before, consisting of 50% NaF, 44.5% ZrF), and 5.5% UF, , may turn out to be too corrosive and it causes trouble due to vaporization of the 2rF). The Pummermne ow behavior of beryllium under the thermal cycling which will occur isuncertain, The effects of irradiation on materials, especially on corrosion by the fused salts, are difficult to determine and may prove quite serious, Pratt and Whitney, which has been in this program less than a year, seems deeply concerned over the number and magnitude of new problems to be solved outside as well as inside the reactor, including pumps and plumbing for fused salts and radiators for heating air with hot radioactive sodium. We were not sufficiently informed of their studies on the engine and on the integration of the reactor- ; engine system with the aircraft to be able to judge progress and prospects. The present schedule is necessarily quite tentative. ORNL has full responsibility for the first Circulating Fuel Reactor Experiment (CFRE), which» SO nat rata anaaar lS aA will be designed for about 60 MW of heat and is scheduled to be operating in 1958. Pratt and Whitney will support this Experiment and will be responsible for the next step, a full-scale ground prototype which is scheduled to operate in 1959. A prototype unit in an airplane is scheduled for 1960-61. Our impression of this program is rather confused and troubled. The fatal illness of the leader of the project has undoubtedly impaired progress at ORNL in tackling the key difficulties in the reactor system. Furthermore, we gathered that the planned close collaboration of ORNL and P&W is slow in getting underway and that mutual confidence and cooperation are not yet well established,