A list of projects, in the areas of nuclear technology and fluorine-based chemicals has been developed. These projects strengthen the interaction between Necsa and the HES and are suitable for Masters and Doctoral research programmes. Assistance will be given by Necsa specialists in the establishment of such projects at universities or technikons by supplying access to Necsa facilities and equipment, if applicable.
Information on existing collaborative programmes, the project list referred to below, and opportunities for research and training collaboration can be obtained from:
Dr Van Zyl de Villiers
Tel: +27 12 305 5630
Email: vanzyl.devilliers@necsa.co.za
- COLOUR INDICATORS
To protect vacuum pumps from attack by corrosive gases, chemical traps filled with e.g. activated Al2O3 are commonly used. To determine if the chemical traps are spent, a selective indicator will have to be used. The following properties are required from such a selective indicator:
- Sharp, irreversible colour change
- PPM sensitivity for corrosive gases
- UV resistant
- Must be impregnated on an inert (with regards to F2 and HF) carrier
- Must be manufactured from chemicals that are readily available
- Must be stable for at least a year under normal atmospheric conditions or a "clean" vacuum
- Must change colour for both HF and F2
- Two indicators, one selective for HF and the other for F2, would also be acceptable
- Must be able to operate under vacuum (1 Pascal)
- DETERMINATION OF THE CORROSION PROPERTIES OF Ni AND Cu-BASED ALLOYS WITH RESPECT TO ANHYDROUS HF + F2 GAS MIXTURES AT ELEVATED TEMPERATURES
NiF2 surface passivation layers have been found to impart F2 gas conveyance lines with increased resistance to ignition under high F2 flow conditions. It is unknown if this layer is as effective when the F2 contains high levels of HF (typically > 5 vol%). If it is shown to be less effective, other materials and passivation procedures will have to be investigated.
- DETERMINATION OF THE CORROSION RESISTANCE OF CERAMIC MATERIALS AND COATINGS IN FLUORINE/FLUORIDE ENVIRONMENTS
Classically F2 and other fluorides are contained in Ni based alloys. However, for cost and other reasons ceramics or ceramic-based coatings may in certain cases offer better performance. Parameters that need to be investigated include temperature, base material adhesion, influence of H2 and O2 on corrosion, etc.
- LOW-LEVEL F2 DETECTION IN PROCESS EXHAUST LINES
The measurement of low levels of F2 gas in different gas mixtures (preferably real-time) is analytically very difficult, especially in the presence of other reactive fluoride gases. Current methods used like GC and UV spectrometry have some unacceptable limitations. New methods will have to be more generally applicable, with ppm sensitivities.
- VISUAL TEMPERATURE INDICATORS
Various chemical dry scrubber columns are used at Necsa. In many cases the columns are operated as plug flow reactors with a sharply defined reaction front. Under abnormal situations the exothermic reactions taking place in these columns may get out of hand, leading to the destruction of the column. Temperature sensitive paints that would change colour within a specific temperature range could be very useful as temperature indicators in such applications. These indicators should have the following properties:
- Stable under atmospheric conditions, including being UV stable
- Colour changes must be reversible
- Must be formulated into a non-toxic paint system
- Must change in less than 1 second in colour upon a temperature excursion
Currently two temperature ranges are of interest, the one being the range 70 - 120 °C with a temperature resolution of 5 °C, and the other the range above 300 °C with a resolution of 50 °C.
- PHOSPHATE-BASED ZEOLITES
It is believed that some phosphate-based zeolites may have improved chemical stabilities with regards to different aggressive chemicals. Such zeolites will have to be identified through a literature survey and will have to be prepared in 500g quantities for evaluation.
- COMPARISON OF ION-EXCHANGE RESINS
Polymerication and anion exchange resins have varying capacities for different solvent molecules. It was noted that the capacity of these resins for solvent molecules is drastically influenced by various factors, e.g. loaded ion, backbone structure, functional group, etc. To make the optimum resin selection for maximum capacity of a given solvent, the influence of these variables needs to be modelled.
