Radiochemical Facilities

Because tritium is radioactive, the number of laboratories that are set up to use this radionuclide in the study of catalysis is very small. This is unfortunate because the radioactivity can be put to good advantage, e.g., in following the rates of very slow reactions in a relatively short time. Nevertheless, proper radiochemical facilities and appropriate experience is required prior to embarking on research using tritiated compounds. 

Before embarking on any tritium work the personnel must become designated radiation workers and be familiar with the appropriate rules and regulations. Ideally there should be both a high level radiochemistry laboratory, as well as a low level laboratory with a separate room for the scintillation counter. One should only use the minimum amount of radioactivity, consistent with the requirements of the research project. Furthermore, it is often useful to carry out initial training studies using deuteriated compoimds, even though the subsequent tritimn work will be carried out 

There are two separate units of radioactivity in use, the first being the Curie (Ci) which is defined as an activity of 3.7 x 10 ° disintegrations per second. This is a large unit — bear in mind that with a modern day liquid scintillation counter radioactivity levels down to a few hundred coimts per minute can be easily measured — so it is very coimnon to use smaller subunits such as the millicurie (10 Ci) and the microcmie (10 Ci). The second, and more recently introduced miit, is the Becquerel (Bq). At one disintegration per second this is an extremely small amoimt of radioactivity. The conversions are 

In a high level radioactivity laboratory one would be expected to handle many millicuries, even curies, whilst in a low level laboratory one would try and limit the radioactivity to less than a millicurie, and often work at the microcurie level. 

Good laboratory practice should ensure that the radiochemical work be carried out over spill trays in a fumecupboard with excellent ventilation. Plastic gloves, sometimes one pair worn over the other, should be used at all times and any radioactive waste be placed in a container filled with ver-miculite. Regular urine samples should provide the necessary reassurance that the work is being performed with due diligence. Satisfactory arrangements for the disposal of radioactive waste should be put in place during early consultation with the radiochemical inspectorate. 

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Ci (curie) = 3.7 x 10 °Bq (becquerel) 1 Bq = 1 s . ] Tritium is one of the least toxic of radioisotopes and shielding is unnecessary however, precautions must be taken against ingestion, and no work should be carried out without appropriate statutory authorization and adequate radiochemical facilities. 

An ETA curve is a plot of emanating power E as a fimction of time and the F/time relationship has been developed and defined by Balek and Tolgyseey. A major difficulty of ETA is that preparation and handling of samples require sophisticated radiochemical facilities coupled with all the associated precautions. However, the net amounts of radioactive gas incorporated into samples are so small that the evolved gas, after dilution with the carrier, does not pose a significant hazard. 

Radiochemical facilities operational safety MOX production, transportation and handling... 

Tritium ( H or T) possesses ideal NMR properties -spin of high sensitivity (21% better than for H, = 1-06664, where ysn/yiH is the gyromagne-tic ratio) and extremely low natural abundance, but because it is radioactive (a weak jS -emitter with a half-life of 12.3 years. Table 1) there is the need for associated radiochemical facilities and trained... 

The /-block consists of the 4/ metals, La-Lu, and the 5/ metals, Ac-Lr. The common terms lanthanide and actinide derive from the names of the first elements of each series, and the symbol Ln, not assigned to any particular element, is a useful way to designate the lanthanides as a class. The older term for lanthanides, rare earths, is sometimes encountered. The actinides are radioactive, and only Th and U are sufficiently stable to be readily handled outside high-level radiochemical facilities t /2 = 4.5 x 10 years Th, ti/2 = 1.4 x 10 years). Even though they have no / electrons, scandium (Sc) and yttrium (Y) in group 3 are also typically considered with the /-block elements because of their rather similar chemistry. 

Finally, the financial implications of meeting a particular threshold for waste disposal or clearance of NORM-contaminated land are enormous, particularly when one considers the volumes created each year by the production and combustion of fossil fuels and the exploitation of industrial minerals. A key component of the supply chain in complying with the new regulations is the availability of radiochemical facilities with the necessary resources and expertise to produce reliable analyses. To date, much of the bmden has fallen on nuclear laboratories however, the demands of the two sectors are very different. 

The NAA measurements on the paper samples were made at the Breazeale Nuclear Reactor Facility at the Pennsylvania State University with a TRIGA Mark III reactor at a flux of about 1013 n/cm2-sec. Samples were irradiated from 2 to 20 min and counted for 2000 sec, after a 90 min decay time for Ba and a 60 hr decay for Sb, Analyses were performed instrumentally, without radiochemical separation, using a 35cm3 coaxial Ge-Li detector and a 4096-channel pulse height analyzer. With these procedures, detection limits for Ba and Sb were 0.02ug and 0.001 ug, respectively. These sensitivities are comparable to those obtained by GA s radiochemical separation procedure, and are made possible by the use of the higher neutron output from the more powerful reactor and in combination with the higher resolution solid state detector... 

