The Thorex Pilot Plant at Oak Ridge National Laboratory was operated during 1955, processing reactor-irradiated thorium slugs to recover U233 and thorium and 12 MTR fuel elements to recover U235 and Np237. The radiation exposure received by operating personnel during this period averaged 60 mrcp/man-week. Most radiation exposure was received in areas that were intended to be only slightly or nonradioactive. However, because insufficient decontamination of process solutions was achieved and equipment surfaces became contaminated from equipment failures, these areas became primary sources of personnel exposure. The installation of additional shielding where needed and the prompt removal of surface contamination successfully reduced the radiation levels and exposures in these areas. Remote control of processing equipment and sampling of very radioactive solutions from process equipment was successfully accomplished, and assisted in the reduction of exposure to operating personnel.
Calculated data and graphs describing the effects of continuous thermal-neutron irradiation of thorium, the usual method of operations of homogeneous reactors, are presented.The buildup and decay of U^233, Pa^233, other heavy isotopes, and fission products are considered on the basis of best available cross-section and fission-yield data. The effects of the heavy isotopes and fission products on neutron economy are discussed.
LITR Fluoride-Fuel Loop. — The inconel loop was dismantled for removal of the samples and for recovery of the uranium by using the remote cutting tools installed in a half cell of the Solid State Building. Disassembly proceeded without incident. An electric-arc cutting technique was developed for removal of the stainless steel enclosure around the pump bowl. Fission power and maximum flux were determined by irradiating a simulated loop, by heat-balance calculations, by radiochemical analyses for fission products in the fuel, by measuring the activation of cobalt foils attached to the loop, and by activation of the loop tubing itself. The determination of the power by these various methods gave 2.5 to 2.8 kw during operation of the loop, and the maximum power density was 0.4 kw/cc. Chemical analyses of the fuel were carried out to determine U, Zr, and the major constituents of inconel: Ni, Cr, and Fe.
The indicated methods for determining the following constituents of Diban, which is an aqueous solution of dibasic aluminum nitrate, Al(OH)2NO3, were evaluated statistically: 1aluminum by gravimetric, volumetric, and spectrophotometric procedures, 2. basicity (hydroxyl value) by formation of an aluminum complex and titration of the free acid with standard alkali solution, 3. total nitrogen by the Kjeldahl method, 4. ammonia by the Kjeldahl method, and 5. nitrates by means of a cation-exchange resin and titration of the liberated acid with standard alkali solution. Recommendations are made regarding the preferred methods of determining the constituents in dibasic aluminum nitrate and regarding means of minimizing errors in these analyses.
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