic with respect to gas egress rate, (2) a increase in gas ingress rate leads to a characteristic increase which is followed by a new steady-state in xenon poisoning, and (3) given a sufficient rate of gas egress, it is possible to remove the iodine pit behavior.