Separate stages of mathematical processing of thermogravimetric data, the difficulties most often encountered, and typical error sources are considered. A complex procedure of automatic acquisition and editing of experimental data, including calculation of effective kinetic parameters, is described and an appropriate algorithm for the 15 BCM-5 microcomputer is presented. The computer calculation of the kinetic parameters of the multistage thermal decomposition of a polyamide fibre is given as an example.
Bone provides an important source of forensic evidence. The storage conditions of bone have been recognised as a factor in
maintaining the integrity of such evidence. Thermogravimetric analysis (TG) has been employed to examine the effects of storage
environments and preparation methods on the structural properties of pig bones. A comparison of oven and freeze drying has
been made to study the effect of storage conditions. A comparison has also been made of ground bone specimens with cut specimens.
Freeze-dried hand ground specimens provided the most consistent results and, thus, this is the recommended method of preparation
of bone specimens for TG analysis.
Composite ion-exchange resins were prepared by coating copper-ferrocyanide (CFC) and hydrous manganese oxide (HMO) powders
on polyurethane (PU) foam. Polyvinyl acetate/Acetone was used as a binder. The foam was loaded with about five times its weight
with CFC and HMO powders. The distribution coefficients of CFC-PU foam and HMO-PU foam for cesium and strontium respectively
were estimated. Under similar conditions the HMO-PU foam showed higher capacity as well as better kinetics for removal of
strontium than CFC-PU foam for Cs. The pilot plant scale studies were conducted using a mixed composite ion-exchange resin
bed. About 1000 bed volumes could be passed before attaining a DF of 10 from an initial value of 60–80. The spent resin was
digested in alkaline KMnO4 and the digested liquid was fixed in cement matrix. The matrices were characterized with respect to compressive strength
and leach resistance.
Authors:Satyabrata Mishra, Falix Lawrence, R. Sreenivasan, N. Pandey, C. Mallika, S. Koganti, and U. Kamachi Mudali
Removal of nitric acid from high level liquid wastes (HLLW) of nuclear fuel reprocessing plants is warranted for simplifying
the procedure for waste fixing. Chemical denitration aims to reduce the waste volume by destroying the acidity and subsequent
concentration by adding suitable reductants. Reduction of nitric acid to gaseous products is an attractive way to accomplish
denitration. Nitric acid reduction with formaldehyde proceeds with the formation of CO2, NO2, NO or N2O depending on the reaction conditions and all the reaction products except water can be eliminated from the system in gaseous
form. The HNO3–HCHO reaction is governed by a complex mechanism of exhibiting relatively long induction period, depending upon the temperature,
concentration of reactants and nitrous acid reaction intermediate. In the present work, a homogeneous denitration process
with formaldehyde which offers safety and is governed by controlled kinetics was demonstrated on a laboratory scale. The induction
period before commencement of the reaction was eliminated by maintaining the reaction mixture at a pre determined temperature
of 98 °C. Based on the results accrued from lab scale experiments, the equipment for pilot plant scale operation was designed,
the reaction efficiency for continuous denitration was determined and the investigation of nitric acid destruction was extended
to full-scale plant capacity. The role of organics in the waste in foaming up of the reaction mixture was also studied using
a synthetic waste solution.
Authors:A.-R. Attiah, R. Blackburn, A. Dyer, and C. Willams
Zeolites A (LTA), gismondine (GIS) and the zeotype CoAPO4-34 (CHA) were synthesised. During the syntheses, additions of Cs-137, Sr/Y-90, U and Th were made. Measurements of residual
activities at the conclusion of the syntheses enabled the estimation of the zeolite efficiency to scavenge the isotopes from
the initial solution. The majority of systems examined showed excellent radioisotope uptakes. PXRD was used to characterise
the synthesis products.
Authors:F. Poineau, T. Hartmann, G. Chinthaka Silva, G. Jarvinen, and K. Czerwinski
A new method for the preparation of Tc metal from pertechnetate is described. Metallic technetium was prepared from TcO4− by initial reduction in dry argon atmosphere at 300 °C followed by a wet argon atmosphere in the presence of carbon between
700 and 910 °C. The higher temperature conditions in the presence of H2O and carbon form H2 and CO, which can drive the reduction of TcO2. This method was applied to the recovery of pertechnetate sorbed on anion-exchange resins resulting in the formation of Tc
metal microspheres. The resulting Tc was characterized by XRD analysis and SEM.