OPERATIONAL PROBLEMS FOR TWO- AND THREE-SHIFT OPERATION OF THE LIVERMORE POOL-TYPE REACTOR

Abstract

The effect of operating an intermediate-power research reactor on a nonsteady-state schedule is discussed. The magnitudes of the xenon, temperature, and fuel-burn effects on the available excess reactivity are covered for power levels of 1, 2, and 5 Mw, and for various operating schedules including one, two, and three shifts per day. The topics discussed are based on the results of operating experience at the 1- and 2-Mw power levels and calculations for the 5- Mw power level. The xenon-poisoning effects were determined by code caiculations (Zorch) normalized to the 1and 2-Mw observed values. The use of equilibrium xenon poisonlng for the determination of total shim-rod worth and core excess reactivity is also covered. For situations not covered by regular schedules, a xenon slide rule was developed to determine the available core excess reactivity at startup. Temperature coefficient effects resulting from the rapid increase in reactor coolant temperature at startup are covered for the specific cooling system characteristics of the LPTR. A fuel cycle program instituted in 1960 is discussed in view of past operational experience. Recent modifications to this fuel cycle program to minimize the excess reactivity swings are presented with the anticipated results. Finally, the over-all effect on available excess reactivity of xenon, temperature, and fuel burn is summarized for intermittent operation of the LPTR at 2- and 5Mw power levels, (auth)