This report addresses the critical mass studies, part X.

With the exception of a brief period of slightly elevated chloride level in the secondary blowdown, water-chemistry conditions during the period were satisfactory. During the period, the reactor was shut down for end-of-core-life testing and rearrangement. A set of specifications covering all electronic and electromechanical mechanisms required to control the SM-1 reactor through the rod- drive motors and clutches was prepared and issued. Installation of instrumentation for plant response and system performance was virtually completed. Work on the interpretation of long-lived radiochemical data obtained at the SM-1 during core lifetime was continued. Analysis of all fissionproduct data collected during Core I life has started. Thirty-eight stationary and seven control subassemblies from SM-1 Core II were checked for alpha contamination by a gas-flow proportional-counting technique. The work on the final design of a waste-disposal system for SM-lA was stopped and an investigation of an interim system containing a bypass sampling system was undertaken. Work continued on tests 202, 203, and 204 in the activitybuildup phase of Test Series 200. Core- physics measurements were taken at end of Core I life to complete the series of measurements made throughout the lifetime of the core. (W.L.H.)

Progress on design studies under Task 3, the mechanical-design portion of the SM-2 core and vessel design, is summarized for the period Oct. 1955 to Mar. 1960. Task 3 covers the mechanical design of the reactor vessel, vessel closure, nozzle penetrations, steel reflector, core support structure, flow divider, control rods, absorbers, and fuel elements. Layouts showing the basic designs, major dimensions, and materials of construction are presented. Stresses for the reactor vessel selected were within ASME Code limits. The report does not contain final results of Task 3 work. (auth)

The Zirflex Process employs a boiling aqueous solution of ammonium fluoride and ammonium nitrate to dissolve zirconium or Zircaloy. Average unoxidized Zircaloy dissolution rates are from 10 to 15 mils/hr for the optimum charge solution of 5.5M NH/sub 4/F-0.5M NH/sub 4/NO/sub 3/ at a F/Zr mole ratio of 7. Zircaloy, which is oxidized by exposure to high-temperature air or water, dissolves at rates of threeto five-fold less. Cores of uranium, uranium- aluminum, and uranium dioxide are not severely attacked by the Zirflex decladding solutions. Only the soluble uranium enters the waste, with losses varying from 0.3 to 3.0 g/l. The Zirflex waste solution is neutralized to a pH of 10 before storage. This requires approximately 0.07 gallon of 50% caustic per gallon of decladding solution. The neutralized waste consists of nearly 20 vol.% of rapidly settling solids, which are easily slurried under turbulent flow conditions. These solids tend to settle out in streamline flow and therefore agitation is required during temporary storage. Conventional nitric acid core dissolution is generally applicable to Zircaloy-clad uranium and UO/sub 2/ elements since the core material is essentially free from zirconium. The addition of aluminum nitrate to the nitric acid dissolvent at an aluminum/ residual …

To determine the thermal stability of SM-2-welded plate type fuel elements, test specimens were subjected to temperature differences across plate width. Thermal deflections caused by the relatively cool side plates restraining the axial expansion of the fuel region were measured along the axial centerline of the test specimens. Region-averaged temperature differences varied from 0 to ll6/sup o/F, or about l35% of expected reactor operating differentials. Test specimens, machined from standard full-sized fuel elements, consisted of a single fuel plate and its proportionate share of element side plates, and displayed an l-shaped cross section. Thermal deflections of 0.005 in. maximum were measured at the expected reactor operating conditions of 87/sup o/F region- averaged temperature differences. With initial (cold) deflections assumed within the SM-2 tolerance of (?) 0.008 in., test results indicated that the total operating deflections will be (?) 0.013 in. maximum. (auth)