All items of equipment must be considered, including balances and volumetric measuring devices, not just the expensive equipment. In terms of instrumentation, while a method using a mass spectrometer may be ideal for the study, if no such equipment is available the job will have to be contracted out to another laboratory, or another approach agreed with the customer. Neutron activation or radiochemical measurements require special equipment and dedicated laboratory facilities and safety procedures. Such techniques are often not generally available and are better left to specialist laboratories. 

The need for special facilities for work involving neutron activation analysis and radiochemical measurements has been referred to above in Section 4.3.6. Other safety factors may also influence your choice of method. For example, you may wish to avoid the use of methods which require toxic solvents, such as benzene and certain chlorinated hydrocarbons, or toxic reagents, such as potassium cyanide, if alternative procedures are available. Where Statutory Methods have to be used, there may be no alternative. In such cases, it is essential that staff are fully aware of the hazards involved and are properly supervised. Whatever method is used, the appropriate safety assessment must be carried out before the work is started. Procedures should be in place to ensure that the required safety protocols are followed and that everyone is aware of legislative requirements. 

The Sr-82 used in these studies was produced by spallation of a molybdenum target with 800 MeV protons at the Los Alamos Meson Physics Facility (LAMPF) and radiochemically separated by the Nuclear Chemistry Group at Los Alamos Scientific Laboratory (LASL) (22). The major radionuclidic contaminant in the Sr-82 is Sr-85 which is present in at least 1 1 ratio relative to Sr-82. The actual ratio depends upon the length of time after the production of radioactive strontium. Because of the 65 day half life of Sr-85 and the 25 day half life of Sr-82, the Sr-85 Sr-82 ratio increases with time. Other radionuclides found by the Hammersmith group in the processed Sr-82/85 shipment were Sr-89 ( 1%), Sr-90 ( 0.01%), Co-58 ( 1%) and Rb-84 ( 1%) from (17). 

Since in-house facilities for handling a large volume of samples for routine analysis were not available, the analytical work was contracted out to three commercial laboratories. We will refer to them as Laboratories A, B, and C. The contractors were selected on the basis of qualification tests which were intended to serve also for interlaboratory calibration. The results were reported to NRDL as d.p.m. or equivalent 285U thermal-neutron fissions at detonation time. All of the radiochemical data obtained from the laboratories are reported in Ref. 5. These values were punched on cards and converted by computer to equivalent fissions of the device, based on mass-chain yield values supplied by the weapons laboratories. At the same time, the calibration factors derived from qualification-test analyses were applied. Values of the ratios, 95, were formed. All of the ratios for a given nuclide i were then selected along with the corresponding values of r89t95, and the data points were fitted... 

In comparison with other laboratories techniques in polymer chemistry, radiochemical synthesis seems to be a large-scaled experiment, expensive, and exotic. But this is only partially true. There exist industrial facilities like electron accelerators and... 

Development of techniques to characterise waste properties - radiochemical, chemical and physical, including facilities for ILW characterisation... 

The availability of high flux thermal neutron irradiation facilities and high resolution intrinsic Ge and lithium drifted germanium (Ge(Li)) or silicon (Si(Li)) detectors has made neutron activation a very attractive tool for determining trace elemental composition of petroleum and petroleum products. This analytical technique is generally referred to as instrumental neutron activation analysis (INAA) to distinguish it from neutron activation followed by radiochemical separations. INAA can be used as a multi-elemental method with high sensitivity for many trace elements (Table 3.IV), and it has been applied to various petroleum materials in recent years (45-55). In some instances as many as 30 trace elements have been identified and measured in crude oils by this technique (56, 57). 

Sr deserves special attention since it is released by nuclear power facilities, accumulates in organisms and replaces Ca (mainly in bones) and has a long half life. °Sr is a pure beta emitter and before measurement (liqiud scintillation counting, proportional counters, etc.) a laborious and time-consuming procedure for radiochemical separation has to be performed (IAEA, 1989). This is practically the best way for reliable determination of this radionuclide (IAEA, 1989). 

It may be a long process between the removal of the irradiated target from the irradiation facility and the pure radiochemical substance or compound to be used in some experiment. The separation procedures needed to make a pure radiation source are chemically the same and (usually) independent of the "size" (i.e. its total radioactivity), but the experiments become more cumbersome — and often slower — when the radiation source is so large as to require considerable shielding. 

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