The ORR operated at an average power level of 29.8 MW for 90.7% of the time during April, May, and June 1981. The reactor was shut down on eight occasions, one of which was unscheduled. Reactor downtime needed for refueling, maintenance, and checks was normal, with the reactor remaining available for operation 91.6% of the time. Maintenance activities, both mechanical and instrument, were essentially routine in nature. In-service inspection completed during the quarter is described.

Routine reactor operation with four end-of-cycle shutdowns resulted in an on-stream time of 92.3% for the quarter. The outer control pates were changed and a semi-annual core component inspection made.

The ORR operated at an average power level of 27.9 MW for 88.9% of the time during January, February, and March of 1981. The reactor was shut down on seventeen occasions, seven of which were unscheduled. Reactor downtime needed for refueling, maintenance, and checks was normal, with the reactor remaining available for use 92.6% of the time. Maintenance activities, both mechanical and instrument, were essentially routine in nature with the exception of one Reactor Instrumentation and Controls Design Change Memo and one Mechanical Design Change Memo. Special tests or measurements completed during this quarter are reported in a summary entitled, ORR Reactivity and Flux Comparisons between a 280 g, 45 Weight Percent Enriched Texas Instrument Fuel Element and a 265 g Standard 93 Weight Percent Enriched Texas Instrument Fuel Element.

The ORR operated at an average power level of 29.9 MW for 83.3% of the time during this period. The reactor was shut down on five occasions, one of which was unscheduled. Reactor downtime needed for refueling and checks was normal. The reactor remained available for operation 93.4% of the time. Maintenance activities, both mechanical and instrument, were essentially routine in nature. Special tests completed during the quarter included results of flux measurements in the HFED experiment, cycles 167-D and 168-A, and results of reactivity worth measurements of MFE-4A Hf core sleeve as installed in core position E-3. In-service inspection completed during the quarter included the internal and external inspection of the pool heat exchanger.

The ORR operated at an average power level of 27.8 MW for 72.6% of the time during April, May, and June of 1978. The reactor was shut down on fifteen occasions, two of which were unscheduled. Reactor downtime needed for refueling, maintenance and checks was higher than normal due to beam-hole-plug maintenance, with the reactor remaining available for operation 82.4% of the time. Maintenance activities, both mechanical and instrument, were essentially routine in nature. Special tests or measurements completed during the quarter included gamma flux (heating) measurements made in core positions E-7, E-5, E-3, and C-7 using lattice configurations as indicated in figure Nos. 5, 6, 7, 8, 9, and 10.