The design, development, and operation of metaldiaphragm service pumps for aqueous homogeneous reactojs are discussed. It is shown that with proper design and materials selection, the dlaphragm heads and check valves can operate continuously for about two years. (C.J.G.)

The measurements reported here are companion measurements to those reported earlier in HW-63585. The only significant difference between the measurements is that 1.8 w/o enrichment UO2 fuel was used for the first set, and 2.6 w/o enrichment UO2 fuel was used for the measurements described in this report. The new results will be presented graphically, and for completeness, the details of the measurement will be included here as well as in HW-63585.

Recent fuel element irradiations demonstrated the structural integrity of spherical uranium-graphite fuel elements at burn-ups in excess of the design requirements of a 125 Mw(e) Pebble Bed Reactor (PBR) power plant. Other irradiations indicated the successful development of a coated fuel particle which permits fabrication of fuel elements meeting the PBR design objectives of a fission-product release rate (R/B) ? /sup 10-6/. beta plus gamma system activity in a 125 Mw(e) PBR is 490 c, assuming complete release of /sup lO-6/ of all fission products volatile at or below 2500 deg F. The low R/B being obtained from PBR fuel elements indicates that decay during diffusion of the short-lived volatile precursors of nonvolatile daughter products will result in further reduction of this system activity, and an increase in the average half life of the fission products remaining in the system will increase the efficiency of a bypass clean-up system. The method of fabricating coated particles by the hydrolysis of metallic chlorides to produce oxides or pyrolysis of hydrocarbons to produce carbon on a suitable substrate, is described, and preirradiation test results are given. An accelerated coated-fuel-particle program is discussed as well as development work on the Pebble Bed REactor concept …

Four capsules containing Al-1.65 w/o Pu and Al-12 w/o Si-1.65 w/o Pu were charged into the MTR. These capsules will be irradiated to a burnup of 80-100% of the plutonium atoms to determine the stability of the material at high exposures. An additional sixteen capsules containing 5 to 20 w/o Pu in Al and Al-Si have been prepared. Eight are awaiting reactor space and should be charged soon. The remaining eight are being recanned to increase the end gap between the core and the can. Also four capsules containing high density UO2-PuO2 pellets canned in Zircaloy are awaiting assignment of reactor space.

The effort on uranium silicide during the repent period was equally divided between synthesis and fabrication. The goal for the synthesizing effort was to make U/sub 3/8i/sub 2/ of higher purity than that made in the past, and the goal for the fabrication effort was to make pellets of density higher than 93%. Both goals were achieved. Experiments in simultaneous synthesis and fabrication of uranium monocarbide are reported in which mixtures of uranium powder and carbon were hot pressed. Sintering experiments on uranium monocarbide produced pellets of 91 to 91% theoretical density; however, cracking and oxidation were observed. Further experiments are planned in which oxidation will be reduced to a minimum. (J.R.D.)

A 19-rod Zircaloy-clad half-length PRTR spike element successfully irradiated to high plutonium burnout at full power in the ETR shoved partial bonding of the core and cladding. Unsatisfactory autoclave films on the Zircaloy cladding of the PRTR Al-Pu fuel elements are delaying final assembly of the first 30 clusters. Further conditioning of the autoclaves and the availability of permanent etching facilities are expected to correct the present difficulties.