Irving Johnson

Oxygen potential of irradiated urania--plutonia fuel pins

Abstract The oxygen-potential gradient in irradiated urania-plutonia fuel pins has been estimated from the distribution of molybdenum between the noble-metal-alloy inclusions and the oxide matrix as measured using an electron microprobe. The values of the oxygen potential were found to be more negative than would be computed for the fuel on the basis of the initial O/M ratio, thus indicating that the overall O/M of the fuel was decreased by irradiation. The O/M gradient has been computed and an oxygen material balance was determined between fuel oxide, fission products, and cladding. The nearly identical oxygen pressure profiles found for fuel pins irradiated for a range of values of the burnup indicates that the oxygen-potential gradient is establsihed early in the irradiation period, probably at the time the structure has been established and then remains nearly constant. The oxygen lost during the restructuring period is determined by the initial O/M of the fuel, the smear density and the temperature gradient. The oxygen lost during the burnup period is proportional to the burnup.

The thermodynamics of pyrochemical processes for liquid metal reactor fuel cycles

Abstract The thermodynamic basis for pyrochemical processes for the recovery and purification of metallic fuel from liquid metal cooled reactors is described. These processes involve the transport of the uranium and plutonium from one liquid alloy to another through a molten salt. The processes discussed use liquid alloys of cadmium, zinc, and magnesium and molten chloride salts. The oxidation-reduction steps are done either chemically by the use of an auxiliary redox couple or electrochemically by the use of an external electrical supply. The same basic thermodynamics apply to both the salt transport and the electrotransport processes. Large deviations from ideal solution behavior of the actinides and lanthanides in the liquid alloys have a major influence on the solubilities and the performance of both the salt transport and electrotransport processes. Separation of plutonium and uranium from each other and decontamination from the more noble and the alkali metal and alkaline earth fission-product elements can be achieved using both transport processes. The thermodynamic analysis is used to make process design computations for different process conditions.

Mass spectrometry studies of fission product behavior: I. Fission products released from irradiated LWR fuel

Abstract Quadrupole mass spectrometry has been used to study the chemical form and rate of release of volatile fission products (e.g., Xe, Kr, Cs, Te, and I) effusing from irradiated LWR fuel samples. In experiments up to a temperature of 2120 K, krypton, xenon, cesium, and tellurium were identified as the species released from the fuel. A weak signal was observed for atomic iodine at 1325 K. The source of the atomic iodine (e.g., it could be either dissociation of cesium iodide or dissociation of molecular iodine) has yet to be resolved. A most significant finding was lack of observation of molecular cesium iodide. The observed rate of release of xenon was several orders of magnitude lower than previously reported. The xenon release rate, however, increased significantly after the fuel was oxidized. In complementary experiments on nonradioactive simulated fuel, it was found that the release of tellurium was hindered by dissolution in Zircaloy cladding. Above 1300 K, gaseous SnTe was observed; its formation was attributed to reaction of the tellurium with tin in the cladding.

Fluidized-bed coal combustion: In-bed sorbent sulfation model

Abstract A model is developed to account for sulfur capture within the sorbent bed of a fluidized-bed coal combustor. The model is expressed in an analytical form that contains two sorbent specific parameters. The sorbent parameters, which describe the kinetics of the sulfation reaction are obtained from thermogravimetric analysis data on the SO 2 -sorbent reaction. Various hydrodynamic and mass transfer properties in relation to the bubbling phenomena are taken into consideration in the model. The predictions of the model which are made without arbitrary parameters, compare favorably with the experimental data on sorbent performance from large scale experimental fluidized-bed coal combustors.

THERMODYNAMICS OF CADMIUM- AND ZINC-RICH ALLOYS IN THE Cd--La, Cd--Ce, Cd-- Pr, Zn--La, Zn--Ce, AND Zn--Pr SYSTEMS.

AbstractThe thermodynamics of the cadmium- and zinc-rich alloys in the Cd−La, Cd−Ce, Cd−Pr, Zn−La, Zn−Ce, and Zn−Pr systems have been studied with a high-temperature galvanic cell method. The values of the standard free energy of formation (kcal per mole) of the intermetallic compounds are given by the equations:

Cadmium-neptunium a partial phase diagram of the system☆

\begin{gathered} (LaCd_{11} ), \Delta Gf^ \circ = - 72.3 + 43.6 \times 10^{ - 3} T (670^ \circ to 804^ \circ K) \hfill \\ (CeCd_{11} ), \Delta Gf^ \circ = - 70.5 + 44.6 \times 10^{ - 3} T (638^ \circ to 884^ \circ K) \hfill \\ (PrCd_{11} ), \Delta Gf^ \circ = - 69.1 + 44.8 \times 10^{ - 3} T (635^ \circ to 825^ \circ K) \hfill \\ (LaZn_{11} ), \Delta Gf^ \circ = - 92.6 + 48.0 \times 10^{ - 3} T (705^ \circ to 793^ \circ K) \hfill \\ (CeZn_{11} ), \Delta Gf^ \circ = - 87.9 + 45.0 \times 10^{ - 3} T (710^ \circ to 1018^ \circ K) \hfill \\ (PrZn_{11} ), \Delta Gf^ \circ = - 85.3 + 42.7 \times 10^{ - 3} T (696^ \circ to 875^ \circ K) \hfill \\ \end{gathered}

The thermodynamics of plutonium and uranium in liquid alloys and application to pyrochemical reprocessing of fast breeder reactor fuels

Equations are also given for the partial molar excess free energies of the lanthanide in dilute solutions of the lanthanide in liquid cadmium or zinc. The enthalpy of formation of the intermetallic compounds is discussed in terms of the crystalline structure of these intermetallic compounds. It is shown that the enthalpy of formation is a linear function of the ration/Vc, wheren is the number of zinc or cadmium atoms which are near-neighbors of the lanthanide atom andVc is the volume of the cage formed by the near-neighbor cadmium or zinc atoms. A linear dependence of the enthalpy of formation onn/Vc is also found for the intermetallic compounds in several other binary systems. These empirical correlations are discussed in terms of a model which involves localized bonds between the lanthanide and zinc or cadmium atoms.

Light element thermodynamics related to actinide separations

Abstract A thermogravimetric analyzer was used to measure the reactivity of several limestone with SO 2 . The laboratory results can be directly used to predict coal combustion results for pilot-plant atmospheric pressure fluidized beds. Also, the TGA information was fitted to two different straight-line least-squares fits. These equations allowed prediction (by two different methods) of calcium utilization in atmospheric-pressure pilot plant fluidized-bed combustors (FBCs) from knowledge of only the CaCO 3 content of the limestone. When the predictions based on laboratory work for seven limestones were compared with the pilot-plant experimental results of Pope, Evans and Robbins, Argonne National Laboratory, Consolidation Coal Co., and Morgantown Energy Research Center, agreement was good for all three methods.