J. Magill

Equation of state of uranium oxide

Abstract The total and partial pressures over liquid UO2 have been measured and calculated up to 5000K. A review of previous work is given. The equation of state of UO2 as the main constituent of the fast breeder oxide fuel is required up to at least 5000K in order to estimate the energy release in a loss of flow (LOF) driven hypothetical core disruptive accident (HCDA) of the liquid metal fast breeder reactor (LMFBR). Two models, a macroscopic “mixture” model and a microscopic “defect” model have been developed to determine the oxygen potential of UO200 up to 5000 K. A combination of mass spectrometric, Langmuir probe and high tension diode studies, applied for the first time to the laser vaporization process, revealed large quantities of ions emitted directly from the surface, and resolved previous discrepancies between measured and calculated vapour pressures by an enhanced rate of evaporation due to ion emission. As shown theoretically intrinsic ion emission can contribute to the net evaporation rate only if the resulting positive space charge can be neutralised. It is proposed that this can be accomplished by the presence of “hot” electrons in the plasma. The recommended equilibrium total pressure over liquid UO2.00, valid between the melting point and 5000K, is log p (MPa) = − 2.717 − 20131/T + 1.925 log T .

Transmutation characteristics in thermal and fast neutron spectra: application to americium

Abstract In this paper, a method is introduced which allows a quick and accurate evaluation of the overall transmutation rate of a nuclide in fast and thermal neutron spectra. The method is applied to 241 Am, a main contributor to the waste toxicity in the nuclear fuel cycle. Results show good agreement with the detailed calculations using ORIGEN code.

Present state of vapour pressure measurements up to 5000 K, and critical point data prediction of uranium oxide☆

Abstract A new dynamic laser pulse heating technique, allowing thermophysical property measurement and equation of state studies above 3000 K is described. The vapour pressure measurements of uranium oxide up to 5000 K, as required for reactor safety analysis are presented. The present state of experimental work above the melting point is summarised. A complete survey on predicted critical point data of uranium oxides reviewing the various theoretical models is given. The various dynamic pulse heating techniques are outlined. For a study of the high temperature vapours and the gas dynamic expansion phenomena of the gas jet, the laser surface heating equipment has been extended to include high speed diagnostics such as multi-channel spectroscopy, time of flight mass spectrometry, and image converter photography in both the framing and streak recording mode. The evaporation process and thermodynamic interpretation of the data are discussed. A kinetic theory description of the laser induced vapour jet using a monoatomic gas dynamical model is given. The optical absorption in the gas jet, giving an upper temperature limit for the applicability of optical pyrometry has been calculated. The reduction of ionisation potential was found to be of minor importance.

Frequency dependence of the acoustic agglomeration rate of a glycolfog

The concentration of liquid aerosol particles subjected to high intensity sound has been measured as a function of the acoustic irradiation time. Experiments were performed at sound wave frequencies of 9.4 and 21 kHz on aerosol with geometric mean particle diameter 0.8 μm standard geometric deviation o = 1.35, and initial particle concentrations in the range of 104 − 107 cm3. The results are only partially consistent with the orthokinetic mechanism of agglomeration

Characteristics of an electro-acoustic precipitator (EAP)

Abstract Results of a laboratory scale investigation to remove sub-micron particles from a gas stream, using a combined acoustic module and electrostatic precipitator (ESP), are presented. In these experiments, 1kW of electrical power is required per 1000m 3 of gas treated to increase the particle separation efficiency of the ESP from 90 to 95%.

Acoustic agglomeration of liquid and solid aerosols: a comparison of a glycol fog and titanium dioxide

Abstract Acoustic agglomeration rates of a liquid and a solid aerosol have been measured using a 21kHz sound source in a 0.6m 3 chamber. The agglomeration efficiency of a glycol fog varies from 4 to 3500 depending on the initial concentration, whereas that for a Ti0 2 aerosol lies between 5 and 20 and is independent of the initial concentration.

Plutonium Incineration in Lwrs

Much attention has been paid recently to the present and future build-up of plutonium stocks and the various “Bury or Burn” strategies[1] for management of this material. The plutonium arises from the dismantling of nuclear weapons (W-Pu) and from reprocessing of spent fuel (C-Pu). In this paper, the incineration of C-Pu in various matrices--in urania as MOX, in thoria as TMOX and in inert matrices such as MgAl2O4as IMOX -- is considered. This constitutes a first fuel cycle stratum based on LWRs and once through recycling with a view to decreasing the Pu stockpile in spent fuel. In the second stratum which is not the subject of this paper, minor actinides and long lived fission products are partitioned and then, transmuted in a dedicated actinide burner.

A survey of aerosol research in European community programmes

Abstract In the European Commissions 3rd Framework Programme (1990–1994) of community research and technological development, aerosol problems are of particular importance in the specific programmes Environment, Nuclear Fission Safety (with emphasis on Reactor Safety and on the Decommissioning of Nuclear Installations), Industrial and Materials Technologies , and Measurement and Testing . Under Environment , significant efforts are directed towards monitoring natural and anthropogenic aerosols in the atmosphere, understanding the role played by aerosols in ecosystem regulation, and the development of techniques to reduce aerosol emission from industrial plants. To ensure Nuclear Fission Safety , investigations are necessary to identify the mechanisms and determine the quantities of fission product aerosols released in the event of an accident and to develop measures for aerosol retention in such cases. The release of radioactive aerosols from nuclear installations in case of fire has been studied, and methods of aerosol abatement by acoustic techniques are under investigation. In decommissioning of nuclear installations the problem of aerosol formation and dispersion arises during dismantling operations. Industrial and Materials Technologies require information on aerosols ranging from welding fumes, asbestos fibres, lead compounds and quartz particles to aerosol/vapour mixtures of toxic products, aerosols from biotechnology industries and airborne micro-organisms. Finally, for Measurement and Testing , reference aerosols are needed for calibration purposes and to improve and harmonize particle counting and characterisation. A brief summary of examples for each of the above activities, carried out in the form of EC cost shared actions or at the Commissions Joint Research Centre, will be given, together with a description of some aerosol problems still to be solved.