Gas sorption phenomena can be used to characterise porous solids and dispersed materials. Usually isotherms of nitrogen and noble gases like He, Ar, Kr are measured at low temperatures (77–90 K). Other gases and vapours like water, CO2 and benzene are used at near ambient conditions of pressure and temperature. From the amount of gas adsorbed on the (external or internal) surface characteristic quantities like the specific surface area, specific pore volume and pore spectrum of the material are derived by standardised methods. Experimental techniques most often used are the carrier gas, the volumetric/manometric and the gravimetric method. A comprehensible overview of today's available instruments, their advantages and drawbacks is given.
Disposal of Department of Energy (DOE) radioactive waste into repositories such as the Waste Isolation Pilot Plant (WIPP)
and the Nevada Test Site (NTS) requires characterization to ensure regulatory and transportation requirements are met and
to collect information regarding chemistry of the waste for processing concerns. Recent addition of an inductively coupled
plasma quadrupole mass spectrometer in a radioactive contaminated laboratory at the Oak Ridge National Laboratory (ORNL) has
allowed the evaluation of advantages of using ICP-MS over traditional techniques for some of these characterization needs.
The measurement of long-lived beta nuclides (i.e.99Tc) by ICP-MS has resulted in improved detection limits and accuracy than the traditional counting techniques as well as reducing
the need for separation/purification techniques which increase personnel exposure to radiation. Using ICP-MS for the measurement
of U isotopes versus the traditional Thermal Ionization Mass Spectrometer (TIMS) technique has reduced cost and time by more
than half while still maintaining the needed accuracy to determine risk assessment of the waste tanks. In addition, the application
of ICP-MS to ORNL waste tank characterization has provided the opportunity to estimate non-routine radionuclides (i.e.135Cs and151Sm) and non-routine metals (i.e. Li, Ti, rare earths, etc.) using a rapid low cost screening method. These application methodologies
and proficiencies on ORNL waste samples are summarized throughout the paper.
The operation and maintenance of a complex analytical instrument such as an inductively coupled plasma mass spectrometer in
a radioactive contaminated environment presents unique problems and challenges that have to be considered in the purchasing
and installation process. Considerations such as vendor experience, typical radiation levels, sample matrices encountered
during sample analysis, instrument accessability for maintenance, and upkeep must be incorporated into the decision process.
The Radioactive Materials Analytical Laboratory (RMAL) at Oak Ridge National Laboratory (ORNL) recently purchased and installed
an inductively coupled plasma mass spectrometer for the analysis of Department of Energy (DOE) radioactive waste streams.
This presentation will outline the purchasing decision, installation of the instrument, and how the modifications needed to
operate in a radioactive contaminated laboratory do not significantly impact the daily operation and maintenance requirements
of the instrument. Also, a contamination survey of the system will be presented which demonstrates the contamination levels
in the instrument from the sample introduction system to the detector.
By using slow damped oscillations of a torsional pendulum, it is possible to determine the mass adsorbed on the surface of
a porous sorbent without buoyancy effects from the frequency and the logarithmic decrement of the pendulum motion. In principle,
it is then possible to determine directly the buoyancy-related volume Vas of the sorbent/sorbate system by combining the results with gravimetric measurements.
Measurements with a preliminary testing pendulum are presented for N2 and CH4 on the activated carbon Norit R1 Extra at ambient temperature in the pressure range 0<p<0.5 MPa. Values for Vas calculated from these measurements and gravimetrically determined data are presented and discussed to a certain extent.
Authors:E. Robens, J. Keller, C. Massen, and R. Staudt
In sorption measurements, volumetric or gravimetric procedures are commonly used to determine the amount adsorbed. At low
pressures, thermomolecular flow and pressure differences according to Knudsen's law disturb measurements. In volumetry, calibration
of the dead space is required; in gravimetry, the influence of buoyancy has to be taken into account. In both cases, adsorption
of the calibrating gas, usually helium, may disturb the measurements . From the calibration measurements, the density of
the sample can in principle be calculated. However, it has been observed in many experiments that its value depends on the
Authors:X. Wang, W. Zimmermann, K. Ng, A. Chakraboty, and J. Keller
This article presents results of the experimental investigation on the adsorption of the water vapor on silica gel. Two independent
experimental methods has been used, viz. the constant-volume-variable-pressure (CVVP) system and variable pressure thermogravimetry
(TG). Results from these two methods are compared with each other. Also the isosteric heat of adsorption of this system has
been determined from the equilibrium data. The silica gels investigated here are Fuji Davison type 'A' and type 'RD'. Adsorption
isotherm of water vapor have been measured under a variety of conditions all referring to chiller operation cycles, i.e. temperatures
from 303 to 358 K and pressures from 500 to 7000 Pa. The data collected from the two independent experiments compare very
favorably with each other and their trends are consistent with those of the adsorption chiller manufacturer. This lends significant
weight to our experimental data on silica gel+water systems as being valuable to the adsorption chiller manufacturers and
the scientific community.
Authors:K. Szalay, B. Keller, R. Rák, N. Péterfalvi, L. Kovács, J. Souček, F. Sillinger, and A. Jung
One of the biggest challenges of raspberry production in Hungary nowadays is reducing the unfavorable effects of climate change. The maturation phase of main varieties within this region falls in a period of extremely high temperature and atmospheric drought detaining desirable fruit growth. Dedicated plant breeding alone is not enough. An immediate action is required. There has been a need for physical protection against excessive direct radiation. In order to restore, or even save the domestic raspberry production and market, introducing of greenhouse or polytunnel solutions are needed. Experimental plantations of three different raspberry varieties were set in two repetitions: covered and uncovered versions. Each cover has characteristic interaction with light which can generate different environmental conditions and also differences in plant growth and fruit quality. Besides the monitoring of elementary biological indicators, a wide range of sensors (temperature, humidity, solar irradiation) was used to identify differences and to find the optimal tunnel material for maximal plant productivity. Within the framework of the project we also tested a portable spectroradiometer and a snapshot imaging camera to study the practical value of proximal sensing in water- and photosynthetic light use efficiency and vitality mapping.