Gross-activities

These results underline the fact that gross-activities based on TOFs or half-lives only are not appropriate to compare catalytic systems that are characterized by pre-equilibria. Rather, only an analysis of gross-kinetics on the basis of suitable models can provide detailed information concerning the catalysis. 

Molecular structure determines the gross activity of an organic compound, as it is responsible for the molecular volume, water solubility, vapor pressure, density, and electrical charge of the compound. The three-dimensional structure of an organic... 

To determine rubidium, the irradiated coal sample and added rubidium carrier are digested and the organic matter destroyed by heating with nitric and sulfuric acids, followed by nitric and perchloric acids. The rubidium is separated from the gross activity of the sample by precipitation with ferric hydroxide. The rubidium is then precipitated as the cobaltinitrite and finally as the chloroplatinate. The activity of the chloroplatinate caused by the 1.8 MeV /T particle of 18.7-day 86Rb is counted with a Geiger counter. 

Errors in timing. For the determination of elements yielding short half-life indicator radionuclides (such as in the determination of oxygen via 7.3 sec16N), accurate timing is extremely important. For these cases electronic scaler timers are to be preferred over electromechanical types of timers. Errors due to variable detector dead-time must also be considered when the gross activities of the sample and the standard differ appreciably and the indicator radionuclide is short-lived. 

One simple approach to the preparation of appropriate standards where the gross activity of the sample may be large with respect to the activity of interest is to use the method of standard addition. In this technique a number of aliquants of the sample are spiked with varying amounts of the element to be determined and irradiated along with a similar sized unspiked sample. The specific activities of the spiked and unspiked samples are then plotted vs. the weight of added element as illustrated in Fig. 12. Extrapolation of this curve to zero specific activity will easily permit calculation of the unknown amount (x) of the element... 

Calculations indicate that accumulated radioactivity is generally concentrated in reactor internals and reactor vessels. The activity of central caisson and the bottom of metal-water protection tank is less than 2% of gross activity. Pressme hull activity is about 0,04 % of gross radioactivity. 

Gross activity of main radionuclides generated in case of SNR at the moment of flash end will be 1.69xl0 Bq, maximmn activity after flash will be 1.82xl0 Bq. Activity escape into the atmosphere in accordance with radionuclides determining the radiation situation is 1.25xl0 Bq. 

Maximum gross activity cumulative in NPP of Victor II Submarine will be 1.4xio Bq (for one reactor) after three years of holding. SNF is the main source of activity value. SNF unloading will lead to threefold reduction of reactor compartment activity. 

Table 2.5.3 shows the available data for the seaward perimeter zones of reefs other than fringing reefs. There are a number of differences between these results and those from the total reef systems (Table 2.5.2). With the exception of the bare algal pavement at One Tree Reef the results suggest a reasonably uniform gross activity for seaward shallow water zones with little or no latitudinal variation and, significantly, little correlation with variation in community structure. However, net gain is quite variable with...

It can also be used as a follow-up screen once gross activity from a particular combinatorial sample has been established. 

The acid flowsheet was found to give a better plutonium recovery than the acid deficient process. However, the latter gave better decontamination from gross activity, especially for uranium, with DF/ y figures of 3.1 x 10 for uranium and 2x 10 for plutonium being attained after two cycles. Comparable values for the acid flowsheet were respectively 1.6 x 10" and 6.3 X 10. Although... 

If the sample contains more than one radionuclide, the method of activity measurement can still be used with the following modifications. The total (gross) activity of a sample containing several independently decaying radionuclides is... 

Finally the temperature dependence of die reaction rate may be estimated. The gross activation energy is a combination of ... 

In almost all cases the activation energy of the decomposition reaction is significantly higher than those of the other two elementary steps. Consequendy, in a first approximation, the gross activation energy amounts to roughly half the value of the activation energy of the decomposition reaction. 

An aliquot of the sample as liquid or slurry usually is dried on a planchet and then counted for gross activity measurement. In some instances, the radionuclides are coprecipitated by a carrier such as ferric hydroxide or manganese dioxide that is expected to collect many of them (ICRU 1972), and this solid is filtered or poured onto the planchet as slurry and then dried. Under favorable circumstance. 

An aqueous sample may be added to the cocktail directly, after minor prior processing, or at the end of a radiochemical separation procedure. Direct addition is the equivalent of gross activity counting discussed in Section 7.2.4 except that some spectral analysis may be possible. Alpha particles can be differentiated from beta particles by deposited energy, pulse shape, and decay time. Self-absorption is of no concern. Quenching and luminescence, discussed in Section 8.3.2, often occur. Identification by maximum beta-particle energy is approximate, and requires comparison to radionuclide standards. 

Analysis is planned for the radionuclides that are expected from the object of monitoring, with emphasis on radionuclides for which relatively large amounts are estimated to occur, be released, and reach the sample. Under some circumstances, radionuclides that are measured most readily or most sensitively may be used as tracers for accompanying radionuclides. Gamma-ray spectral and gross activity analyses are useful for testing predictions of radionuclide amounts, releases, and transfers, and also to seek unexpected radionuclides. 

To calculate the gross "-activity of the water, the measured rate - minus the background rate - is corrected to take account of the degree of efficiency of the counting set-up as determined by calibration. 

In measuring food, water, and environmental contamination, a sampling and in many cases sample preparation is required. This is performed in fixed laboratories, although some measurements could be performed in mobile laboratories. The quantity measured is activity concentration, expressed generally in Bq/kg or Bq/1. This can be gross activity (alpha, beta, or gamma) or can be radionuclide-specific. 

The measurement of gross activity which requires other assumptions to be made on the composition of radionuclides ... 

The value of 6 can be readily obtained from the measurement of the fast-fission factor. Aluminum catcher foils in contact with uranium foils of two different enrichments will have different gross fission product activations, so that from a plot of gross activity versus enrichment the following factor "F" is determined from the equation... 

On semilog paper plot the measured gross activity as a function of time since t. Choose a certain time ordinate, and read the activities of all the foils at this time. Enter the results in Table 13.4. 

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