plate, arranged in a box-type configuration, with a meat of Zr-U alloy and a Zircalloy cladding. Extensive metallurgical research on alloys, in collabo- ration with other laboratories, has developed additions and treatments which markedly improve stability, until it is now felt that corrosion under irradiation is a more critical question than stability. Corrosion is an inherent fuel element problem in all heterogeneous water-cooled reactors and calls for intensive research and development through=out early reactor operations as well as in planning and design. Dr. Zinn refers to the Hanford experience in holding down slug failures in spite of great power increases over the years of operation as characteristic, It mist be expected that fuel plates will warp considerably with long burn-up in the Boiling Reactor; corrosion resistance which relies on jacketing may be adequate, but efforts to develop a corrosion-resistant "meat" in the sandwich are strongly justified. we oe ee Sa pS FlatpIAteSandwiches have been chosen for the Boiling Reactor at Argonne because their use involves less extrapolation from present knowledge, even though they present difficult problems of manufacture. There is some expectation that jacketed tubes may ultimately be preferred, but the necessity for "freezing" the core design and beginning its fabrication by next July to meet the tight schedule of criticality by the end of 1956 dictates the sandwich plate element. The degree of radioactive contamination of the steam—power equipment and its effect on regular operations end servicing is hardly answerable until the system is operating. Entrainment in commercial steam practice indicates that the liquid carry-over of radioactive water from the reactor in the steam _.4. S wi} o& e te ass Cte ae” ste! we!s