Tritiated waste

As previous examples have shown the development of microwave-enhanced labeling technology means more than accelerating reactions - it provides alternative opportunities. It follows therefore that some previously used methods now become much more attractive and this is the case for certain aromatic decarboxylations which can now be used for tritiations as well as in the treatment of tritiated waste. In previous studies [69] of the reaction the overriding feature was the harsh experimental conditions required. 

N.E. Bibler and E.G. Orebaugh, Radiolytic gas production from tritiated waste forms—gamma and alpha radiolysis studies, Report No. DP-1459 (Savannah River Laboratory, 1977). 

Tosh et al. proposed the use of Pd/Ag-based membrane reactors for the recovery of hydrogen and its isotopes from tritiated water in a closed loop process that includes both the forward and reverse water-gas shift reactions [24]. The aim of this process was to avoid any production of tritiated wastes and any consumption of CO. In the system, the retentate stream, rich in CO2, was recycled to the reactor. The water-gas shift stops when all the water reacts and aU the hydrogen is recovered at the permeate side. Then, hydrogen is added, and the CO2 in the stream is completely converted to CO by the reverse water-gas shift reaction, thanks to the continuous removal of the produced water in a condenser. Figure 9.13 shows the proposed process. 

The dry off-gas treatment systems are simpler and more economical to operate. These systems may preferably be used if there are no specific reasons for the incorporation of wet scrubbers. The dry systems keep the off-gas temperature well above the dewpoint so that corrosion by acid gas condensation can be minimized. A dry system may be selected when processing tritiated wastes (subject to regulatory conditions and to tritium concentrations) since it will release tritium, together with the dry-filtered off-gas, into the envirotunent. This practice may present a lesser radiological hazard when compared with the aqueous scrubbing of tritium and the consequent need for the handling and conditioning of the tritiated scrub solutions. 

CHARACTERISATION OF HIGHLY TRITIATED WASTE STREAMS RESULTANT FROM THE OPERATION OF THE CHAPELCROSS POWER STATION PROCESS PLANT (CXPP) FOR THE PURIFICATION OF TRITIUM... 

The highly tritiated waste streams discussed here represent a legacy waste from the operation of the Chapelcross Process Plant (CXPP) production line. This facility was operated until 2006 to produce purified tritium for the Military of Defence weapons programme. The primary (although not only) source of contamination in the waste is machine lubricating oil from rotary vacuum pumps used in the process line to evacuate air from the tritium purification process. The innovative design of the plant however led to substantial oil tritiation. The current activity of which is governed by two factors the extent of tritiation whilst in use (i.e. duration of service) and subsequent decay time since termination of service. 

Despite these limitations both methods represent the best techniques currently available and a marked improvement in the knowledge of the tritium inventory of this highly tritiated waste stream when compared to historical Chapelcross paper records which are now superseded. Previous work to determine the specific activity utilised the application of a highly conservative activity conversion factor from liberated gaseous tritium in equilibrium with a solid matrix inside a sealed container to an in-situ P measmement of gaseous tritium. Consequently the maximum specific activity has been determined to be < 25 % of the previous assessment and provides sufficient surety of true activity to support the appropriate onward waste management routing decision for this unique waste stream. 

So far this remains the only microwave-enhanced borohydride deuteration study. Corresponding tritiation studies can be anticipated in due course, especially with the wider range of tritiated reducing agents, referred to previously, becoming available. Significant reductions in radioactive waste can be anticipated. 

Seawater DOM has numerous sources and sinks and a range of potential reactions. Sources of the sub-micron components include exudation from phytoplankton, microbial degradation of bioparticles, animal wastes (excretion), viral infection of bacteria, sloppy feeding by zooplankton and other animals, and input of dissolved molecules from rivers and surface sediments. Removal mechanisms include photodegradation, sorption to sinking particles, and microbial utilization. Tritiated thymidine and leucine uptake experiments indicate that up to half of the carbon formed by photosynthesis is shunted via dissolved organic molecule intermediates into bacteria. 

The fundamental problem of tritium waste management is that there is no simple way to reduce the volume of tritiated water. There are techniques available to minimize the volume generated in reprocessing, e.g., reuse of tritiated water to feed steam jets, and strict confinement of tritium in the first extraction cycle. These techniques, however, add complications to the process. If, therefore, an inexpensive way were available to dispose of untreated tritiated water, severe generation restrictions would not be appropriate. If, however, expensive methods were to be applied, such as solidification or even concentration by isotopic enrichment, the volume generated has to be limited as much as possible. 

Deep well disposal. Injection of tritium-containing liquid into isolated aquifers or depleted oil horizons is the most interesting option. This technique has been used increasingly for almost 20 years to dispose of industrial wastes. In the United States, for instance, some hundred injection wells have been drilled and are actually in operation at depths between 60 m and 3600 m. Although there are still licensing problems, this is a safe and economic way to dispose of tritiated water. 

The future is challenging and full of promise. The central issue is the need to be able to do more radiochemistry in a shorter time interval using less radioactivity whilst at the same time minimizing the amount of radioactive waste produced. The recent development of microwave-enhanced tritiation technology means that many labelled compounds can now be prepared in a matter of minutes. As a result of the improvement in NMR spectrometer performance H NMR spectra can be obtained using less radioactivity than... 

Bomea, A. et al.. Laboratory studies for development of a plant to concentrate the radioactive waste from tritiated water,... 

Two recent developments are likely to improve the attractions of this particular isotope. First, a whole range of microwave-enhanced procedures have been developed which allow tritiations to be carried out more rapidly, sometimes more selectively, and, finally, with the production of less radioactive waste. The latter can frequently be converted to tritiated water that can then be reused. This represents a good example of Green Chemistry . 

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