 An unexpected consequence of processing the salt was that its physical properties were altered slightly so that more than the usual amount of gas was entrained from the fuel pump into the circulating loop.The circulating gas and the power fluctuations that accompanied it were eliminated by operating the fuel pump at slightly lower speed.Operation at high power for several months permitted accurate measurement of the capture-to-fission ratio, for 233U in this reactor, completing the objectives of the 233U operation.