- DETERMINATION OF TOTAL ORGANIC CONTENT IN ANHYDROUS HYDROFLUORIC ACID (AHF)
A method needs to be developed for the determination of the total organic content in AHF. The expected organic compounds will mostly be hydrocarbons, partially fluorinated hydrocarbons and perfluorinated compounds, sometimes containing functional groups like ethers or carbonyls. The total organic content will typically be lower than 2%, and the method must have a sensitivity up to 10 ppm in organic content.
- MEASUREMENT OF TWO PHASE FLOWS
Measurement of two phase flows at various Reynolds numbers and a wide range of viscosities.
- COOLING WATER DISTRIBUTION FOR OPTIMUM HEAT EXCHANGE
Design and verify experimentally a heat exchanger (for a specified application) with a complex water flow path.
- PROCESS CONTROL OF A COMPLEX GAS FLOW CIRCUIT
The hazardous gas flow circuit has two sources and various depletion points. The demand and supply could vary with time. An analysis must be made of the control elements as envisaged.
- SYNTHESIS OF PHOSPHORUS CONTAINING LIGANDS
There is a need for the expertise of an organophosphorus synthetic chemist for the development of therapeutic radiopharmaceuticals. This includes the synthesis of modified phosphonate ligands (that have not been synthesised before) and the addition of DOTA groups to phosphonate-containing water soluble polymers.
- SYNTHESIS OF 33P-PHOSPHONATE LIGANDS
Development of simple (preferably "one pot") synthetic routes for the synthesise of phosphonate ligands is required. These procedures are to be used to synthesize phosphonate ligands from carrier free 33P-orthophosphate in a glove box.
- POLAROGRAPHIC DETERMINATION OF FORMATION CONSTANTS
There is a need to complement potentiometry with polarography for complexometric systems in which the first technique fails. Furthermore, comparing results found with both techniques for the same systems can confirm the results obtained by other techniques.
- RESEARCH ON WASTE STORAGE AND DISPOSAL CONTAINERSM
Necsa is obliged to store and dispose of both metal and concrete radioactive waste packages for extended periods of time. Uncertainty exists about how long these containers will last under storage and disposal conditions. A number of studies can be conducted at post-graduate level to show, for example, what the effects of radioactivity will be on concrete, metal and the waste form itself. Other avenues to be considered could be the effect of sulphates and chlorides on the waste packages at the Vaalputs disposal site as well as the effects of the atmosphere on metal drums in storage at Pelindaba. The electrochemical protection of metals (especially Al) in saline soil and specifications for waste containers for use in potentially corrosive environments also need to be investigated.
- TERMITES AT VAALPUTS
Termites have been identified as one of the critical pathways by which radioactivity can be brought to the surface at Vaalputs. Very little is known about the behaviour of termites in general and of the particular species that digs deep tunnels at Vaalputs. An MSc thesis on the subject would provide extremely useful data for the Vaalputs Safety Assessment.
- TECHNOLOGIES FOR POLLUTED AQUIFER REMEDIATION
A study on remediation methods for fluoride-contaminated aquifers is required.
- TECHNOLOGIES FOR RADIOACTIVE WASTE PROCESSING
Processes for the treatment of some types of radioactive waste need to be developed.
- NEOTECTONICS OF THE VAALPUTS AREA
Ongoing research work by Necsa has found that there is evidence of neotectonic activity at
Vaalputs. Preliminary findings need further investigation.
- CHARACTERISATION OF AREAS WITH ENHANCED NATURAL RADIOACTIVITY
The ongoing debate about standards for naturally occurring radioactive materials (NORM) has led to the need for the characterisation of areas with enhanced levels of NORM. This research should be complementary to that already being undertaken by the National Nuclear Regulator and the Council for Geosciences.